Segregation Analysis of Microsatellite (SSR) Markers in Sugarcane Polyploids

Sugarcane flowers often self-pollinate and emasculation is either impractical or inefficient causing problems in cross quality and the genetic purity of mapping populations. There is no report on segregation analysis of DNA markers involving both pollen and self-progeny. To fill in this knowledge gap, two lately developed laboratory techniques, i.e., capillary electrophoresis- and fluorescence-based DNA fingerprinting and single pollen collection and PCR, were employed to investigate the segregation of SSR markers among 964 single pollens and 288 self-progenies of a sugarcane cultivar LCP 85-384. Five polymorphic SSR primer pairs primed the amplification of 20 alleles. Segregation analysis of each allele among both pollen and self-progeny (S1) populations showed the following: 1) Only 11 out of the 20 SSR alleles (55%) segregated in accordance with Mendelian segregation ratios expected from pollen and S₁ populations; 2). The polymorphism information content values of SSR markers were greater on pollen than S₁ population; 3). Fewer SSR genotypes were observed among S₁ than pollen population; and 4). Only one non-parental SSR allele was observed out of 2,392 total PCR reactions. The results from this study will provide some guidance for sugarcane breeders in selecting crossing parents, estimating optimum size of seedling population, and promoting efficient selection. The genetic knowledge from this study will provide some guidance for molecular genetics research and marker-assisted breeding in sugarcane. (The study was conducted at the USDA-ARS, MSA, Sugarcane Research Unit, Houma, LA 70360, U.S.A.)