Genetic improvement of the seringueira tree (Hevea spp.) for the state of São Paulo

Abstract

The primary objective of Hevea breeding is latex production, a citoplasmic fluid from the laticiferous cells which can be continually extracted from the tree by repeatedly slicing off a thin layer of the bark of the trunk by a process called tapping. However the expression of this genetic potential can be influenced by several other inherent factors of the tree (e.g. vigour, bark thickness tree dryness, deseases etc.) and by environmental factors (e.g. edaphic, climatic and biotic, etc.). The cycle of Hevea breeding folowed by the Instituto Agronômico and others institutions of research takes three selection stages. The general method used involves the following steps: choice of parents, hybridization, selection of superior seedlings, selection of superior clones and testing of clones for adaptation under different agroclimatic condition. Selection of superior seedlings is conducted when they are about three years old in the nursery. The clones made are tested in a small scale trial. Once the trial has been tapped for one year the promising clones are selected on yield and observed for a further year. The clones that have good yield and acceptable secondary characters are multiplied and tested for adaptation under different agroclimatic conditions as in large scale trials. In these trials, at least 10-15 years of evaluation is necessary before recommendation for wide-scale planting can be reliably made. In addition to yield and growth vigour, there are many other important secondary characters desired by rubber breeders. Based on the above methodology the main objective of the project is to obtaining rubber superior clones. The project has 28 experiments involving three groups of experiments. The first one related to selection of superior seedlings; the second one are those concerned to small scale trial and a third one, those related to adaptation tests under different agroclimatic condition as in large scale trials. The three groups of trials complete the selection cycle from hand pollination. The following characteristics are taken into consideration when, selecting a clone for further testing: yield, vigour, crown shape and branching, thickness of primary and renewed bark, incidence of leaf diseases, incidence of wind damage and brown bast. (AU)