Resistance of common bean to Fusarium oxysporum f. sp. phaseoli. / ResistÃncia do feijoeiro a Fusarium oxysporum f. sp. phaseoli

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

The Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. phaseoli, is a severe vascular disease in the common bean, and occurs in all regions where the common bean is cultivated. The better way of controlling the disease is through the use of resistant cultivars. Three kinds of research were done aiming to get informations for making the breeding program more efficient. In the first research, the aim was to get information to improve the selection efficiency for resistance to Fusarium oxysporum f. sp. phaseoli. Seven inoculation methodologies were evaluated in four common bean lines, with different levels of susceptibility to the fungus. The disease progress was evaluated at seven, 14, 21 and 28 days after inoculation (DAI), to identify the best time for evaluation; plants age for inoculation was seven, eight, nine, ten, 12 and 14 days after sowing; the ideal number of replications was determined through simulations, of five to 15, from an experiment including 20 lines and 15 replications. The best methodology to discriminate the lines was root immersion in a suspension of spores with or without cutting the roots; the ideal plant age to inoculate is ten days after sowing; disease evaluation must be done at last 21 DAI; and it was also shown that five replications are sufficient to classify efficiently the lines to the Fusarium wilt. In the second research, the aim was to classify the lines from the germoplasm bank of Federal University of Lavras, in relation to disease. Genetic and phenotypic parameters were estimated, to help future breeding programs for this character. Therefore, 349 lines from the germoplasm bank and 18 from the Value of Cultivation and Use (VCU) experiment of 2005/06 were evaluated. The inoculation was by immersion of cut roots, and the symptoms evaluated at 21 DAI. Resistance was observed in 36.5% of the lines, and heritability was high, indicating success with selection. The third kind of research aimed to study the genetic control of resistance. Six crosses between resistant and susceptible lines were done, and variances and average components were estimated, from parents, F1, F2 and F3 generations. Inoculation was by immersion of cut roots, and the symptoms evaluated at 21 DAI. The genetic control of resistance involve genes with dominance, although additive effects are also expressive; heritability is high, showing that selection should be easy, since efficient inoculation and selection methods are used; one or few genes, with dominant allele(s) are responsible for resistance.

ASSUNTO(S)

eficiÃncia de seleÃÃo genetic control patÃgenos de plantas strategies of selection estratÃgias de seleÃÃo melhoramento vegetal plant breeding plant pathogens controle genÃtico melhoramento vegetal selection efficiency reaÃÃo de linhagens lines reaction

ACESSO AO ARTIGO

Documentos Relacionados