QTL mapping of Cucurbit yellow stunting disorder virus resistance in melon accession PI 313970

Authors: Tamang, Prabin; ANDO, KAORI - Former ARS Employee; Wintermantel, William - Bill; McCreight, James - Jim

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2020
Publication Date: 2/18/2021
Citation: Tamang, P., Ando, K., Wintermantel, W.M., McCreight, J.D. 2021. QTL mapping of Cucurbit yellow stunting disorder virus resistance in melon accession PI 313970. HortScience. 56(4):424-430. https://doi.org/10.21273/HORTSCI15495-20.
DOI: https://doi.org/10.21273/HORTSCI15495-20

Interpretive Summary: Cucurbit yellow stunting disorder virus (CYSDV) is a devastating viral disease of melon in that can cause significant yield and quality losses. This disease emerged in 2006 as a major concern in the desert southwest United States and is a major problem in many melon growing regions across the world. Co-infection by Cucurbit chlorotic yellow virus (CCYV) was recognized in 2018 but its importance remains largely unknown. Host plant resistance to these viruses is an economical and effective way to manage them. A F2:3 population was developed from a cross of ‘Top Mark’ (susceptible to both viruses) with PI 313970 (resistant to CYSDV but susceptible to CCYV). Phenotypic data (foliar yellowing) from both years were not useful for mapping CYSDV resistance quantitative trait loci (QTL) for resistance to CYSDV due to uniform yellowing symptoms from co-infection by both viruses. Analysis of the relative titer of CYSDV identified one QTL for CYSDV resistance on chromosome 3 that explained 20 % of virus titer variation in 2018 but was undetected in 2019. A QTL on chromosome 5 was identified in 2018 and 2019 that explained 16% and 35% of the variation in CYSDV titer, respectively. Markers flanking this 2019 QTL were developed and can be utilized in marker assisted breeding of CYSDV-resistant melons. One or both of the markers were present in six of 10 other putative CYSDV resistance sources.

Technical Abstract: Cucurbit yellow stunting disorder virus (CYSDV) is a devastating viral disease of melon that can cause significant yield and quality losses. This disease has recently emerged as a major concern in the Southwest United States and is a major problem in many melon growing regions across the world. Co-infection of melon by Cucurbit chlorotic yellow virus (CCYV) was recognized in Imperial Valley and neighboring production areas of California and Arizona in 2018 but its importance remains largely unknown. Identifying and deploying resistance from elite germplasm is an economical and effective way to manage the disease. A F2:3 population was developed from a cross of susceptible ‘Top Mark’ with CYSDV-resistant PI 313970, which was shown to possess a single recessive gene for resistance to CYSDV. Both parents are susceptible to CCYV. The F2:3 population was phenotyped in the field in response to natural, mixed infections by two viruses, CYSDV and CCYV in the Fall melon seasons of 2018 and 2019. Phenotypic data (foliar yellowing) from both years were not useful for mapping CYSDV resistance QTL, as PI 313970 and CYSDV-resistant F2:3 plants exhibited yellowing symptoms from CCYV co-infection. QTL analysis of the relative titer of CYSDV calculated from RT-qPCR data identified one locus on chromosome 3 at physical location of S5-28,571,859 bp that explained 20 % of virus titer variation in 2018 but was undetected in 2019. A locus on chromosome 5 between S5-20,880,639 to S5-22,217,535 bp explained 16 % and 35 % of the variation in CYSDV titer in 2018 and 2019, respectively. One or both of the markers were present in six of 10 other putative CYSDV resistance sources. Markers flanking this 2019 QTL were developed and can be utilized in marker assisted breeding of CYSDV-resistant melons.