Controle genético e seleção de genótipos resistentes à murcha-de-ceratocystis causada por Ceratocystis fimbriata em Tectona grandis

Abstract

Ceratocystis wilt caused by Ceratocystis fimbriata Ellis & Halst, Bull. is one of the most important disease on Tectona grandis plantations since can lead the plant to death and the damage caused in the wood is irreversible. The most efficient method of control of the disease is by planting resistant genotypes. Although efforts have been employed to select resistant clones, the genetic basis of resistance to ceratocystis wilt in teak is unknown. It is essential to guide breeding programs to develop resistant genotypes. Studies involving genetic basis of resistance, should preferably be performed in segregating families from controlled crossings. However, due to the small size of the flowers, flowering phenology variation and the high abscission of the fruits, the breeding studies of teak have been done with populations derived from open pollination. Thus, the present study aimed to understand the inheritance of resistance to ceratocystis wilt in progenies of three commercial clones and to select resistant genotypes. The studies were conducted by inoculation of the pathogen on controlled conditions of the parentals CR1, CR2, and CS1 and on 364 plants derived from the following crosses CR1 x CR1, CR2 x CR1, CR1 x CS1 and CS1 x CR1. Susceptible plants showed typical symptoms of the disease, such as darkening of the wood, wilt, and plant death. In general, a higher frequency of alleles favorable to resistance was observed in crosses between resistant parents, CR1xCR1 and CR2 x CR1. It was possible to select 99 resistant genotypes, of which 23 genotypes derived from families involving the susceptible parent CS1, 16 genotypes from self-pollinating of CR1 and 60 genotypes derived from the family CR2 x CR1. The results of this study show that the inheritance of resistance to ceratocystis wilt in teak is quantitative with a prevalence of genes with additive effects.