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.

大豆（Glycine max）是巴西经济的重要商品。然而，截头炭疽菌被认为对降低大豆种子的发芽和活力起重要作用。本研究旨在确定病原体生长的最佳温度，以验证在受控条件下不同种子接种电位对大豆种子萌发和病原体发生率的影响。我们评估了改良马铃薯葡萄糖琼脂在 18、21、24、27 和 30 °C 下的最大菌丝生长。对于接种物潜力评估，在病原体生长的最佳温度下，将种子暴露于病原体 0、24、48、72 和 96 小时。发现测试菌株的最大菌丝生长温度范围为 27.0-29.3°C。随着接种物潜力的增加，观察到大豆种子的发芽百分比降低。C. truncatum的发病率在 48 小时的暴露时间内，种子中的含量为 100%。本研究概述了使用具有高接种潜力的大豆种子的风险，因为暴露于病原体的时间越长，对种子萌发的负面影响越严重，大豆种子中截顶状孢霉的发生率越高。