ANTIBIOSIS AND ANTIXENOSIS IN TOMATO GENOTYPES AGAINST Helicoverpa armigera HUBNER

Background. Farmers rely on the use of synthetic insecticides in managing Helicoverpa armigera, hole-boring insect pest on tomato, but they are detrimental to human health. Therefore a more reliable and ecofriendly control measure is needed such as host plant resistance. Objective. To assess the mechanisms of resistance in tomato varieties: NGB00724, NGB00724, Anaya, Kelvin, Mona, Roma VF (susceptible varieties), Tropimech and UC82B in laboratory and screen house. Methodology. Second larval instars were fed with leaves of the different tomato varieties and their development was observed till adult stage. Study was done in the screen house where number of larvae and eggs were also observed. Larval period and weight, and percentage adult emergence were assessed in tomato varieties. Metabolites (phenol, flavonoids, terpenoids, protein, reducing sugars and total sugars) in tomato leaves were determined following standard procedures. Results. Helicoverpa armigera fed with tomato leaves, Anaya recorded the lowest larval period (9.67 days). Also, larvae fed on Anaya and Mona had the lowest larval weight (0.19 g and 0.25 g). Also significantly lower percentage of adult emergence was observed on Anaya and Mona (16.7%) Mona, NGB00725 and Anaya significantly harbored the lower number of Helicoverpa armigera adult (0.1, 0.4, 0.4). The lowest number of eggs (0.5) was recorded from adults placed on Anaya variety. There was high and negative significant correlation of r = -0.865 between phenols and adult emergence. Phenols and oviposition were significantly negatively correlated (r = -0.816). Implication. Anaya and Mona hinder the development of Helicoverpa armigera larvae when fed on it. Phenol has negative impact on the development and oviposition of Helicoverpa armigera. Conclusion. It was revealed through this study that availability of promising resistant varieties can effectively combat the damage caused by Helicoverpa armigera and lessen the shortcomings related with the application of conventional chemical insecticides in tomato production.