EVALUATION OF IMPROVEMENT IN SORGHUM RANDOM-MATING POPULATION NP3R USING S1 FAMILY TESTING VS. TESTCROSSING TO AN INBRED LINE

Improvement of Sorghum bicolor (L.) Moench populations through recurrent selection was investigated using two types of family evaluation. S(,1) families were developed from base cycle (C(,0)) and an advanced cycle (C(,3)) of NP3R random-mating populations. S(,1) families from each cycle were crossed to a male-sterile inbred line tester (KS56). Evaluation of S(,1)\u27s and their testcrosses was made in a 2-year experiment at Mead, Nebraska. The objective was to investigate recurrent selection in improving sorghum populations through intrapopulation (S(,1)) and interpopulation (S(,1) x tester) methods. Realized and expected gains in yield manifested the superiority of S(,1) family testing over S(,1) testcrossing. The superiority of S(,1) family testing was an indication of the prevalence of additive and additive x additive types of gene action in sorghum populations. Improvement of yield was accompanied by late maturity, which might limit the genetic gains from recurrent selection, especially in areas where testing is affected by late stresses (e.g. cold or dry conditions). Phenotypic and genetic correlations between the two selection methods indicated a strong relationship which could have predictive value due to high r(\u272)-values associated with them; the highly significant homogeneous correlations between the two testing methods at both cycles of selection for yield are also evidence of the importance of additive and additive x additive types of gene actions. The phenotypic and genetic correlations among characters indicated the positive association of yield with bloom and height and a negative correlation of yield with oil and protein. The heterogeneity in correlations between yield and bloom in different cycles of selection indicated the effectiveness of cyclic recombination in breaking linkage between these characters. Consequently, the possibility exists through selection indices to improve the yield of sorghum populations coupled with controlled maturity