Fruit trait and seed size measurements and molecular phylogenetic analysis of Kazakhstan melon as an example of melon development on the Silk Road

Abstract Melons from the famous Silk Road have not been studied for their population structure, phylogenetic relationship, and diversity, which suggests their need for genetic study and breeding. Measurements of fruit and seed traits and a phylogenetic analysis of five chloroplast genome markers, 17 RAPD markers and 11 SSR markers were conducted for 87 Kazakh melon accessions with reference accessions. Fruit weight and shape was highly variable across Kazakh melons and was highly correlated with fruit length, fruit width, and pulp thickness. Fruit length could characterize Kazakh melon groups, while pulp thickness associated with fruit width was conserved due to culinary use, as was pulp sweetness. Molecular phylogeny showed that two unique genetic groups, STIa-2 with Ib-1/-2 cytoplasm and STIa-1 with Ib-3 cytoplasm, and one admixed group, STIAD combined with STIa and STIb, were prevalent across all Kazakh melon groups. STIAD melons that phylogenetically overlapped with STIa-1 and STIa-2 melons were frequent in the eastern Silk Road region, including Kazakhstan. Evidently, a small population contributed to melon development and variation in the historical record of the eastern Silk Road. Conscious preservation of fruit traits specific to Kazakh melon groups, with andromonoecy, is thought to play a role in the conservation of Kazakh melon genetic variation during melon production, where hybrid progenies were generated through open pollination. This overview of fruit phenotypic and molecular variation supports the belief that recurrent selection for edible parts after crop domestication involves varietal variation.