Laboratory of Plant Disease Science, United Graduate School of Agricultural Science, Gifu University, Japan
14C-labeled chlamydospores of Fusarium solani f. sp. phaseoli were exposed to soil at 5, 15, 25, or 30°C at pH 5 or 8 and water potential of -1 kPa or to soil at 0, -1, or -10 kPa at 25°C at pH 6.9. Total carbon loss was greatest at 25 or 30°C at pH 8 and -1 kPa. 14CO2 from respiration of chlamydospores and from soil microbes utilizing chlamydospore exudates accounted for the largest share of total carbon loss under all conditions. 14(CO)2 from soil microbial metabolism of 14CO2 exudates of chlamydospores was greatest in soil at 15, 25, and 30°C, pH 8, and at either -1 or -10 kPa. Chlamydospore germinability in the absence of a C source (nutrient independence), viability in potato-dextrose broth, and virulence to kidney bean declined rapidly after exposure to soil at high temperatures (25 and 30°C), pH 8, and the higher matric potentials (0 to-1 kPa). By contrast, germinability remained high (>50%), as did virulence, in soil at 5°C and -10 kPa even after 70 days of incubation. Carbon loss was inversely correlated with germinability, viability, and virulence after exposure to soil at different pH levels, temperatures, and matric potentials.