Influência da interação genótipos por ambientes no melhoramento do cafeeiro

Abstract

Coffee is a perennial plant of a longproduction cycle and pronounced seasonality. Therefore, several consecutive years of production assessment are necessary to estimate the productive potential of the genotypes, which demands rigor and precision in the statistical selection methods. The mixed model approach allows the selection of genotypes with a lower number of harvests by estimating the genetic parameters and predicting more accurate genetic values. The objective of the present work was to evaluate the influence of the genotype x environment interaction on genotype selection in different groups of coffee cultivars in test environments, and the possibility of reducing the number of harvests for selecting Coffea arabica progenies when using the mixed models approach. We evaluated three groups of coffee experiments, conducted by the Agricultural Research Company of Minas Gerais (EPAMIG), in which were evaluated: 1) 11 Icatu genotypes and 4 witnesses; 2) 15 Catuaí genotypes and 5 witnesses; 3) 34 genotypes of Mundo Novo genotypes and one witness. The experiments were implemented in the private farms of Ouro Verde in Campos Altos-MG and Resplendor in Capelinha-MG, Brazil. We used a completely randomized blocks experimental design, with four replicates and six plants per plot. We analyzed the data from six consecutive harvests encompassing the period from 2001/2002 to 2006/2007. Individual analyzes per harvest were conducted in the scheme of plots subdivided into harvest periods at each site and jointly of productivity sites (sc/ha) using the mixed models approach and the R software using the Asreml package. We estimated the Spearman's classificatory correlation between the predicted genetic values (BLUP) considering the combined harvests and the total number of harvests. Furthermore, we estimated the genetic gain and the coincidence index with the selection intensities of 10, 20, and 30% for all analyzes. The presence of genotype x environment interaction demonstrates low or no coincidence of genotypes in different environments, making it difficult to recommend and release new cultivars for the coffee-producing regions in Minas Gerais. It is impossible to conduct an early selection before the fourth harvest for the genotypes of the Icatu, Catuaí, and Mundo Novo groups.