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Alfenas R.F.,Federal University of Mato Grosso | Freitas R.G.,Federal University of Viçosa | Pereira O.L.,Federal University of Viçosa | Coutinho M.M.,Clonar Resistencia a Doencas Florestais | And 3 more authors.
Forest Pathology | Year: 2016

Calonectria leaf blight (CLB), caused by Calonectria pteridis, is a major foliar disease of eucalypt plantations in warm and high rainfall regions in Brazil. The use of resistant genotypes is the best method for disease control in the field, so identification of sources of resistance is strategic for the long-term genetic breeding programmes of eucalypt. In this study, resistance of 13 species of Eucalyptus and 3 species of Corymbia to CLB was evaluated by spray inoculation of a spore suspension (1 × 104 conidia ml-1) of the pathogen, under controlled conditions. Eucalyptus brassiana, E. saligna, E. scias and E. agglomerata were the most resistant, while E. robusta, E. urophylla, E. camaldulensis, E. longirostrata and C. toreliana were moderately resistant and E. cloeziana, E. pellita, E. tereticornis, E. pilularis, C. maculata, E. grandis, E. dunnii and C. citriodora were the most susceptible. The broad inter and intraspecific variability of the species tested demonstrates the potential for introgression of resistance genes into valuable genotypes as a strategy for the breeding programmes and commercial plantation of eucalypt. © 2016 Blackwell Verlag GmbH.

Zarpelon T.G.,Clonar Resistencia a Doencas Florestais | Zarpelon T.G.,Federal University of Viçosa | da Silva Guimaraes L.M.,Federal University of Viçosa | Faria D.A.,EMBRAPA - Empresa Brasileira de Pesquisa Agropecuária | And 6 more authors.
Tree Genetics and Genomes | Year: 2014

Calonectria leaf blight (CLB) caused by Calonectria pteridis is one of the main leaf diseases in Brazilian Eucalyptus plantations in warm climates with prolonged periods of rain. The main symptoms are leaf spots followed by intense defoliation in highly susceptible plants. Exploiting the existing inter- and intraspecific variability for defoliation is the best option to control this disease. Nevertheless, nothing is known about the genetic architecture of resistance to CLB in Eucalyptus. We built microsatellite-based genetic maps for E. urophylla × E. camaldulensis (EU11 × EC06) F1 family of 89 plants. Four or five clonal replicates per individual offspring were clonally propagated, totalling 445 plants which were phenotyped for defoliation in the basal third of the branches at 30 days following controlled inoculation with a single-spore isolate. Genetic mapping was performed using a pseudo-testcross, and QTLs detected using composite interval mapping. Five QTLs were detected for resistance to CLB; of them, only one could be validated in two unrelated pedigrees, and its effect was conservatively estimated as controlling between 5 and 10 % of the phenotypic variation when the bias derived from the limited size of the mapping population was taken into account. This work provides a starting point for future studies of the genetics of resistance to CLB, and adds further evidence to the challenge of ascertaining the effects of QTLs detected in a single biparental background across unrelated families. © 2014, Springer-Verlag Berlin Heidelberg.

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