Instabilidade genética de variedades de cana-de-açúcar em diferentes estágios de corte e regiões de cultivo

Abstract

Sugarcane culture is a semi-permanent agricultural activity which exhausts itself after several production years, with urgent demands of plantation renewal. Although studies on the sugarcane vegetative multiplication by analyzing management and morphological characteristics have been undertaken, no molecular marker studies have been performed to investigate the genetic variability between the stages of sugarcane cutting. Current study analyzes genetic diversity in 12 loci EST-SSR (repeated simple sequences in expressed DNA sequence loci) in the varieties RB72454 and RB867515 cultivated in the same region at different stages of vegetative multiplication so that the genetic stability throughout the different cutting stages could be evaluated. Varieties RB92579 and SP81-3250 cultivated in the states of Paraná and Pernambuco, Brazil, were also evaluated for the genetic divergence between plant samples at the same cutting stage, cultivated in the southern and northeastern regions of Brazil. Polymorphism and high genetic divergence rates in the locus EST-SSR showed that genetic instability (genetic variability) exists during the vegetative multiplication stages of the varieties RB72454 and RB867517. Results show that the identification of cut stage is required to estimate the genetic divergence between and within sugar cane varieties. There is a high index of somatic mutations, from vegetative multiplication, which contribute towards the existence of the great genetic differences among plants of the same sugar cane variety throughout the cuttings. Cultivated sugar cane plants cannot be considered cane clones.