Relative Resistance of Cotton Lines to Pink Bollworm
Pink bollworm (PBW), Pectinophora gossypiella Saunders, is a serious insect pest of cotton, Gossypium hirsutum L., in the irrigated deserts of the southwestern USA. Several sources of resistance to PBW have been identified in cotton. The objectives of this study were to determine whether certain other sources are equal or superior to a resistance standard. AET-5 (as shown by the amount of seed damage sustained by the plants), and whether F1 hybrids show higher levels of resistance than expected based on parental response. A series of diallel and generation-mean experiments was grown in the field at Tempe and Maricopa, AZ, from 1982 to 1987. No insecticide was applied. The diallel analyses revealed significant general and specific combining ability (GCA and SCA) and reciprocal effects, as well as year ✕ GCA and year ✕ SCA interactions, which complicated the interpretation of the data. However, it was clear that of the 13 lines evaluated, only Stoneville 7A okra leaf was equal to AET-5 as a source of PBW resistance. The line 7203-14-104, while showing some PBW resistance, was inferior to AET-5. Furthermore generation-mean analysis of AET-5 ✕ 7203-14-104 data revealed large nonadditive genetic effects, which would make it difficult to combine or transfer resistance. Texas 39C-1-L behaved inconsistently with respect to PBW resistance; however, this line has a higher yield potential than AET-5 and, from this standpoint, deserves continued evaluation. No F1 hybrid and only one F1 reciprocal hybrid had significantly lower seed damage than that of the lowest parent.
Copyright © 1990.