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Title: Phylogenetic analyses confirm the unique status of the wild new world melon, Cucumis melo ssp. agrestis var. texanus, and suggest it be tentatively designated Group Texanus in the recent revision of melon nomenclature

Author
item Ando, Kaori
item Wintermantel, William - Bill
item McCreight, James - Jim

Submitted to: American Society of Horticulture Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 5/7/2018
Publication Date: 7/30/2018
Citation: Ando, K., Wintermantel, W.M., McCreight, J.D. 2018. Phylogenetic analyses confirm the unique status of the wild new world melon, Cucumis melo ssp. agrestis var. texanus, and suggest it be tentatively designated Group Texanus in the recent revision of melon nomenclature. American Society for Horticultural Science Annual Conference, July 31-August 3, 2018, Washington, DC.

Interpretive Summary:

Technical Abstract: Cucumis melo ssp. agrestis var. texanus Naudin is a wild melon found from the southeastern U.S. to eastern and western Mexico (Decker-Walters et al. 2002. Plant Systematics Evolution 233:183–197). It is weedy, prolific, and bears many small non-sweet fruit with small seeds, and is a potential source of powdery mildew and nematode resistances. Var. texanus was, until classified as a separate varietas, considered a member of C. melo ssp. melo var. chito, a small melon from Central America and the Caribbean Islands, or var. dudaim, a small fragrant melon from the Middle East and Central Asia. The U.S. National Plant Genetic Resources System (NPGS) maintains 2000+ C. melo Plant Introductions (PI). Forty-four of them are var. texanus, and they were sequenced using the genotyping-by-sequenced method to analyze the phylogenetic position of var. texanus in relation to the other 16 melon varietas. Principal component and phylogenetic analyses placed var. texanus in its own cluster with 8 non-texanus PIs. A nearby cluster consisted mainly of a mix of vars. chito and dudaim. Mean 100-seed weight was not significantly different (P<0.0001) between var. texanus and the 8 non-texanus PIs in the texanus cluster; the var. texanus PIs did, however, differ significantly from the rest of the NPGS C. melo accessions. A majority of the var. texanus PIs (93%) were negative for cucumis melo endorna virus (CmEV), a pollen-transmitted, persistent virus of melon thought to have co-diverged with the C. melo progenitor. Partial CmEV sequences of three CmEV-positive var. texanus PIs were subjected to phylogenetic analysis with 25 CmEV-positive melons representing 11 varietas. One CmEV-positive var. texanus grouped with ‘Ananas’ (var. ameri) and ‘Védrantais’ (var. cantalupensis), while the other two were together with ‘Ogon 9’ (var. makuwa) and ‘Freeman’s Cucumber’ (var. conomon). This result suggests that pollen from nearby cultivated or domesticated C. melo introduced CmEV to var. texanus, and that var. texanus is distinct among melons. A recent revision of melon classification replaced the two C. melo subspecies and 16 varietas with 19 horticultural groups (see Pitrat. 2016. Melon genetic resources: phenotypic diversity and horticultural taxonomy, pp. 25-60. In: R. Grumet, N. Katzir, and J. Garcia-Mas (eds.). Genetics and Genomics of Cucurbitaceae. Springer Science+Media, New York; Brickell et al. 2009. Scripta Horticulturae 10:184 pp.). We propose var. texanus either be re-designated Group Texanus or placed as a sub-Group alongside Chito.