Agro-morphological description, genetic diversity and population structure of sugarcane varieties from sub-tropical India.

Genetic diversity in 92 sugarcane varieties of sub-tropical India was assessed using 30 morphological descriptors and 643 simple sequence repeat (SSR) marker loci. Out of the 30 morphological descriptors, 14 were found polymorphic, and significant variability was recorded for plant height, cane diameter and number of millable canes. Grouping traits like plant growth habit, leaf blade curvature and leaf sheath adherence were found to be predominantly monomorphic. There were a few pairs of varieties (e.g., CoP 9702 and CoP 9302, CoP 9301 and CoSe 01424, UP 05 and Co 1336, CoS 96258 and CoH 110) that showed similar DUS profiles except differing for a few descriptors. The STRUCTURE profile suggest that all the 92 sugarcane varieties had admixtures and no sub-group had a pure unblemished structure profile. An average Nei's genetic distance of 0.49 was found to be a better measure of diversity, whereas, the average band informativeness (Ib) value of all the 80 SSR primers was 0.434. Although, the mean Ib values for EST-SSR and genomic-SSR primers were same (0.43), the range of Ib of EST-SSR (0.04-0.85) was more compared to genomic-SSR (0.12-0.63) primers. The segregation of the varieties based on morphological traits was not in accordance with their geographical distribution or maturity groups, but principal component analysis was able to group the sugarcane varieties that had similar pedigree together. Results indicate that the SSRs have a potential use in the DNA fingerprinting of varieties to prevent any malpractice like unauthorised re-registration of a previously registered sugarcane variety under PPV&FR Act. The marker profiles could also be utilised for variety identification and release, since at present, it has been made mandatory to include it in addition to the morphological descriptors.