Eucalypts are susceptible to a wide range of diseases. One of the most important diseases that affect Eucalyptus plantations worldwide is caused by the rust fungus Puccinia psidii. Here, we provide evidence on the complex genetic control of rust resistance in Eucalyptus inter-specific hybrids, by analyzing a number of full-sib families that display different patterns of segregation for rust resistance. These families are totally unrelated to those previously used in other inheritance studies of rust resistance. By using a full genome scan with 114 genetic markers (microsatellites and expressed sequence tag derived microsatellites) we also corroborated the existence and segregation of a resistance locus, explaining 11.5% of the phenotypic variation, on linkage group 3, corresponding to Ppr1. This find represents an additional validation of this locus in totally unrelated pedigree. We have also detected significant additive 9 additive digenic interactions with LOD [10.0 on several linkage groups. The additive and epistatic QTLs identified explain between 29.8 and 44.8% of the phenotypic variability for rust resistance. The recognition that both additive and non-additive genetic variation (epistasis) are important contributors to rust resistance in eucalypts reveals the complexity of this host-pathogen interaction and helps explain the success that breeding has achieved by selecting rust-resistant clones, where all the additive and nonadditive effects are readily captured. The positioning of epistatic QTLs also provides starting points to look for the underlying genes or genomic regions controlling this phenotype on the upcoming E. grandis genome sequence.

-Rust (Puccinia psidii), ceratocystis wilt (Ceratocystis fimbriata) and cylindrocladium leaf blight (Cylindrocladium pteridis) are important diseases of eucalyptus. Planting of resistant genotypes is the most suitable control strategy of forest diseases under field condition. Resistance level of 23 Eucalyptus pellita clones was evaluated by artificial inoculations. Among the inoculated clones, 12 were resistant to rust, 16 to ceratocystis wilt and 12 to cylindrocladium leaf blight, and three of them were resistant to all three diseases. The high intra-specific variability found in this study demonstrates the importance of E. pellita as a disease resistance source to be employed for introgression of novel resistance genes in eucalyptus genetic breeding programs.

Ceratocystis wilt caused by the fungus Ceratocystis fimbriata, is currently one of the major diseases in commercial plantations of Eucalyptus trees in Brazil. Deployment of resistant genotypes has been the main strategy for effective disease management. The present study aimed at identifying genomic regions underlying the genetic control of resistance to Ceratocystis wilt in Eucalyptus by quantitative trait loci (QTL) mapping in an outbred hybrid progeny derived from a cross between (Eucalyptus dunnii × Eucalyptus grandis) × (Eucalyptus urophylla × Eucalyptus globulus). A segregating population of 127 individuals was phenotyped for resistance to Ceratocystis wilt using controlled inoculation under a completely randomized design with five clonal replicates per individual plant. The phenotypic resistance response followed a continuous variation, enabling us to analyze the trait in a quantitative manner. The population was genotyped with 114 microsatellite markers and 110 were mapped with an average interval of 12.3 cM. Using a sib-pair interval-mapping approach five QTLs were identified for disease resistance, located on linkage groups 1, 3, 5, 8, and 10, and their estimated individual heritability ranged from 0.096 to 0.342. The QTL on linkage group 3 overlaps with other fungal disease-resistance QTLs mapped earlier and is consistent with the annotation of several disease-resistance genes on this chromosome in the E. grandis genome. This is the first study to identify and attempt to quantify the effects of QTLs associated with resistance to Ceratocystis wilt in Eucalyptus.

Ceratocystis wilt, caused by Ceratocystis fimbriata, is one of the most damaging diseases in eucalyptus plantations worldwide. Although there are resistant genotypes, the genetic basis of resistance is still poorly understood. In this paper we studied the resistance level by a stem inoculation experiment of genotypes of Eucalyptus grandis and E. urophylla and estimated the heritability and gains of selection in families derived from controlled interspecific crosses. In both species, highly resistant as well as highly susceptible genotypes to Ceratocystis wilt were found. Out of 21 parents assessed, twelve were resistant and nine susceptible. Estimates of individual narrow (50 %) and broad (59 %) sense heritability suggested a high degree of genetic control and low allelic dominance of the trait. There was great genetic variation among and within families, a fact that contributes to high heritability and genetic gain. A genetic gain in lesion size of up to -74.4 % was obtained from selection of the 50 best clones in the evaluated families, i.e., the mean lesion length in the progeny population can be reduced by 74,4 %.

ABSTRACT. Bromeliads are greatly represented in the Atlantic Forest, although many species are threatened with extinction owing to habitat fragmentation and intense extraction for ornamental purposes. Therefore, it is necessary to conduct studies generating knowledge about genetic 15893 Genetic variability in Pitcairnia flammea (Bromeliaceae) ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (4): 15892-15901 (2015) diversity and the distribution of this diversity among and within natural populations to establish conservation strategies. These studies can be performed with the use of molecular markers. Molecular markers are advantageous for studies of natural populations, for conservation programs, and to aid in properly classifying plant species. This study aimed to evaluate the genetic diversity among and within natural populations of Pitcairnia flammea, occurring in three fragments of the Atlantic Forest in the southern State of Espírito Santo through the use of inter-simple sequence repeat (ISSR) markers. DNA samples from 55 individuals were amplified with 18 ISSR primers, generating 180 bands, 159 of which were polymorphic. The Shannon genetic diversity index ranged from 0.348 to 0.465, with an average of 0.412. The Bayesian approach for the molecular data indicated the existence of two genetic groups. Analysis of molecular variance indicated the existence of 90.3% diversity within the population and 9.74% among populations. The amount of genetic differentiation of populations was moderate (0.0974), indicating that gene flow rates may be enough to counteract the effects of genetic drift. Greater genetic variability found in population B indicates that this area is an important source of genetic variability.