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) as an alkylating agent 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 M1 generation, the MEP had huge phenotypical variations, for instance, >3000 chlorophyll-deficient mutants, 2519 compact spikes, and 1692 male sterile spikes; there were also rare mutations, including 30 independent tillers each with double heads. Some M1 variations of chlorophyll-deficiency and compact spikes were inheritable, appearing in the M2 or M3 generations. To advance the entire MEP to higher generations, we adopted a single-seed descendent (SSD) approach; all other seed composites of M2 were used to screen other agronomically important traits, such as for tolerance to the herbicide quizalofop-P-methyl. The MEP is available for collaborative projects, and provides a valuable toolbox for wheat genetics and breeding for sustainable agriculture.