Genetics of Height and Branching in Faba Bean (Vicia faba)

Abstract

A better understanding of the genetics of plant architecture, including height and branching, could improve faba bean breeding for varieties with better fit into specific cropping systems. This study aimed to determine the inheritance and genetic interactions of the sources of the dwarf gene (dwf1) and semi-dwarf gene (dwarf1), and to investigate the genetics of branching in the faba bean. We chose inbred lines IG 12658 (dwarf, carrying dwf1) and Rinrei (semi-dwarf, carrying dwarf1) along with Aurora/2 and IG 114476 as sources of non-dwarf faba bean genotypes and crossed them (Aurora/2 × IG 12658, IG 114476 × IG 12658, Rinrei × IG 12658, IG 114476 × Rinrei, and Rinrei × Aurora/2). IG 114476 was also used as a genetic source of a highly branching phenotype and crossed with IG 12658, Rinrei, and Aurora/2 to study the genetics of branching. Parental lines, F1s, and F2 populations were evaluated under growth chamber and field conditions in 2018. The segregating F2 populations were tested for 3:1 single recessive gene inheritance using Chi-square tests. Both dwarfing/semi-dwarfing genes fit 3:1 recessive, and 15:1 for double recessive. Rinrei was not a true dwarf, and the gene creating the dwarf appearance reduced the initial growth rate, but this corrected over time. Multiple F2 populations were also tested for a 3:1 single dominant gene hypothesis for highly branched phenotypes. These populations showed a bell-shaped phenotypic distribution for branch number, with no discernable classes, and revealed that branching was likely quantitatively controlled. In conclusion, dwarfism and branching in faba bean were controlled qualitatively and quantitatively, respectively.