Early Generation Bulk Hybrid Yield Testing of Adapted Hard Red Spring Wheat Crosses¹

The parents, F 1 , F 2 through F 5 bulks, and 519 F 5 , lines from 28 crosses of a diallel produced from adapted high‐yielding hard red spring wheats ( Triticum aestivum L.) were grown in standard nursery plots at two locations in 1975. Our objective was to determine the value of 1975 midparent, F 1 , and bulk generation yields and 1971‐73 midparent and bulk generation yields as predictive criteria for identifying crosses producing high proportions of superior‐yielding F 5 lines in 1975. Except for the 1971‐73 midparental performance, all predictive criteria were significantly correlated with mean cross yield of F 5 lines. The highest correlation (r=0.81. P≤ 0.01) was between F 5 line means and the 1975 F 2 bulk performance. Of the F 5 lines which yielded at least two standard deviations above the overall line mean, 67 and 56% were derived from sets of seven crosses (upper 25%) chosen on the basis of the 1975 mean F 2 + F 3 bulk yields and the 1971‐73 mean F 2 + F 3 bulk yields, respectively. This compared with 37 and 43% respectively, when 1975 and 1971‐73 midparental performances were used to choose sets of seven crosses. While bulk yields were more useful than midparent yields in identifying superior crosses at the 25% selection intensity, the superiority of the bulks was not as great at a cross selection intensity of 50%.