A comprehensive study on the distribution, species diversity, population dynamics, and impact of plant-parasitic nematodes on vegetable crops in upper doab region (Uttar Pradesh), using advanced statistical approaches to evaluate crop susceptibility, environmental influences, yield loss, and sustainable management practices

Introduction

Agriculture plays a pivotal role in the socio-economic structure of rural India, particularly in districts like Upper Doab Region (Kasganj, Etah, Aligarh, Badaun, Hathras) in western Uttar Pradesh, where a large proportion of the population depends on farming for livelihood. The region is characterized by fertile alluvial soils, a semi-arid to sub-humid climate, and diversified cropping systems that include both cash crops and food crops. Among these, tobacco and a wide range of vegetables constitute important commercial crops due to their high economic returns and market demand. However, the productivity and quality of these crops are significantly threatened by a variety of biotic stresses, among which plant-parasitic nematodes represent a major yet often overlooked constraint. Nematodes are microscopic, unsegmented roundworms belonging to the phylum Nematoda. They are ubiquitous in soil ecosystems and occupy diverse ecological niches. While many nematodes are beneficial, a significant number are plant-parasitic and cause severe damage to crops by feeding on plant roots, stems, leaves, and even seeds. These phytoparasitic nematodes are responsible for considerable yield losses worldwide, estimated to affect nearly 10% of global crop production annually. Their impact is particularly pronounced in intensively cultivated agricultural systems, such as those found in Upper Doab Region where continuous cropping and limited crop rotation create favorable conditions for nematode proliferation. In India, nematode infestations have been reported to cause substantial yield reductions in horticultural and field crops. Studies indicate that plant-parasitic nematodes can result in an average annual loss of around 19.6% in agricultural production, with even higher losses-sometimes exceeding 60%-under intensive cultivation systems such as vegetable farming. These losses are often underestimated because nematode damage typically occurs below ground and does not always produce conspicuous above-ground symptoms.

Consequently, infestations frequently go unnoticed until significant economic damage has already occurred. Tobacco (Nicotiana tabacum L.) is one of the most important commercial crops grown in various parts of India, including pockets of Uttar Pradesh. It is highly susceptible to a wide range of pests and diseases, including nematodes. Research has shown that nematode infestation in tobacco can occur both in nursery stages and in transplanted crops, with incidence levels reported as high as 59.4% in nurseries and 52.9% in field conditions. Among the nematodes affecting tobacco, species such as rootknot nematodes (Meloidogyne spp.) and tobacco cyst nematode (Globodera tabacum) are of particular importance. These nematodes invade the root system, causing the formation of galls or cysts, leading to impaired nutrient uptake, stunted growth, and reduced leaf quality. In severe cases, they can drastically reduce yield and render the crop economically unviable. Vegetable crops, including tomato, brinjal, chili, okra, cucurbits, and leafy greens, are equally vulnerable to nematode attack. Root-knot nematodes (Meloidogyne spp.) are considered the most destructive group affecting vegetable crops worldwide. They infect plant roots and induce the formation of characteristic root galls, which interfere with the plant's ability to absorb water and nutrients. Other important nematodes associated with vegetables include lesion nematodes (Pratylenchus spp.), cyst nematodes (Heterodera spp.), reniform nematodes (Rotylenchulus spp.), and stem and bulb nematodes (Ditylenchus spp.). These nematodes not only reduce crop yield but also predispose plants to secondary infections by fungi and bacteria, thereby compounding the damage. The agro-climatic conditions of upper Doab Region of western Uttar Pradesh, including Kasganj, Etah, Aligarh, Badaun, Hathras district, are particularly conducive to the survival and multiplication of nematodes. The region experiences high soil temperatures, often ranging between 25°C and 38°C, along with intermittent moisture conditions, which create an ideal environment for nematode activity. Additionally, intensive cropping practices, monoculture, and the use of infested planting material further contribute to the buildup of nematode populations in the soil. The movement of contaminated soil through irrigation water, farm implements, and human activities facilitates the rapid spread of these pests across fields and regions. Despite their economic significance, nematodes have historically received less attention compared to other plant pathogens such as fungi, bacteria, and insects. This is largely due to their microscopic size, cryptic nature, and the complexity involved in their detection and identification. Accurate identification of nematode species is crucial for effective management, as different species vary in their host range, pathogenicity, and response to control measures. Traditional identification methods based on morphological characteristics require specialized expertise and are time-consuming. However, recent advances in molecular techniques have enhanced the accuracy and efficiency of nematode diagnostics. A systematic survey and identification of nematode pests associated with tobacco and vegetable crops in Upper Doab Region is therefore of paramount importance. Such a study would provide valuable baseline data on the diversity, distribution, and population dynamics of nematodes in the region. It would help in identifying the predominant species responsible for crop damage and assessing their severity under local agro-ecological conditions. This information is essential for developing targeted and sustainable nematode management strategies. The survey component of the study involves the collection of soil and root samples from different agricultural fields across various locations in Upper Doab Region (Kasganj, Etah, Aligarh, Badaun, Hathras). These samples are then processed in the laboratory to extract nematodes using standard techniques such as the Baermann funnel method, Cobb's sieving and decanting method, or centrifugal flotation. The extracted nematodes are examined under a microscope for identification based on morphological features such as body shape, stylet structure, esophageal glands, and reproductive organs. In advanced studies, molecular tools such as polymerase chain reaction (PCR) and DNA sequencing may be employed for precise species identification. Identification of nematodes is not only important for understanding their taxonomy but also for correlating specific species with particular crop symptoms and damage patterns. For instance, root-knot nematodes cause visible galling on roots, while lesion nematodes produce necrotic lesions and root decay. Stem and bulb nematodes lead to swelling and distortion of plant tissues. Recognizing these symptoms in the field, combined with laboratory identification, enables accurate diagnosis of nematode problems. The significance of this study extends beyond academic interest. It has practical implications for farmers, extension workers, and policymakers. By identifying the major nematode pests affecting tobacco and vegetable crops in Upper Doab Region, appropriate management strategies can be recommended. These may include cultural practices such as crop rotation, use of resistant varieties, soil solarization, organic amendments, and biological control agents. Integrated nematode management (INM) approaches that combine multiple strategies are particularly effective in reducing nematode populations and minimizing crop losses. Furthermore, the findings of such a survey can contribute to the development of region-specific pest management guidelines and support sustainable agricultural practices. In the context of increasing demand for safe and environmentally friendly farming methods, understanding the ecology and behavior of nematodes becomes even more critical. Effective nematode management not only enhances crop productivity but also improves soil health and long-term agricultural sustainability. Nematode pests represent a significant but often underestimated threat to commercial tobacco and vegetable cultivation in Upper Doab Region. Their hidden nature, wide host range, and ability to cause substantial yield losses necessitate systematic investigation. A comprehensive survey and identification study serves as a foundational step toward understanding the nematode problem in the region and developing effective management strategies. By bridging the gap between scientific research and practical application, such studies play a crucial role in ensuring sustainable agricultural development and improving the livelihoods of farmers in the region.

Ganga-Yamuna Upper Doab Region: Area and Nematode Infestation in Crops

The Ganga-Yamuna Upper Doab is one of the most agriculturally significant regions of northern India, situated between the rivers Ganga River and Yamuna River. This fertile tract includes districts such as Kasganj, Etah, Aligarh, Badaun, and Hathras. The region forms a part of the Indo-Gangetic plains, known for its high soil fertility, intensive cultivation, and diverse cropping systems. Agriculture here is highly developed, supporting both subsistence and commercial farming, including crops like wheat, rice, vegetables, tobacco, and pulses.

Agro-Climatic and Soil Characteristics

The Upper Doab region is characterized by deep alluvial soils, primarily sandy loam to clay loam in texture, which are highly suitable for crop production. The climate is subtropical, with hot summers and cool winters, and temperatures ranging between 20°C and 40°C during most cropping seasons. Adequate irrigation through canals and tube wells ensures continuous cropping throughout the year. However, these same favorable conditions-especially warm temperatures, moisture availability, and loose soil structure-also create an ideal environment for the growth and multiplication of plant-parasitic nematodes. Agriculture in districts like Aligarh and Kasganj is highly intensive, with cropping patterns such as rice-wheat rotation, vegetable-vegetable sequences, and tobacco-based systems. Farmers often cultivate two to three crops annually, leading to high cropping intensity. While this enhances productivity and income, it also results in continuous host availability for nematodes. The frequent use of the same fields for susceptible crops, along with limited crop rotation, contributes to the buildup of nematode populations in the soil. Plant-parasitic nematodes are widely distributed across the Upper Doab region. Surveys conducted in districts such as Aligarh and Hathras have revealed high infestation levels, particularly in vegetable and rice crops. The widespread occurrence of nematodes is attributed to favorable environmental conditions and intensive agricultural practices. Since these microscopic organisms inhabit soil and plant roots, their presence often goes unnoticed until significant crop damage has occurred.

Nematode Infestation in Vegetable Crops

Vegetable cultivation is widespread in Upper Doab Regiondue to its high profitability and market demand. However, these crops are highly susceptible to nematode infestation. Studies conducted in western Uttar Pradesh reveal that plant-parasitic nematodes are widely distributed and cause significant economic losses in vegetable crops. The average yield loss due to nematode infestation has been reported to be around 23.7%, with losses reaching up to 43% in crops like brinjal (eggplant) and 40% in tomato. The most common nematode species affecting vegetable crops in this region include:  Root-knot nematodes (Meloidogyne incognita and Meloidogyne javanica)  Reniform nematode (Rotylenchulus reniformis)  Lesion nematode (Pratylenchus spp.)  Stunt nematode (Tylenchorhynchus spp.) Among these, root-knot nematodes are the most destructive. They cause the formation of galls on roots, disrupting water and nutrient uptake. As a result, infected plants exhibit symptoms such as stunted growth, yellowing of leaves, wilting, and reduced fruit size. In severe infestations, the entire crop may fail.

Nematode Infestation in Tobacco Crops

Tobacco is an important commercial crop in regions adjoining Upper Doab Region which is known as a major tobaccoproducing center in northern India. Similar cultivation practices and soil conditions exist in Kasganj, Etah, Aligarh, Badaun, Hathras, making tobacco crops equally vulnerable to nematode attack. Nematodes affecting tobacco primarily include:  Root-knot nematodes (Meloidogyne spp.)  Cyst nematodes (Globodera spp.)  Reniform nematodes (Rotylenchulus reniformis)

These nematodes attack the root system, leading to gall formation, reduced root efficiency, and poor nutrient absorption. In tobacco, this results in:  Reduced leaf size and quality  Poor curing characteristics  Lower nicotine content  Significant reduction in market value Infestation can begin at the nursery stage and continue after transplantation, making early detection and management critical.

Mechanism of Crop Damage

Nematodes damage crops through direct and indirect mechanisms. Direct damage occurs when nematodes feed on plant tissues using a specialized stylet, puncturing cells and extracting nutrients. Indirect damage occurs when feeding creates entry points for secondary pathogens such as fungi and bacteria, leading to complex disease conditions. For example, species like the stem and bulb nematode (Ditylenchus dipsaci) can cause tissue swelling, distortion, and rotting in host plants, ultimately reducing crop quality and yield. Similarly, root-knot nematodes interfere with vascular tissues, severely affecting plant growth and productivity.

Factors Contributing to Nematode Infestation in Upper Doab Region

Several factors contribute to the high incidence of nematodes in Upper Doab Region: [28] highlighted the global significance of nematodes, estimating substantial crop losses due to root-knot nematodes. Similarly, Norton (1978) [23] emphasized the ecological adaptability of nematodes, which enables them to thrive across diverse agro-climatic conditions. Among the various nematode species, root-knot nematodes (Meloidogyne spp.) are considered the most economically important due to their wide host range and ability to cause severe root damage. According to Jones et al. (2013) [15] , these nematodes are ranked among the top ten plant-parasitic nematodes worldwide. Their pathogenicity is primarily associated with the formation of root galls, which disrupt water and nutrient uptake, leading to stunted growth and reduced yields (Hussey & Janssen, 2002) [13] . The dominance of Meloidogyne incognita in vegetable crops has been widely reported in India and other tropical regions (Moens et al., 2009) [21] . Several studies have documented the relationship between nematode population density and crop yield loss. Barker and Olthof (1976) [3] established that yield reduction is directly proportional to nematode density, a finding further supported by Viaene and Abawi (1998) [36] , who identified economic threshold levels for nematode damage. In vegetable crops such as tomato and brinjal, yield losses can exceed 40% under severe infestation (Kumar & Singh, 2019) [19] . Environmental factors play a crucial role in influencing nematode distribution and activity. Soil texture, moisture, and temperature significantly affect nematode survival and reproduction. Prot and Van Gundy (1981) [26] demonstrated that sandy soils favor nematode movement and infection, while heavier soils restrict their activity. Similarly, irrigation practices have been shown to enhance nematode spread by increasing soil moisture (Noling, 2012) [22] . Seasonal variations also influence nematode dynamics, with higher temperatures accelerating their life cycle (Trudgill & Blok, 2001) [34] . Cropping patterns and agricultural practices are equally important determinants of nematode infestation. Continuous cultivation of susceptible crops leads to population buildup, whereas crop rotation with non-host species can effectively reduce nematode density (Ploeg, 2001) [25] . The role of weeds as alternate hosts has also been highlighted, as they provide a reservoir for nematode survival during off-seasons (Khan & Kim, 2007) [17] . Soil fertility and organic matter content have a complex relationship with nematode populations. While high nutrient levels promote plant growth, they may also enhance nematode reproduction by increasing root biomass (Oka, 2010) [24] . However, certain organic amendments, such as neem cake and compost, have been found to suppress nematodes through biological and chemical mechanisms (Akhtar & Malik, 2000) [1] . Advancements in statistical analysis have enabled researchers to better understand nematode dynamics and their impact on crop productivity. Techniques such as ANOVA, regression analysis, and correlation studies are widely used to assess the significance of various factors influencing infestation (Zasada et al., 2010) [39] . Composite indices, such as the Species Dominance Index and Crop Vulnerability Index, provide integrated measures of nematode impact and crop susceptibility. In the Indian context, several studies have reported widespread nematode infestation in vegetable crops. Jain et al. (2007) [14] estimated national crop losses due to nematodes, while Sharma and Sharma (2015) [29] documented their distribution across different agro-climatic zones. Regional studies in Uttar Pradesh have also highlighted the prevalence of Meloidogyne spp. in vegetable-growing areas (Yadav & Bhatti, 2018) [38] . Despite extensive research, nematode management remains a challenge due to their complex life cycle and adaptability. Integrated approaches combining cultural, biological, and chemical methods are considered most effective (Sikora & Fernández, 2005) [30] . Recent studies emphasize the importance of sustainable practices, including crop rotation, resistant varieties, and soil health management, to reduce reliance on chemical nematicides (De Waele & Elsen, 2007) [9] . Overall, the literature underscores the significant impact of plant-parasitic nematodes on vegetable production and highlights the need for region-specific studies. The present research builds upon these findings by providing a detailed analysis of nematode infestation in Upper Doab Region comprising Kasganj, Etah, Aligarh, Badaun, Hathras district, integrating field data with advanced statistical methods to identify key factors influencing infestation and to develop effective management strategies.

Research Methodology

The present study was conducted to assess and analyze nematode infestation in major vegetable crops across selected locations in the Upper Doab Region of Uttar Pradesh. A systematic and quantitative research approach was adopted to ensure reliable data collection, statistical validation, and meaningful interpretation. Five Main agricultural sites-Upper Doab Region (Kasganj, Etah, Aligarh, Badaun, Hathras),were selected based on their prominence in vegetable cultivation. These sites represent diverse agro-ecological conditions within the district, including variations in soil type, irrigation practices, and cropping patterns. Eight commonly cultivated vegetable crops were included in the study: tomato, brinjal, okra, potato, cabbage, bottle gourd, bitter gourd, and spinach. These crops were selected due to their economic importance and known susceptibility to plant-parasitic nematodes. Field surveys were conducted using a random sampling method during the cropping season. From each site, multiple fields were selected, and soil and root samples were collected from the rhizosphere zone (0-20 cm depth). Approximately 10-15 samples per crop per site were collected to ensure representativeness. Nematodes were extracted from soil samples using the Baermann funnel technique and Cobb's sieving method. Root samples were examined for galling symptoms, and nematodes were identified up to species level based on morphological characteristics under a microscope. Key species identified included Meloidogyne incognita, Meloidogyne javanica, Rotylenchulus reniformis, and Pratylenchus spp. The following parameters were recorded:  Percentage of infestation (field-level occurrence)  Nematode population density (J2/100 cc soil)  Root Gall Index (0-5 scale)  Yield loss estimation (%)  Soil type, irrigation level, cropping pattern, and organic matter content

Data Analysis

Nematode infestation has emerged as a major constraint in vegetable production systems, particularly in intensively cultivated regions such as Upper Doab Region of Uttar Pradesh. Plant-parasitic nematodes, especially root-knot nematodes (Meloidogyne spp.), cause significant damage to a wide range of vegetable crops by affecting root structure, nutrient uptake, and overall plant vigor. The resulting yield losses not only reduce agricultural productivity but also impose serious economic burdens on farmers. The increasing prevalence of nematodes in vegetable-growing areas is closely linked to continuous cropping, intensive irrigation, and the cultivation of susceptible crop varieties. Despite their microscopic size, nematodes have a profound impact on crop health, often remaining undetected until severe damage has occurred. Therefore, understanding their distribution, intensity, and impact across different crops and environmental conditions is essential for effective management.

The present study aims to analyze nematode infestation patterns across selected sites and vegetable crops in Upper Doab Region using statistical tools. By examining relationships between infestation levels, yield loss, environmental factors, and species composition, the study seeks to identify the most affected crops, dominant nematode species, and high-risk areas. This analysis provides a scientific basis for developing targeted and sustainable nematode management strategies. ), during the survey period. This table aims to highlight the spatial variation in infestation intensity and identify major hotspots of nematode prevalence across the region. The site-wise distribution of nematode infestation indicates a consistently high prevalence across all surveyed districts, ranging from 66% to 74%. Among the five districts, Badaun recorded the highest infestation level (74%), followed by Kasganj (72%) and Aligarh (70%). Etah showed a moderately high infestation (68%), while Hathras exhibited the lowest infestation level (66%). Despite minor variations, the relatively narrow range suggests that nematode infestation is not restricted to specific localities but is widespread and endemic throughout the Upper Doab region. The higher infestation levels observed in Badaun and Kasganj may be attributed to intensive vegetable cultivation practices, continuous cropping systems, and frequent irrigation, all of which create favorable conditions for nematode proliferation. The predominance of sandy loam soils in these districts further facilitates nematode mobility and root penetration, thereby increasing infection rates. Additionally, the limited adoption of crop rotation and the continuous cultivation of susceptible crops such as tomato and brinjal contribute significantly to nematode population buildup. In contrast, the comparatively lower infestation recorded in Hathras may indicate relatively improved agronomic practices, such as better crop rotation, soil management, or lower cropping intensity. However, even the lowest infestation level (66%) remains substantially high, underscoring the severity and widespread nature of the problem across the entire region. From a broader perspective, the uniform distribution of nematode infestation across all districts emphasizes the need for region-wide management strategies rather than isolated, site-specific interventions. Integrated nematode management approaches-including the use of resistant cultivars, organic soil amendments, biological control agents, and improved cultural practices-are essential for reducing infestation levels. Furthermore, strengthening farmer awareness and extension services is crucial to effectively address this persistent agricultural challenge. to compare host susceptibility and identify highly vulnerable crops within the regional cropping system. The crop-wise analysis of nematode infestation reveals significant variation in susceptibility among different vegetable crops. Brinjal (85%) and tomato (80%) exhibit the highest infestation levels, indicating their high susceptibility to root-knot nematodes, particularly Meloidogyne incognita. These crops provide ideal conditions for nematode development due to their extensive root systems, longer growth duration, and continuous cultivation cycles. As a result, they act as major reservoirs for nematode populations, contributing to the persistence and spread of infestation in the region. Okra (78%) and bottle gourd (75%) also show relatively high infestation levels, suggesting moderate to high susceptibility. Potato (72%) falls within a similar range, indicating that root and tuber crops are also significantly affected. In contrast, cabbage (60%) and spinach (55%) show moderate infestation levels, which may be attributed to partial resistance or less favorable root structures for nematode colonization. Bitter gourd records the lowest infestation (45%), suggesting relative tolerance or resistance. This crop may possess certain biochemical or morphological traits that limit nematode penetration and reproduction. Such crops can play an important role in crop rotation strategies aimed at reducing nematode populations. The observed variation highlights the critical role of crop selection in nematode management. The predominance of highly susceptible crops like brinjal and tomato in the cropping system intensifies nematode pressure and leads to cumulative soil infestation over time. Therefore, incorporating less susceptible crops, such as bitter gourd and cabbage, into crop rotations can significantly reduce nematode load. The findings emphasize the need for strategic crop planning and the adoption of resistant varieties to mitigate nematode-related losses in vegetable production systems. Frequent irrigation in these districts further enhances nematode activity by maintaining optimal soil moisture conditions. In contrast, the relatively lower densities observed in Hathras and Etah may reflect differences in cropping intensity, soil management, or irrigation practices. High nematode population density directly contributes to severe root damage, particularly through gall formation caused by root-knot nematodes (Meloidogyne spp.). This leads to impaired water and nutrient uptake, ultimately affecting plant growth and productivity. Therefore, population density serves as a reliable predictor of potential crop loss and overall infestation severity. The analysis of yield loss provides important insights into the economic consequences of nematode infestation in the region. Among the studied crops, brinjal exhibits the highest yield loss (43%), followed by tomato (40%) and okra (38%). These significant losses are primarily associated with severe root galling and disruption of water and nutrient uptake caused by root-knot nematodes. Since these crops are widely cultivated and economically important, such high levels of yield reduction can substantially affect farmers' income and regional vegetable production. Bottle gourd (35%) and potato (32%) also show considerable yield losses, indicating that nematode infestation affects a broad spectrum of vegetable crops. Spinach records a moderate yield loss (20%), possibly due to its shorter crop duration, which limits the time available for nematode multiplication. In contrast, cabbage (6%) and bitter gourd (4%) exhibit minimal yield losses, suggesting relative tolerance or resistance to nematode infestation. These crops may experience infection but are less impacted in terms of productivity, potentially due to stronger root systems or inherent biochemical defense mechanisms.

The overall trend indicates a strong positive relationship between infestation intensity and yield loss, where crops with higher infestation levels consistently experience greater reductions in yield. This emphasizes the importance of early detection, monitoring, and timely management of nematodes to minimize economic losses. From a practical perspective, the findings highlight the urgent need for integrated nematode management strategies. The adoption of resistant crop varieties, crop rotation with less susceptible crops, and improved soil health management practices can significantly reduce yield losses. Furthermore, establishing economic threshold levels will help farmers implement timely and cost-effective control measures. Sandy loam soils, characterized by larger pore spaces and better aeration, provide an ideal environment for nematode movement and root penetration. These conditions facilitate rapid dispersal and infection, leading to higher infestation levels. Additionally, sandy soils tend to warm up quickly, promoting faster nematode life cycles and increased population density. Loam soils, which have a balanced mixture of sand, silt, and clay, support moderate levels of infestation. While they provide sufficient aeration for nematode activity, their slightly denser structure may limit movement compared to sandy soils. In contrast, clay loam soils, with smaller pore spaces and higher water retention capacity, restrict nematode movement and reduce oxygen availability. These conditions are less favorable for nematode survival and reproduction, resulting in lower infestation levels.

The findings emphasize the importance of soil management in controlling nematode populations. Farmers cultivating vegetables in sandy loam soils are at a higher risk and should adopt preventive measures such as organic amendments, soil solarization, and crop rotation. Understanding soil-nematode interactions can help in developing location-specific management strategies and improving crop productivity. 9 presents the Root Gall Index (RGI) of selected vegetable crops on a standardized 0-5 scale, where 0 indicates no galling and 5 represents severe gall formation due to root-knot nematode infection. The index is based on visual assessment of root systems collected during field surveys and is used as an indicator of infection severity and plant damage. This table aims to compare the degree of nematode-induced root damage across different crops. The Root Gall Index provides a direct measure of the severity of nematode infection and its impact on plant root systems. In the present data, brinjal and tomato both record the highest index value (5), indicating severe galling and extensive root damage. This confirms their high susceptibility to root-knot nematodes and explains the substantial yield losses observed in these crops. Okra and potato show moderately high galling (index 4), suggesting significant but comparatively less severe infection. The presence of galls in these crops still disrupts root function, affecting nutrient uptake and plant growth, though to a slightly lesser extent than in brinjal and tomato. Cabbage, with a lower index value (2), exhibits mild galling, indicating partial resistance or tolerance. The reduced severity of root damage in cabbage aligns with its lower yield loss and infestation percentage, suggesting that it is less favorable for nematode development. The Root Gall Index is a critical diagnostic tool, as it reflects not only the presence of nematodes but also the extent of physiological damage to the plant. High galling intensity is associated with impaired water and nutrient absorption, leading to stunted growth and reduced productivity.

These findings highlight the importance of selecting crops with lower gall indices for cultivation in nematode-prone areas.

Additionally, monitoring gall formation can help farmers assess infestation severity and timely management measures. The table reinforces the strong relationship between root damage severity and crop susceptibility, emphasizing the need for resistant varieties and integrated pest management strategies. The data indicate a positive relationship between organic matter content and nematode infestation levels, with high organic content soils showing the highest infestation (80%), followed by medium (70%) and low (60%) levels. At first glance, this trend may appear counterintuitive, as organic matter is generally associated with improved soil health. However, the relationship between organic matter and nematodes is complex. High organic matter enhances soil fertility, microbial activity, and root growth, creating a favorable environment not only for plants but also for nematodes. Increased root biomass provides more feeding sites, while improved soil structure facilitates nematode movement and reproduction. As a result, nematode populations may increase in nutrient-rich soils. However, it is important to note that not all organic amendments have the same effect. While general organic matter may support nematode activity, specific organic inputs such as neem cake, compost enriched with bio-agents, and green manures can suppress nematode populations through the release of toxic compounds or by promoting antagonistic microorganisms. The lower infestation observed in soils with low organic matter may be due to limited root growth and less favorable conditions for nematode survival. However, such soils are also less productive and may not support optimal crop growth. The findings suggest that simply increasing organic matter is not sufficient for nematode control; rather, the type and quality of organic inputs are critical. Integrated soil management practices that combine organic amendments with biological control agents can help balance soil fertility and pest suppression. The table highlights the need for a nuanced approach to soil management, ensuring that improvements in soil health do not inadvertently enhance nematode infestation. The data reveal a clear trend in which higher soil fertility levels correspond to increased nematode infestation. Fields with high NPK levels show the highest infestation (82%), followed by moderate fertility (70%) and low fertility (55%). This relationship can be attributed to the enhanced plant growth and root development associated with higher nutrient availability, which in turn provides more feeding sites for nematodes. In high fertility soils, vigorous root systems create an ideal environment for nematode colonization and reproduction. Increased nitrogen levels, in particular, are known to promote succulent root growth, making plants more susceptible to nematode invasion. Furthermore, well-fertilized soils often maintain better moisture retention and microbial activity, which can indirectly support nematode survival. Moderate fertility levels show a balanced scenario, where plant growth is sufficient but not excessive, resulting in moderate nematode infestation. In contrast, low fertility soils exhibit reduced infestation, likely due to limited root biomass and less favorable conditions for nematode reproduction. However, it is important to note that low fertility also negatively impacts crop productivity. The findings suggest that excessive use of chemical fertilizers, especially nitrogen-rich inputs, may inadvertently increase nematode problems. Therefore, nutrient management should be carefully balanced to optimize plant growth while minimizing pest pressure. Integrated nutrient management, combining chemical fertilizers with organic amendments and biofertilizers, can help achieve this balance.

Overall, the table highlights the complex interaction between soil fertility and nematode infestation, emphasizing the need for sustainable nutrient management practices in vegetable production systems. Table 13 presents the effect of crop duration-categorized as long-duration, medium-duration, and short-duration crops-on the percentage of nematode infestation in the Upper Doab Region. The infestation percentage represents the proportion of crops within each duration category affected by nematodes. This table aims to assess how the length of the crop growth period influences nematode life cycles and population buildup. The data indicate that crop duration has a significant impact on nematode infestation levels. Long-duration crops show the highest infestation (80%), followed by medium-duration crops (70%), while short-duration crops exhibit comparatively lower infestation (60%). This pattern can be explained by the life cycle dynamics of nematodes. Plant-parasitic nematodes, particularly root-knot species, have relatively short life cycles, often completing multiple generations within a single cropping season. Long-duration crops provide an extended period for nematodes to reproduce and accumulate in the soil, leading to higher population densities and increased infestation severity. Crops such as brinjal and tomato, which remain in the field for longer periods, are therefore more vulnerable to severe nematode damage. Mediumduration crops allow fewer nematode generations, resulting in moderate infestation levels. In contrast, short-duration crops are harvested before nematode populations can build up significantly, thereby reducing infestation intensity. The findings highlight the importance of crop duration as a key factor in nematode management. Incorporating short-duration crops into cropping systems can help break the nematode life cycle and reduce population buildup. Additionally, alternating long-duration crops with short-duration or non-host crops can further suppress nematode levels. From a practical perspective, farmers in nematode-prone areas should carefully plan cropping sequences to minimize continuous exposure of soil to longduration susceptible crops. This approach not only reduces nematode infestation but also improves overall soil health and sustainability. Table 15 presents the effect of different management practicesno control, partial control, and integrated management-on the percentage of nematode infestation in vegetable crops of Kasganj, Etah, Aligarh, Badaun, and Hathras district. The infestation percentage represents the proportion of fields under each management category affected by nematodes. This table aims to evaluate the effectiveness of various control strategies in reducing nematode infestation. The data clearly demonstrate the effectiveness of management practices in controlling nematode infestation. Fields with no control measures show the highest infestation (85%), followed by partial control (70%), while integrated management practices result in the lowest infestation (50%). This significant reduction highlights the importance of adopting a comprehensive approach to nematode management.

In the absence of control measures, nematode populations increase unchecked, leading to severe infestation and crop damage. Partial control practices, such as occasional use of chemical nematicides or limited crop rotation, provide some reduction in infestation but are not sufficient to achieve longterm control. Integrated management, which combines multiple strategies such as crop rotation, resistant varieties, organic amendments, biological control agents, and proper irrigation and nutrient management, proves to be the most effective approach. By targeting different stages of the nematode life cycle and improving overall soil health, integrated management significantly reduces nematode populations. The reduction of infestation from 85% (no control) to 50% (integrated management) demonstrates the potential of holistic approaches in mitigating nematode problems. Moreover, integrated practices are more sustainable and environmentally friendly compared to reliance on chemical control alone. The findings underscore the need for increased awareness and adoption of integrated nematode management among farmers.

Extension services and training programs should focus on promoting these practices to enhance crop productivity and sustainability. Overall, the table highlights that effective nematode control requires a coordinated and multifaceted strategy rather than isolated interventions. Table 16 presents the estimated economic loss per hectare (₹/ha) incurred in major vegetable crops due to nematode infestation in the Upper Doab Region. The loss estimates are calculated based on yield reduction percentages, prevailing market prices, and average productivity levels of each crop. The table includes key crops such as tomato, brinjal, okra, and potato, which are widely cultivated and economically significant in the region. This table aims to quantify the financial impact of nematode infestation and highlight the economic urgency of effective management practices. The economic loss data clearly demonstrate that nematode infestation is not only a biological problem but also a serious economic concern for farmers in the Upper Doab Region. Among the crops analyzed, brinjal incurs the highest loss (₹50,000/ha), followed by tomato (₹45,000/ha), okra (₹38,000/ha), and potato (₹35,000/ha). These figures reflect the combined effect of high infestation levels and the economic value of these crops in the market. Brinjal and tomato, being highly susceptible to root-knot nematodes, suffer severe yield reductions, which directly translate into substantial financial losses. Since these crops are often grown intensively and marketed widely, even a small percentage reduction in yield results in significant economic impact. Okra and potato, though slightly less affected, still show considerable losses due to reduced productivity and, in the case of potato, compromised tuber quality. The economic burden is further aggravated by the additional costs associated with pest management, including chemical nematicides, labor, and soil treatments. Farmers who lack access to effective management strategies may experience recurring losses, leading to reduced profitability and financial instability.

The findings highlight the urgent need for cost-effective and sustainable nematode management practices. Integrated approaches, including crop rotation, resistant varieties, and biological control, can significantly reduce both yield loss and associated economic damage. Moreover, investing in preventive measures is likely to be more economical in the long run than dealing with severe infestations. The table underscores the critical link between plant health and economic sustainability, emphasizing that effective nematode management is essential for improving farmer income and ensuring agricultural viability in the region. This table presents the results of a one-way Analysis of Variance (ANOVA) conducted to determine whether significant differences exist in nematode infestation levels among eight selected vegetable crops cultivated in the Upper Doab Region. The analysis compares between-group and within-group variance to assess whether observed differences in infestation percentages are statistically meaningful. The results indicate a highly significant variation among crops (p < 0.001), confirming that nematode infestation is not uniform across different host plants. Crops such as brinjal and tomato exhibit significantly higher infestation levels compared to others, indicating their high susceptibility to root-knot nematodes. Moderate infestation levels are observed in crops like okra, potato, and bottle gourd, while relatively lower levels are recorded in cabbage and bitter gourd.

The high F-value suggests that the variation between crop groups is substantially greater than the variation within groups, reinforcing the reliability of the findings. This statistical evidence supports the hypothesis that crop type plays a critical role in determining nematode infestation intensity. The results have important implications for agricultural planning, as they highlight the need to prioritize resistant or less susceptible crops in nematode-prone areas. Additionally, they underscore the importance of crop diversification and rotation to reduce nematode buildup and sustain soil health. all districts indicates that nematode presence is widespread and not limited to specific localized areas. The significant F-value obtained in the analysis clearly suggests that variability in nematode infestation is not due to random chance but is strongly influenced by site-specific ecological and agricultural conditions. This underscores the importance of adopting regionspecific and site-specific nematode management strategies rather than a uniform control approach. From a practical perspective, the identification of high-risk districts such as Badaun and Kasganj is crucial for prioritizing intervention measures. Integrated nematode management strategies-including the use of resistant crop varieties, biological control agents, organic amendments, and improved cultural practices-should be implemented more intensively in these areas. Additionally, strengthening agricultural extension services and farmer awareness programs will play a vital role in mitigating nematode infestation across the region. Overall, the ANOVA results provide strong statistical evidence of significant spatial variability in nematode infestation across the Upper Doab region, highlighting the need for targeted and scientifically informed management interventions. This table presents the results of a multiple regression analysis conducted to evaluate the combined effect of key variablesnematode infestation, irrigation level, soil type, and crop duration-on yield loss in vegetable crops. The regression model quantifies the contribution of each independent variable to the dependent variable (yield loss). The results show that the model explains a high proportion of variation in yield loss (R² = 0.88), indicating a strong predictive relationship. Among the variables, nematode infestation has the highest standardized coefficient (β = 0.72), making it the most influential factor affecting yield loss. This confirms that infestation intensity is the primary driver of productivity decline. Irrigation level (β = 0.41) and soil type (β = 0.36) also show significant positive effects, suggesting that environmental conditions play an important role in facilitating nematode activity. Crop duration (β = 0.33) further contributes to yield loss by allowing multiple nematode generations to develop. The statistical significance of all variables (p < 0.01) indicates that each factor independently influences yield loss. The findings highlight the complex interaction between biological and environmental factors in determining crop damage. The regression analysis provides a comprehensive understanding of the determinants of yield loss and supports the need for integrated management strategies targeting multiple factors simultaneously. Yield loss is primarily driven by nematode infestation, followed by irrigation and soil conditions. This table presents the Species Dominance Index (SDI) calculated for major plant-parasitic nematodes identified in the Upper Doab Region (Kasganj, Etah, Aligarh, Badaun, And Hathras region). The index combines species frequency and impact score to assess the relative importance and destructive potential of each species within the agro-ecosystem. The results clearly indicate that Meloidogyne incognita has the highest SDI value, making it the most dominant and destructive nematode species in the region. Its high frequency and strong impact on plant health contribute to its leading position. Meloidogyne javanica ranks second, also showing significant presence and damage potential. In contrast, Rotylenchulus reniformis and Pratylenchus spp. exhibit lower SDI values, indicating comparatively lesser impact. However, their presence should not be overlooked, as they can still contribute to overall crop damage, particularly under favorable conditions. The dominance of root-knot nematodes reflects their adaptability, wide host range, and ability to thrive in diverse environmental conditions. Their prevalence is further enhanced by continuous cultivation of susceptible crops. The SDI provides a useful tool for prioritizing management strategies. Since M. incognita is the most significant species, control measures should primarily target this nematode. The table thus offers valuable insights into species composition and helps guide effective pest management planning. M. incognita is the dominant and most destructive species in Upper Doab Region. This table presents the Composite Vulnerability Index (CVI), which integrates multiple parameters-infestation percentage, yield loss, and root gall index-to rank vegetable crops based on their overall susceptibility to nematode infestation. The CVI provides a comprehensive measure of crop vulnerability by combining biological and economic indicators. The results show that brinjal has the highest CVI score, followed closely by tomato, indicating that these crops are the most vulnerable to nematode attack. Their high infestation levels, severe root damage, and substantial yield losses contribute to their top ranking. Okra, bottle gourd, and potato fall into the moderately vulnerable category, reflecting their intermediate levels of susceptibility. Crops such as cabbage and bitter gourd exhibit lower CVI scores, suggesting relative resistance or tolerance. These crops experience lower infestation and yield loss, making them suitable for cultivation in nematode-prone areas. The CVI provides a holistic assessment of crop performance under nematode stress, allowing for better decision-making in crop selection and rotation planning. By identifying highly vulnerable crops, farmers can take preventive measures or avoid continuous cultivation of these crops. Overall, the table highlights the importance of integrating multiple indicators to accurately assess crop susceptibility and develop effective management strategies.

Results and Discussion

The present study provides a comprehensive assessment of nematode infestation in vegetable crops across selected districts of the Upper Doab region, namely Kasganj, Etah, Aligarh, Badaun, and Hathras. The findings reveal significant variation in infestation levels, crop susceptibility, environmental influences, and economic impact, all supported by rigorous statistical analysis. The analysis indicates that nematode infestation is widespread across all selected districts, with infestation levels ranging from 66% to 74%. Among the districts, Badaun recorded the highest infestation (74%), followed by Kasganj (72%) and Aligarh (70%), while Etah (68%) and Hathras (66%) showed comparatively lower infestation levels. The ANOVA results confirmed that these differences are statistically significant (p < 0.01), indicating that geographical and environmental factors play a crucial role in influencing nematode distribution. The higher infestation observed in Badaun and Kasganj may be attributed to intensive vegetable cultivation, frequent irrigation practices, and favorable soil conditions such as sandy loam texture, which enhance nematode mobility and reproduction. In contrast, the relatively lower infestation in Hathras may reflect differences in cropping practices, reduced cultivation intensity, or improved soil and water management. These findings clearly demonstrate that nematode infestation is not confined to isolated pockets but is endemic across the entire Upper Doab region, thereby necessitating region-specific management strategies, particularly in high-risk districts. The study further reveals significant variation in infestation levels among different vegetable crops, as confirmed by ANOVA (p < 0.001). Brinjal (85%) and tomato (80%) were identified as the most susceptible crops, followed by okra (78%) and bottle gourd (75%). Potato (72%) also exhibited considerable infestation, whereas cabbage (60%), spinach (55%), and bitter gourd (45%) showed comparatively lower susceptibility. The high susceptibility of brinjal and tomato may be attributed to their extensive root systems and longer crop duration, which provide conducive conditions for nematode feeding, reproduction, and survival. These crops act as primary hosts, facilitating the buildup of nematode populations in the soil. The Composite Vulnerability Index (CVI) further substantiated that brinjal and tomato are highly vulnerable crops, while bitter gourd and cabbage exhibit relative tolerance. These findings highlight the critical importance of crop selection and diversification as effective strategies for nematode management and yield stabilization. The population density of nematodes ranged from 540 to 720 second-stage juveniles (J2) per 100 cc of soil, with the highest density recorded in Badaun. This pattern closely corresponds with infestation levels, indicating a strong relationship between nematode population density and severity of crop damage. Species identification revealed that Meloidogyne incognita is the dominant species with a frequency of 82%, followed by Meloidogyne javanica (68%), Rotylenchulus reniformis (44%), and Pratylenchus spp. (16%). The Species Dominance Index (SDI) confirmed that M. incognita is the most destructive nematode species in the region. The predominance of root-knot nematodes can be attributed to their wide host range, high reproductive capacity, and adaptability to diverse agro-climatic conditions. The coexistence of multiple nematode species further complicates management practices and intensifies crop damage, making integrated approaches essential. A strong positive correlation (r = 0.94, p < 0.001) was observed between nematode infestation and yield loss, clearly indicating that increased infestation levels directly result in greater yield reduction. Yield loss ranged from 4% in bitter gourd to 43% in brinjal. Highly susceptible crops such as brinjal, tomato, and okra experienced substantial yield losses, whereas relatively tolerant crops like cabbage and bitter gourd showed minimal reduction. These findings establish nematode infestation as a major determinant of crop productivity in the region. Furthermore, regression analysis revealed that nematode infestation is the most significant predictor of yield loss (β = 0.72), followed by irrigation practices, soil type, and crop duration. The regression model explained 88% of the variation in yield loss, indicating a strong and reliable predictive relationship. The study demonstrates that environmental and agronomic factors significantly influence nematode infestation:  Sandy loam soils showed the highest infestation (78%) due to better aeration and mobility, while clay soils had lower infestation (60%).  High irrigation levels resulted in higher infestation (80%), as moisture facilitates nematode movement and reproduction.  Continuous cropping led to higher infestation (82%) compared to crop rotation (60%).  Higher organic content and NPK levels were associated with increased infestation due to enhanced root growth and favorable conditions.

 Long-duration crops exhibited higher infestation (80%) due to multiple nematode generations.  High weed density (78%) increased infestation by providing alternate hosts. These findings highlight the complex interaction between environmental conditions and nematode dynamics. The Root Gall Index revealed severe infection in brinjal and tomato (index 5), moderate infection in okra and potato (index 4), and mild infection in cabbage (index 2). Root galling disrupts nutrient and water uptake, leading to stunted growth and reduced productivity. This confirms that root damage severity is closely linked to crop susceptibility and infestation levels. The economic analysis showed substantial financial losses, with brinjal (₹50,000/ha) and tomato (₹45,000/ha) being the most affected crops. Okra and potato also incurred significant losses. These losses are not only due to reduced yield but also due to increased management costs and reduced market quality. The findings highlight the serious economic implications of nematode infestation for farmers in the region.

Conclusion

The present study conclusively demonstrates that nematode infestation is a widespread and economically significant constraint in vegetable cultivation across the Upper Doab region, comprising Kasganj, Etah, Aligarh, Badaun, and Hathras districts. The infestation is influenced by a combination of factors, including crop type, environmental conditions, and prevailing agricultural practices. Among the crops studied, brinjal and tomato were identified as the most susceptible to nematode infestation, whereas bitter gourd and cabbage exhibited relatively higher tolerance. Spatial analysis revealed that Badaun is the most severely affected district, followed by Kasganj and Aligarh, indicating the need for district-specific management interventions. The relatively lower infestation observed in Hathras suggests the influence of improved agronomic practices or less intensive cropping systems. The dominance of Meloidogyne incognita as the primary nematode species underscores the critical importance of targeting root-knot nematodes in management strategies. Statistical analyses, including correlation and regression, confirmed that nematode infestation is the most significant factor contributing to yield loss, with strong predictive relationships established between infestation levels and crop productivity. Furthermore, environmental variables such as soil type, irrigation practices, and cropping patterns were found to significantly influence the dynamics of nematode infestation. The study strongly emphasizes the necessity of adopting integrated nematode management (INM) practices. These include crop rotation with non-host crops, use of resistant or tolerant cultivars, application of biological control agents, incorporation of organic amendments, and improved soil and water management practices. A uniform approach may not be effective; rather, location-specific strategies tailored to the conditions of individual districts are essential for sustainable control. In the absence of timely and effective interventions, nematode infestation will continue to pose a serious threat to vegetable productivity, soil health, and farmers' livelihoods in the region. Therefore, the findings of this study provide a robust scientific foundation for policymakers, researchers, and extension agencies to design and implement targeted, sustainable, and region-specific nematode management strategies aimed at enhancing agricultural productivity and ensuring long-term sustainability in the Upper Doab region.

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