DNA Profiling And Genetic Diversity Of Sugarcane Germplasms By SSR Loci

Sugarcane is the most important sugar crop in the world. Marker-assisted selection is one technique which can accelerate and improve the efficiency of plant breeding. Marker analysis and identification of sugarcane germplasm based on molecular marker are the basis for molecular breeding. The construction of molecular fingerprints will support the protection of plant breeders’rights and the identification of sugarcane genotypes. The highly polymorphic microsatellite DNA markers were for the first time in China used to study the molecular genetic diversity of 136 important clones, including Erianthus arundinaceus (Retz) Jeswiet, wild sugarcane clones, primitive sugarcane cultivars, and modern sugarcane cultivars. Both DNA and digital profiling of these sugarcane germplasms were constructed based on the analysis of SSR loci. The results will set up the technologic and information basis for marker-assist breeding.The genetic diversity of 136 clones was investigated using 14 SSR loci. A total of, 389 alleles was detected, with an average of 27.8 alleles per locus, ranging from 17 to 50 alleles. A total of 330 polymorphism alleles was detected. The percentage of polymorphic loci was 84.83%. The polymorphism information content (PIC) was ranged from 0.740 to 0.892 and the average was 0.813. This suggested that the 14 SSR loci were richly polymorphic in the sugarcane genome.The results of cluster analysis dendrogram of 136 sugarcane clones based on SSR markers showed the genetic similarity coefficient ranged from 0.75 - 0.96. With an incision at 0.772, the tested materials were divided into three groups. Group I, Group II and Group III contained mainly primitive cultivars of S. sinense, wild sugarcane clones, and modern sugarcane cultivars (Saccharum Complex), respectively. The results of principal component analysis showed that 136 clones also could be divided into three relatively separate groups. The genetic distance between Group I and Group III was the most farthest and the closest distance was found between II and Group III.A total of 67 alleles were detected by two SSR loci of SMC119CG and SMC31CUQ and the DNA fingerprintings and the digital fingerprintings of 136 clones were constructed based on these two SSR loci. According to the different breeding institutes, all modern sugarcane cultivars could be divided into 8 different main series of Yuetang, Guitang, Yacheng, Funong, Yunzhe, ROC, CP, and HoCP series. The genetic diversity was different in these series. Among them, Yacheng series was richest with the rate of polymorphism 58.35 % and HoCP series was lowest of 38.30 %.According to the cultivars released period in China, the tested modern sugarcane cultivars could be divided into 7 series including released during 1956-1980, 1981-1985, 1986-1990, 1991-1995, 1996-2000 and 2001-2005. Among them, cultivars released during 1996-2000 were highest polymorphism rate of 64.27% and lowest rate of 39.59% were observed in the group of 1981-1985.