Multi-Location and Multi-Year Field Trials Revealed Broad-Spectrum Resistance of Sorghum (Sorghum bicolor (L.) Moench) to Anthracnose (Colletotrichum sublineola)

Abstract

Ethiopia is one of the centers of origin for sorghum (Sorghum bicolor (L.) Moench), where distinct agro-ecological zones have significantly contributed to its genetic diversity. Although the magnitude varies among the country's regions, sorghum production is severely constrained by anthracnose caused by Colletotrichum sublineola, causing significant grain and biomass losses. This study was conducted to identify sorghum landraces grown in Ethiopia with broad-spectrum resistance and to assess the effect of environments on sorghum anthracnose interaction. In the 2022 cropping season, 285 sorghum accessions, the vast majority of which were landraces, were evaluated at five diverse locations, i.e., Assosa, Bako, Chiro, Haramaya, and Pawe in 2015, 2016, and 2022. Accessions were evaluated according to their initial, final, and mean anthracnose severity scores and the area under the disease progress curve. Analysis of variance (ANOVA) revealed significant differences among accessions, locations, and genotype-by-environment interactions. Based on their reaction to the disease, accessions were categorised into different resistance classes. Most of the accessions were susceptible to anthracnose in the western sites of the country (Assosa, Bako and Pawe) than in the eastern part (Chiro and Haramaya). Among the tested accessions, landraces ETSL100267, ETSL100152, ETSL100388, ETSL100090, ETSL100284, ETSL100107, IS38279, and ETSL101249, and the variety Bonsa were resistant across all locations in the 2022 field trials, suggesting that these landraces might harbour genes with broad-spectrum resistance or have accumulated multiple resistance genes. This study provided insights into the sources of anthracnose resistance and how environmental conditions affect it, which is highly useful for breeders to select germplasm to develop anthracnose-resistant sorghum varieties that are suitable for both specific environments and a broad adaptation.