Taxa de cruzamento de capim-elefante (Cenchrus purpureus) por meio de marcadores microssatélites

Abstract

The Napier grass (Cenchrus purpureum) is a perennial grass used as forage crop mainly in dairy cattle. Nowadays, the Napier grass has been used as energy feedstock, due to high biomass yield, producing thermal energy (direct combustion, charcoal and residues), mechanical energy (biofuels and bio-oils) and electrical energy (through gas combustion, gasification and burn). C. purpureum is, preferably, a vegetative propagation species, that reproduces through stems. Its seeds have low quality, making difficult its expansion in extensive areas. Thus, it is necessary to extend the knowledge about the reproductive biology and selection of superior genotypes in Napier grass breeding programs. The aim of this study was to estimate the outcrossing rate of Napier grass in order to understand the reproductive behavior of this species. For that, 378 individuals were selected and divided in 18 parental and its progenies groups. DNA was extracted from all individuals and selected microsatellite regions were amplified by PCR. A total of 19 microsatellite markers were tested and six were successful in the amplification of polymorphic DNA bands. A dendrogram was generated with parental individuals to identify the relationship among them and a low similarity (<0.75) was found. AMOVA revealed 86% of variability within progenies which correlates with species predominantly alogamic. The allogamy was confirmed through analysis of outcrossing rate: the multilocus rate (0.957), unilocus rate, (0.900), selfing rate (0.043), inbreeding coefficient (-0.200), and correlation of paternity (0.045). These results indicate that heterosis is present and few individuals share the same parental origin. These findings are important to understand the outcrossing rate in this species and may help to define new strategies in breeding programs.