Seasonal dynamics of soil-borne inoculum and severity of Fusarium root rot of common beans affected by sequential planting of legume or cereal crops

Abstract

The seasonal population dynamics of Fusarium solani f. sp. phaseoli (Fsp) in naturally infested soil and the severity of Fusarium root rot were studied. Areas were sequentially planted (2 to 4 sowings) with the same legume crop (common bean, pigeonpea, sunn hemp, and jack bean) or cereal crop (corn, pearl millet and signalgrass) during the year, which were then compared to background bare soil. Counts of colony forming units (CFU) of Fsp populations during 12 sampling times spaced around one month were high at the first sowing and decreased in the bare soil and cereal crops. CFU reached zero after 9 months in the maize and pearl millet plots and after 11 months in the bare soil and signalgrass plots. The count of CFU in the legume plots peaked during the summer and decreased during the winter, in a pattern that followed monthly air temperatures. Disease severity was higher in common bean than in the other crops and tended to increase over time. Planting of legumes should be avoided in infested soil and cereal crops may be an option to reduce and even eradicate inoculum as part of an integrated disease management of Fusarium root rot.