WHITE-MOLD AVOIDANCE AND AGRONOMIC ATTRIBUTES OF UPRIGHT COMMON BEANSGROWN AT MULTIPLE PLANTING DENSITIES IN NARROW ROWS

The putative yield advantage associated with growing upright beans (Ph aseolus vulgaris L.) at high planting densities in narrow (0.23-m) row s might be compromised by a higher risk of white mold [Sclerotinia scl erotiorum (Lib.) de Bary] because of reduced air flow through the crop canopy, This four-year study was undertaken to compare the white-mold avoidance and agronomic attributes of upright bean lines and to deter mine whether their yields can be increased by raising planting density . Four upright lines and a viny line as a control were established in narrow rows at planting densities ranging from 25 to 60 plants/m(2) in a field artificially infested with sclerotia of S. sclerotiorum. On a verage, the four upright lines had lower incidence of white mold and s maller disease severity indices than the control, 'UI36', indicating t hat the development of white mold is reduced in dense, erect canopies. There were differences in disease response among the upright lines, w ith 'ISB82865' and 'UI906' being the least and most susceptible entrie s, respectively. Increases in planting densities resulted in higher yi elds and influenced the development of white mold but had no effect on vine length, lodging, and maturity. However, the planting density eff ect on the disease response was not consistent among entries in 2 of t he 4 years, The results of this study indicate that upright beans can be grown at high planting densities without greatly increasing the ris k of a white-mold outbreak, The choice of the most appropriate plantin g density for upright beans depends largely on the cost of seed.