BREEDING FOR PREHARVEST SPROUTING TOLERANCE IN WHITE-SEED-COAT SPRING WHEAT

White seed-coat is a desirable quality attribute for many uses of wheat (Triticum spp.). Unfortunately white seed coat has traditionally been associated with low tolerance to preharvest sprouting. The objective was to assess our breeding progress to improve the preharvest sprouting tolerance of white genotypes. In 1987 and 1988, two groups of white genotypes, developed in our breeding program, were compared with 20 genotypes differing in seed-coat color (red or white), preharvest sprouting tolerance, and class of wheat. Three categories of tests were used to evaluate sprouting tolerance: (i) artificial rain (AR) treatment of intact heads, (ii) germination (G) of hand threshed heads, and (iii) field weathering (FW). The AR and G tests differentiated and ranked genotypes in agreement with previous information, while the FW test proved unsatisfactory, probably due to insufficient rainfall during the field weathering periods. The white genotypes developed from two tolerant parents (2TP) displayed higher levels of tolerance than those developed from a single tolerant parent (1TP). Only tolerant red genotypes and registered hard red spring cultivars had more tolerance than the 2TP group. The 2TP group was judged to be equal in tolerance to 'Laura', a hard red spring wheat with a reasonable level of sprouting tolerance, and better than eight groups comprised of 19 genotypes. The results suggest that white-seed-coat cultivars can be developed with high levels of preharvest sprouting tolerance. Observed differences between wheat classes probably reflect current cultivars and applied selection pressure, either direct or indirect during cultivar development, rather than inherent differences between classes.