Chlamydospore concentration for assessment of Fusarium root rot on common bean

Fusarium root rot caused by Fusarium solani f. sp. phaseoli (Fsp) is widely distributed in Latin America. Experiments involving artificial inoculations could be better compared whether the number of Fsp infective propagules is well quantified by using chlamydospores. This study aimed to define the adequate concentration of chlamydospores of Fsp for assessment of the disease severity under controlled conditions. In greenhouse, two experiments were performed, where common bean susceptible genotypes were sown in a substrate infested with 0, 1000, 2000, 3000, 4000, 5000 or 6000 chlamydospores g-1 of substrate. Plants were rated for disease severity at 30 d after emergence. Linear response plateau was used to represent the relationship between disease severity and concentration of chlamydospores in the substrate. According to our results, concentrations between 4500 and 5000 chlamydospores g-1 of substrate maximizes the disease severity and can be recommended to evaluate large-scale screenings of bean germplasm.