Carbon Loss and Germinability, Viability, and Virulence of Chlamydospores of Fusarium solani f. sp. phaseoli After Exposure to Soil at Different pH Levels, Temperatures, and Matric Potentials

Abstract

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.