Lisa Brünjes & Wolfgang Link

Theoretical and Applied Genetics August 2021; vol. 134: 2411–2427

Key message

Faba bean genotypes showed significant and marked genetic differences in their success as pollen donors to cross-fertilized seeds. The findings may improve exploitation of heterosis in synthetic cultivars.

Abstract

In partially allogamous crops such as faba bean (Vicia faba L.), increasing the share of heterosis in a synthetic cultivar can improve yield and yield stability. The share of heterosis in such synthetic cultivars is increased by higher degrees of cross-fertilization. This trait is defined as percentage of cross-fertilized seeds among all seeds and is a crucial parameter in breeders’ yield predictions. Current approaches use degree of cross-fertilization to predict inbreeding and share of heterosis, they even consider genotype-specific degrees; yet, all genotypes are assumed to contribute equally to the cross-fertilized seeds. Here, we expect faba bean genotypes to differ in their success rates as pollen donors, i.e. in paternal outcrossing success. To quantify the variation of both, the degree of cross-fertilization and the paternal outcrossing success, we assessed these parameters in inbred lines and F1 hybrids, grown in four polycrosses composed of eight genotypes each. We identified the paternal genotype of 500 to 800 seeds per genotype and polycross using SNP markers. In both traits, we found marked and significant variation among inbred lines and among F1 hybrids, as well as between inbred lines and F1. Based on our findings, we discuss how differential paternal outcrossing success influences the amount of inbreeding in synthetic cultivars. Our findings offer the potential for a better management and exploitation of heterotic yield increase in faba bean.

See https://link.springer.com/article/10.1007/s00122-021-03832-z

Figure 3: Degree of cross-fertilization of the faba bean genotypes in different sets of genotypes: a set 0 in one year (2014) and at one location (GAR), b set A in two years (2015, 2016) and at one location (DRA), and c set B in one year (2016) and at one location (DEP). For each set, different letters show significant differences among least square means (p = 0.05, multiple comparisons of means with user-defined contrasts and Bonferroni correction). Vertical lines show 95-percent confidence intervals. Least square mean values for each environment (combinations of year × location) are shown in Supplementary Table 6.