Location: Hard Winter Wheat Genetics Research
Project Number: 3020-21000-012-033-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 1, 2026
End Date: Jun 30, 2028
Objective:
1. Evaluate winter wheat breeding lines for wheat stem sawfly resistance
Winter wheat is primarily grown in the Golden Triangle area of Montana which is also known for heavy sawfly pressure. Solid stem has been a primary mode of resistance against wheat stem sawfly, as such solid stemmed lines often come with a yield drag. Cooperator will evaluate winter wheat breeding lines in sawfly prone environments to assess stem solidness, stem cutting rates, grain yield, and agronomic performance.
2. Host and manage the USDA-ARS Sawfly Regional Observation Nursery at Loma, Montana
The USDA-ARS Sawfly Regional Observation Nursery comprises of breeding lines submitted by public and private winter wheat programs and will be evaluated for wheat stem sawfly resistance at Loma, Montana.
3. Characterize variation in stem solidness expression
Stem solidness is commonly treated as a qualitative trait and is phenotyped non-parametrically by scoring pith density on a 0-5 scale for each internode. This ordinal scoring system provides limited resolution to detect minor genetic effects in marker-trait association studies. Therefore, cooperator will initiate a metabolomic-genomic-wide-association study (mGWAS) to enable higher resolution quantitative characterization of variation associated with pith development.
Approach:
1. Evaluate winter wheat breeding lines for wheat stem sawfly (WSS) resistance
The cooperator will establish a replicated yield trial at the Northern Agricultural Research Center (NARC), Havre, MT to evaluate 44 winter wheat breeding lines and 5 check varieties for their resistance to WSS. These entries are selected from the unreplicated screening nursery conducted at Loma, MT in 2025 based on stem cutting scores ranging from 0-40%. Plots (18ft x3ft) will be managed under standard agronomic practices followed at NARC, without any fungicide or insecticide application to maintain sawfly pressure. Lines in the trial will be genotyped with USDA-ARS, Kansas. During the growing season, the cooperator will collect data on winter survival, days to heading, plant height, stem solidness and stem-sawfly cutting. At physiological maturity, the cooperator will harvest the plot to estimate grain yield, test weight and protein. To stem solidness assessment, fifteen stems will be collected at random from each plot approximately fifteen days after heading and processed at the MSU Plant growth center (PGC). Stem solidness will be evaluated at each internode and rated between 1-5, where 1 is hollow and 5 is solid. Average stem solidness scores per plot will be reported on a scale of 5-25 which 5 being hollow and 25 being solid. Lines with high grain yield, protein and reduced sawfly cutting will be advanced for further multi-location evaluations.
2. Host and manage the USDA Sawfly Regional Observation Nursery at Loma, MT
The USDA Sawfly Regional Observation Nursery comprising of 300 breeding lines will be planted at Loma, MT in 2 replications and evaluated for WSS resistance. Cooperator will record days to heading and score stem-sawfly cutting at the end of the growing season. Breeding lines will also be genotyped with USDA-ARS, Kansas. All data collected will be shared with collaborators.
3. Characterize variation in expression of stem solidness
Cooperator will conduct a mGWAS study enabling higher-resolution quantitative characterization of variation associated with pith development. A set of 150 winter wheat lines will be selected from crosses between hollow- and solid-stem varieties, resulting in a population that will be structured yet segregating for stem solidness. Study will be planted in replicated small plots at Carter, MT and stem samples will be collected as described above for solidness rating. Stem samples will also be collected and pooled across reps for untargeted or widely targeted metabolomic profiling.
Differential metabolite analysis will be conducted, and significantly different metabolites (DEMs) will be identified using a Bonferroni-adjusted threshold. DEMs not involved in carbohydrate accumulation, cell wall biosynthesis, and pith tissue development will be filtered out. The metabolomic profile will be validated with stem-solidness score. A metabolome-genome-wide association study will then be performed by integrating DEMs with SNP marker data. The MTWW program maintains genotyping-by-sequencing data for advanced breeding lines (F7), along with corresponding corresponding phenotypic data.