Melon Team | 2023 Progress Report

cuccap

View the PDF version of this 2023 CucCAP Melon Team Report.

Team members:

  • Jim McCreight (USDA, ARS)
  • Shaker Kousik (USDA, ARS)
  • Pat Wechter (USDA, ARS)
  • Bill Wintermantel (USDA, ARS)

CucCAP Affiliated Postdocs and Graduate Students

  • Shaonpius Mondal, USDA-ARS, Salinas (McCreight, Wintermantel)
  • Venkata Rao Ganaparthi- PhD Candidate (Wechter & Branham)

Map and develop markers for disease resistance

QTL mapping of resistances

  • Powdery mildew, Ph, Q, F. Completed QTL mapping in the MR-1xAY RIL population and narrowed the QTL intervals by adding KASP markers to the GBS data. Developed KASP markers for two major QTL and validated them in a set of unrelated cultivars population.
  • Fusarium, Ph, Q, F. Completed QTL mapping in the MR-1xAY RIL population and narrowed the QTL intervals by adding KASP markers to the GBS data. Developed KASP markers for the single major QTL for races 1 and 2 and validated them in a set of unrelated cultivars. population.
  • Downy mildew, Ph, Q, F. Completed QTL mapping in the MR-1xAY RIL population and narrowed the QTL intervals by adding KASP markers to the GBS data. Developed KASP markers for the major QTL. Manuscript accepted in Theoretical and Applied Genetics.
  • Powdery mildew: The F2:3 PI 313970 x Top Mark developed in CA will be planted in a greenhouse at Charleston in November to evaluate for resistance to powdery mildew.
  • downy mildew
  • CYSDV: Two QTL for resistance in were found in F2:3 PI 313970 x Top Mark, on chromosomes 3 and 5. The QTL on chromosome 5 was observed in naturally infected field tests in 2018 and 2019, and explained 16 % and 35 % of the variation in CYSDV titer, respectively. The QTL on Chromosome 3 explained 20 % of virus titer variation in 2018 but was undetected in 2019 (Tamang et al. 2021). Single gene recessive, Mendelian resistance was previously reported in PI 313970 (McCreight and Wintermantel, 2011).

Eight F2:3 lines with low virus titer as determined by RT-qPCR (Mondal et al. 2023) resembled PI 313970 for the two flanking markers, which can, therefore, be utilized in marker assisted breeding of CYSDV-resistant melons. The eight F2:3 lines were evaluated to date for resistance reaction in a controlled inoculation, growth chamber test. The lines segregated for resistance reactions and flanking markers. Some of the high-titer plants (low CT value) were frequently asymptomatic or exhibited mild yellowing. Low-titer plants with one or both PI 313970 markers and asymptomatic/mild symptoms been advanced to next generation.

Marker development and verification

  • Powdery mildew, M, V. KASP markers for powdery mildew race 1 resistance were developed in the MR-1xAY RIL population and were validated with a set of commercial cultivars.
  • Fusarium, M, V. KASP markers for Fusarium wilt races 1 and 2 resistance were developed in the MR-1xAY RIL population and were validated with a set of commercial cultivars.
  • Downy mildew, M. KASP markers for Fusarium wilt races 1 and 2 resistance were developed in the MR-1xAY RIL population. Manuscript accepted in Theoretical and Applied Genetics.
  • CYSDV: see above

Introgress, pyramid/stack resistances into advanced breeding lines
Melon

  • Fusarium wilt races 1 and 2/Powdery mildew race 1, B,I,A. Using KASP markers developed under this project and a backcross/ phenotype/genotype strategy, we are currently making seed for BC2F3 populations from the three-way cross of [Top Mark x Majik Melon (resistance donor) x Charentais]. Selections have been made in the early phases of the project for a Charentais-type line and a Top Mark-type line with subsequent backcrosses to either Charentais or to Top Mark. Current lines have high brix, firm flesh, powdery mildew race 1 resistance, sulphur tolerance, and Fusarium race 1 and 2 resistance.
  • CYSDV: see 2.1.2 above

Figure 1. Development of varieties resistant to multiple diseases in the PDF version of this report.

View Figure 1. on page 36 of the PDF version of the 2023 CucCAP Melon Team Report.

Literature Cited

  • McCreight, J.D. and W.M. Wintermantel. 2011. Genetic resistance in melon PI 313970 to Cucurbit yellow stunting disorder virus. HortScience 46:1582–1587.
  • Mondal, S., L. Jenkins Hladky, and W.M. Wintermantel. 2023. Differential seasonal prevalence of yellowing viruses infecting melon crops in southern California and Arizona determined by multiplex RT-PCR and RT-qPCR. Plant Dis. DOI: 10.1094/PDIS-06-22-1512-RE
  • Tamang, P., K. Ando, W.M. Wintermantel, and J.D. McCreight. 2021. QTL mapping of Cucurbit yellow stunting disorder virus resistance in melon accession PI 313970. HortScience 56:424–430. DOI: 10.21273/HORTSCI15495-20.