Effect of temperature on Colletotrichum truncatum growth, and evaluation of its inoculum potential in soybean seed germination

Abstract

Soybean (Glycine max) is an important commodity for the Brazilian economy. However, Colletotrichum truncatum is considered to play a significant role in reducing germination and vigor of soybean seed. This study aimed to determine the optimal temperature for pathogen growth, to verify the effect of different seed inoculum potentials in soybean seed germination and pathogen incidence under controlled conditions. We evaluated the maximum mycelial growth on modified potato dextrose agar at 18, 21, 24, 27, and 30 °C. For inoculum potential assessment, the seeds were exposed to the pathogen for 0, 24, 48, 72, and 96 h under the optimal temperature of pathogen growth. It was found that the maximum mycelial growth temperature ranged from 27.0–29.3 °C among strains tested. A decrease in the germination percentage of soybean seeds was observed as inoculum potential increased. The incidence of the C. truncatum in the seeds was 100% at 48 h exposure time. This study provides an overview of the risk of using soybean seeds with high inoculum potential, since longer exposure times to the pathogen led to more serious negative effects on seed germination and a higher incidence of the C. truncatum in the soybean seeds.