Date of Award

1987

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Enviromental and Soil Sciences

First Advisor

Jack E. Jones

Abstract

Seventeen advanced La cotton breeding strains having Heliothis spp. resistance attributed to morphological characters and allelochemics were evaluated for field resistance and flowerbud gossypol content at Baton Rouge, LA. in 1982 and 1983. These experimental cottons averaged less than 50% of the Heliothis spp. larvae and feeding-damaged fruit of two cotton cultivars recommended for production in Louisiana. These strains also had at least 25% less feeding-damaged fruit and 15% fewer live Heliothis spp. larvae than two Heliothis spp. resistant cotton germplasm lines. Results suggested that high flowerbud gossypol pigment glandulosity, rather than flowerbud gossypol content per se, played an important role in decreasing Heliothis spp. populations and larval activity. Generation means and diallel analyses were conducted at Clinton, LA. in 1985 to obtain estimates of gene effects and general and specific combining ability (GCA and SCA) for Heliothis spp. resistance and flowerbud gossypol content among advanced La cotton strains. Sources of resistance for these experimental cottons include high flowerbud gossypol pigment glandulosity (HG), and T-27 and T-254 "x" factors. Results indicated that additive gene effects were important for parents with HG and T-27 and T-254 "x" factor resistance and GCA was of importance for parents with HG and T254 "x" factor resistance sources. Additive gene effects and GCA estimates for flowerbud gossypol were also the most important forms of gene action and combining ability. These results indicated that it should be possible to fix and select for resistance to Heliothis spp. when utilizing these or related parents in a breeding program. Intrapopulation recurrent selection was suggested as an efficient breeding strategy for improving and combining Heliothis spp. resistance with important agronomic properties in cotton. Near-isogenic red cotton strains having the $R\sb1$ (red leaf), $R\sb1\sp{\rm dar}$ (Darwinii red), $R\sp{\rm S}$ (red stem), $R\sp{\rm V}$ (red vein) and $R\sp{\rm M}$ (red margin) traits were evaluated for field resistance to Heliothis spp. in 1983 and 1984. The red near-isolines were not found to have significantly less feeding-damaged fruit or fewer Heliothis spp. larvae than Stoneville 213 or their normal green recurrent parent in either year, suggesting that red pigmentation does not confer meaningful resistance to these pests.

Pages

167

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