A comparative assessment of diversity of greater yam (Dioscorea alata) in China

Dioscorea alata is a species of yam that is widely cultivated throughout the world, including China. Nevertheless, there is very limited knowledge on this type of yam diversity in China. In the present study, we assessed the genetic diversity of Chinese greater yam by analyzing their morphology, genotype, chromosome and ploidy. 142 cultivated greater yams were collected from eight geographical regions of China. 16 morphological characters were used for phenotypic variation assessment. Genotypic diversity was analyzed using 186 EST-SSR markers, while the chromosomes counting and ploidy evaluation were detected by flow cytometry. A broad morphological diversity was found, i.e. significant differences among accessions were found at each quantitative trait. The genetic similarity coefficients ranged from 0.42 to 0.91 with an average of 0.70. UPGMA and PCA indicated that the population was separated into two major clusters. The variation within pops accounted for 99.0%. 10 chromosome counts genotypes showed mainly 2n = 40, Da176 was a mixoploid with 20 and 40 chromosomes. Four levels of ploidy were detected by flow cytometry technology, and 87.3% of accessions had 40 chromosomes. Our findings demonstrated a broad variation of cultivated greater yam at phenotypic, genotypic and ploidy levels in two groups of observed cultivars.