ARS | Publication request: Genetic Variation of Seed Dormancy in Synthetic Hexaploid Wheat-Derived Populations

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2010
Publication Date: July 1, 2010
Citation: Gu, X., Zhang, L., Glover, K., Chu, C., Xu, S.S., Faris, J.D., Friesen, T.L., Ibrahim, A. 2010. Genetic Variation of Seed Dormancy in Synthetic Hexaploid Wheat-Derived Populations. Crop Science. 50:1318-1324.

Interpretive Summary: Seed dormancy acquired during seed development provides wild species with an adaptive mechanism to prevent sprouting on the plants. Cereal crops, such as barley, rice and wheat, partially or completely lost this mechanism due to artificial selections for rapid, uniform germination during domestication and breeding activities. Lack of dormancy causes pre-harvest sprouting (PHS) when harvest is delayed by humid environmental conditions or untimely rain. The PHS damage has been a serious problem in wheat production as it frequently causes loss of yield and reduction in grain end-use quality. Breeding efforts have been made to incorporate a moderate degree of seed dormancy into commercial varieties to prevent loss from PHS. However, progress in this area has been limited by availability of valuable genetic resources. Goat-grass species Aegilops tauschii, the D-genome donor of bread wheat, has very strong seed dormancy and genes controlling the trait may be used in breeding programs to manipulate germinability of improved cultivars. Thus, this research was conducted to initiate a project to identify dormancy genes from Ae. tauschii-derived synthetic hexaploid wheat lines and integrate them into commercial cultivars that are susceptible to PHS. Four permanent segregating populations, developed by crossing four SHW lines with a common wheat line, were grown in a field from 2006 to 2008, to evaluate dormancy with threshed seeds (kernels) and intact seeds on the spikes by germination at 20°C for 10 d. Significant genetic and year effects on both kernel and on-spike seed dormancy were detected in each population. Seeds on the spikes were much more dormant than kernels, indicating the presence of germination inhibitors in the covering tissues. Significant correlations between kernel and on-spike seed germination rates were detected in all populations. It was concluded that available SHW lines could be an alternative source of dormancy genes for enhancing resistance of wheat cultivars to PHS.

Technical Abstract: Aegilops tauschii, the D-genome donor of wheat (Triticum aestivum), has very strong seed dormancy and genes controlling the trait may be used in breeding programs to manipulate germinability of improved cultivars. Thus, this research was conducted to initiate a project to identify dormancy genes from Ae. tauschii-derived synthetic hexaploid wheat (SHW) and integrate them into commercial cultivars that are susceptible to pre-harvest sprouting (PHS). Four permanent segregating populations, developed by crossing four SHW lines with a common wheat line, were grown in a field from 2006 to 2008, to evaluate dormancy with threshed seeds (kernels) and intact seeds on the spike by germination at 20°C for 10 d. Significant genotypic and year effects on both kernel and on-spike seed dormancy were detected in each population, with heritability estimates of about 0.4 (0.32 – 0.48) across the years. Seeds on the spikes were much more dormant than kernels, indicating the presence of germination inhibitors in the covering tissues; prior to germination a warm, dry after-ripening treatment could be used to better display genetic variation for on-spike seed dormancy in segregating populations. Significant correlations between kernel and on-spike seed germination rates were detected in all populations; the estimated correlation coefficient (r) was greater for genotypic (0.80) than for phenotypic (0.63) or environmental (0.51) component. It was concluded that available SHW lines could be an alternative source of dormancy genes for enhancing resistance of wheat cultivars to PHS.