2009 Annual Report
1a.Objectives (from AD-416)
To characterize experimental Nebraska-adapted hard white wheats in terms of tolerance to preharvest sprouting, and to determine whether DNA markers may be used as an alternative means of selection for the trait.
1b.Approach (from AD-416)
Five genetic populations, each composed of approximately 100 recombinant in-bred lines (RICLs), have been developed. Each involves matings of the keystone sprouting tolerant cultivar RioBlanco, and hard white wheat experimental breeding lines or cultivars adapted to Nebraska. These populations are grown in an augmented design, along with several hard red and hard white check cultivars. In the augmented design, individual RICLs are un-replicated, but randomly assigned to blocks; check cultivars are planted within each block, and used to provide an experiment-wise error estimate. The experiment has been grown in 2008 harvest years, and will be seeded for observation and data acquisition again in September, 2008. In addition, all hard white wheats from the University of Nebraska wheat breeding program, advanced from the 2008 NIN, TRP and DUP nurseries, will be included. Sprouting tolerance is assessed by snapping heads after before harvest maturity, drying in a greenhouse, and storing at –20 C until assayed in a misting chamber. DNA markers, derived from literature and database searches, will be used to test their utility as an alternate means of selection. After the 2009 data collection, sprout-tolerant hard white winter wheats will be selected and entered in USDA-ARS regional nurseries for testing of disease responses and agronomic performance.
Preharvest sprouting occurs in wheat as a consequence of periods of excessive moisture and warm temperatures during the ripening phase of wheat development. During preharvest sprouting, the germ and aleurone cell layers release amylases and proteases, enzymes responsible for the digestion of starch and seed storage proteins. Preharvest sprouting results in diminished test weight, reduced germination, and a loss of processing quality. Sprouting tolerance was assessed in more than 1000 winter wheat lines obtained from the 2007 harvest year. Tolerance was assessed by misting wheat heads (ears) harvested jut before harvest maturity, and stored frozen. Evaluation of the same entries from the 2008 harvest year is under progress. A wide range of sprouting tolerance was observed amongst Nebraska adapted hard red and hard white cultivars and advanced breeding line. Camelot and Wesley were identified as highly tolerant HRW cultivars. However, the hard white wheat cultivars Nuplains and Trego were nearly as tolerant as Wesley and Camelot. Amongst experimental white wheats tested from several breeding populations, a wide range of response was observed. Approximately 100 lines with tolerances similar to the tolerant red wheat Wesley were identified. Forty of these lines also showed preliminary indications of resistance to leaf rust. These lines will be entered in an advanced breeding trial in 2010. Hard white winter wheats with tolerances similar to Wesley were not uniformly distributed across the tested breeding populations. More than ½ of the tolerant lines were observed in the two populations having Nuplains as a parent. Nuplains, a hard white wheat cultivar developed and release by USDA-ARS, may serve as an effective parent for future breeding efforts to develop preharvest sprouting tolerant wheats.