Managing crop residue is essential to conservation farming systems that enhance soil quality and reduce soil erosion. Growers, and the seed dealers they work with, regularly request information on residue decomposition of winter wheat cultivars, but none is currently available. Previous analysis of winter wheat residue has shown that hard and soft cultivars differ significantly in their neutral detergent fiber, acid detergent fiber, acid detergent lignin, carbon (C), nitrogen (N), C/N ratio, and near infrared spectroscopy (NIR) readings, and that many can be categorized as having characteristics for either “rapid” or “slow” residue decomposition. A recombinant inbred line (RIL) population between Finch (slow breakdown) and Eltan (fast breakdown) and a diversity panel of 480 lines was grown under field conditions at Spillman Farm, Pullman, WA and Mansfield, WA, in 2015, 2016, and 2017. Residue was collected at harvest, scanned using NIR, and validated using traditional forage fiber, carbon and nitrogen analyses. Populations were genotyped using the 9K and 90K Infinium wheat SNP chip. Significant QTL were found on chromosomes 1A, 1D, 3B, 4A, 5A, 6B, and 7D and are associated with the different traits tested. None of the QTL were consistent across locations or traits, and most only accounted for 2-6% of the phenotypic variation. NIR prediction models were only moderately correlated to trait values, attributed to the narrow genetic divergence between the two parents used. The diversity panel should have enough genetic diversity present to develop better NIR prediction models, although these analyses are still under development and not proven yet. A genetic analysis of the 2016 data from the diversity panel shows a similar genetic story as the RIL population showed. Significant marker-trait associations were identified, yet again most were minor QTL which did not span traits or environments. The genetic composition of straw breakdown traits is complex, and highly influenced by the environment. It is unlikely that a marker-assisted selection program could be used to select new cultivars based on breakdown potential. NIR prediction appears to have promise as a high-throughput method of estimating straw breakdown potential in wheat.
- Principal Investigator(s): Carter, A.
- Grant Amount: $39,774
- Principal Investigator(s): Carter, A.
Roa, A., Kruse, E., Stubbs, T., and Carter, A.H. 2018. QTL analysis of straw residue components as it relates to the rate of straw decomposition. To be submitted to the Journal of Agriculture and Food Chemistry.
Additional Funds Leveraged
Funds have been obtained from a USDA-NIFA grant and from the Washington Wheat Commission to make NIR testing a standard process within the WSU winter wheat breeding program. We secured funding from private endowment funds to hire Nathan Nielsen to continue the work on the QAM population in the 17/18 crop year (OA Vogel and Willard Hennings Endowment). Nathan submitted a research grant to the Western SARE program, and was awarded funds for his research stipend to continue the work on the QAM population and the NIR prediction models into the next academic year. Upon completion of the project, breeding lines will be tested annually for this trait and used in the selection process.
Short-Term: The short-term knowledge gained upon completion of the project will be information on the residue decomposition potential of two diverse collections of winter wheat germplasm (containing almost all currently grown cultivars), and the ability of NIR to predict residue quality traits. Information gathered using traditional wet chemistry fiber characterization methods, and combustion methods for nutrient analysis will be compared to the ability of NIR to predict those same traits and relate to residue decomposition. QTL identified begin to give plant breeders an understanding of the genetic control of straw decomposition.
Intermediate-Term: We will gain the ability to quickly process and scan small quantities of winter wheat residue from large numbers of samples, such as breeding populations, using NIR analysis to screen for residue decomposition potential. This information will be useful in determining suitability of potential new varieties for conservation farming systems in both high rainfall, annual cropped regions and low rainfall, winter wheat-fallow regions. Use of this tool for residue screening would occur in the year following completion of the research.
Long-Term: The ability to process and test a small quantity of winter wheat residue for the characteristics that determine decomposability using NIR predictions will become a standard test toward deciding which potential cultivars move forward in developing new varieties at Washington State University. Use of NIR to screen winter wheat residue for decomposition characteristics would be used in subsequent years following completion of the research. Cultivars that decompose slowly will help to protect soils in low rainfall regions where conventional tillage with fallow is practiced. Cultivars that decompose rapidly and allow for ease of direct seeding will hasten adoption of conservation farming practices; minimize the need for conventional tillage, burning and winter wheat residue removal; and lead to practices that build soil quality. There may also be impact with regards to decisions about bailing straw residue and removing it from the farm, as well as impact of new wheat pulping facilities.