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Genetics of common bean resistance to white mold

Crop Breeding and Applied Biotechnology 11: 165-173, 2011

Brazilian Society of Plant Breeding. Printed in Brazil

NOTE Genetics of common bean resistance to white mold
Flávia Fernandes Carneiro1*, João Bosco dos Santos1, Paulo Roberto Carvalho Gonçalves1, Rafaela Priscila Antonio2 and Thaís Paula de Souza3 Received 20 December 2009Accepted 21 December 2010

ABSTRACT - The objective of the research was to investigate the nature and magnitude of the genetic factors involved in the resistance of the common bean to white mold. The lines G122 (resistant) and M20 (susceptible) were crossed to yield F1 and F2 generations and F2:3 progenies. The experiment was set up using the random block design with two replications, each of which wasevaluated twice with fungal inoculations being performed on 28 and 38 day-old plants using the straw test method. Six to eight days after inoculation evaluations were conducted on individual plants and at the level of means of progenies using a diagrammatic scale ranging from 1 to 9. The additive-dominance model adopted was efficient, and the genetic control of resistance was predominantly dueadditive effects. Estimates of broad-sense heritability indicated that selection would be more efficient when based on the means of progenies and when successive inoculations are employed. Key words: Sclerotinia sclerotiorum; Phaseolus vulgaris; genetic parameters.

INTRODUCTION Sclerotinia sclerotiorum (Lib.) de Bary, the causal agent of white mold, is a soil borne necrotrophic fungus, and one ofthe most devastating diseases of the common bean (Phaseolus vulgaris L.). There are, however, a few reports concerning the genetic factors responsible for the resistance of the bean to this disease, and the results that have been obtained are controversial. According to Antonio et al. (2008) the character is controlled by a single gene. Genchev and Kiryakov (2002) reported monogenic dominant (inthe field) and recessive (in the greenhouse) on the control for white mold resistance in the dry bean breeding line A 195. Abawi et al. (1978) and Schwartz et al. (2006) also reported a single dominant gene controlling resistance to white mold in different inter-specific P. vulgaris/P. coccineus populations. In contrast to single inheritance, more than ten quantitative trait loci (QTL) have beenidentified that influence
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resistance to white mold, mostly with small to moderate effects (Milkas et al. 2001, Park et al. 2001, Kolkman and Kelly 2003, Milkas et al. 2003, Ender and Kelly 2005). Resistance QTL have been located on all linkage groups (chromosome) except 9, 10 and 11 of the integrated common bean map (Kelly et al. 2003, Miklas et al. 2006). Since the results relating to geneexpression depend on the type of genetic material studied in one plant species, it is injudicious to attempt to generalize for all plant species, especially when the genetic control involves many loci. Furthermore, when the influence of environmental factors is pronounced, it becomes more complex to acquire evidence concerning the underlying contribution of genetic factors for the character underconsideration (Vencovsky and Barriga 1992). The improvement of white mold resistance has been very slow because of the low heritability, the cumbersome screening methods due to the environmental influences and the use of inefficient breeding methods. Also, it is

Universidade Federal de Lavras (UFLA), Departamento de Biologia, C.P. 3037, 37.200-000, Lavras, MG, Brazil. *E-mail:bioffc@yahoo.com.br Universidade Federal Rural do Semi-Árido, Departamento de Ciências Vegetais, C.P. 1373, 59.625-900, Mossoro, RN, Brazil 3 Universidade de São Paulo, Escola Superior de Agricultura “Luiz de Queiróz”, Departamento de Genética, C.P. 83, 13.400-970, Piracicaba, SP, Brazil

Crop Breeding and Applied Biotechnology 11: 165-173, 2011

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important to consider the...
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