Dry Bean and Anthracnose Development from Seeds with Varying Symptom Severity.

Anthracnose, caused by the fungal pathogen Colletotrichum lindemuthianum, is a damaging seed-transmitted disease of dry beans that causes reduced seed quality and yield. Seed-to-seedling transmission of C. lindemuthinum has been documented as high as 15% in asymptomatic seeds under greenhouse conditions. Increasing pathogen colonization in seeds has been correlated with increasing anthracnose seed symptoms via qPCR, but stem colonization has not been quantified. Previous studies also have characterized seed yield and quality losses due to planting C. lindemuthinum infected seeds, but none evaluated the effect of growing asymptomatic seeds on disease and plant development under field conditions. The real-time qPCR assay developed in this study and used to detect C. lindemuthianum in the stems of seedlings as early as 15 days after planting, the first date evaluated. Field trials measured the seed-to-seedling transmission of C. lindemuthianum across levels of anthracnose symptoms in seeds ranging from healthy to severely discolored. Results from these two field trials indicated that emergence and yield decreased and foliar symptoms, pathogen detection, and incidence of symptoms on progeny seeds increased as the severity of infection in planted seeds increased. In both years, planting asymptomatic seeds resulted in higher anthracnose severity than planting healthy seeds. Yield, seed weight and incidence of symptoms on progeny seeds were not increased in asymptomatic seeds over healthy seeds in 2014 where moderate disease pressure was observed. However, these factors were significantly different in 2015 where anthracnose severity was driven up to 75% by conducive weather conditions. This serves as a strong warning to growers that planting seed grown in a field where anthracnose was present, even if those seeds are asymptomatic, can result in yield and quality losses. Planting certified dry bean seed is always recommended.