QTL Mapping for Gummy Stem Blight Resistance in Watermelon (Citrullus spp.)

Area of Science:

• Plant genetics
• Plant pathology
• Agricultural science

Background:

• Gummy stem blight (GSB) significantly impacts watermelon (Citrullus lanatus) cultivation globally.
• Developing GSB-resistant watermelon varieties is crucial for crop yield and economic viability.

Purpose of the Study:

• To identify quantitative trait loci (QTLs) associated with gummy stem blight resistance in watermelon.
• To develop high-throughput markers for selecting GSB-resistant watermelon.

Main Methods:

• An F2 population was created from susceptible (C. lanatus) and resistant (C. amarus) watermelon lines.
• Genetic linkage map constructed (1070.2 cM) to analyze QTLs for leaf lesion (LL) and stem blight (SB) resistance.
• QTL analysis identified resistance loci on chromosomes 8 and 6.

Main Results:

• Two major QTLs (qLL8.1, qSB8.1) on chromosome 8 explained 10.5% and 10.0% of phenotypic variation for LL and SB, respectively.
• A minor QTL (qSB6.1) on chromosome 6 explained 9.7% of SB variation.
• Four candidate genes associated with GSB resistance were predicted on chromosome 8.

Conclusions:

• QTLs identified provide a foundation for marker-assisted selection of GSB resistance in watermelon breeding.
• Developed markers can be used to select resistant watermelon accessions and commercial cultivars.
• This research facilitates the development of GSB-resistant watermelon cultivars.