Genetic Diversity of Populations of Saccharum spontaneum with Different Ploidy Levels Using SSR Molecular Markers

Saccharum spontaneum L. plays a key role in the improvement of stress resistance and yield of sugarcane cultivars by serving as wild parent sources, especially lines of different ploidy. To better understand the genetic diversity and potential breeding value of S. spontaneum with different ploidy levels, 62 clones from four ploidy types (2n = 64, 72, 80, and 96) were screened using 30 pairs of SSR primers and with population genetics methods. The results showed that the decaploid and octaploid populations had a higher diversity than nonaploid and dodecaploid populations at 30 SSR loci with > 98 % percentage of polymorphic bands and > 0.92 polymorphic information content. Both the octaploid and decaploid populations shared more common bands with commonly used parents than the nonaploid or dodecaploid populations. The analysis of Nei's genetic distance and UPGMA tree indicates that the decaploid population had the closest genetic relationship with the octaploid population and that the two populations had a close genetic relationship with commonly used parents (controls). According to the population divergence analysis, the four different ploidy populations did not show an obvious genetic divergence (Gst) (0.0880), but clearly had large amounts of gene flow (Nm) (5.1840). Octaploid and decaploid populations appeared to have undergone more genetic exchange with commonly used parents, as indicated by the low Gst value (0.1254 and 0.1276) and high Nm value (3.4872 and 3.4186). These results may provide important insight into utilizing the diversity of clones with different ploidy levels in S. spontaneum for future sugarcane breeding.