Analysis of Genetic Diversity in Polymers of Saccharum spontaneum L. and Their Hybrid Progenies

Saccharum spontaneum L. (wild sugarcane) possesses advantages such as strong perenniality, high stress resistance, and broad adaptability, making it the most successfully utilized wild species in sugarcane hybrid breeding. However, previous exploitation of S. spontaneum has been limited. To further explore its breeding potential, this study employed recurrent selection to improve the population of S. spontaneum (S0) before its application in germplasm innovation. Subsequently, S1 (containing two S. spontaneum bloodlines) were developed and optimized. Using S1 as dual parents, S2 (containing three or more S. spontaneum bloodlines) were further created and selected. Genetic diversity among 199 materials from seven populations (S0, S1 and S2) was evaluated using simple sequence repeat (SSR) markers. The results showed that an unweighted pair-group method with arithmetic means (UPGMA) cluster analysis based on genetic distance classified the 199 S. spontaneum materials into seven groups, largely consistent with their original population divisions. Compared to their parents, the S1 population generated an average of 18.79 novel loci (mutation rate: 25.00%), while the S2 population produced an average of 15.40 novel loci (mutation rate: 19.00%). The polymer of S. spontaneum exhibited rich genetic diversity, with Nei’s gene diversity index of 0.3390 and Shannon information index of 0.5082. Due to the increased number of original parents and trait pyramiding, the polymer of S. spontaneum demonstrated expanded genetic backgrounds and enhanced heterogeneity. Furthermore, hybridization and recombination generated novel elite loci compared to their parents, further enriching the overall genetic background and diversity of the polymer of S. spontaneum.