2011 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.
Marked demand for hard white wheat is rapidly increasing, due to many applications in the food industry and the increasing awareness of the benefits of a diet rich in whole grain. Hard white wheats, however, are more susceptible to pre-harvest sprouting than hard red wheats. Pre-harvest sprouting occurs during prolonged exposure to high humidity between flowering and harvest maturity, and results in a loss of processing quality and seed vigor. Thus, pre-harvest sprouting negatively impacts both producer and end-user. The development of hard white wheats with tolerance to pre-harvest sprouting is the goal of this project. Sprouting is induced using an artificial screening procedure that emulates field sprouting conditions. A delay of harvest in 2010 due to wet conditions afforded an assessment of actual field tolerance to pre-harvest sprouting, via determination of grain stirring numbers, a technique that measures starch degradation. Stirring number values were highly and significantly correlated with the sprouting tolerance indices calculated from the artificial assay. This is an important observation, as field-induced pre-harvest sprouting is too intermittent to allow direct selection in breeding programs. The artificial assay was used to assess tolerance to pre-harvest sprouting in more than 600 USDA-developed hard white breeding lines. Data were collected from harvest years 2007 through 2010. Four-year average responses of the top 30 wheats in the trial indicated many of the USDA-developed hard white winter wheats are similar in sprouting tolerance to Nebraska adapted red wheat cultivars, and to the Kansas-developed tolerant hard white wheat ‘Danby’. Forty experimental hard white wheats, displaying both tolerance to pre-harvest sprouting and resistance to field infections by leaf rust, were advanced to replicated yield trials. Seed supplies of two of these selections were increased, and the lines will be entered in regional trials in the fall of 2011. Seven additional hard white wheats with both tolerance to pre-harvest sprouting and excellent disease resistance, all developed by USDA-ARS, were identified for seed increase in 2011/2012, to be followed by further testing.
In a separate study, hard red wheats were evaluated for their potential to contribute genes for resistance to pre-harvest sprouting when used as parents in white wheat breeding. Using automated seed sorting technologies developed by USDA-ARS, all-white seeded populations were developed after matings between a panel of both white and red wheats. Sprouting tolerance was assessed in derived populations, and the hard red winter wheats Jagalene, Niobrara, and NE98466 were identified as excellent sources of sprouting tolerance when used as parents for new white wheats. White wheat breeding populations, from which new tolerant white wheats will be selected, were developed. ADODR monitoring is accomplished via phone calls, e-mails and personal contact at professional meetings and during site visits.