EVALUATION OF GROUNDNUT MUTANTS FOR RESISTANCE TO Spodoptera AND THRIPS
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Date
1997
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UNIVERSITY OF AGRICULTURAL SCIENCES, DHARWAD
Abstract
The present investigation was carried out to identify genotypes resistant/tolerant to Spodoptera Jitura and thrips, besides good productivity attributes. The 22 mutants derived from VL 1 were screened against S. litura during Kharif1996 and against thrips during Summer 1997 along with susceptible (JL 24) and resistant (GBFDS 272) checks. The mutants 28-1, 28-2, 45 and 110 were resistant to S.litura. Along with these, the mutants 2-1, 139-1, and VB type were also found to be resistant to thrips. The mutants (28-2,45 & 11 0) possessed good pod and kernel featuresand matured early by 10 to 15 days than resistant germ plasm. The above features of mutants {28-2,45 & 11 0) were comparable to popular Spanish Bunch varieties cultivated in Karnataka. The mutants 28-2, 45 and 11 0 showed high level of resistance to leaf spots and variable level of resistance to rust, indicating their potentiality in genetic improvement of groundnut for multiple pest and disease. In laboratory rearing of S.litura on selected genotypes the mutant 45 recorded lesser number of larvae and higher percentage of mortality throughout the life cycle. The mutant 28-2 showed significantly low larval weight and low gain in weight at all the stages of larval period indicating the possible existence of two independent mechanisms of resistance. The mutants 28-2 and 45 extended the larval period by 3 days and affected the fecundity of moths as well ,reflecting the possible role of antibiosis as a mechanism of resistance. The genotypes showed significant variation for various leaf anatomical parameters but no perceptible association with resistance was evident. The genotypes also differed significantly for general group of chemicals viz., phenols, 00 phenols, tanins and total sugars but their differences were not associated with resistance to S.litura and thrips indicating the possible role of specific chemical factors in antibiosis.
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