Improving Perennial Ryegrass Seed Production in Northern Minnesota: Developing Metabolomics-Assisted Selection Techniques for Crown and Stem Rust Resistant Cultivar Development

View the project final report

Commodities

• Additional Plants: ornamentals

Practices

• Education and Training: technical assistance
• Pest Management: genetic resistance
• Sustainable Communities: sustainability measures

Perennial ryegrass seed, produced for sale as turf and forage grass seed, is grown in rural agricultural areas of northern Minnesota and contributes $15-20 million to rural economies annually. As a perennial, perennial ryegrass has many environmental benefits in a crop rotation including decreased erosion, reduced leaching, high organic matter production, and greater habitat for wildlife due to fewer tillage operations. From a farmers standpoint, perennial ryegrass is a desirable crop rotation option because it is profitable, tolerant of diverse weather conditions, requires less labor than annual crops, and harvest occurs earlier than for annual crops so labor requirements are spread throughout the season. Minnesota farmers have indicated that crown and stem rust pathogens are a severe issue in seed production fields (causing up to 80% yield reduction) and that new cultivars that are resistant to crown and stem rust pathogens would be desirable. Currently the only way to control rust pathogens is to spray fungicides which are costly and harmful to human and environmental health. The goal of the proposed research is to develop a method for rapid, and accurate selection for resistance to rust pathogens in perennial ryegrass germplasm based on plant chemical compounds (a “metabolic fingerprint”) associated with rust resistance. Termed metabolomics-assisted breeding, this technique will lead to faster rust resistant cultivar development, ultimately reducing fungicide use and making perennial ryegrass seed production a more profitable, marketable and sustainable option for farmers in rural communities in northern Minnesota as well as the Pacific Northwest and Canada.

Introduction:

Stem rust (Puccinia graminis) and crown rust (Puccinia coronata), the causal agents of rust diseases in Minnesota, are serious fungal diseases of most agriculturally important grass species and currently affect all 72,000 hectares of perennial ryegrass seed production within the United States. Rust pathogens also affect perennial ryegrass when grown as a turfgrass and can reduce turf quality and lead to increased water and nutrient use (4). Significant efforts have been made to combat rust pathogens in small grains but little attention has been given to rust in perennial ryegrass.

Perennial ryegrass seed produced for sale as turf and forage grass is grown in rural agricultural areas of northern Minnesota, Oregon, and Canada. Currently there are around 60,000 acres of perennial ryegrass seed production in northern Minnesota as well as 120,000 and 25,000 acres in Oregon, and Canada respectively. A perennial ryegrass seed crop is under-seeded in a spring wheat crop or planted into spring wheat stubble in the fall, then overwinters as a living cover crop and is harvested for seed the following summer. This double cropping approach reduces the number of field tillage operations required by farmers, protects against leaching and erosion, and spreads work load throughout the year because seed harvest occurs during summer before other annual crops are harvested (1, 11). Perennial ryegrass as a seed crop, along with the associated processing and distributing businesses, contribute significantly to rural economies (valued at $15-20 million in Minnesota). If demand for seed from European and Asian markets continues to grow and seed production remains sustainable and profitable compared to annual-type agricultural crops, perennial ryegrass acreage in Minnesota could increase to over 150,000 acres.

Although perennial ryegrass has been a desirable crop rotation option, Minnesota farmers have indicated that rust pathogens are a severe issue in seed production fields (causing up to 80% yield reduction) (19). Fungicides (costing $125 per acre per application) are routinely applied to obtain adequate seed yields suggesting that rust resistant cultivars would improve sustainability of the crop (15, 16). Through a Minnesota Rapid Agricultural Response grant we have been successful in conducting some phenotypic screening for rust resistant perennial ryegrass germplasm (13). Phenotypic screening however, can be time consuming, costly, and unpredictable do to pathogen and environment unpredictability (12). In addition we need a way to select for rust resistance in the absence of the actual pathogen in order to be able to select for other traits simultaneously and speed cultivar development. Metabolomics-assisted breeding has recently emerged a technique to select for desired traits based on chemical profiles that have been previously correlated with a trait of interest (5).

Chemical compounds within plants (particularly secondary metabolites) are the end products of complex biochemical pathways that are regulated by genes and are often used directly as stress mediation or plant defense mechanisms making them closely associated to plant phenotypes (3, 9). Some plant produced chemicals can also stimulate growth of rust pathogen structures involved in the infection process (7, 20). The potential for using secondary metabolites as biomarkers for selecting desired traits in plants has been demonstrated in arabidopsis, grapes, wheat, and conifer (14, 6, 8, 17). Selecting for quantitative rust resistance in a recurrent selection program is a viable and desirable option for perennial ryegrass considering a lack of research on the genetics of resistance in this crop (12, 5). Our research, studying relationships between perennial ryegrass-produced chemicals and rust pathogens, is a significant step towards succesful implementation of a metabolomics-assisted selection strategy for selecting durable, quantitative rust resistance and faster development of rust resistant perennial ryegrass cultivars.

Objective 1: Quantify and verify levels of durable, quantitative resistance to crown and stem rust in an advanced perennial ryegrass breeding population using a controlled environment.

Objective 2: Determine metabolic fingerprints associated with crown rust resistance.

The long term goal of this research is to develop a method for rapid, and accurate selection of resistance to rust pathogens in perennial ryegrass germplasm based on plant chemical compounds (a “metabolic fingerprint”) associated with rust resistance. Termed metabolomics-assisted breeding, this technique will lead to faster cultivar development, ultimately reducing fungicide use and making perennial ryegrass seed production a more profitable, marketable and sustainable option for farmers in rural communities in northern Minnesota as well as the Pacific Northwest and Canada.

Short-term outcomes:
1) Thorough analysis and verification of rust resistance variability of important perennial ryegrass germplasm in our breeding program.
2) First development of metabolomics-assisted selection techniques for high-throughput, accurate, and dependable crown rust resistance screening in a plant breeding program.
3) Improved knowledge of the biological basis for plant resistance to rust pathogens plus greater farmer and researcher understanding of ryegrass and pathogen interactions.

Intermediate-term outcomes:
1) Rust resistant perennial ryegrass lines identified in this study will be incorporated into our breeding program.
2) This research will result in our breeding program having a fast, reliable metabolomics-assisted selection method to supplement often unpredictable phenotypic screening methods leading to faster delivery rust resistant cultivars to farmers.
3) The crown rust resistance selection model will be adapted for stem rust resistance selection.

Long-term outcomes:
1) New crown and stem rust resistant cultivars will make perennial ryegrass seed crops a more profitable and environmentally sustainable crop rotation option for farmers in northern Minnesota.
2) Seed from rust resistant cultivars will be more marketable to end users and will result in more environmentally sustainable turfgrasses.
3) Our methods could be used as a model for metabolomics-assisted selection in other important agricultural crops or for other traits in perennial ryegrass.