Seed size and seed growth rate in relation to cotyledon cell volume and number in common bean

Abstract

Seed yield is negatively associated with cultivar seed size in common bean ( Phaseolus vulgaris L.). Large-seeded cultivars are predominantly from the Andean center of origin while small-seeded cultivars are from the Mesoamerican center. The objective of this study was to determine the relationship of cotyledon cell number and individual cell volume to seed size and seed growth rate (SGR) in common bean, and to examine the basis for a previously reported decline in seed size and SGR for large-seeded Andean lines when grown in warm environments. Crop growth analyses were conducted with 16 lines of common bean in Palmira (965 m elevation, warm) and Popayan (1850 m elevation, cool), Colombia, and mature seed size, cotyledon cell number and volume per cell were determined. SGR (dry matter basis) increased with both increasing cell number per seed and increasing cell volume. Growth rate per cell was linearly related to cell volume at both sites. The association of large cell size with Andean background was the dominant factor responsible for large seed size and rapid SGR of Andean genotypes. The smaller seed size and SGR of Andean lines at the warmer site appeared to be a result of smaller cell number without compensating increases in cell volume or cell growth rate.