Desenvolvimento inicial, caracterização morfológica e genética de nogueira-pecã no sul do Brasil

Abstract

The objective of the present study was to carry out the morphological and genetic characterization of some cultivars and selections found in the orchards, as well as to evaluate the initial growth of pecan tree cultivars in an organic production system in the southern region of Brazil. In the genetic characterization analysis, forty accessions were collected and genotyped in 11 SSR (Simples Sequencia Repetida) loci. Twenty-four polymorphic alleles were identified. The genetic similarity matrix, based on the Jaccard coefficient, ranged from 0.125 to 1.0; the overall mean of similarity was 0.46. In the analysis of the genetic variability present in pecan cultivars and selections, using SSR markers, a high genetic variation can be verified, in addition to some duplicates in the germplasm under study. The SSR loci analyzed in this study are good markers for the genetic identification of pecan germplasm. In the morphological characterization of pecan tree cultivars, we sought to facilitate the identification of plants in the field, with the aim of helping to differentiate materials and the behavior of cultivars in the region. More than twenty cultivars were observed, where some of them are in large proportions in the orchards of the region, an effort was made to characterize the morphology and also individual aspects of each of these materials under study. This identification guide will help to disseminate information about the crop and will also facilitate the recognition of the different pecan cultivars present in the orchards. In the follow-up work on the initial development of some pecan cultivars grown in an organic system in the South region, evaluations were carried out from 2018 to 2022 on 16 pecan cultivars, in the experimental area of the Cascata Experimental Station. These plants were arranged in a completely randomized design, with three replications and three plants per plot. The spacing used was 10 m x 10 m and the planting density was 100 plants.ha-1. The phenological stages, growth and incidence of diseases in the area implanted with pecan tree were evaluated. Regarding phenology, the Chickasaw, Cape Fear, Sioux and Elliot cultivars are earlier in relation to sprouting, while 'Barton', 'Stuart'and 'Sumner' are later in the climatic conditions of the southern region of Rio Grande do Sul . It was observed that all cultivars under study are susceptible to scab, but Cape Fear, Chickasaw, Choctaw, Imperial, Mahan and Sioux cultivars had higher levels of disease severity. Barton, Elliot, Success and Stuart cultivars are less susceptible to scab. Cultivars Sumner, Stuart, Desirable, Success and Imperial have a higher initial growth under experimental conditions.