Evaluation of combining ability of selections from different backcross cycles of the sorghum conversion program

Abstract

The objectives of this study were: (i) to evaluate combining ability of segregates from different backcross cycles of exotic sorghums conversion program, and (ii) to determine whether there are changes in combining ability among selected groups of sorghum with successive backcrosses. Answers to these questions would be of benefit in determining how to best utilize germplam from the conversion program. F₂ seed of BC₀, BC₁, BC₂, BC₃, and BC₄ populations for each of twelve SC lines representing six groups of sorghum (Caudatum, Caudatum-Kafir, Zerazera, Durra, Caudatum-Kaura, Conspicuum) was made available by the Texas Agricultural Experiment Station. This seed was produced by using the exotic line as the recurrent parent and a short, early U.S. variety ('B Tx406') as the non-recurrent parent. BC₀, BC₁, and BC₂ were made using the exotic line as the male parent. The exotic line was used as a female in either BC₃ or BC₄ in order to return the converted line to its original cytoplasm. In 1970, at least five short, early plants were selected from each F₂ backcross population. No selection for yield was practiced, the only selection criteria being for shortness, earliness, and a resemblance to the exotic parent. ...