Spatial Distribution of Seed Yield within Plants of Bean

Seed yield in common bean (Phaseolus vulgaris L.) is subjected to various stresses including high plant populations. Thus, yield may depend on the spatial distribution of vegetative and reproductive structures. This study was initiated to determine the spatial and temporal distribution pattern in terms of main stem and branch node positions of seed yield in four dry bean cultivars: ‘Red Kidney’, ‘Sacramento’, ‘Sutter Pink’, and ‘T-39’. These cultivars were planted at Davis, CA, in the summer of 1983. Each plot was two rows per bed, spaced 76 cm apart, and thinned to an intrarow spacing of 23 cm. Each plot consisted of five randomly selected plants. Beginning at first flower, each flower that opened each day was tagged daily over the next 20 days. The spatial distribution pattern (a result of pods being set at various main stem and branch nodes) of yield showed approximately 70% of the total yield to be in the lower portion of the canopy, i.e., Branches and main stem Nodes 1 to 3 in Red Kidney, Sacramento, and Sutter Pink, and Nodes 1 to 5 in T-39. Considering the branches only, 70% of the total yield was produced on branch Nodes 1 to 3 in Red Kidney, Sacramento, and Sutter Pink, and branch Nodes 1 to 5 in T-39. The main stem yield varied among cultivars, ranging from 7 to 23% of total yield. Distribution of pods at nodes along the main stem varied among cultivars, with those of Red Kidney and Sacramento concentrated at Node 5 or 6 while Sutter Pink and T-39 had pods distributed over a greater portion of the stem and had maximum main stem pod production at Node 6 (Sutter Pink) or 9 to 10 (T-39). Combining spatial and temporal data showed that the percentage of early pods set at a single location was greatest near the main stem and decreased at more distant nodes. The majority of pods produced on the main stem were set during the first 11 days of the reproductive period. Present architecture of the four cultivars tested shows that a large percentage of the yield is located on the lowest branches. Therefore, the development of new cultivars for direct combining higher planting densities will require plant types with more pods on the main stem and/or a major portion produced on the higher branches.