Combining Ability for Tolerance to Pre-Harvest Sprouting in Wheat.

Combining ability for tolerance to pre-harvest sprouting in wheat.  Juthamas Fakthongphan, R. Graybosch, P. S. Baenziger

Pre-harvest Sprouting (PHS) of wheat (Triticum spp.), the premature germination of wheat heads, takes place in a field under conditions of high humidity during senescence. This problem can have large negative economic effects on both farmers and end-users. Wheat breeders have tried to diversify the wheat production system in Nebraska by introducing hard white winter wheat cultivars. The grain yield potential and disease resistance have been increased but hard white winter wheats typically are less tolerant of pre-harvest sprouting than hard red wheats. The adapted hard red winter wheat genepool, however, might serve as a reservoir of genes for tolerance to PHS, independent of genes conditioning seed coat color. To identify red wheat parents capable of donating genes for tolerance to PHS an MXN mating scheme was imployed in which the hard white wheats Nuplains, NW99L7068, RioBlanco, Cayuga, NW97S218, and Peck were mated in all combinations to the hard red wheats Niobrara, Wesley, Arapahoe, NE98466, CO960293-2, Jagalene, NI01812, and Plainsman V. Seed of progeny was sorted to obtain pure hard white populations. Tolerance to PHS was assessed in samples obtained from four Nebrasksa environments, using both a misting chamber assay and falling number determinations of field-grown samples. Among red wheats, Jagalene, and Niobrara were found to be able to donate PHS tolerance which is independent of genes encoding red seed coat. RioBlanco, and Nuplain, were identified as hard white wheats with good GCA for PHS tolerance. Both carry the PHS gene(s) on chromosome 3As. Cayuga and Peck previously described as tolerant, did not display good GCA.  This could be due to GxE or gene x genetic background.