Natural occurring epialleles determine vitamin E accumulation in tomato fruits

Vitamin E (VTE) content is a low heritability nutritional trait for which the genetic determinants are poorly understood. Here, we focus on a previously detected major tomato VTE quantitative trait loci (QTL; mQTL9-2-6) and identify the causal gene as one encoding a 2-methyl-6-phytylquinol methyltransferase (namely VTE3(1)) that catalyses one of the final steps in the biosynthesis of γ- and α-tocopherols, which are the main forms of VTE. By reverse genetic approaches, expression analyses, siRNA profiling and DNA methylation assays, we demonstrate that mQTL9-2-6 is an expression QTL associated with differential methylation of a SINE retrotransposon located in the promoter region of VTE3(1). Promoter DNA methylation can be spontaneously reverted leading to different epialleles affecting VTE3(1) expression and VTE content in fruits. These findings indicate therefore that naturally occurring epialleles are responsible for regulation of a nutritionally important metabolic QTL and provide direct evidence of a role for epigenetics in the determination of agronomic traits.L.Q. was recipient of a fellowship of Agencia Nacional de Promoción Científica y Tecnológica and Consejo Nacional de Investigaciones Científicas y Técnicas in Argentina and supported by a postdoctral fellowship from Investissements d’Avenir ANR-10-LABX-54 MEMO LIFE in France. J.A. and L.B. were recipients of a fellowship of Fundação à Amparo da Pesquisa do Estado de São Paulo (Brazil). J.V.C.d.S. was recipient of a fellowship of Conselho Nacional de Desenvolvimento Científico e Tecnológico (Brazil). R.A., L.B. and F.C. are members of Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina). This work was carried out in compliance with current laws governing genetic experimentation in Brazil and in Argentina. This work was supported with grants from Instituto Nacional de Tecnologia Agropecuária, Consejo Nacional de Investigaciones Científicas y Técnicas and Agencia Nacional de Promoción Científica y Tecnológica (Argentina), Fundação à Amparo da Pesquisa do Estado de São Paulo, Conselho Nacional de Desenvolvimento Científico e Tecnológico and Universidade de São Paulo (Brazil); Max Planck Society (Germany); the Agence Nationale de la Recherche (Investissements d’Avenir ANR-10-LABX-54 MEMO LIFE and ANR-11-IDEX-0001-02 PSL* Research University to V.C.); and the European Union (EpiGeneSys FP7 Network of Excellence number 257082 to V.C. and the European Solanaceae Integrated Project FOOD-CT-2006-016214 to F.C., M.R. and A.R.F.)

Soybean cultivars performance towards soybean Asian rust, in relation to chemical control programs

Soybean rust is caused by an obligatory parasite (Phakopsora pachyrhizi) which is being spread in Brazil at each new season since 2001 and, despite the efforts to control the disease, losses have occurred every year. It s control demands several tactics and chemical control with fungicides is the main method and still is indispensable. Control strategies such as the use of partial resistance cultivars are desirable, but still are not commercially available. The present study analyzed the existing differences among the reaction of short, medium and long cycle soybean cultivars to Asian rust and their response to fungicide sprays. The experiment was conducted at Uberlândia-MG, in field conditions from December of 2007 to May of 2008, on Syngenta Seeds Experimental Station. The studied variables were: visual severity (percentage of leaf area infected), number of pustules per cm2, percentage defoliation, productivity on kg per hectare and one thousand grains weight. The area under disease progress curve (AUDPC) was calculated from the variables visual severity and number of pustules per cm2. The variance analysis and the comparison of averages test Tukey (5% significance) were done for all variables studied. Significant differences were observed between the effects of cultivars and chemical control programs studied. Based on the studies of the present work, it was concluded that the cultivars M-Soy 8199RR and Emgopa 315RR were less susceptible to disease, and that the control program called monitoring (on which the appearance of new pustules of the pathogen were monitored to make the decision at each fungicide spray) was the most effective.Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorMestre em AgronomiaA ferrugem asiática é causada por um parasita obrigatório (Phakopsora pachyrhizi) que vem se disseminando no Brasil, a cada safra, desde 2001 e, apesar de todos os esforços para conter a doença, as perdas têm sido elevadas a cada ano. Seu controle exige a combinação de diversas táticas, sendo o controle químico com fungicidas o principal método, ainda indispensável. Estratégias de controle como a utilização de cultivares com resistência parcial ao fungo são desejáveis, porém, estas ainda não estão disponíveis comercialmente. No presente, trabalho objetivou-se compreender as diferenças existentes entre as reações de cultivares de soja de ciclos precoce, médio e tardio à ferrugem asiática e suas respostas a pulverizações de fungicidas. O experimento foi realizado em Uberlândia-MG, em condições de campo, no período de dezembro de 2007 a maio de 2008, na Estação Experimental da Syngenta Seeds. As variáveis estudadas foram: severidade visual (porcentagem de área foliar infectada), número de pústulas por cm2, porcentagem de desfolha, produtividade em kg por hectare e peso de mil grãos. Calculou-se a área abaixo da curva de progresso da doença através das variáveis severidade visual e número de pústulas por cm2. A análise de variância e teste de comparações de médias Tukey (5% de significância) foram realizados para todas as variáveis estudadas. Foram observadas diferenças significativas entre os efeitos dos cultivares e programas de controle químico estudados. Com base nos estudos do presente trabalho, concluiu-se que os cultivares M-Soy 8199RR e Emgopa 315RR foram menos susceptíveis à doença, e que o programa de controle chamado de monitoramento (no qual era monitorado o surgimento de novas pústulas do patógeno para a tomada de decisão a cada pulverização do fungicida) foi o mais eficaz