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Title: The impact of weather conditions on response of sorghum genotypes to anthracnose (Colletotrichum sublineola) infection

item Prom, Louis
item PERUMAL, RAMASAMY - Kansas State University
item ISAKEIT, THOMAS - Texas A&M University
item RADWAN, GHADA - Texas A&M University
item ROONEY, WILLIAM - Texas A&M University
item MAGILL, CLINT - Texas A&M University

Submitted to: American Journal of Experimental Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/8/2014
Publication Date: 4/1/2015
Citation: Prom, L.K., Perumal, R., Isakeit, T., Radwan, G., Rooney, W., Magill, C. 2015. The impact of weather conditions on response of sorghum genotypes to anthracnose (Colletotrichum sublineola) infection. American Journal of Experimental Agriculture. 6(4):242-250.

Interpretive Summary: Anthracnose is one the most common fungal diseases of sorghum and can cause yield losses of up to 100% in infected fields. Weather conditions are important factors in determining the growth and spread of the anthracnose fungus within a sorghum field. Therefore, effective and accurate evaluation of sorghum for resistance to anthracnose may depend upon testing under optimal conditions for disease establishment. To test the effectiveness of disease resistance screening under varying environmental conditions, we screened the same materials in replicated tests under dry and wet growing conditions. Our work showed that the amount of rain, frequency of rainfall, and relative humidity were important factors in the development of the disease in the field. Thus, to accurately identify anthracnose disease resistance sources, testing should occur under reliable environmental conditions.

Technical Abstract: Rainfall is a major climatic factor influencing anthracnose development and in this study, 68 sorghum accessions were evaluated for anthracnose resistance under dry and wet growing conditions at the Texas A&M Agricultural Experiment Station, near College Station, Texas. Accessions, planted in a randomized complete block design with three replications, were inoculated with a mixture of Colletotrichum sublineola isolates 30 days after planting. Under dry growing conditions, three accessions showed a susceptible response across replications, whereas 41 accessions exhibited susceptibility under wet growing conditions. Also, 15 accessions that showed variation in susceptibility across replications under dry conditions were rated as susceptible across replications under wet growing conditions. Nineteen accessions consistently showed a resistant response under both dry and wet growing conditions. There was no significant correlation between weather variables and anthracnose development during the dry growing season, suggesting unfavorable climatic conditions for disease development. In contrast, there was a significant positive correlation between total rainfall and anthracnose infection, and moderately significant relationships between number of days with rain and minimum relative humidity, with anthracnose infection during wet growing conditions. These results would indicate that cumulative rainfall, frequency of rainfall, and relative humidity are critical factors for disease development.