Caracterização genotípica e fenotípica de genótipos de cana-de-açúcar coletados no sul do Brasil.

Abstract

Rio Grande do Sul producers use sugarcane genotypes that were introduced in the early eighteenth century which come from abroad and from other regions of Brazil in the last decades. Many of these genotypes already show great adaptation to temperate climate region. These can be considered genetic resources in use by the farmers and that can be used in sugarcane breeding programs, aiming its development in this region. Therefore, the objective of this work was to characterize the genetic variability of a collection of sugarcane genotypes collected in Rio Grande do Sul and Santa Catarina. Experiment I was carried out at Embrapa Clima Temperado, Pelotas, RS, in which 192 sugarcane genotypes were characterized with the use of molecular markers SSR type and phenotypic markers separately and jointly. In experiment II 50 genotypes of this collection were evaluated in two environments localized in Pelotas, RS during the 2015/2016 and 2016/2017 crops. The evaluated characteristics were: tons of sugarcane stalks per hectare; ton of Brix per hectare; reaction to diseases, maturation and cold resistance. In the experiment I, the SSR markers amplified 47 bands, being 96.61% polymorphic, with the formation of 21 different groups. The joint analysis of the markers resulted in the formation of 22 distinct groups. In experiment II the interaction genotype X environment X crop cycle was observed. The genotypes presented higher productivity in environment 2 and in the first ratoon cycle. Concerning cold, the genotypes presented low damage. As for diseases, genotypes showed good to high resistance to brown rust and brown spot, although there are few susceptible genotypes. Regarding maturation, 17 genotypes behaved as early, 9 as medium and 24 as late maturing genotypes. There is genetic variability in the Embrapa Clima Temperado sugarcane collection, which is very important for use in breeding, since these genotypes are cultivated in Rio Grande do Sul and Santa Catarina for many years and are adapted to this environment.