Abstract
Since 2013, the sugarcane aphid (SCA), Melanaphis sacchari (Zehntner), has been a serious pest that hampers all types of sorghum production in the U.S. Our understanding of sugarcane aphid resistance in sorghum is limited to knowledge about a few genetic regions on chromosome SBI-06. In this study, a subset of the Sorghum Association Panel (SAP) was used along with some additional lines to identify genetic and genomic regions that confer sugarcane aphid resistance. SAP lines were grown in the field and visually evaluated for SCA resistance during the growing seasons of 2019 and 2020 in Tifton, GA. In 2020, the SAP accessions were also evaluated for SCA resistance in the field using drone-based high throughput phenotyping (HTP) and visual scoring under greenhouse conditions. Plant height and flowering time were also recorded in the field to confirm that our methods were sufficient for identifying known quantitative trait loci (QTL). This study combined phenotypic data from field-based visual ratings, reflectance data, and greenhouse evaluations to identify genome-wide associated (GWAS) marker-trait associations (MTA) using genotyping-by-sequencing (GBS) data. Several MTAs were identified for sugarcane aphid-related traits across the genome, with a few common markers that were consistently identified on SBI-08 and SBI-10 for aphid count and plant damage as well as for reflectance indices-based traits on SBI-02, SBI-03, and SBI-05. Candidate genes encoding leucine-rich repeats (LRR), Avr proteins, lipoxygenases (LOXs), calmodulins (CAM) dependent protein kinase, WRKY transcription factors, flavonoid biosynthesis genes, and 12-oxo-phytodienoic acid reductase are identified near SNPs that had significant associations with different SCA traits. In this study, plant height and flowering time-related genes were also identified. The total phenotypic variation explained by significant SNPs across SCA-scored traits, plant height, and flowering time ranged from 0 to 74%, while the heritability value ranged from 4 to 74%. These results supported the existing literature, and also revealed several new loci. Markers identified in this study will support marker-assisted breeding for sugarcane aphid resistance.
Sugarcane Aphid Resistance in Pearl Millet
