Early generation testing of common bean (Phaseolus vulgaris L.) populations in sole crop and in maize/bean intercrop

Few plant-breeding studies have examined methodology for improving common b ean (Phaseolus vulgaris L.) yields by selecting in an intercrop situation. We hypothesized that early-generation testing would be as useful in a maize (Zea mars L.)/bean intercrop as in sole crop for identifying superior bean populations for yield. F-2 to F-5 bulks of six selected crosses and their F-5-derived advanced lines were evaluated in sole crop or intercrop. The F- 2 and F-5 bulks were evaluated together in a preliminary trial in one locat ion, while the advanced lines were evaluated with the F(3)s in one location , and with the F(4)s in two locations. Within sole crop, selection of the b est three populations, based on F-2 performance, provided 67% of the top ad vanced lines. The rank correlation between average bulk yield across genera tions and the average line yield was positive and significant. Within inter crop, selection of the best three populations provided 56% of the top advan ced lines. The rank correlation between advanced line yield and bulk yield across generations was positive but not significant. Also, the top three F- 2 populations selected in sole crop produced 89% of the top advanced lines in intercrop. Advanced line performance showed a positive significant corre lation with mean F-4 bulk performance for grain yield, 100-seed weight and seeds per pod within sc,le crop, while positive significant correlation was seen with pods per plant and seeds per pod in intercrop. Results indicate that F-2 bulk yields can be used to discard the least promising crosses in both cropping systems.