Marcadores moleculares associados aos teores de sacarose e fibra em cana-de-açúcar

Abstract

The sugarcane (Saccharum spp.) is among the most economically important species in the world, constituting a major source of production of sugar and ethanol. It has high biomass production and wide phenotypic variability for the attributes of interest. The economic and technological aspects of the cultivation and crop need to be improved in order to attend the needs of the sugar-energetic sector. Among them, the genetic breeding of the crop for yield of sucrose and fiber quality has required significant effort. An important development regarding its genome has arisen with the use of molecular markers, especially those linked to genes of interest, such as ESTs- SSRs. The analysis of ESTs (Expressed Sequence Tags) is a strategy that addresses the expressed portion of the genome, ideal for polymorphism studies of transcribed regions of complex genomes highly redundant, as the sugarcane. The aim of the this study was to develop molecular markers multi-allelic functional, robust and discriminatory heterotic groups with phenotypes related to plant structure, sucrose and fiber production, economic characteristics important for integration into breeding programs of sugarcane. The population genotyping was performed with eight EST-SSRs primer combinations, selected from the database of ESTs and applied to the 81 progenies in the first selection phase (T1) derived of biparental crosses with contrasting genitors for the characteristic fiber and sucrose. Initially, primers were applied to contrasting genotypes in 4 phenotypic classes with 12 genotypes in each, characterized for the high and low sugar and fiber contents. After linkage analysis showed that some amplicons dos primers 1.4 βMEH, DPB, and CytB5 PKL showed the best values of Z-score, indicating high connection with the corresponding phenotype. These primers were applied on the population of 81 progenies T1.Verified that on average 12.5 amplicons were amplified for each gene, number greater than the basic genome from plant, evidencing the gene duplication. The molecular markers 1,4βMEH minor 600 pb they are discrimint for characteristics sucrose low production and higt level of fibers.The Polymorphism Information Content was between 0.51 and 0.66. Genotypic analysis structured six groups whose genotypes were organized according to the phenotype displayed in four distinct groups and the other two groups were composed of genotypes phenotypic values intermediates. The genetic divergence between heterotic groups according to multivariate analysis was ~0.15. This study showed that the phenotypic character can be more efficiently controlled by some specific amplicons that the total set, and the contribution of these alleles coding for a higher or lower phenotypic expression.