Novel inflorescence architecture in gamma radiation-induced faba bean mutant populations

Purpose: Inflorescence architecture is an important trait in the seed production of grain legumes. As several genes are responsible for this trait, any mutation, on these genes, may cause change in the inflorescence architecture. This study was conducted to evaluate inflorescence architecture in faba bean exposed to gamma radiation and to characterize the inflorescence architecture mutants phenotypically. Materials and methods: Faba bean M₂ seeds (4898) generated from M₁ generation of cultivars Hassawi 2 and ILB4347 were used in this study. M₁ seeds were produced by irradiation treatments at two doses of gamma radiations (25 and 50 Gy). Faba bean M₂ seeds were planted under field conditions. A total of 4032 mutant plants out of 4898 M₂ seeds were evaluated for their inflorescence architecture. Results: A total of 20 determinate mutants were found and classified into four different types. Determinate type 1 was characterized by the formation of single terminal inflorescence on shoot apical meristem (SAM), type 2 by the formation of multiple inflorescences on SEM and generated upper branches that act as indeterminate type. Type 3 was characterized by the formation of a panicle-like inflorescence. While type 4 was characterized by the formation of primary and secondary panicle-like inflorescence. All of the determinate mutant types had shorter plant height and earlier maturity than control indeterminate type but had lower biological yield and seed yield. Among the determinate mutant types, determinate type 1 was only mutant that had a higher harvest index than the control indeterminate type. This promising mutant can be used to further breeding program to increase biological yield and seed yield. Conclusions: This study indicated potential of gamma radiation in inducing novel inflorescence architecture in faba bean. The mutants developed are valuable resources to study genes related to inflorescence architecture through forward genetics approach.