Sequencing of an Anthracnose-Resistant Sorghum Genotype and Mapping of a Major QTL Reveal Strong Candidate Genes for Anthracnose Resistance
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Crop Science Society of America. Anthracnose, caused by the fungal pathogen Colletotrichum sublineolum Henn. ex. Sacc. and Trotter 1913, is an economically damaging disease of sorghum [Sorghum bicolor (L.) Moench] in hot and humid production regions of the world. Control of anthracnose is almost exclusively through the use of genetic resistance. To further elucidate genetic resistance to anthracnose, a recombinant inbred line population derived from the cross of BTx623 (susceptible) and SC748-5 (resistant) was created. A linkage map was constructed using 117 F5 individuals that were genotyped using Digital Genotyping, a genotyping-by-sequencing method developed specifically for C4 grasses, on an Illumina GAIIx. The linkage map consists of 619 single nucleotide polymorphism markers and three microsatellites with a total map length of 1269.9 cM. The population was phenotyped for anthracnose in four different environments. Using both composite interval mapping and inclusive composite interval mapping (ICIM), one major quantitative trait locus (QTL) on chromosome 5 was consistently identified as the source of anthracnose resistance in all environments. Sequencing genomic DNA from SC748-5 and comparison to BTx623 genomic sequence revealed numerous amino acid changes in annotated disease-resistance genes located in the area under the anthracnose QTL. This suggests that the genetic architecture for anthracnose resistance in SC748-5 is not under the control of one gene but, more likely, a linkage block containing several resistance genes.