Diversity, prevalence and phylogenetic positioning of Botrytis species in Brazil.

Botrytis is a necrotrophic fungal genus of great economic importance worldwide. Together, the Botrytis species are able to infect over one thousand host plant species, including dicotyledons and monocotyledons. As the identification of Botrytis species in Brazil has mostly been based only on morphological characterization and comparisons of the rDNA ITS region, which is not informative in the genus, its diversity remains unknown. Thus, in this study we determined the diversity and prevalence of Botrytis spp. in Brazil by multilocus phylogeny. Phylogenetic reconstruction of the genus was performed using the nuclear genes glyceraldehyde-3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60) and RNA polymerase II second largest subunit (RPB2). From analyses of 56 Botrytis isolates obtained from different hosts and geographical regions in Brazil, we found that Botrytis cinerea is the most prevalent species with considerable intraspecific genetic diversity detected by nuclear genes. Two new hosts to B. cinerea and eight host never previously reported in Brazil were found. We also reported for the first time the occurrence of Botrytispseudocinerea associated with Accasellowiana (Myrtaceae). Due to the new phylogenetic positioning of Botrytispelargonii and Botrytiseucalypti, a taxonomic review of these species was suggested.

Transcriptome analysis of Eucalyptus grandis genotypes reveals constitutive overexpression of genes related to rust (Austropuccinia psidii) resistance.

Key Message A resistant E. grandis genotype showed a constitutive overexpression of genes related to resistance to myrtle rust caused by A. psidii. Abstract Myrtle rust caused by Austropuccinia psidii is considered one of the most important fungal diseases affecting Eucalyptus spp. plantations in Brazil. Although the selection and planting of resistant eucalypt genotypes have been the major strategies to manage the disease in Brazil, the molecular mechanisms involved in resistance are still unclear. In this study, we evaluated the gene expression profile of two contrasting Eucalyptus grandis genotypes in resistance level to rust by RNA-Seq. The two genotypes showed a very different background gene expression level even without A. psidii infection. The resistant genotype had a constitutive overexpression of a large number of protein-coding genes compared to the susceptible genotype. These genes were mainly associated with signal transduction, photosynthesis, regulation and response to salicylic acid (SA), and protein kinase leucine-rich receptors (PK-LRR). PK-LRR and SA mediated disease resistance are well known to be effective against obligate biotroph pathogens, such as A. psidii. In addition, at 24 h after infection, the susceptible genotype was able to activate some response, however, several resistance-related proteins had their expression level reduced with A. psidii infection. Here, we present the first analysis of E. grandis genotypes transcriptomes infected by A. psidii and it reveals a constitutive overexpression of several resistance-related genes in the resistant genotype compared to the susceptible one. Our findings have the potential to be used as candidate molecular markers for resistance to myrtle rust.

Comparative genomic and transcriptomic analyses reveal different pathogenicity-related genes among three eucalyptus fungal pathogens.

Ceratocystis fimbriata is an important plant pathogen known to cause Ceratocystis Wilt (CW), a prevalent fungal disease known to affect Eucalyptus spp. plantations in Brazil. To better understand the molecular mechanisms related to pathogenicity in eucalyptus, we generated a high-quality assembly and annotation of the Ce. fimbriata LPF1912 isolate (LPF1912) genome, as well as the first transcriptome of LPF1912 from 16 eucalyptus clones at three infection incubation periods (12, 18, and 24 h). The LPF1912 genome assembly contains 805 scaffolds, totaling 31.8 Mb, with 43% of the genome estimated to be coding sequence comprised of 7,390 protein-coding genes of which 626 (8.5%) were classified as secreted proteins, 120 ribosomal RNAs, and 532 transfer RNAs. Comparative genomic analysis among three eucalyptus fungal pathogens (Ce. fimbriata, Ce. eucalypticola, and Calonectria pseudoreteaudii), showed high similarity in the proteome (21.81%) and secretome (52.01%) of LPF1912 and Ce. eucalypticola. GO annotation of pathogenicity-related genes of LPF1912 and Ce. eucalypticola, revealed enrichment in cell wall degrading enzymes (CWDEs), and lipid/cutin metabolism for Ca. pseudoreteaudii. Additionally, a transcriptome analysis between resistant and susceptible eucalyptus clones to CW infection indicated that a majority (11) of LPF1912 differentially expressed genes had GO terms associated with enzymatic functions, such as the polygalacturonase gene family, confirming the crucial role of CWDEs for Ce. fimbriata pathogenicity. Finally, our genomic and transcriptomic analysis approach provides a better understanding of the mechanisms involved in Ce. fimbriata pathogenesis, as well as a framework for further studies.

First Draft Genome Sequence of Xanthomonas axonopodis pv. eucalyptorum, Causal Agent of Bacterial Leaf Blight on Eucalypt.

Here, we report the annotated draft genome sequence of Xanthomonas axonopodis pv. eucalyptorum pathotype strain LPF602 (synonym Xanthomonas axonopodis BSC45a), isolated from eucalypt leaves showing bacterial blight symptoms in Brazil. The availability of these genomic data will help improve the understanding of the evolution and molecular mechanisms involved in the pathogenesis of this microorganism.

A host specialized form of Ceratocystis fimbriata causes seed and seedling blight on native Carapa guianensis (andiroba) in Amazonian rainforests.

Ceratocystis fimbriata Ellis & Halsted recently was recorded causing seed and seedling blight on Carapa guianensis Aubl. (andiroba), a tree species native to the Amazon Rainforest and prized for its valuable timber and medicinal seed oil. C. fimbriata more commonly causes wilt type diseases in woody hosts, especially on non-native host trees. However, on andiroba the disease occurs on seedlings and seeds, affecting the species regeneration. We studied 73 isolates of C. fimbriata on andiroba from three regions of the Amazon Basin to see if they represented natural or introduced populations. Analysis of ITS rDNA sequences and phylogenetic analysis of mating type genes revealed new haplotypes of C. fimbriata from the Latin American Clade that were closely related to other Brazilian populations of the fungus. In mating experiments, andiroba isolates were inter-fertile with tester strains of C. fimbriata from Brazil and elsewhere, confirming that they belong to a single biological species. Using microsatellite markers, 14 genotypes and populations with intermediate levels of genetic variability were found, suggesting that the fungus is indigenous to the Amazon Basin. Inoculation tests indicated that the andiroba isolates are host-specialized on andiroba, supporting the proposition of the special form C. fimbriata f. sp. carapa.

Draft Genome Sequence of Erwinia psidii, Causal Agent of Bacterial Blight of Guava (Psidium guava) and Dieback of Eucalypt (Eucalyptus spp.).

Here, we present a draft genome sequence of the type strain IBSBF 435 of Erwinia psidii (Enterobacteriaceae), a phytopathogen that causes bacterial blight on guava (Psidium guava) and dieback and wilt on eucalypt (Eucalyptus spp.), both of which are important emerging diseases.