Melon Genome Regions Associated with TGR-1551-Derived Resistance to Cucurbit yellow stunting disorder virus

Abstract

Cucurbit yellow stunting disorder virus (CYSDV) is one of the main limiting factors of melon cultivation worldwide. To date, no commercial melon cultivars resistant to CYSDV are available. The African accession TGR-1551 is resistant to CYSDV. Two major quantitative trait loci (QTLs) have been previously reported, both located near each other in chromosome 5. With the objective of further mapping the gene or genes responsible of the resistance, a recombinant inbred line (RIL) population derived from the cross between TGR-1551 and the susceptible cultivar ‘Bola de Oro’ was evaluated for resistance to CYSDV in five different assays and genotyped in a genotyping by sequencing (GBS) analysis. The major effect of one of the two QTLs located on chromosome 5 was confirmed in the multienvironment RIL assay and additionally verified through the analysis of three segregating BC1S1 populations derived from three resistant RILs. Furthermore, progeny test using the offspring of selected BC3 plants allowed the narrowing of the candidate interval to a 700 kb region. The SNP markers identified in this work will be useful in marker-assisted selection in the context of introgression of CYSDV resistance in elite cultivars.

Advanced Genetic Studies on Powdery Mildew Resistance in TGR-1551

“…On the other hand, the family BC 3 S 1 -146 was also susceptible but it segregated at the position of the marker cysdv63, whereas it was homozygous for the BO allele at the locus cysdv65 (chr5: 26,408,895 bp), narrowing the candidate interval to a region of ~622 kb between markers cysd63 and CMPSNP464 . This same region had been described as related to CYSDV resistance derived from ‘TGR-1551’ [ 44 ].…”

“…These selected plants were also genotyped in the Agena Bioscience platform with the markers set as CYSDV1, which contained 16 additional SNP markers located in chromosome 5 (markers set CYSDV1) [ 44 ] and with the markers sets WMV1 and WMV2 [ 43 ], which had 13 and 3 SNP markers in this region, respectively ( Supplementary Table S2 ) ( Table 1 ). The selfing progenies and BC 4 offspring (10 to 20 plants) of these 20 plants were genotyped with the set of markers CYSDV1 and CYSDV2 ( Supplementary Table S2 ) [ 44 ]. Moreover, those plants were genotyped with the previously developed HRM markers cysdv63 and cysdv65 [ 44 ].…”

“…The selfing progenies and BC 4 offspring (10 to 20 plants) of these 20 plants were genotyped with the set of markers CYSDV1 and CYSDV2 ( Supplementary Table S2 ) [ 44 ]. Moreover, those plants were genotyped with the previously developed HRM markers cysdv63 and cysdv65 [ 44 ]. These generations were used to finely map the regions associated with resistance.…”

“…The candidate region also includes the virus aphid transmission resistance gen ( Vat ) (ten of the predicted genes are annotated as “Vat protein”) [ 45 ] carried by TGR-1551 [ 61 ]. Moreover, the resistance to CYSDV derived from TGR-1551 has been mapped in the same region [ 44 ], which would explain why—while developing a resistant line to CYSDV—the selected plants resulted in being resistant to Px and Aphis gosypii as well, even though no previous selection against the fungus nor the aphid had been made [ 62 ].…”

RNA-Seq Transcriptome Analysis Provides Candidate Genes for Resistance to Tomato Leaf Curl New Delhi Virus in Melon

“…In addition, we identified other DEGs implicated in virus resistance distributed over the melon genome, most of them located in clusters at chromosomes 1, 5, and 9. The two largest NBS-LRR gene clusters in melon are located at chromosomes 5 and 9, where resistance to other cucurbit viruses has been mapped ( Morata and Puigdomènech, 2017 ; Pérez-de-Castro et al, 2020 ). Chromosome 5 not only includes differentially regulated pathogenesis and R genes, but also lipoxygenase hormone biosynthesis genes induced in WM-7 and downregulated in PS.…”