Abstract
Problem statement: Sorghum anthracnose (Colletotrichum sublineolum) is a highly variable pathogen and new sources of host plant resistance are required for the development of resistant sorghum varieties. Germplasm collections are an important source of host plant resistance and screening germplasm will be essential to identify new sources of resistance. Approach: The sorghum (Sorghum bicolor) collection from the Mopti region of Mali was inoculated with Colletotrichum sublineolum and evaluated for foliar anthracnose disease response in Isabela, Puerto Rico during the 2004 and 2005 growing seasons using a partially balanced lattice design with three replications. Results: A resistant response was observed for 45 of the 97 accessions in the collection and mean infection severity for the 52 susceptible accessions was 27.6%. An association was observed between resistance and the administrative district where the germplasm was collected. More than 50% of the accessions from the Bandiagara and Bankass districts showed a resistant response. The lowest frequency of resistant germplasm was observed for the Mopti district with 25% of the accessions showing a resistant response. The susceptible accessions from the Mopti district, however, showed the lowest mean infection severity. Approximately 44% of the accessions from the Douentza district showed a resistant response with the susceptible accessions showing the highest mean infection severity. These results suggest an association between annual rainfall and anthracnose resistance, with sorghum accessions from drier regions showing greater susceptibility. Anthracnose resistance also showed an association with sorghum race classification and race guinea accessions were more frequently resistant as compared to accessions classified as race durra or durra-bicolor. Conclusion: The results indicated that anthracnose resistant sorghum germplasm is frequent in the Mopti region of Mali and that ecogeographic origin and sorghum characterization information can be used to aid in germplasm selection or germplasm acquisition to identify anthracnose resistant sources.
Highlights
Anthracnose is considered one of the most destructive diseases for sorghum (Sorghum bicolor (L.) Moench) production due to the rapid development of the disease on susceptible cultivars
Ninety-seven landraces from the Mopti region of Mali maintained in the NPGS sorghum collection were identified using available passport information and seed samples were obtained from the USDA-ARS Plant Genetic Resources Conservation Unit, Griffin, Georgia
46% of the landraces from the Mopti region showed a resistant response suggesting that this region of Mali could be an important source of anthracnose resistant germplasm
Summary
Anthracnose is considered one of the most destructive diseases for sorghum (Sorghum bicolor (L.) Moench) production due to the rapid development of the disease on susceptible cultivars. The disease occurs worldwide, but is more commonly observed in tropical or subtropical environments where frequent rainfall, high relative humidity and warm temperatures enhance the development and spread of the disease (Casela et al, 2001; Hess et al, 2002; Marley et al, 2001; Néya and Le Normand, 1998; Ngugi et al, 2002; Thakur and Mathur, 2000; Thomas et al, 1996; Valério et al, 2005). Sorghum anthracnose will typically appear on infected leaves approximately 30 to 40 days after seedling emergence; infection can occur at every stage of plant development. Anthracnose infection can be observed on all above ground tissues of the sorghum plant, including the leaf, stalk, panicle and seed (Hess et al, 2002; Thakur and Mathur, 2000).
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