View all tables and figures in pages 37 – 40 of the pdf version of this report.
Melon 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)
- Prabin Tamang, postdoc, USDA-ARS, Salinas (McCreight, Wintermantel)
Obj. 2. Map and develop markers for disease resistance
2.1.2 QTL mapping of resistances – Melon
Powdery mildew, Ph, Q, F
- 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.
- 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. Branham et al. 2021.
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. Branham et al. 2018.
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. Toporek et al. 2023.
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). One or both of the two markers flanking the gene on Chromosome 5 were present in six of 10 other putative CYSDV resistance sources. Eight F2:3 lines with low virus titer resembled PI 313970 for the two flanking markers, which can, therefore, be utilized in marker assisted breeding of CYSDV-resistant melons.
One of the eight F2:3 lines with low virus titer in 2019 has been evaluated to date for resistance reaction in a controlled inoculation, growth chamber test. Plants will be selfed and backcrossed with CYSDV-susceptible ‘Top Mark’. The other seven F2:3 families are in preparation for screening. Testing was initially delayed due to a permit modification issue, but is now in progress. QTL mapping of these lines will be evaluated concurrently with evaluation of resistance reactions.
New virus threat to Cucurbit production: It should be noted that during the spring and fall of 2023, changes were observed in the prevalence of CCYV during the spring melon season in the lower desert region of Arizona. CCYV has been the dominant yellowing virus in spring melons since its establishment in the desert, whereas CYSDV has been the dominant yellowing virus during the fall season (Mondal et al., 2023). In contrast to recent years, CYSDV dominated spring yellowing of melons grown in the Yuma region in 2023, whereas the adjacent Imperial Valley production region had a more typical pattern, with infections dominated by CCYV. This was followed by the identification of a new virus, watermelon chlorotic stunt virus (WmCSV) in fall 2023 in the Yuma production region as well as in adjacent Imperial Valley, CA. Virtually all fall melon plants infected with WmCSV were co-infected with CYSDV, but again, very few plants were infected with CCYV. These changing dynamics in desert production regions warrant further monitoring to determine impact of WmCSV on virus epidemiology, and how this may influence the need for advancement of resistance to this new virus. WmCSV is known to infect all cucurbits, and is particularly severe on watermelon. A source of resistance has been identified in watermelon (Ali-Shtayeh et al., 2024) and advancement of this material into watermelon germplasm may be warranted. No resistance to WmCSV is known in other cucurbit crops.
2.2.2. Melon 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 downy mildew mating groups 1 and 2 resistance were developed in the MR-1xAY RIL population. Toporek et al. 2020 and 2023 - -CYSDV: see 2.1.2 above
Obj. 3.2 Introgress, pyramid/stack resistances into advanced breeding lines in Melon
- powdery mildew: see 2.1.2 above
Develop breeding lines (B), introgress into cultivated (I), advanced lines (A), release to breeders (R) - Fusarium wilt races 1 and 2/Powdery mildew race 1, B,I,A
Over the past 12 months we have continued with selections of more advanced lines from an initial four-way cross of MR-1 (resistant to Powdery mildew race 1, Fusarium oxysporum f. sp. melonis race 1 and race 2 and sulfur) x Top Mark x Charentais (Figure 1). Selections have been made following two breeding paths, one as backcrossed into Top Mark and on as backcrossed into Charentais. Selections have been made using a combination of KASP markers and phenotyping. We currently have BC2F1 possessing resistance alleles in the heterozygous state for all traits. Additionally, we have just finished generating BC2F2 seed. The BC2F1 individuals were also selected for horticultural traits such as fruit shape, flesh color, brix, flesh texture and netting. We have also made selections from the Charentais breeding path for autonomous selfing and growth habits in Controlled Environment Agricultural (CEA), hydroponic-based systems. Current generations of all families (Table 1) will be evaluated for horticultural traits in replicated field trials summer 2024. - CYSDV: see 2.1.2 above
Image: Development of varieties resistant to multiple diseases
Table 1. Breeding progress for development of multi-disease resistant cantaloupe Crop Current seed being generated Number of families (selections)
Literature Cited
Ali-Shtayeh, M.S., R.M. Jamous, O.B. Mallah, and S.Y Abu-Zeitoun. 2014. Molecular characterization of watermelon chlorotic stunt virus (WmCSV) from Palestine. Viruses. 6(6):2444-62.
Branham, S.E., C. Kousik, M.K. Mandal, and W.P. Wechter. 2021. Quantitative Trait Loci Mapping of Resistance to Powdery Mildew Race 1 in a Recombinant Inbred Line Population of Melon. Plant Disease 105:3809-3815
Branham S.E., A Levi., M. Katawczik, Z. Fei, and W.P. Wechter. 2018. Construction of a genome anchored, high-density genetic map for melon (Cucumis melo L.) and identification of Fusarium oxysporum f.sp. melon is race 1 resistance QTL. Theoretical and Applied Genetics 131(4): 829-837.
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. 107(9):2653-2664.
Pitter, P.L., S. Mondal, P. Gaye Chang, L. Myers Morgan, S. Aikman, and P.F. Tennant, 2023. First report of cucurbit yellow stunting disorder virus infecting cucurbit crops in Jamaica. Plant Disease (First Look) .
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.
Toporek S., S.E. Branham, M. Katawczik, A.P. Keinath, and W.P. Wechter. 2020. QTL Mapping of Resistance to Pseudoperonospora cubensis Clade 1, Mating Type A2, in Cucumis melo. Theoretical and Applied Genetics 134(8): 2577-2586.
Toporek S.M., S.E. Branham, A.P. Keinath, and W.P. Wechter. 2023. QTL Mapping of Resistance to Pseudoperonospora cubensis Clade 2, Mating Type A1, in Cucumis melo and Dual-Clade Marker Development. Theoretical and Applied Genetics.
