Genetic Gain in Grain Yield Potential and Associated Agronomic Traits in Haricot Bean (Phaseolus vulgaris L.)

Abstract

A yield potential experiment was conducted with 16 haricot bean varieties (10 released and 6 elite lines) developed by Ethiopian bean breeding program from 1972 to 1998 along with one local check (farmers’ variety). The objectives were to understand the genetic gain made in grain yield potential and to determine changes produced on agronomic traits associated with genetic yield potential improvement. The varieties were evaluated in RCB design at Awassa Agricultural Research Center experimental field to estimate the genetic gain in grain yield and the other fifteen agronomic traits. The analysis of variance revealed significant difference among varieties for all traits except the harvest index. The overall increase in grain yield over the local check, Red Wolayta, was estimated to be 1,604 kg/ha (82.4%). Based on the regression analysis, the estimated average annual rate of increase in grain yield potential was 69.45 kg/ha/year with an annual relative genetic change of 3.24%/year. Genotypic change was an important source of increased grain yield potential during the period studied. Absence of plateau indicated a possibility of further progress in grain yield using the same procedure, i.e. developing varieties from introduced germplasm. Correlation analysis indicated that grain yield was positively correlated with yield per plant, biomass yield, the number of seeds per plant, seed growth rate, grain yield per day and biomass production rate. The stepwise regression analysis showed that biomass yield was greatly contributed to the variation among the varieties in grain yield. Improvement for high grain yield was potential in haricot bean occurred over the past 26 years, in part, by grain yield improvement per se. However, the improvement was also associated with paralleled increase in biomass yield, the number of seeds per plant, seed growth rate, grain yield per day and biomass production rate.