Solarized IPM Module for Biocontrol of Root-knot Nematode on Tomato at Nursery Level in District G.B Nagar, Uttar Pradesh

The phasing out of methyl bromide and the ban on, or withdrawal of, other toxic soil fumigants and non-fumigant nematicides belonging to the organophosphate and carbamate groups are leading to changes in nematode-control strategies (Kaanan et al., 2018; Goswami and Mittal, 2004). Among several approaches, soil solarization is an approach for disinfection of soil for management of nematodes, fungi and weeds that boosts involves low-risk management for farmers that could also boost crop yield (Chellemi, 1997; Singh et al., 2015) through which farmers can manage the pests and pathogens in an eco-friendly, non-chemical manner. Soil solarization is one of the non-chemical method that induces natural soil suppressiveness and acts as a potential component of environmentally sustainable management option for of soilborne plant pathogens (Baker, 1962; Katan, 1981; Abdel-Rahim et al., 1988; Oka et al., 2002; Gupta et al., 2017). This pre planting method is used for controlling soil borne pathogens (Fungi, bacteria and nematodes) and weeds in different field crops. (Horowitz and Herzlinger, 1983; Katan, 1981; Nanjappa et al., 2005). It is one of the most effective methods and compatible with many other soil disinfestation strategies.
       
The role of soil solarization in reduction of soil borne pathogens viz. fungi, bacteria, nematodes and weeds has been by established by several researchers in more than 50 countries including India (Katan, 1981; Stapleton et al., 1993; Singh et al., 2015). It involves capturing solar radiations for 4-6 weeks during the summer months May-June when the soil receives the maximum sunlight using a polythene mulch. Its effectiveness depends on ambient temperature, duration of the treatments and soil moisture. This not only acts as a soil disinfectant but also as soil decontamination. It includes various changes in the soil like physical, chemical and biological properties. In soil solarization, the thickness of plastic sheet and color are important considerations.
       
A transparent or clear plastic is more effective for solarization, as the incident rays from the sun passes through the sheet and are trapped to heat the soil below. A black plastic which is less effective because it absorbs and deflects part of the heat, rather than trapping as clear plastic does (Stapleton et al., 1993). Soil intercepts the energy radiated from the sun and its temperature rises to the level which results in mortality of soil-borne pathogens. It also improves soil texture and the nutrients availability in the soil which are essential for plant growth and development. Besides the reduction in soil-borne pathogens, soil solarization also leads to increased plant growth. It integrates well with other techniques such as soil amendments to enhance its overall effectiveness against pests to increase crop yield (Gamliel and Stapleton, 1993).
       
The objective of this study was to evaluate soil solarization as a component in IPM packages. In the present investigation, the effect of solar solarization with other IPM components viz., neem oil-seed cake, locally isolated biopesticide Trichoderma harzianum (Th7) and Arbuscular Mycorrhizal fungus (AM) Glomus intraredices alone and in combination was evaluated for combating root-knot nematode on tomato at nursery level. which was carried out at “hot spots” in district G.B Nagar U.P. Soil solarization with organic amendment of neem cake for three weeks followed by application of biopesticide and biofertilizer showed significant reduction in root knot nematode M.incognita population as compared to non-solarized nurseries. The mechanism of action is based on increased soil temperature (commonly in the range of 45°C-55°C) at soil depth of 5 cm underneath transparent polysheets and the decomposition of oil seed cake also releases the nematicidal and fungicidal compounds which causes mortality of soil borne pathogens (Katan, 1981; Chellemi, 1997). In the present investigation, the resultant solar assisted IPM module-4 constitutes other sustainable components, local strain of biocontrol agent, Trichoderma harzianum (Th7) and AM fungus Glomus intraradices showed promising results in biocontrol of root knot nematode M. incognita at tomato nurseries in district G.B Nagar.

The field to lab and vice-versal based investigations were carried out at Amity Centre for Biocontrol and Plant Disease Management, Amity University, Uttar Pradesh, Noida during the hot summer months (May to June) 2021-2022 at identified tomato nurseries in district G B Nagar where heavy infestation (10-12 J2/cc soil) of root knot nematode, Meloidogyne incognita (Kofoid and White) Chitwood was recorded. The treatments comprised of sustainable components viz. deoiled seed cake of neem, a Arbuscular Mycorrhizal fungus Glomus intraradices and indigenous fungal strain of Trichoderma harzianum, (Th7) alone and together applied at solarized and unsolarized sets. The treatments were replicated thrice in randomized block design. Under microplot trials, the entire solarized treatments were carried out measuring 3 × 1 sq. meter each in which one set of all the treatments including control covered with clear transparent polythene sheet (400 μ gauge) for solarization. The neem cake @ 500 g/m² was also applied for a period of 3 weeks prior to sowing of seeds in treatments 1, 2 and 4 while for the other set uncovered as unsolarized treatments (Chauhan et al., 1998). The sheets were removed one day prior to application of the treatments with other components like T. harzianum @ 50 g/m² and G. intraradices 50 ml/m² respectively.  
       
Following this, sowing of highly susceptible desi variety of tomato cv. Pusa Ruby after surface sterilization with 0.01% Hgcl₂ was done in each plot of the nursery. The treatments were:-
1) Glomus intraradices (AM) + Neem Cake (T1) - IPM Module1.
2) Trichoderma harzianum (Th7) + Neem Cake (T2) - IPM module 2.
3) Glomus intraradices (AM) + Trichoderma harzianum (T3) IPM module 3.
4) Neem Cake + AM fungus Glomus intraradices + T. harzianum - (T4) - IPM module 4.
5) Control (C). 
       
The observations were also recorded in respect to germination, plant biomass, root knot nematode population in both soil and root after 45 days in respect to each of the above treatments after termination of the field experiment prior to transplantation to the main field. The data were statistically analyzed by using two factorial analysis of variance (ANOVA). The critical difference (CD) values at 0.05 P were used to determine significance of treatment mean differences.

Effect on plant growth parameters
 
The present field based investigation was carried out at ‘hot spot’ or naturally infested  tomato nurseries located at Birampur village in district G.B Nagar during 2021-2022. The field based investigation was initiated in hottest months ‘May to June’ for solarization at tomato nurseries and the average high temperature lies in the range of 29.4°C to 42.2°C.
       
Observations of the experiments in respect to plant growth parameters i.e germination percentage and biomass in addition to that soil and root population of root knot nematode M. incognita were recorded after 45 days from the solarized nursery bed and also unsolarized ones separately. In general, soil and root population of root knot nematode were reduced significantly in solarized treatments as compared to unsolarized ones. The plant growth parameters i.e. germination percentage and biomass were recorded high in IPM module-4 where soil solarization with neem cake amendment three weeks before seed sowing and followed by application of AM fungus (Glomus intraradices) and local strain of biocontrol agent T. harzianum (Th7) (Table 1). The root knot nematode population in both soil and root were also reduced  significantly in solarized sets as compared to unsolarized ones (Table 2).
 

 

 
Effect on soil and root population of root knot nematode M. incognita
 
The performance of IPM-3 module was also noteworthy where T. harzianum (Th7) and AM fungus G. intraredices were applied together in reducing M. incognita population and enhancing plant growth. Among all the solarized and unsolarized IPM modules, however, the solarized  IPM-4 module showed significant results and outstanding performance in reducing M. incognita population in both soil and roots where both the sustainable components T. harzianum and G. intraredices were applied together in neem cake amended soil than that of corresponding unsolarized ones. In all the treatments, excepting control, the soil is amended with neem cake which is known to possess nematicidal properties (Goswami et al., 2007) and rich in manural contents which is attributed to enhance the tolerance of the tomato plant against root knot nematode and enriching the soil as well in the present investigation which is advisable for farmers to be included in the amendment for better health of the soil and plant also.
       
Regarding the performances of the treatments taken up in the present investigation, two solarized treatments i.e. IPM module 2 where locally isolated  T. harzianum (Th-7) is applied to neem cake amended soil and IPM module 1 in which AM fungus G. intraredices was used alone showed almost at par or same performance in which the former helped in suppressing the root knot nematode population while the latter helped in making the host more tolerant with some role in protecting root against maladies (Subhashini and Ramakrishnan, 2011). The reduction in number of galls in mycorrhizal plants were also observed by (Jalaluddin et al., 2008).
       
However the best performance of higher percentage germination, more biomass of the seedlings and also outstanding reduction in both nematode population and root population by adding  biocontrol agent and biofertilizer in the solarized IPM module-4 is proposed for tomato nurseries due to the cumulative effect of nematicidal and fungicidal properties of neem cake and fungal bioagent that of biofertilizer being responsible as a ‘root protectant’ through occupying the cortical regions of the root particularly in the zone of elongation  by ‘Vesicles and Arbuscules’ (Bhagwati et al., 2000; Goswami et al., 2007; Goswami et al., 2008).
       
The biocontrol potential of Trichoderma harzianum through rhizosphere competence against root-knot nematode in soil has also been reported by earlier workers (Babu and Kamara, 2021). The soil solarization in integrated management practices is recorded to aggravates beneficial microflora which is antagonistic to soil borne pathogens through reducing the infestation of soil by these organisms besides increasing plant growth and yield in nurseries and fields. (Chen et al., 1981; Katan, 1979, 1981, 1988). Similar findings with organic amendments aggravated by soil solarization have been demonstrated to have reduced the disease incidences with increased plant vigour (Gaur and Dhingra, 1991; Kim, 1988; Stapleton et al., 1993). Solarization works like a “solar hot panel” and shows catalytic properties with amendments for disinfecting soil within three weeks and preserves soil fertility also (Nanjappa et al., 2005).

In the present findings, soil-solarization has been observed in enhancing the potentiality of integrated pest management against root-knot nematode infesting tomato. In our country, most of the rural farmer are not aware about the utilization of soil solarization and other sustainable components, oil seed cakes and locally available antagonistic bioagents/plants in their premises for soil borne pest and disease management. The present investigation is non-chemical cost-effective integrated approach for quality production of disease free tomato seedlings. Capacity building programs will be conducted for popularizing the evolved IPM module for combating root knot nematode among the farmers and rural communities in and around G.B Nagar in near future.

The authors are highly thankful to the growers of the identified hot spots in district G.B Nagar for their support during soil sampling and  field trials. We acknowledge the constant encouragement and moral support of Hon’ble Founder President Sir Dr. Ashok K. Chauhan, Hon’ble Chancellor-Dr. Atul Chauhan, Hon’ble Vice-Chancellor, Dr Balvinder Shukla and Dr. W. Selvamurthy, President, Amity Science and Technology Innovation Foundation, Amity University, Sector - 125, Noida (U.P.) last but not the least Dr. Nutan Kaushik, Director General, Food and Agriculture Foundation for her kind support.