QTL mapping and molecular characterization of the sugarcane aphid [Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae)] resistance gene in sorghum [Sorghum bicolor (L.) moench]

Abstract

Sorghum [Sorghum bicolor (L.) Moench] is the fifth most important cereal crop in the world. Sugarcane aphid, Melanaphis sacchari (Zehntner), is a new invasive pest of sorghum species in North America, which causes severe damages and significant yield loss to sorghum crop. The first objective of this research project focused on the genetic basis of the host plant resistance to sugarcane aphid in sorghum. Molecular mapping was used to analyze an F2:3 mapping population of sorghum developed by crossing susceptible cultivar BTx623 and sugarcane aphid resistant source Tx2783, led to the identification of quantitative trait loci (QTL) linked to sugarcane aphid resistance in sorghum. One major QTL was identified on chromosome 6 of sorghum and this locus accounted for a large portion of phenotypic variation observed for plant responses to sugarcane aphid infestation. SSR markers linked to this region were developed as a tool for marker-assisted selection in future breeding programs for genetic improvement of sugarcane aphid resistance in sorghum. The second objective of this study aimed at identifying and characterizing candidate genes against this pest. For this purpose, functional genomics and DNA sequencing were used to analyze the potential candidate genes in this region and the resulted molecular data allowed the identification of the first sugarcane aphid resistance gene of sorghum. In summary, discovery of the sugarcane aphid resistance gene and development of DNA markers linked to the sugarcane aphid resistance will contribute both the resistance gene and DNA markers for further genetic studies of the resistance mechanism as well as an efficient selection tool for breeding sugarcane aphid resistance in sorghum.