Factors determining the performance of synthetics in Vicia faba L. 1. Heterogeneity,heterozygosity, and degree of cross-fertilization

Summary The relative performance of synthetic varieties in faba beans (Vicia faba L.) as compared with line varieties is the result of the joint effect of several factors. Factors investigated in the present study were (1) effects of heterogeneity and (2) heterozygosity on agronomic performance, (3) genetic variance for the degree of cross-fertilization among inbred lines and (4) genetic variance among homozygous and heterozygous genotypes for yield. The evaluation was based on multilocational trials in Germany with 36 inbred lines and derived entries with contrasting population structure (levels of heterozygosity and heterogeneity). When inbred lines and F₁-hybrids are included in the same mixture of genotypes, the resulting heterogeneity had a positive effect on yield. Relative mid-parent heterosis for yield was between 33% and 51%. The average degree of cross-fertilization was 53.5%, and its genetic standard deviation was 8.3%. The estimates for genetic standard deviation for yield among inbred lines were between 3.4 q/ha and 5.3 q/ha. The highest yielding synthetic variety is expected to outyield markedly the highest yielding line.