Plant parasitic nematodes: A burning problem in protected cultivation systems in Haryana

Under varying climatic conditions, plant parasitic nematodes (PPNs) cause substantial economic damage to a wide variety of agricultural and horticultural crops. A survey of polyhouses in different districts of Haryana was conducted during 2020-25 to determine the incidence of important PPNs on vegetable crops mainly, cucumber, tomato, chili and bell peppers grown in protected conditions. In this respect, a total of 250 roots and rhizosphere soil samples were collected from the surveyed plants such as cucumber, tomato, chili and bell peppers from different districts (Jind, Kaithal, Bhiwani, Hisar, Fatehabad and Palwal). Soil and root samples were collected from each polyhouse and analyzed mainly for the presence of PPNs. Out of these, 178 samples were found infested withroot-knot nematodes (RKNs) with 71.2% frequency of occurrence. Frequency of occurrence of each species was highly variable from field to field. During the survey, different PPNs genera viz., Meloidogyne, Pratylenchus, Rotylenchulus, Hoplolaimus, Helicotylenchus, Tylenchorhynchus were detected from soil samples. Based on incidence, population density and associated damage on affected crops, M. incognita was considered to be the most important parasites of the crops under local condition. The average population density range of RKN was recorded to be 70-670 J2s/200cc soil. The frequency of occurrence of M. incognita was 82.5% in Fatehabad, 73.3% in Jind, 70.0% in Hisar, 68.0% in Kaithal, 60.0% in Bhiwani and 50.0% in Palwal district, respectively.

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Nematode Population vs. Polyhouse AgeClose ×

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Frequency of occurrence (%): Jind vs Kaithal vs Bhiwani vs Hisar vs FatehabadClose ×

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Introduction

The adoption of protected cultivation techniques has significantly enhanced vegetable productivity in India, by offering numerous advantages such as extended growing seasons, increased yield and better control over environmental conditions. The most common crops cultivated in polyhouses include vegetables; mainly, tomato, cucumber, capsicums, green beans, beetroot, eggplant, lettuce, sweet peas, chilli, okra, spinach, spring onion, cabbage and chinese leek. Among fruits crops, strawberries, muskmelon, watermelon and grapes; and among ornamentals anthuriums, carnations, gerberas, gladioli, roses, chrysanthemums and orchids are common (Singh, 2016) [14] . Growing of crops in plastic greenhouses has reinvigorated farmers' interest in growing off-season or year-round crops for increased economic gains (Kumar et al., 2009) [11] . However, the ecological conditions created in protected houses are propitious to certain pests and diseases, which are not frequently confronted by crops grown in open field cultivation conditions (Sharma et al., 2009) [13] . Growing crops under protected cultivation has multifaceted benefits; however, the adoption of sequential cropping pattern in these closed structures has led to the prevalence of soil borne pathogens, plant parasitic nematodes (PPNs) and pest incidence, which became a major hindrance to the sustainable agriculture. Among PPNs, such as root-knot nematodes (RKNs) and reniform nematodes, can survive in the congenial conditions of higher temperature and humidity present in the protected cultivation structures. The most widespread, economically important, and dominant group of PPNs are the RKNs (Kayani et al., 2012) [9] . In India, Meloidogyne incognita is the most frequently observed species among the genus followed by M. javanica and M. arenaria in vegetable cultivation. Moreover, M. hapla is known to infest vegetables crops grown in temperate hilly regions. Other PPNs genera also cause significant economic damages, although their impact is often underestimated due to the indistinct symptoms exhibited by infested plants (Hallmann and Meressa, 2018) [5] . Nematode infestations can cause significant damage to the root systems of plants, leading to reduced water and nutrient uptake, stunted growth and lower yields and symptoms like chlorosis, wilting and stunting will appear after the significant damage. Besides the direct damage, RKNS act as predisposing agent for the entry of soil borne fungal and bacterial pathogens and aggravate the problem still further leading to development of disease complexes. Prevalence and distribution of PPNs and ecological factors understanding the drivers of the distribution of PPNs community in an area and a specific crop are critical issues for the development of sustainable management strategies. Hence, a comprehensive survey was conducted to evaluate the and distribution of PPNs in the soil rhizosphere of different crops in protected cultivation of different districts of Haryana.

Materials and Methods

A survey of polyhouses in different districts (Jind, Kaithal, Bhiwani, Hisar, Fatehabad and Palwal) of Haryana was conducted during 2020-25 to determine the incidence of important PPNs on vegetable crops mainly, cucumber, tomato, chili and bell peppers. In this respect, a total of 250 roots and rhizosphere soil samples were collected from the surveyed plants such as cucumber, tomato, chili and bell peppers. The samples were collected from individual fields from villages within tehsils (administrative subunit of a district) of each of the six districts. Soil and root samples were collected from each polyhouse and analyzed mainly for the presence of PPNs. These samples were collected from poorly growing plants which showed stunting and chlorosis symptoms on the foliage from a depth of 20-25 cm. Soil samples were collected in polythene bags, labeled, handled and refrigerated at 7-10 0 C before processing. When the samples were being collected, the farmers and villagers were interviewed to collect data on previous crop history, cropping pattern, fertilizer, irrigation and pesticide inputs. Extraction of nematodes from soil samples was done by modified Cobb's sieving and decanting technique (Christie and Perry, 1951) [3] . Genera of important PPNs in the suspension were identified and counted under the stereo binocular microscope. Data on nematode population densities were analysed to assess the average density of each nematode species, and frequency of occurrence in each district. The severity of the infection was recorded on the basis of root-knot index (Table 1).

No. of galls/plant	Root-knot index (RKI)
No galls	1.0
1-10 galls	2.0
11-30 galls	3.0
31-100 galls	4.0
More than 100 galls	5.0

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Root-knot index (RKI) on 1-5 scale (Hartman and Sasser,

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Table 1:

Root-knot index (RKI) on 1-5 scale (Hartman and Sasser, 1985) [6] No Hoplolaimus, Helicotylenchus and Tylenchorhynchus was detected from soil samples. However, M. incognita was found to be the major PPN under protected conditions. Frequency of occurrence of RKN was recorded to be 63.1% and population density range was 30-10000 J2s/200cc soil (Patil et al., 2017) [12] . The prominence value was found maximum for RKN in all the vegetable crops viz., tomato, capsicum and cucumber having 592.9, 223.4 and 910.6 J2s/200 cc, respectively. The data also revealed that M. incognita absolute frequency in tomato and tomato+capsicum mixed cropping was 100% and in cucumber was 92.9% (Kranti et al., 2023) [10] . A total of 40 polyhouses visited and collected 158 root and soil samples during 2 years survey. In results, it was keen observed that all samples of both soil and root were infected with M. incognita. After the examination of roots 40 to 142 galls/5 g roots and 26 to 135 egg masses/5 g root of cucumber found in polyhouses of different locations. It was also recorded that 100% occurrence with above ETL of RKN found in visited polyhouses (Bhati and Baheti, 2020) [1] . A survey conducted by Ismail et al., 2012 [8] to determine the incidence and distribution of Meloidogyne spp. infecting cucumber in open-field and plastic tunnel and found that two root-knot nematode species. M. incognita and M. javanica were found from 200 samples. M. incognita was predominantly found species compare to M. javanica. Singh and Khanna [15] carried out survey about 81 polyhouses from 52 localities of different districts of Himachal Pradesh and reported that M. incognita, M. hapla, Pratylenchus sp., Helicotylenchus spp., Mesocriconema sp., Tylenchorhynchus sp. and Hoplolaimus sp. are major PPNs of polyhouse. Out of these PPNs, M. incognita was found mostly followed by Helicotylenchus dihystera. Due to controlled environmental condition and continuous growing of susceptible crops, the RKNs (Meloidogyne spp.) has emerged as a major problem, most destructive, causing enormous yield loss and difficult to control. The population build-up is rapid in polyhouse and the nematode population reaches five to six times the threshold levels within 18-24 months, making protected cultivation a wasteful exercise. The micro-parasitic abundance in an agro ecosystem is directly linked to the degree of host damage and economic loss of the crops. Individual parasite, by their own accord inflicts minor damage that plants can withstand (Irvin et al., 2006) [7] , although climate change and global warming seem to favor higher development of the poikilothermic parasites (Culos and Tyson, 2014) [4] , as apprehensible for the PPNs. Moreover, warmer temperature changes the geographical distribution pattern of the nematodes. This creates the major problem of pest invasion into new areas, and also helps to grow minor pests as major ones for range expansion of the species.

Conclusion

In summarizing up of the findings of the survey concluded that M. incognita is a major key pest of protected cultivation in Haryana. It causes severe infection in polyhouses and cause great losses to cucumber. It was observed during survey that incidence of RKN fluctuates with the age of establishment of polyhouses structure. RKNs population increase with the increase the exposure of time of polyhouses and nematodes population found minimum in the newly established polyhouses. Therefore, additional research is required to identify the nematode species on molecular basis so that an appropriate and effective management plan may be developed to keep the PPN, population below the economic threshold and at a

Acknowledgement

AcknowledgementsThere are no acknowledgements to declare.

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Occurrence and population status of root-knot nematode, Meloidogyne incognita on cucumber under protected cultivation in

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Root-knot nematode infected cucumber roots collected from the farmer’s polyhouse during the survey

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