Genetics of seed dormancy in wheat and barley

Abstract

Montana producers have many biotic and abiotic stresses to contend with. One of interest to avoid is preharvest sprouting (PHS), which is the precocious germination of grains before harvest. PHS affected grain is discounted at the elevator, resulting in grain being unsuitable for many foods and direct losses to producers. PHS is not widespread every year in Montana but in some years causes large economic loss. Although PHS is a response to environmental cues it is largely controlled by genetics. Genes that control seed dormancy are the most likely candidate genes for PHS resistance and the series of studies presented in this dissertation examine the impact of several genes upon small grain PHS susceptibility. The studies used several methods to assess PHS susceptibility and determine which alleles of individual genes were present. The methods included seed dormancy screening assays, alpha amylase enzyme activity analysis, falling numbers analysis, genotyping by direct sequencing and via use of various markers, RNA-sequencing, and gene expression analysis. The first study served as a PHS susceptibility survey and provides PHS tolerance information on MT grown wheat varieties. This study also found that of the three most reported PHS associated genes (TaMFT 3A, TaMKK3 4A, and TaVp1 3B), only TaMFT 3A was associated with PHS in Montana winter wheats, even though the previously reported variation was observed in all three genes. The second study looked at PHS susceptibility among current and historically grown barley varieties. It was found that malt varieties vary greatly in their susceptibility to PHS with the top grown AMBA recommended varieties among the most susceptible. It was also found that a previously unstudied mutation in the HvMKK3 gene is associated with PHS susceptibility. Interestingly, HvMKK3 and HvAlaAT1 affect dormancy at different time points in grain maturity indicating dormancy may be tailored to a specific timeframe (high dormancy at harvest with rapid decay of dormancy after harvest). The final study revisited winter wheat PHS and found that the TaMFT 3B and 3D homeologs are associated with PHS which has not been shown to date.