Yield‐Determining Processes in Relation to Cultivar Seed Size of Common Bean

Abstract

Cultivar seed size and yield potential of common bean (Phaseolus vulgaris L.) are negatively associated. Large‐seeded cultivars are predominately of Andean background, while small‐seeded cultivars are predominately of Mesoamerican background. Crop growth analyses were conducted to examine the association of cultivar seed size with crop growth rate (CGR), seed growth rate (SGR) on a land‐area basis, intensity of partitioning to seed (land‐area SGR divided by CGR), and effective seed‐filling period. Sixteen cultivars, ranging in seed size from 190 to 540 mg seed−1, were grown at two sites in Colombia at elevations of 1000 m (warm) and 1800 m (cool). The seed size groups did not differ in CGR at either site. At the warmer site, the small‐seeded Mesoamerican lines had greater mean partitioning to seed (1.29 vs. 0.97 for the Mesoamerican and Andean lines, respectively), greater land‐area SGR (11.7 vs. 8.3 g m−2 d−1), and higher yield ( 2030 vs. 1750 kg ha−1) than did the large‐seeded Andean lines. At the cool site, the seed size groups did not differ in any of these variables. At both sites, the Mesoamerican lines flowered ≈6 d later and acquired more total N than did the Andean lines. It is postulated that the greater land‐area SGR and yield of the Mesoamerican lines at the warmer site was due to their greater accumulation of N, which allowed them to sustain greater rates of canopy photosynthesis during seed‐filling.