Isolating QTL controlling sugarcane leaf blight resistance using a two-way pseudo-testcross strategy

Abstract

Sugarcane leaf blight (SLB), caused by Stagonospora tainanensis, is one of the most harmful fungal diseases, threatening the sugarcane industry and causing high losses of cane yield and sugar in susceptible cultivars. Using a two-way pseudo-testcross mapping strategy in combination with array genotyping, two high-density genetic maps were constructed for sugarcane cultivars YT93-159 and ROC22 with mean densities of respectively 3.0 and 3.5 cM per marker, and covering respectively 4485 and 2720 cM of genetic distance. The maps showed highly conserved colinearity with the genome of the ancestral species Saccharum officinarum, supporting the reliability of the linkage configurations of the maps. Quantitative trait loci (QTL) analysis of SLB resistance revealed six QTL (qSLB-1–qSLB-6). The major QTL qSLB-1 explaining 16.4% of phenotypic variance was assigned as the main QTL, and the total percentages of phenotypic variance explained in YT93-159 and ROC22 were 37.9% and 17.6%, respectively. Nine transcription factor and seven pathogen receptor genes lying in the qSLB-1 interval were highly expressed and are proposed as candidate causal genes for SLB resistance.

Keywords

• Sugarcane
• Genetic map
• Leaf blight
• QTL mapping
• Causal gene