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Resistance to preharvest sprouting has been observed in several white wheat (Triticum aestivum L.) genotypes, but the mode of resistance has not been determined. Studies were conducted to characterize the strong preharvest sprouting resistance in Clark's Cream genotype to facilitate breeding for the trait. Clark's Cream and five other hard red and white wheat genotypes were grown in the glasshouse and field and effects of simulated rain, embryo maturity, inhibitors in floral parts and GA, endogenous inhibitors, and ABA and GA combinations on sprouting were measured. The six genotypes differed significantly in sprouting after simulated rain, a-amylase activity, and response to GA and ABA. Embryo maturity and inhibition levels in floral parts and caryopses were nearly similar for all genotypes. Clark's Cream appeared to differ most in high embryo sensitivity, which was fairly nonspecific for ABA, GA, and endogenous inhibitor, and in low a-amylase production during sprouting. Breeding procedures that lead to the preharvest sprouting resistance of Clark's Cream are discussed.

Preharvest sprouting resistance is a major breeding criterion in many regions where white wheat (Triticum aestivum L.) is produced. Availability of genetic sources of sprouting resistance should significantly advance this goal. Objectives of the present investigation were to determine heritabilities and genetic variation of sprouting resistance in progeny of six susceptible genotypes and Clark's Cream, a cultivar with excellent sprouting resistance. Sixty-five randomly selected F2:F3 lines from the six parental combinations were evaluated in blocks-within-replication designs at two locations during 1984–85. Falling number, a-amylase activity, and sprouting percentage in simulated rain were usually more favorable in F2:F4 grain than in grain of the susceptible parents and frequently equalled levels in grain of the resistant parent. Broad sense heritability estimates were moderate to high for falling number and a-amylase activity, low to moderate for visual sprouting, and inconsistent for embryo germination in ABA. Phenotypic correlations with sprouting were significant most often for falling number and least often for the agronomic traits, days to heading and kernel weight. We concluded that increased preharvest sprouting resistance is an attainable objective when genetic sources of strong resistance and appropriate selection criteria, such as sprouting after simulated rain, are used.

Hard white winter wheat (HWWW) occupies a very limited area of the USA, but its purported advantages suggest that its production in the major hard red winter wheat (HRWW) region may be feasible. Objectives of our investigations were to develop experimental HWWW lines that combined desirable attributes-grain yield, functional grain quality, and resistance to preharvest sprouting-in single genotypes for comparison with popular cultivars in the major US RHWW region. Forty-four lines from seven parental combinations were tested in randomized complete block designs at three Kansas locations during the 1981–82 and 1982–83 seasons. Agronomic traits, grain yield, grain quality, and preharvest sprouting were measured. Plant characteristics and grain yield were similar in the HWWW experimental lines and the HRWW check cultivar, Newton. Mean grain SDS-sedimentation value and grain protein content of most experimental lines equaled or exceeded that of the check. Dough mixing times frequently were shorter for the experimental lines than for the check cultivar, whereas loaf volumes were greater. Falling number usually was similar in all geneotypes, but a-amylase was higher in field-harvested grain of white lines than the check; both measures were more favorable than grain trade standards. We concluded that production of high yielding, high quality hard white winter wheat genotypes is feasible in the US ‘breakbasket’.