Caracterização de acessos de cupuaçuzeiro baseada em variáveis foliares, florais e de fruto

Abstract

This work aimed to study the genetic diversity among accessions of the Active Bank of Cupuassu tree Germplasm - Nova Ipixuna Collection, through the morphological characterization of leaf, floral and fruit characters, in order to collect subsidies to contribute to the breeding program and genetic resources of the Eastern Amazon Embrapa. The accessions came from native populations of Nova Ipixuna, PA. They were cloned by grafting and were installed at the physical base of Embrapa Amazônia Oriental, in Tomé Açu, PA. The experiment consists of 20 cupuassu tree accessions (clones), implanted in 2005 in consortium with banana tree, to provide provisional shading, and this species was removed from the area in the sixth year. The design was in randomized blocks with 20 treatments and three replications. For leaf characterization, nine mature, healthy and whole leaves were evaluated using 13 variables: Limb length; Limb width at base, middle and apex; Petiol Length and Diameter, Apex Length and Width; Angulation of the ribs at the base, middle and apex; Ribbing Distance and Number of Ribbed Pairs. For floral characterization, five striated buds (close to the anthesis) and five completely open flowers per plant were collected, totaling 15 flowers/buds per access. Sixteen variables were evaluated: Striated Bud Length and Diameter, Flower Size, Distance between Stigma and Anther, Peduncle Length and Diameter, Sepal Blade Length and Width, Petal Blade Length and Width, Cucula Length and Width, Staminoid Length, Stylus Length and Ovary Length and Diameter. For fruit characterization, five fruits per plant were used in each crop, where eight variables were evaluated: Fruit Length and Diameter, Peel Thickness, Average Fruit Weight, Relative Percentage of Seeds, Pulp and Peel, and Average Number Seeds. In order to discard the least responsive variables, the main components method was used, which allowed the discard of eight leaf variables (62%), 11 flower variables (69 °%) and three fruit variables (38%). With the selected variables, dendrograms were constructed using Ward's similarity method to know the genetic structure of this population. The dendrogram separated the accessions into two large groups for the three characterizations. When assembling the minimum list of descriptors, the following may be indicated for Leaf: limb length, base limb width, petiole diameter, rib distance, rib angle at base; Flower: diameter of striated bud, width of sepal laminae, width of petal laminae, length of staminoids and ovary length; Fruit: fruit diameter, peel thickness, fruit weight, pulp percentage and peel percentage. It was observed that the variability between the accesses is distributed between and within the farms, but for a Recollect, it would be more interesting to choose geographical points distant from each other.