Morphological and chemical characteristics of tomato foliage as mechanisms of resistance to Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) larvae
Morphological characters and chemical composition of tomato (Lycopersicon esculentum Miller) leaves were measured and compared among nine tomato varieties (Roma VFN, NARC-1, Fs-8802, Tommy, Pant Babr, Rio Grande, Nova Mecb, Pakit and Sahil) exhibiting varying levels of host plant resistance to Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) as based on fruit infestation. The variety, Sahil, was resistant, whereas Roma VFN was the susceptible variety. Hair length and hair density on lower leaf surface, as well as thickness of leaf lamina significantly correlated with larval population and fruit infestation. Leaf hair density accounted for 92.0% of the variation in fruit infestation and 77.0% of the variation in larval population. Ferrous (Fe2+) and phosphorous content in the leaves were negatively correlated with fruit infestation and larval population; whereas, nitrogen, calcium, magnesium, manganese and zinc content were positively correlated with fruit infestation and larval population. The resistant variety, Sahil, produced the maximum yield as compared to susceptible variety, Roma VFN.
Keywords: Helicoverpa armigera, tomato fruit borer, host plant resistance, Lycopersicon esculentum