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Monitoring races of Bremia lactucae on lettuce, advancing lettuce resistant progenies and genotype x environment interaction


Lettuce is the group most consumed vegetables in Brazil; however, the difficulty of producing it has been increasing, mainly due to infestation of production areas by Bremia lactucae, which causes downy mildew, major disease of lettuce, and the development of cultivars resistant measures for the control more efficient and economical. Despite the benefits provided by planting resistant cultivars, the use of resistance genes in lettuce, have a short duration, because of the wide genetic variability of B. lactucae. Thus, it appears that the annual monitoring of places for the presence or absence of new strains of B. lactucae is of great importance, since it becomes possible to select genes that confer resistance to disease. Given the above, the aim of this study: advancing the progenies of lettuce resistant to B. lactucae, SPBl: 01 to SPBl: 09 races, developed by the Genetic Improvement Program of UNESP-FCAV until the F6 generation and to study the genotype x environment interaction of these progenies in ten places in two cultivation times in São Paulo and, monitor the races of B. lactucae in lettuce main producing places of São Paulo. The project will be conducted in two stages. The first step is performed in the Department of Vegetable Crops and Medicinal, Aromatic (UNESP-FCAV). This will consist in advancing the lines of the F3 generation to generation F6, with the comprovation resistant test for F6. The second step is the study of genotype x environment interaction in ten places in the State of São Paulo (Jaboticabal, Monte Alto, Ribeirão Preto, Araraquara, Bauru, Marilia, Mogi das Cruzes, Biritiba Mirim, Salesópolis and Registry) in two cultivation times (spring-summer and autumn-winter). The experiment of genotype x environment interaction will be conducted in a randomized block design, using the advanced progenies, two commercial cultivars and three replications. After harvesting the variables to evaluate will be: shoot fresh weight, shoot dry mass, diameter, plant height, plant volume, number of leaves per plant and productivity (kg ha-1). To processing of data, will perform the following analyzes: individual variance analysis for the different environments, analysis of variance, analysis of adaptability and stability, environmental stratification by dissimilarity and multivariate cluster analysis. Along with the advancement of evaluation of progeny and genotype x environment interaction will be collected isolates of B. lactucae from different lettuce producing areas in the State of Sao Paulo in 2012 and 2013. The isolates collected will be taken to the Laboratory of Genetics and Breeding vegetable crops, the Department of Plant Production (UNESP-FCAV) were inoculated on the susceptible cultivar Solaris, until you get the amount of sporangia enough to use in the test for differentiation of races. After the isolates will be inoculated on the differential cultivar and, on the same day of the first onset of sporulation in the susceptible cultivar 'Green Tower (DM 0)', the differential cultivar were evaluated for presence or absence of lesions sporulating and necrotic spots. All materials that have proved susceptible to certain race will have their values summed within each group and the result is separated by a slash, and we could identify the breeds present in each isolate. (AU)

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
DORA ENITH TOBAR-TOSSE; WILLAME DOS SANTOS CANDIDO; MARCUS VINICIUS MARIN; RITA DE CASSIA PANIZI; JOSE CARLOS BARBOSA; LEILA TREVISAN BRAZ. Resistência de linhagens de alface-crespa às raças de Bremia lactucae identificadas no Estado de São Paulo. Summa Phytopathologica, v. 43, n. 1, p. 55-57, Mar. 2017.
RENATA DE CASTRO NUNES; RENATA CASTOLDI; RAFAELLE FAZZI GOMES; DORA ENITH TOBAR-TOSSE; LEILA TREVISAN BRAZ. Levantamento de raças do agente causador do míldio da alface no Estado de São Paulo em 2012 e 2013. Summa Phytopathologica, v. 42, n. 1, p. 53-58, Mar. 2016.

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