Morphological and biochemical basis of resistance in rice genotypes against two major lepidopteran pests

Experiments were carried out to assess the reaction of rice genotypes viz., hybrid, local and advanced lines in response to the infestation by yellow stem borer (YSB) Scirpophaga incertulas (Walker) and rice leaf folder (RLF) Cnaphalocrocis medinalis (Guenee) along with the designated resistant and susceptible varieties. Plant morphological characters such as number of tillers, number of trichomes, leaf width and plant height were correlated with infestation. Number of tillers showed significant negative correlation with a deadhearts; number of trichomes was significantly negatively correlated; and leaf width showed a positive correlation with RLF infestation. Least % damage was observed in TKM 6 followed by Kesari and Kiruvana against YSB and RLF. A significant increase in phenol, tannin, potassium and silicon occurred in the infested resistant TKM6 and in one of the local rice genotype i.e., Kiruvana. Decrease in leaf protein content was evident invariably in all the infested genotypes. It was also evident that biochemicals such as phenol, tannin, potassium and silicon were negatively correlated with YSB and RLF damage; but total sugar and leaf protein content were positively correlated. Thus, it is concluded that the morphological traits and elevated levels of biochemicals play a vital role in resistance to lepidopteran pests. The implication of the study in insect resistant rice breeding is discussed.