Divergência genética entre progênies de café robusta

Abstract

Estudou-se a divergência genética de 21 progênies de meios-irmãos - 19 do grupo Congolês e duas do grupo Guineano - de introduções do germoplasma de café robusta (Coffea canephora) do IAC. O estudo baseou-se em análises multivariadas de 14 características morfo-agronômicas, com o propósito de selecionar as progênies mais divergentes, visando à definição de população-base para posterior seleção e produção de híbridos. Avaliou-se também a importância das características discriminantes para análises de divergência, visando ao descarte das variáveis, segundo suas contribuições relativas. O experimento foi plantado e desenvolvido em campo experimental localizado no Pólo Regional do Nordeste Paulista, Mococa (SP), em blocos casualizados, com 21 tratamentos e 24 repetições. O agrupamento dos genótipos foi realizado com base nos métodos de Tocher e UPGMA. A matriz de dissimilaridade genética foi obtida por meio da distância generalizada de Mahalanobis, que serviu de base para a formação dos grupos. Os métodos empregados foram eficientes em detectar ampla variabilidade genética entre as progênies avaliadas. Vários grupos dissimilares foram identificados. As progênies IAC 2262, IAC 2290, IAC 2286, IAC 2292 e IAC 2291 são indicadas para compor programas de intercruzamentos, por terem sido consideradas as mais promissoras na obtenção de populações segregantes ou híbridos heteróticos. As características que menos contribuíram para a divergência genética foram, hierarquicamente: diâmetro da copa antes da poda, altura da planta antes da poda e área foliar.

Development of clonal seedlings of promising Conilon coffee (Coffea canephora) genotypes

“…The results of the UPGMA method ( Figure 1) were similar to those of Tocher's optimisation method, particularly when a lower limit of 50% similarity among genotypes was imposed. Guedes et al (2013) and Ivoglo et al (2008) also observed similarities among results obtained through Tocher's optimisation and UPGMA, especially when the lower limits were set at 45 and 15% similarity, respectively. It is noteworthy that the distribution of individuals in the dendrogram does not follow a criterion for group formation, since the main aspect of this method consists of the branches that are obtained (Cruz et al, 2004).…”

“…The number of groups demonstrates the broad variability among the genotypes tested. Fonseca et al (2006), working with 32 genotypes of Conilon coffee, and Ivoglo et al (2008), with 21 offspring that were genetically half Conilon coffee, observed the formation of three and four groups, respectively. Dias et al (2005) evaluated 25 progenies of Arabica coffee, observed the formation of five distinct groups.…”

“…However, propagation through cutting has been used for many years because it has several advantages, such as the retention of genetic characteristics of the stock plant, greater crop homogeneity, increased productivity, and the ability to separate crops based on their maturation cycle (Bragança et al, 2001;Partelli et al, 2014b). Genetic variability in the population is required for any genetic improvement program because it allows the selection of superior genotypes (Ivoglo et al, 2008) that are adapted to the soil and climate conditions of the cultivation region. Several authors working with different genotypes of C. canephora, have obtained success in the identification of genotypes adapted to new growing regions , of materials more dissimilar for the establishment of programs of directed crosses (Cecon et al, 2008) and in population base training for later selection and production of hybrid (Ivoglo et al, 2008).…”

“…Genetic variability in the population is required for any genetic improvement program because it allows the selection of superior genotypes (Ivoglo et al, 2008) that are adapted to the soil and climate conditions of the cultivation region. Several authors working with different genotypes of C. canephora, have obtained success in the identification of genotypes adapted to new growing regions , of materials more dissimilar for the establishment of programs of directed crosses (Cecon et al, 2008) and in population base training for later selection and production of hybrid (Ivoglo et al, 2008). Denoeud et al (2014) found C. canephora to be a useful reference species for understanding the evolution of genomic structure in asterid angiosperms.…”

Genetic dissimilarity and definition of recombination clusters among green corn half-sib progenies

“…On the other hand, ear number, ear weight and diameter, number and diameter of commercial ears were the traits with minor contributions to divergence ( Table 2). Variables that contributed little to the genetic divergence are strongly correlated with other traits and more likely to be discarded because they explain the same type of information (Ivoglo et al 2008;Rotili et al 2012;Simon et al 2012). In this work, the variables number of ears and the number of commercial ears can be discarded because, together, they explain less than 2% of the genetic divergence between corn genotypes and are strongly correlated with the yield of husked ears.…”