Leveraging Crop Wild Relatives and Ploidy Level for Climate-Resilient Annual Ryegrass

Leveraging crop wild relatives and chromosome manipulations are powerful tools for developing climate-resilient agroecosystems. Yet, the combined effects of polyploidy and diverse genetic makeup on plant responses to climate-induced stresses remain generally underexplored, particularly in annual ryegrass (Lolium multiflorum Lam.), a major cool-season forage species. In a two-year controlled environment study, we assessed phenotypic responses of a wildtype and the cultivar Marshall at diploid (2x = 14) and tetraploid (4x = 28) levels. Plants were grown under 540 and 800 ppm [CO2] and at full and 50% evapotranspiration regimes. Anatomical and physiological differences between populations and ploidy levels were limited. Despite genetic background, total biomass production increased by 44% from 540 to 800 ppm [CO2], driven by enhanced aboveground growth. While the 2x-wildtype showed a lower leaf-to-stem ratio (a proxy for forage quality) than 2x-Marshall, this gap diminished at the tetraploid condition. These differences, and the lack thereof, highlight the importance of considering both chromosome manipulation and the genetic sourcing of crop wild relatives to expand diversity in cultivated species. Our findings reveal that wild populations can achieve comparable productivity and efficiency to improved populations under climate-change induced environments, while contributing adaptive traits valuable for resilient cropping systems. HIGHLIGHTWildtype ryegrass matched improved high-yield cultivar under stress and elevated [CO2], suggesting the need for both local adaptation potential and for new breeding targets under climate change.