Genetic progresses from over three decades of faba bean (Vicia faba L.) breeding in Ethiopia

Eleven faba bean ('Vicia faba' L.) varieties released between 1977 and 2007, and two promising genotypes, were evaluated to estimate the genetic progresses made in 33 years of faba bean breeding in Ethiopia. The study was conducted at eight environments during 2007 and 2009 cropping seasons in a randomized complete block design with four replications. Records taken on grain yield, seed size and chocolate spot ('Botrytis fabae') severity were subjected to statistical analysis. Combined analysis of variance revealed highly significant differences among the genotypes and the test environments for all traits, the G E interaction effects being significant for grain yield and seed size. Regression of mean performance at all environments on year of varietal release showed positive relationship for grain yield (r = 0.48) and seed size (r = 0.80**) but negative for chocolate spot (r = -0.60*). The annual rates of genetic progresses were 8.74 kg ha-1, 8.07 g 1000 seeds-1 and -0.27% for grain yield, seed size and chocolate spot, respectively. The average cumulative gains over 33 years of breeding was, therefore, 288.4 kg (8.1%) for grain yield, 266.3 g (51.12%) for seed size and -8.9% for chocolate spot severity. Seed size showed the most dramatic response to breeding for the last 33 years may be because of a lesser polygenic nature of this trait and better availability of best donor parents as compared to grain yield. The relatively slower responses of grain yield and chocolate spot to breeding may be associated with the polygenetic nature of the former and shortage of good donor parents for the later. The prior release of an exceptionally stable and better adapted variety, CS20DK, in 1977 might also seemingly undermined progresses of later efforts. It is, therefore, strategically advisable that breeding efforts in the future should give due attention to building on the shortcomings of widely adapted varieties like CS20DK.