Comparison of intra- and inter-pool crosses in faba beans (Vicia faba L.). I. Hybrid performance and heterosis in Mediterranean and German environments

Two recently detected, promising CMS systems in faba bean have opened up new possibilities in hybrid breeding. This study was conducted to determine hybrid performance and heterosis of 33 intra-pool and 66 inter-pool crosses from a factorial of six European small-seeded (Minor), six European large-seeded (Major), and eight Mediterranean faba bean lines. The parent lines and F₁ crosses were evaluated at two German and seven Mediterranean environments for anthesis, maturity, yield, yield components and plant height. Yield in the Mediterranean environments was 60% of that in the German environments. European Minor lines and their intra-pool crosses were unadapted to Mediterranean environments and yielded only 31 % compared with the Mediterranean lines and their crosses, whereas European Major genotypes yielded 58%. In German environments the European crosses yielded 107% of the Mediterranean crosses. Heterotic yield increase over the parental mean was largest for European Minor x Mediterranean inter-pool crosses, amounting to 95% in the Mediterranean and 73% in German environments. Our results confirmed the expectation of an increased heterosis in inter-pool over intra-pool hybrids and poor adaptation of European genotypes in Mediterranean environments. In the latter, Mediterranean intra-pool hybrids were the most promising, whereas in Germany inter-pool hybrids of the European Minor × Mediterranean type were most promising.