Genotype x environment interactions in climbing bean cultivars in monoculture and associated with maize

Interactions of genotypes of indeterminate, climbing beans (Phaseolus vulgaris L.) with planting system and cropping season were evaluated at the CIAT location in Colombia, 1,000 m elevation and 4 degree N lat. Since most climbing beans in Latin America are grown in association with maize (Zea mays L.), the objective was to determine whether selection of beans in monoculture would be a valid approach to genetic improvement. Climbing bean cultivars were tested in monoculture and associated with maize in three seasons in 1975 and 1976. Significant correlations for yield were obtained for the cultivars tested in association with maize and in monoculture in two seasons (r=0.90, r=0.81). Bean yields averaged 2,200 kg/ha in monoculture and 680 kg/ha in association over three seasons, with coefficients of variation of 15.2 and 22.5 percent, respectively. Higher yields, more precise evaluation of differences among cultivars, and significant positive correlations with associated crop yields favor the monocrop system as most efficient for early generation selection and testing of climbing beans. Season X cultivar interactions in both planting systems could complicate selection for broad adaptation and confident early generation selection in a breeding program. This early selection should concentrate on qualitative traits such as disease and insect resistance, seed color, and desired maturity, with decisions on yield potential delayed until replicated trials in more than one season or more than one location provide adequate evaluation of yield. eng