Genetic analysis and characterization of faba bean (vicia faba) for resistance to chocolate spot (Botrytis fabae) disease and yield in the Ethiopian highlands.

Abstract

Faba bean (Vicia faba L.) is one of the most important food legumes cultivated in Ethiopia. However, its production has been limited by several factors, among which include chocolate spot (CS) disease caused by the fungus Botrytis fabae. This is an important disease reducing faba bean yields and hence food security in the Ethiopian smallholder sector and other countries where the crop is grown. This study, conducted from 2011 to 2013 in Ethiopia, was designed to assess (i) farmers’ awareness of chocolate spot and their influence on faba bean varieties of their preference; (ii) the genetic diversity, potential of several landracees for CS resistance; (iii) the mode of inheritance to CS and (iv) breeding potential of CS resistant lines in hybrid combinations. Simple sequence repeat (SSR) markers were used for genetic diversity study, while the full diallel mating design was used for genetic analysis of CS resistant moderately resistant and susceptible faba bean lines from Ethiopia breeding programme and International Center for Agriculture Research in the Dry Area (ICARDA). This study revealed that CS is a major production constraint in Ethiopia with high incidence and severity levels in the farmers’ fields. The level of CS resistance in locally grown landraces thus needs to be improved. Farmers preferred new varieties that combined early maturing, high yield potential and CS resistance. The study also showed that faba bean genotypes with a wide genetic variation to CS existed in the Ethiopian germplasm, with nine of the local landraces being potential sources of resistance. Additive gene effects were more important than non-additive gene effects for CS resistance, suggesting that selection would be useful for improving the resistance of chocolate spot in faba bean. Lines ILB-4726, ILB-938 and BPL-710 had good resistance to CS and were good combiners for yield. Non-additive gene action was important for grain yield, implying that hybridization would be effective as a strategy for faba bean yield improvement. No maternal effects were recorded in the inheritance of CS resistance. Further genotypes x environment interactions were significant for CS resistance in faba bean, suggesting breeding for specific adaptation. These strategies will be recommended to programmes that emphasize CS resistance in faba bean.