Antibiosis Mechanism of Resistance to Early Shoot Borer, Chilo infuscatellus in Sugarcane

Studies on antibiosis mechanism of resistance to early shoot borer, Chilo infuscatellus Snellen in different sugarcane genotypes, viz., four least susceptible (Co 0110, 98 A 165, Co 6806 and 98 A 125), four moderately susceptible (97 A 85, 2000 A 105, 99 A 5 and Co 62175) and four highly susceptible (93 A 11, 99 A 33, 94 A 124 and Co M 9902) in comparison with one susceptible Check, i93 A 145 were carried out on artificial diet under laboratory conditions at Regional Agricultural Research Station, Anakapalle during 2009–10. The results on antibiosis mechanism of resistance on artificial diet impregnated with shoot powders of different sugarcane genotypes indicated that larval period of ESB was longest (21.32 to 22. 26 days) on LS genotypes (98 A 125, 98 A 165, Co 6806 and Co 0110) while it was shortest (16.56 to 18.78 days) on HS genotypes (Co M 9902, 94 A 124, 93 A 33 and 99 A 11) and the larvae took less time to pupate on HS than on LS genotypes. Larvae fed on HS genotypes were heavier (149.3–179.9 mg larva⁻¹) than on MS (94.8–124.3 mg larva⁻¹) and LS genotypes (79.9 -84.6 mg larva¹) after 15 days after inoculation (DAI). Larval survival rate was lowest on LS genotypes (26–30%) compared to 50–60 per cent observed in MS and 64 - 84.20 per cent in HS genotypes at 15 DAI resulting in highest mean growth index on HS (3.51- 4.71) followed by MS (2.39–2.94) and LS genotypes (1.53–1.73). Reduced larval survival and weight, prolonged larval period on LS genotypes compared to HS genotypes as well as susceptible check, 93 A 145 indicated the poor development of Chilo infuscatellus Snellen on LS genotypes due to either inadequate nutrition and/or possession of higher degree of antibiotic factor(s) as compared to HS genotypes.