A Genetic and Breeding Study of Pink Bollworm Resistance and Agronomic Properties in Cotton1

Abstract

A breeding stock of upland cotton (Gossypium hirsutum L.) designated as AET‐5, consistently sustains less seed damage by pink bollworm(PBW)[Pectinophora gossypiella (Saunders)] than do cultivars.This stock is deficient in most agronomic and fiber properties, with the exception of lint percentage. Wec rossed AET‐5 to DES 24‐8ne, an advanced breedingl line which lacks extrafloral nectaries [nectariless (2 ne1, ne2)], a morphologicalt rait whichi mparts resistance to PBW in large field plantings. Parents and hybrid generations were compared for 2 years in insecticide‐free environments. The objectives of these studies were to determine the inheritance of the AET‐5 level of seed damage and of several agronomic properties and to predict the ease of transfer of the low seed damage and high lint percentage into a desirable agronomic background by backcrossing. The seed damage expected in a stock combining the AET‐5 type of resistance with the nectariless character should be lower than in stocks carrying only one of those two resistance characters. Analyses of tests grown for 2 years indicated that gene action was primarily additive for both seed damage and lint percentage, that narrow‐sense heritability estimates were significant, and that few genes conditioned those properties. A combined analysis of variance revealed that genotype ✕ environment interactions were not significant for those traits. Therefore, it should not be difficult to transfer the AET‐5le vel of resistance and its associated high lint percentage into desirable backgrounds. Additive effects were also shownin two of the three tests for the other agronomic properties measured. Dominance, epistasis, or both were also shown. Heritability estimates were not consistently significant. Those non‐additive effects shouldn ot be regarded as obstacles to breeding progress because our ultimate objective is to transfer by backcrossing only low seed damage and high lint percentage, but otherwise to reconstitute the phenotype of the nectariless parent.