2018 ASHS Annual Conference

Cucumis melo ssp. agrestis var. texanus Naudin is a wild melon found from the southeastern U.S. to eastern and western Mexico. 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-sequencing 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 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 No. 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. We propose var. texanus either be re-designated Group Texanus or placed as a sub-Group alongside Chito.