Distribution and occurrence of root-knot nematode, Meloidogyne spp., associated with Brinjal (Solanum melongena L.) in different agro-climatic zones of Rajasthan, India

Introduction

Brinjal (Solanum melongena L.) is one of the most important solanaceous vegetable crops cultivated throughout tropical and subtropical regions of the world. It is valued for its nutritional quality, adaptability to diverse agro-climatic conditions and economic importance. Crop fruits are good sources of calcium, phosphorus, iron and vitamins, particularly vitamin B. It is valued for its tender unripe fruits, used as a cooked vegetable, rich in medicinal values generally being used as an excellent remedy for those suffering from liver complaints and white brinjal is said to be good for diabetic patients. The green leaves of brinjal plant are the main source of Vitamin 'C' (Nayak and Pande, 2015) [13] . India is the second largest producer of brinjal after China and contributes substantially to global production. According to the National Horticulture Board (2023), brinjal is cultivated on 711.3 thousand hectares with an annual production of 13.56 million tonnes in India. In Rajasthan, the crop occupies about 5.14 thousand hectares with a production of 23.36 thousand tonnes and is extensively cultivated in districts such as Sri Ganganagar, Udaipur, Jaipur, Kota, Alwar and Ajmer. Brinjal fruits are rich in carbohydrates, minerals, dietary fibre and vitamins, making the crop an important component of human nutrition and vegetable production. Brinjal productivity is constrained by several biotic stresses, among which plant-parasitic nematodes are considered one of the major limiting factors. More than 100 species of plantparasitic nematodes have been reported to infect vegetable crops; however, root-knot nematodes (Meloidogyne spp.) are regarded as the most destructive because of their wide host range, worldwide distribution and high reproductive potential.

Among the economically important species, Meloidogyne incognita is the predominant species associated with brinjal cultivation in India. Vegetable crop losses owing to Meloidogyne spp., primarily M. incognita and M. javanica, have been estimated to be 17 to 20% for brinjal (Solanum melongena L), 18 to 33% for melon and 24 to 38% for tomato (Sasser, 1979). In India, yield losses in brinjal are reported to be 18% (Bhatti and Jain, 1977) [4] , Infection by root-knot nematodes results in the formation of characteristic root galls, which interfere with water and nutrient uptake, leading to stunted growth, chlorosis, wilting, reduced plant vigour and significant yield losses. Under severe infestation, the nematodes also interact with other soil-borne pathogens, resulting in disease complexes that further aggravate crop damage. The distribution and severity of root-knot nematodes are greatly influenced by soil type, temperature, moisture, cropping pattern and cultivation practices. Continuous cultivation of susceptible host crops under favourable environmental conditions promotes rapid multiplication and establishment of nematode populations in agricultural fields. Therefore, information on the distribution and occurrence of Meloidogyne spp. is essential for identifying infestation hotspots, assessing the level of nematode pressure and formulating effective integrated nematode management strategies. Several workers have reported the widespread occurrence of root-knot nematodes in vegetable-growing regions of different countries, including Pakistan, Jordan, Ethiopia and Tanzania. Rajasthan encompasses diverse agro-climatic conditions that may influence the distribution and population dynamics of root-knot nematodes. Despite the economic importance of brinjal cultivation in the state, systematic information on the occurrence and severity of Meloidogyne spp. in different districts is inadequate. Such information is essential for understanding the geographical distribution of the pathogen and for developing region-specific management strategies. Therefore, the present investigation was undertaken to determine the distribution and occurrence of root-knot nematodes (Meloidogyne spp.) associated with brinjal in major brinjal-growing districts of the I-B and IV-A agroclimatic zones of Rajasthan. The study aimed to assess the incidence and intensity of nematode infestation under field conditions and to generate baseline information that could support future integrated nematode management programmes for sustainable brinjal production.

Materials and Methods

Survey

An extensive field survey was conducted during 2025 and 2026 to determine the distribution and occurrence of rootknot nematodes (Meloidogyne spp.) associated with brinjal in two major agro-climatic zones (Zone I-B and Zone IV-A) of Rajasthan. The survey covered six important brinjalgrowing districts, namely Sri Ganganagar, Hanumangarh, Rajsamand, Bhilwara, Chittorgarh and Udaipur. A total of 582 soil and root samples were collected randomly from farmers' fields. The samples were properly labelled, transported to the laboratory and stored under refrigerated conditions until processing.

Soil Sampling

Soil samples were collected randomly from the rhizosphere of the plants with the help of khurpi from 4-5 places in each at a depth of 20-30 cm, homogenized, filled in a polythene bag, labeled and tagged with supporting information, viz. date of sampling, locality, host plant. These samples were then tied with the rubber band brought to the laboratory and stored in a refrigerator at about 10 °C. The samples were processed within a week.

Processing of Samples

Initially, 200 cc of soil from each sample was refined by using Cobb's decanting and sieving technique (Cobb, N.A, 1918) [7] , followed by Baermann's funnel technique (Christie and Perry 1951) [6] . After 24-48 hours, suspension was drawn in a beaker from the funnel and kept for some hours to allow the nematode to settle down at the bottom. The supernatant liquid was gently removed to get a concentrated nematode population. The suspensions were made up to 100 ml, bubbled and only 5 ml was drawn with the help of a pipette and poured in a counting disc. An average of three times was taken and then multiples to total suspension counts exercise was taken. The root-knot nematode and other plant parasitic juveniles were counted under a stereoscopic binocular microscope.

Estimation of Root Population

Infested roots were washed thoroughly and stained with 0.1 percent acid fuchsin lactophenol at 80 o C for 2-3 minutes (McBeth et al. 1941) [11] . After a gentle wash in tap water, roots were kept in clear lactophenol for at least 24 hours and then they were examined under a stereoscopic binocular microscope. After staining, the roots were teased out and the number of root-knot nematodes and other plant parasitic nematodes was recorded under a stereoscopic binocular microscope.

Results and Discussion

The present investigation was undertaken to determine the distribution and occurrence of root-knot nematode, Meloidogyne spp. associated with brinjal cultivation in I-B and IV-A agro-climatic climatic zones of Rajasthan. Among the surveyed districts, the highest occurrence of root-knot nematode was recorded in Sri Ganganagar (76.67) followed by Udaipur district (73.00%), Hanumangarh (70.67%), Bhilwara (69.51), Rajsamand (68.97%) and Chittorgarh (63.33%). Similarly, higher nematode infestation in terms of number of galls per plant, number of galls egg mass per plant and final nematode population per 200cc soil was observed in Udaipur and Sri Ganganagar districts. The maximum number of galls (114.28 galls/plant), egg masses (102.14 egg masses/plant) and final nematode population (1102 larvae/200 cc soil) were recorded from Thur village of Udaipur district, whereas Anupgarh village of Sri Ganganagar district recorded 113.87 galls/plant, 97.75 egg masses/plant and 1080 larvae/200 cc soil. The findings of the present investigation are in close agreement with the observations of Gul and Saeed (1990) [9] reported the wide distribution of Meloidogyne species on several vegetable crops including eggplant, tomato and okra in Pakistan. Similarly, Yousef and Jacob (1994) [17] observed that M. incognita and M. javanica were among the most damaging nematodes associated with vegetable crops in Jordan. The present observations further corroborate the findings of Rao et al. (2007) [14] reported the occurrence of Meloidogyne spp. along with other plant-parasitic nematodes in vegetable crops including brinjal in Andhra Pradesh. Similar observations were made by Chandel et al. (2010) [5] who recorded high populations of M. incognita in vegetable nurseries and protected cultivation systems of Himachal Pradesh. Anwar and McKenry (2010) [2] also identified M. incognita and M. javanica as the predominant root-knot nematode species associated with vegetable crops in Punjab. The higher frequency and incidence of root-knot disease observed in the present study are comparable with the reports of Esfahani (2009) [8] and Anamika et al. (2011) [1] documented substantial levels of root-knot nematode infestation in different vegetable-growing regions. The widespread distribution of Meloidogyne spp. reported by these researchers suggests that root-knot nematodes continue to be a major constraint in vegetable production under diverse environmental conditions. The present findings on brinjal are in close conformity with the observations of Yadav and Kumar (2016) [16] reported severe root-knot disease incidence in brinjal fields of Agra with disease frequencies exceeding 80 percent in several localities. Their findings indicate that brinjal serves as a highly suitable host for Meloidogyne spp. resulting in significant nematode multiplication and spread. Particularly relevant to the present investigation are the reports from Rajasthan. Bhati and Baheti (2020) [3] observed 100 percent occurrence of M. incognita in polyhouse-grown cucumber across different locations of Rajasthan, while Kumari et al. (2023) [10] reported severe infestation of M. incognita in protected cultivation systems of Udaipur district. Furthermore, Meena et al. (2024) [12] recorded Meloidogyne spp. as the most predominant plant-parasitic nematode in Jaipur district. These findings strongly support the present observations and indicate that Meloidogyne spp. is widely distributed throughout different agro-ecological regions of Rajasthan. Overall, the present survey confirms that root-knot nematodes are among the most important plant-parasitic nematodes associated with brinjal cultivation in Rajasthan. This might be due to variation in soil type, crop and variety, environmental conditions, cropping pattern etc. The widespread occurrence and high frequency of Meloidogyne spp. observed in the surveyed areas emphasize the need for regular monitoring and the adoption of integrated nematode management strategies to minimize crop losses and sustain brinjal productivity.

Conclusion

The survey established that root-knot nematodes (Meloidogyne spp.) are widely distributed throughout the major brinjal-growing districts of Rajasthan. Sri Ganganagar recorded the highest occurrence of infestation, while Udaipur exhibited the greatest severity in terms of gall formation, egg masses and final nematode population/200cc soil. The results identify important hotspot areas for nematode infestation and provide baseline information for developing location specific integrated nematode management strategies. Regular surveillance and implementation of sustainable management practices are essential for minimizing crop losses and improving brinjal production under Rajasthan conditions.

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