S Arrendell; JC Wynne; JO Rawlings
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Abstract: Effective manipulation of the symbiotic relationship between peanut (Arachis hypogaea L.) and Bradyrhizobium is aided by an understanding of the genetic mechanisms governing the host contribution. This study was conducted to obtain genetic variance estimates and evaluate the effectiveness of selection for acetylene reduction. The population under study consisted of 80 F5 lines derived from the single cross of the Virginia-type ‘Florigiant’ and the Spanish-type ‘CES 101’. Estimates of genetic variance components for acetylene reduction were obtained at three sampling dates at each of two locations. Standard errors of the estimates were Generally large; however, the tendency was for additive genetic variance to be important at Dates 1 and 3 and for the additive ? additive genetic variance to be important at Date 2. The five lines with the highest mean acetylene reduction and the five with the lowest mean acetylene reduction were selected and evaluated in the F6 generation. The mean acetylene reduction of the high selection group, 79.1 ?moles C2H4 plant?1 h?1, was significantly greater than the mean of the low selection group, 52.2 ?moles C2H4 plant-1 h-1, but not different from the mean of the better parent, 89.9 ?moles C2H4 plant?1 h?1. Twenty-eight vegetative, fruit, and seed characters were used to assign the selected lines and original parents to morphological groups. Variability for these traits existed within each of the selection groups. selected lines, regardless of selection group, did not group with either parent. Adequate genetic variability existed in this late generation population and host genotypes with differing abilities to fix N2 were identified by selection. When the breeding objectives is improvement of the N2-fixing ability of Spanish-type peanuts, direct selection for morphological characters may be required if the base population has been derived from a Virginia ? Spanish cross.