Analysis of genetic similarity detected by AFLP and coefficient of parentage among genotypes of sugar cane ( Saccharum spp.).

Despite the economical importance of sugar cane, until the present-date no studies have been carried out to determine the correlation of the molecular-based genetic similarity (GS) and the coefficient of parentage ( f)-estimates generated for cultivars. A comprehensive knowledge of the amount of genetic diversity in parental cultivars, could improve the effectiveness of breeding programmes. In this study, amplified fragment length polymorphism (AFLP) and pedigree data were used to investigate the genetic relationship in a group of 79 cultivars (interspecific hybrids), used as parents in one of the Brazilian breeding programmes, and four species of Saccharum ( Saccharum sinense, Saccharum barberi and two of Saccharum officinarum). The objectives of this study were to assess the level of genetic similarity among the sugar-cane cultivars and to investigate the correlation between the AFLP-based GS and f, based on pedigree information. Twenty one primer combinations were used to obtain the AFLP molecular markers, generating a total of 2,331 bands, of which 1,121 were polymorphic, with a polymorphism rate, on average, of 50% per primer combination. GSs were determined using Jaccard's similarity coefficient, and a final dendrogram was constructed using an unweighted pair-group method using arithmetic average (UPGMA). AFLP-based GS ranged from 0.28 to 0.89, with a mean of 0.47, whereas f ranged from 0 to 0.503, with a mean of 0.057. Cluster analysis using GS divided the genotypes into related subgroups suggesting that there is important genetic relationship among the cultivars. AFLP-based GS and f were significantly correlated ( r= 0.42, P< 0.001), thus the significance of this r value suggests that the AFLP data may help to more-accurately quantify the degree of relationship among sugar-cane cultivars.