Genetic architecture of some insect resistant traits in upland cotton

Abstract

Insect pest infestation is a major constraint in cotton production and causes heavy yield losses every year. Some studies report that insect pests attack on genotypes/cultivars with the traits, frego bracts, okra leaf, and red leaf color is comparatively lower. The genotypes/cultivars with these traits were planted and separated by fine netting to assess insect pest infestation in comparison to commercial cultivars. The Gossypium arboreum cultivar, FH-170 had minimum number of population buildup of sucking and chewing insect pests. Among hirsutum genotypes/cultivars, minimum population buildup of thrips, mites, spotted bollworm and American bollworm was found on Gumbo Okra. Minimum aphid was recorded on Russian Red. PBG-Fb-5 showed the most resistant response against pink bollworm. Population buildup of thrips, mites and aphid was relatively higher under water deficit conditions compared to well watered conditions whereas, population buildup of jassid, and white fly was higher under well watered conditions but was non-significant. Populations of parents, F1 and segregation pattern of F2 and backcross populations of crosses involving okra leaf, frego bract and red leaf traits showed that the traits were monogenic, okra leaf type and red leaf color being incompletely dominant and frego bract as recessive trait. Gene action of agronomic traits (plant height, number of bolls, number of monopodial branches, number of sympodial branches, boll weight, lint percentage, seed index, fiber fineness, fiber strength, and fiber length) in the crosses involving okra leaf, frego bract and red leaf color were different. Heritability estimates for different agronomic traits in the crosses of okra leaf, frego bract and red leaf color varied from 0.26 to 0.95. These results showed the interaction of the insect resistant traits with agronomic traits. Correlation of the traits, okra leaf, frego bract and red leaf color with agronomic traits showed that okra leaf positively correlated with sympodial branches, lint percentage, fiber fineness (measurement scale has inverse relationship with fiber fineness) and fiber length whereas, negative correlation of okra leaf was observed with plant height and seed index. Frego bract had negative correlation with boll weight and lint percentage. Red leaf color had positive association with lint percentage and negative correlation with number of bolls and sympodial branches and fiber strength. Negative correlation of these insect resistant traits with some desirable agronomic traits reveal that very large F2 population would be required to find insect resistant recombinants with desirable agronomic attributes. The correlations among agronomic traits in the crosses involving different insect resistant traits were different which suggest that while incorporating each insect resistant trait into a strain, a different breeding strategy will have to be followed. Simple qualitative nature of the traits, okra leaf, frego bract and red leaf color reveals that the traits may easily be incorporated into commercial cultivars.