MSc

ABSTRACT
The study entitled ‘Management of root-knot nematode, “Meloidogyne incognita (Kofoid and White) Chitwood in vegetable cowpea” was conducted at Department of Nematology, College of Agriculture, Vellayani, Thiruvananthapuram during 2018-2020. The objectives were to screen varieties for resistance and to evaluate efficacy of biocontrol agents, organic amendment and new nematicide fluopyram for the management of root-knot nematode in vegetable cowpea.
Seven varieties of vegetable cowpea (5 KAU released and 2 local) were screened for their resistance against Meloidogyne incognita in pot culture under glass house condition. The experiment was laid out in CRD with 7 treatments and 3 replications. The results revealed that local variety collected from Kadakkal was highly resistant to root-knot nematode with root-knot index 1. The local variety performed best in reducing the multiplication of nematodes. Lowest number of egg masses 5g root-1 (2.33), eggs egg mass-1 (63.33) and nematode population 200cc soil-1 (7.33) was observed in the local variety and it showed statistically significant variation compared to the KAU released varieties. Regarding the number of nodules 5g root-1 also the Kadakkal variety showed significant superiority (22.67 nodules 5g root-1). KAU variety VS 50 was highly susceptible to M. incognita infestation with root-knot index 5. Highest number of egg masses 5g root-1(224.33) and number eggs egg mass-1 (147.00) was recorded in VS 50.
Pot culture experiment was laid out in completely randomized design to standardize the dosage of fluopyram for the management of M. incognita in cowpea. The treatments were fluopyram 400 SC @ 500g a.i ha-1 as basal application, fluopyram 400 SC @ 500g a.i ha-1 as basal application + 500g a.i ha-1 25 days after first treatment, fluopyram 400 SC @ 250g ai ha-1 as basal application + 250g a.i ha-1 25 days after first treatment, fluopyram 400SC @ 250g a.i ha-1 as basal application, Untreated. All the dosages of nematicide were applied as soil drenching to the root knot nematode infected soil. Basal application of fluopyram 400 SC @ 250g a.i ha-1 was the effective dosage for managing M. incognita in vegetable cowpea. Phytotoxicity symptoms were not observed in any of the treatments. Nematode penetration in roots and life cycle completion was observed in untreated control plants. M. incognita juveniles, adult female and male were not observed in roots of fluopyram treated cowpea plants. Galls and egg masses were observed in uprooted cowpea plant roots in untreated whereas in fluopyram applied treatments it was zero. Regarding final nematode population also, no nematodes were observed in soil samples were collected from fluopyram treated plants while in untreated control plants it was 761.5. Number of rhizobium nodules was significantly lower in untreated plants (17.75) while in fluopyram treated plants it ranged from 24.25 to 27.5 in 5g roots of cowpea plants.
Field experiment was conducted by using the susceptible variety (VS 50) to study the comparative effect of bio agents (Purpureocillium lilacinum) and organic amendment (neem cake) in comparison with chemicals fluopyram and carbosulfan. The experiment was laid out in RBD with 8 treatments and 3 replications. All the treatments significantly reduced nematode population in soil and root compared to untreated control. Effect of soil application of P. lilacinum (cfu 2x106 g-1) @ 10 g m-2 + neem cake @ 50 g m-2 found equally effective to basal application fluopyram 400 SC @ 250g a.i ha-1 in reducing the nematode population in soil (93.03 per cent reduction over untreated) and root (86.94 per cent reduction over untreated). Regarding yield also effect of these two treatments was statistically on par giving 53.70 to 54.63 per cent increase over untreated. Plants treated with P. lilacinum (cfu 2x106 g-1) @ 10 g m-2 + neem cake @ 50 g m-2 showed significant superiority in number of nodules (29.33) in root (5g). Results on reisolation of bioagents at the time of harvest revealed that addition of organic substrate neemcake increased the persistence of bioagent (8.33x103 cfu g soil-1) in soil. Residue of fluopyram and carbosulfan was found to be less than limit of quantification (LOQ) in cowpea pods, which were safe for consumption.
From this study, it is concluded that vegetable cowpea variety Kadakkal local is resistant to M. incognita. Soil application of P. lilacinum (cfu 2x106 g-1) @ 10 g m-2 + neem cake @ 50 g m-2 can be recommended for management of M. incognita in organic cultivation of cowpea.