Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2011
Publication Date: May 30, 2012
Citation: Erpelding, J.E. 2012. Anthracnose resistance in sorghum germplasm from the Segou Region of Mali. Journal of Crop Improvement. 26(3):397-414. Interpretive Summary: Anthracnose is one of the most destructive fungal diseases of sorghum. In the United States, the disease has been successfully managed using resistant varieties; however, the pathogen can undergo rapid genetic changes resulting in a loss of resistance, which requires the identification of new sources of resistance for the development of improved sorghum varieties. Germplasm collections have been used as the primary source of new resistance genes. Africa is an important source of genetic diversity for sorghum and the germplasm collection from the Segou region of Mali was evaluated for anthracnose resistance at the USDA-ARS Tropical Agriculture Research Station farm in Isabela, Puerto Rico. Twenty-one of the 59 germplasm lines included in the experimental evaluation showed resistance when challenged with the disease. These resistant lines represent new sources of resistance for sorghum improvement. Within the Segou region, germplasm from the southern administrative districts that receive higher annual rainfall were more frequently rated as resistant compared to germplasm from the drier, northern district. With nearly 45,000 germplasm lines in the USDA-ARS sorghum collection, these results would indicate that the geographic location where the seed sample was collected could be used to target germplasm lines from specific region for disease evaluation. Screening germplasm from these specific regions of Africa could increase the likelihood of identifying new and diverse sources of anthracnose resistance. One of the best methods to prevent the loss of resistant varieties as the pathogen undergoes genetic changes is to combine several new and diverse resistance genes into a single sorghum variety. To increase the diversity of resistance genes available to researchers in order develop these improved sorghum varieties, anthracnose evaluations of the germplasm collection will need to continue and geographic locations within Africa where anthracnose resistant germplasm is more frequently identified should be the source of germplasm for these evaluations.
Technical Abstract: Sorghum germplasm from Mali is an important source of anthracnose resistance and 59 accessions from the Segou region were inoculated with Colletotrichum sublineolum and evaluated for anthracnose resistance to determine the prevalence of resistant accessions from this region. Disease evaluations were conducted at the Tropical Agriculture Research Station in Isabela, Puerto Rico, during the 2005 and 2009 growing seasons. Twenty-one accessions were rated as resistant across replications and growing seasons and showed reddening of inoculated leaves without acervuli development. These accessions represent new sources of anthracnose resistance for sorghum improvement. Fewer accessions were rated as resistant from the drier, northern Niono district as compared to the San and Segou districts that receive greater annual rainfall suggesting an ecogeographic association. Additionally, susceptible accessions from the Niono district showed higher mean disease severities. Accessions classified as race guinea were more frequently rated as resistant compared to race durra accessions. Mean disease severities were also significantly lower for race guinea accessions. The majority of accessions in the collection were race guinea with most durra accessions collected from the Niono district. However, the frequency of resistant guinea accessions was similar across districts. These results indicate ecogeographic origin and race classification could be used to select accessions for anthracnose screening and to identify regions were resistance is more prevalent for the acquisition of additional anthracnose resistant germplasm.