Production of commercial F₂ cotton (Gossypium) hybrids utilizing a selective male gametocide.

Abstract

Literature was reviewed to substantiate the authors' concept that the F₂ hybrid in Upland cotton (Gossypium hirsutum L.) is a usable product. Obstacles to hybrid cotton production include effective emasculation techniques, economical methods to produce F₁s, including pollen transfer by insect vectors, and identification of parental combinations that demonstrate useful heterosis. F₁ hybrids useful in commercial agricultural crops became the focus of attention of plant breeders in the 1940's when, through mechanical emasculation of one monecious parent, a hybrid could be easily produced and the maximum expression of heterosis exploited. The complete flower of cotton, however, dictates chemical or biological rather than mechanical emasculation and the techniques available create problems of phytotoxicity, cytoplasmic incompatibility, and/or restoration. The author therefore abandoned the use of the F₁ hybrid concept for cotton hybrids and began to evaluate an alternative, the F₂ hybrid. The problems associated with genetic segregation in F₂ generations in other crops delayed acceptance of a F₂ hybrid concept for cotton until the 1980's when the research discussed herein and supported by University of Arizona, Pennwalt Corporation, and American Cyanamid Corporation was made. Trade secret constraints allow only the reporting of summarized data and not the detailed information appropriately on file with the companies. In the 26 year period between 1947 to 1973, only 70 hybrids were created by cotton researchers and evaluated in the F₂ generation for yield performance. Olvey and team created 467 hybrids using chemical emasculation techniques which were evaluated and reported in 1985 and 1986. Other researchers throughout the cotton belt have now studied 69 F₂ hybrids since 1986. The acceptance of the F₂ hybrid concept traces directly to the specific program developed by the author. Research cited substantiates that the chemical TD-1123 (3,4-dicloroisothiazole-5-carbolic acid) is an effective emasculator, that production costs can be reduced considerably by marketing the F₂ hybrid, and that extensive F₂ hybrid yield testing has shown that the F₂ hybrid has promise as a commercially feasible product.