Greenhouse evaluation of a representative subset of the three mapping populations against nine pathotypes found that lines susceptible in the field could be resistant to a single pathotype in the greenhouse. In contrast, anthracnose resistant response in lines Qе…ѓ and IS18760 is controlled by multiple small-effect genes. The latter gene belongs to a family of genes encoding F-box proteins indicating that this resistance response involved in signaling cascades and transcriptional reprograming, rather than recognition of pathotype-associated molecular patterns. Segregation analysis of 1,500 progenies delimited the resistance locus on chromosome 5 to a 23-kb region harboring three candidate genes, including Sobic.005G17230 identified by GWAS of the sorghum association panel (SAP). Anthracnose resistant response in line SC112-14 is controlled by a major locus on chromosome 5. In parallel, three high density recombination maps were constructed and used to identify resistant loci. Over the last three years, our research efforts have been directed to identify new sources of moreВ В» resistance in temperate adapted and tropical germplasm, and to delimited genomic regions associated with the observe anthracnose resistant response.Three biparental mapping populations derived from the resistant lines SC112-14, Qе…ѓ and IS18760 were evaluated for anthracnose resistance response in Texas, Georgia, Florida and Puerto Rico. The most cost-effective and environmentally benign strategy to control anthracnose is through the incorporation of resistance genes. The productivity and profitability of sorghum are limited by several biotic constraints, most notably anthracnose caused by the fungal pathogen Colletotrichum sublineolum. Today, it is of interest as a source of fermentable sugars for the production of renewable fuels and chemicals, and as a source of biomass for co-firing. Sorghum is the fifth most important grain crop behind maize, wheat, rice, and barley.

Further characterization of these regions will facilitate the development of novel germplasm with resistance to anthracnose and other diseases. As observed in other species, sorghum appears to have regions of clustered resistance genes. In addition, genetic analysis following an independent selection experiment of lines derived from a cross between вЂBk7вЂ™ and sweet sorghum вЂMer81-4вЂ™ narrowed the resistance locus on chromosome 9 substantially, validating this QTL. Both loci contain multiple classes of defense-related genes based on sequence similarity moreВ В» and gene ontologies. Segregation data and association analysis identified resistance loci on chromosomes 7 and 9, with the resistance alleles derived from вЂBk7вЂ™. Following a stringent custom filtering protocol, totals of 51 informative SNP markers were identified in the two populations. The population was genotyped by sequencing. Lines were phenotyped in three environments and in two different years following natural infection. To identify anthracnose resistance loci present in the highly resistant cultivar вЂBk7вЂ™, a biparental mapping population of F 3:4 and F 4:5 sorghum lines was generated by crossing вЂBk7вЂ™ with the susceptible inbred вЂEarly Hegari-SartвЂ™.

Resistance to anthracnose is, therefore, of paramount importance for successful sorghum production in this region. In the southeastern United States the acreage of sorghum has been increasing steadily in recent years, spurred by growing interest in producing biofuels, bio-based products, and animal feed. Sorghum, the fifth most widely grown cereal crop in the world, can be highly susceptible to the disease, most notably in hot and humid environments.

The obvious symptoms of anthracnose are leaf blight and stem rot. Colletotrichum sublineola is an aggressive fungal pathogen that causes anthracnose in sorghum.

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