Creating large EMS populations for functional genomics and breeding in wheat

Wheat germplasm is a fundamental resource for basic research, applied studies, and wheat breeding, which can be enriched normally by several paths, such as collecting natural lines, accumulating breeding lines, and introducing mutagenesis materials. Ethyl methane sulfonate (EMS) is an alkylating agent that can effectively introduce genetic variations in a wide variety of plant species. In this study, we created a million-scale EMS population (MEP) that started with the Chinese wheat cultivars 'Luyan 128', 'Jimai 38', 'Jimai 44', and 'Shannong 30'. In the M 1 generation, the MEP had numerous phenotypical variations, such as >3,000 chlorophyll-deficient mutants, 2,519 compact spikes, and 1,692 male sterile spikes. There were also rare mutations, including 30 independent tillers each with double heads. Some M 1 variations of chlorophyll-deficiency and compact spikes were inheritable, appearing in the M 2 or M 3 generations. To advance the entire MEP to higher generations, we adopted a single-seed descendent (SSD) approach. All other seed composites of M 2 were used to screen other agronomically important traits, such as the tolerance to herbicide quizalofop-P-methyl. The MEP is available for collaborative projects, and provides a valuable toolbox for wheat genetics and breeding for sustainable agriculture.