Effects of Soil Moisture and Root Knot Nematode, Meloidogyne hapla (Chitwood), on Water Relations, Growth, and Yield in Snap Bean

Abstract

Abstract Seedlings of the snap bean (Phaselous vulgaris L.), cv. Kentucky Wonder, were inoculated with ≈0, 240, 2400, or 24,000 root knot [Meloidogyne hapla (Chitwood)] nematodes per plant and grown in a sandy soil in the greenhouse at a soil water potential of either −0.025 (high soil moisture) or −0.075 (low soil moisture) MPa. Leaf xylem potential, transpiration, root hydraulic conductivity, and nematode populations in roots, as well as growth and yield data, were collected about 8 weeks after inoculation. Transpiration was reduced by decreasing soil moisture—maximum transpiration occurred about midday at high soil moisture and in the early morning at low soil moisture. Transpiration decreased late in the day with increasing nematode populations at high, but not low, soil moisture. Leaf xylem potential was reduced by low soil moisture and nematodes but interactive effects were not significant. Root conductivity was lower in plants exposed to low soil moisture than in plants maintained at high soil moisture. However, nematodes reduced conductivity in only one of two experiments, and interactive effects were not significant in either experiment. Root and shoot dry weight and leaf area were decreased in response to low soil moisture. Nematodes reduced shoot dry weight and leaf area, but not root dry weight, in one of two experiments and there were no significant interactive effects in either experiment. Total yields of beans were reduced at low soil moisture and in response to nematode inoculum. A significant interactive effect on early bean yield was also evident; nematodes lowered early yields more at high soil moisture than at low soil moisture. These data indicate that although soil moisture and M. hapla populations individually influenced water relations, growth, and yield of bean, the interactive effects were generally not significant. When an interaction could be demonstrated, it was due to a decreased effect of nematodes at low soil moisture.