Mechanisms of Plant Resistance to Rice Leaf Mite, Oligonychus oryzae Hirst (Acari: Tetranychidae)

Due to the changing climatic scenario rice leaf mite, Oligonychus oryzae Hirst becoming one of the major pests of paddy and cause severe yield loss. In this context, field experiment was carried out at Tamil Nadu Agricultural University, Coimbatore to screen popular rice varieties for their resistance against O. oryzae. The results revealed that negative correlation existed between the mite population and the leaf morphological characters viz., the number and length of trichomes, thickness of the leaf lamina and leaf area. ADT 53 a resistant variety recorded 28.48 mg/g of total carbohydrates, while TN 1 susceptible variety recorded 79.59 mg/g. As compared to susceptible variety, the resistant varieties have higher phenol content. The resistant variety Ptb 33 (8.107 changes in OD value min/g of fresh leaf tissue) recorded increased peroxidase activity. Both healthy and infested leaves (0.567 and 0.611 changes in OD value/ min/ g of leaf tissue) from the resistant cultivar Ptb 33 had higher levels of Polyphenol oxidase as compared to other varieties.