Genetic and biotechnological breeding for disease resistance in forest species: A review
Rita de Cássia Sobrosa and Maisa Pimentel Martins–Corder
There have been important research results recently in the area of genetic breeding for disease resistance in forest species. Most studies have been carried out on families, but there are also some on individual trees within families. Induced resistance depends on factors present only after the contact of the pathogen with the host. By definition, it is the opposite of constitutive resistance, which depends on pre-formed factors. Plants disease resistance, which involve induced defense mechanisms, include the accumulation of phytoalexins, deposit of material similar to lignin and increase in the activity of certain hydrolytic enzymes. In response to the growing impact of disease in forest plantations, some programs have emphasized breeding for disease resistance. New techniques and technologies have become important tools in disease resistant plant selection. While they do not replace conventional plant breeding, they search for ways of reaching objectives not attained by conventional techniques. The tissue culture technique has become an important tool in plant breeding to obtain disease resistant plants through micropropagation or cell culture in selective medium, thus informing how to use genetic markers to study resistance mechanisms. The breeding cycle in trees can be accelerated by genetic engineering techniques that allow the transfer, in a tissue culture cycle, of characteristics that are monogenic or oligogenic controlled. The introduction of genes of interest in plants, by genetic engineering, is becoming an additional strategy to be included in plant breeding. Genes from distinct plant species or from genetic distant organisms may be introduced in the plant genome by genetic engineering.