Reservoir and Non‐reservoir Hosts of Bean‐Wilt Pathogen, Fusarium oxysporum f. sp. phaseoli

Abstract

AbstractThe capacity of Fusarium oxysporum f. sp. phaseoli to multiply in the roots of 12 non‐host plant species was determined with the objective of selecting potential candidates for crop rotation and/or green manuring in infested bean fields. The plants were inoculated at the seedling stage by a benomyl‐resistant mutant of the pathogen using the root‐dip technique and transplanted to natural soil. The number of colony forming units/g dry root tissue (CFU/g) was determined at the full bloom stage. Quantitatively, the root colonization differed greatly among the plant species. The roots and lower stem of Dolichos lablab, Phaseolus lunatus, Mucuna aterrima, Canavalia ensiforme and Vigna unguiculata were the most compatible with the pathogen and those of Sorghum bicolor, Crotalaria juncea, Oryza sativa and Zea mays were least compatible. No disease symptoms developed on any plant species. Chlamydospore germination in the rhizosphere also differed significantly among the plant species. There was no correlation between percentage chlamydospore germination in the rhizosphere and extent of root colonization. Most plant species recommended for green manuring in bean fields allowed extensive root and stem colonization by F. o. f. sp. phaseoli and were considered as reservoir hosts. All three of the gramineous species tested and C. juncea were classed as non‐reservoir host, because the pathogen did not colonize the stem and its multiplication in the roots was very low. These plant species appear to be good candidates for long‐term field evaluation to determine their usefulness in an integrated management of Fusarium bean‐wilt.