VARIANCE AMONG A AND B LINES DEVELOPED FROM RANDOM MATING SORGHUM POPULATIONS
Abstract
Random A and B lines from Purdue Populations 9 and 18 (PP9 and PP18) were evaluated. Seventy-four S(,5) B-lines, 34 from PP9 and 41 from PP18, were evaluated in a randomized complete block design in 1981 and 1982. Days to half bloom, yield, plant height, lodging, and seed color were measured. Thirty-four BC(,4) A-lines, 13 from PP9 and 21 from PP18, were evaluated in hybrid combinations using two different testing methods at two locations in 1982. In method I, the A lines were crossed to three elite R lines and estimates of general and specific combining abilities (GCA and SCA) were made. In method II, the A lines were crossed to a broad base population, Purdue Population 24 (PP24), and GCA estimates were made. Significant genotypic variance existed for all traits measured among the PP9 and PP18 B lines. Significant differences were found between PP9 and PP18 for all traits measured. PP9 flowers sooner, is higher yielding, taller, has darker seeds, and has higher genotypic variance for all traits measured except lodging. Significant gains should be made from selection on B lines within PP9 and PP18. Heritabilities and correlations between the traits were calculated. Significant positive correlations were found between height and yield, yield and lodging, and height and lodging. A significant negative correlation was found between lodging and flowering. These correlations are important because of correlated responses from selection. Significant variation for GCA was found among the PP9 and PP18 A-lines for all traits except lodging. Therefore, selection for combining ability should produce gains. The A-line variance component in the testcross progeny was higher when evaluated by method I than method II. The GCA effects estimated from the two methods were highly correlated for all traits except yield. Since yield is of major importance, elite R lines are recommended as testers for evaluating experimental A lines, where the final objective is an elite A line x elite R line hybrid.
Degree
Ph.D.
Subject Area
Agronomy
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