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Planting of resistant clones is the main control strategy for rust caused by Austropuccinia psidii on eucalypts in Brazil. Phenotyping for resistance to rust is performed at the last stage of the breeding programme on genetic material preselected for growth and industrial traits, which therefore may include susceptible genotypes. An alternative way to increase the frequency of resistant individuals in the breeding population is to perform resistance phenotyping during the initial stages of the programme. However, the impact of this approach on other characteristics considered as priority in the selection of genetic material should be assessed. In this study, we evaluated whether early selection for resistance to rust influenced total diameter at breast height (DBH), height (TH), average annual increment (IMA) and basic wood density (BWD), which are important selection criteria in eucalypt breeding. For this, a total of 6 703 plants from 70 full-sib progenies of Eucalyptus grandis, E. urophylla and hybrids of these species were phenotyped for rust resistance before transplanting, under controlled conditions, and again at seven months after transplanting, under field conditions and natural infection. Subsequently, the breeding population was evaluated for BWD indirectly through pilodyn penetration at 24 months after planting, and for DBH, TH and MAI at 37 months. Considering the final phenotype, 25.3% individuals were classified as resistant and 74.7% were susceptible to rust. Comparative genetic analyses between resistant and susceptible individuals showed that selection for resistance, performed early, did not influence DBH, TH, MAI or BWD traits. Thus, the early selection of resistant genotypes speeds up the exclusion of susceptible genotypes, saving time and resources in the development of new commercial clones without interfering with other important traits for tree breeding. [ABSTRACT FROM AUTHOR]

Ceratocystis fimbriata is an important pathogen with a wide host range that causes xylem lesions, wilt and death in different plant species. More adapted populations of C. fimbriata have probably been selected to specific hosts and high genetic and physiological variability can be found within the pathogen populations. Thus, molecular analysis and inoculation studies were performed to investigate the genetic and physiological variability of isolates of C. fimbriata complex obtained from different host species and geographic regions in Brazil. The minimum spanning tree analysis based on 14 simple‐sequence repeat (SSR) markers of C. fimbriata exhibited a clear clustering of isolates according to host, where each groups of isolates differed in at least five loci. In addition, inoculation of eight hosts with 10 isolates revealed a wide variation in aggressiveness. By assessing the length of xylem lesions caused by C. fimbriata isolates, Ficus carica was found to be the most susceptible host, followed by Mangifera indica. Only the isolates from Theobroma cacao and Carapa guianensis proved to be host specialized. Overall, the isolates tested were more aggressive to the hosts from which they were sampled. [ABSTRACT FROM AUTHOR]

Outbreaks of bacterial leaf blight (BLB) frequently affect eucalypt plants under nursery and field conditions in several countries. Although research has been conducted to unveil the causal agent, different bacterial species have been associated with similar disease symptoms in different countries. In order to determine the causal agent of BLB in Brazil, a survey was conducted in nine states to recover bacterial isolates from eucalypt plants exhibiting typical BLB symptoms. A total of 41 yellow‐colony isolates with varying aggressiveness towards a susceptible eucalypt clone were obtained, with 16S rDNA sequences indicating that they belong to the Xanthomonas genus. Rep‐PCR analysis separated the Xanthomonas population affecting eucalypt into six distinct groups revealing its high genetic diversity. The same population formed three clusters together with reference strains of X. citri, X. euvesicatoria and X. phaseoli in a phylogenetic tree constructed with partial dnaK, fyuA, gyrB and rpoD gene sequences. Clustering in the phylogenetic tree was clearly related to grouping based on rep‐PCR. Genome sequence comparisons of representative eucalypt isolates with type strains of validly published Xanthomonas species confirmed that the population consisted of X. citri, X. euvesicatoria and X. phaseoli. Inoculation of tomato, common bean, castor bean and eucalypt plants showed that the representative eucalypt isolates can cause disease in these plant species. Based on the results, the transfer of Xanthomonas axonopodis pv. eucalyptorum to Xanthomonas citri is proposed. These results are relevant for eucalypt BLB management under nursery and field conditions, including selection and deployment of effective plant resistance. [ABSTRACT FROM AUTHOR]

An outbreak of a new and severe disease was observed in Eucalyptus plantations of Bahia state, Brazil. An Ascomycota fungus has been frequently associated with the main symptoms of the disease namely leaf spot, branch cankers, shoot blight, defoliation, and dieback. Based on morphological characteristics, phylogenetic analysis (ITS and TEF‐1α genes), and pathogenicity test on Eucalyptus plants, Pseudoplagiostoma eucalypti was identified as the causal agent of the disease. Although P. eucalytpi has been known from in Brazil since 1998, this is the first report of it causing severe disease and die‐back on Eucalyptus spp. and we also record new symptoms associated with the pathogen. [ABSTRACT FROM AUTHOR]

Bacterial wilt caused by Ralstonia solanacearum is a serious disease of eucalypt in humid and high temperature areas worldwide. Spreading of the bacterium in the field or to other nurseries occurs mainly by symptomless infected plant material. The use of pathogen‐free propagating material as well as planting of resistant genotypes are currently the only strategies used for disease control. Therefore, a reliable and sensitive method for detection of low titres of R. solanacearum in infected plant tissue is essential for the success of management programmes. In this work, we adapted an efficient intercalating dye‐based real‐time PCR protocol to detect the bacterium in symptomless eucalypt plants as well as to investigate its movement in eucalypt clones CLR172 and CLR371, which exhibit resistant and susceptible phenotypes, respectively. We found that the bacterium translocates acropetally and basipetally in inoculated but symptomless cuttings of the resistant clone, as in cuttings of the susceptible clone displaying symptoms. Nevertheless, a smaller concentration of bacterial DNA was detected in tissues of the resistant clone. Mature biofilms occluding the xylem vessels were present in the susceptible clone whereas only single cells or small aggregates were observed in the resistant clone. This work contributes to improve our knowledge of the colonization process of R. solanacearum in eucalypt clones with different levels of susceptibility and to understand how the defence mechanisms against bacterial wilt in Eucalyptus work. Our findings could aid in the selection of the most resistant eucalypt clones to be used in wilt disease management programmes. [ABSTRACT FROM AUTHOR]

Bacterial wilt, one of the world's most destructive diseases in many crops, including eucalypt, is caused by four distinct phylogenetic lineages of the Ralstonia solanacearum species complex, recently classified in three distinct species: R. solanacearum (phylotype II), R. pseudosolanacearum (phylotype I and III) and R. syzygii (phylotype IV). In this study, we characterized 93 Ralstonia isolates obtained from eucalypt grown in different Brazilian regions using phylotype and sequevar designations and genomic fingerprinting with BOX‐PCR. In addition, we evaluated the aggressiveness of a select group of isolates in two eucalypt clones differing in resistance. We found that 89 isolates belong to R. solanacearum (phylotype II) and four to R. pseudosolanacearum (phylotype I). Unlike R. pseudosolanacearum, R. solanacearum was phylogenetically diverse and no correlation was found between sequevar and geographic origin. Most isolates grouped with reference isolates of phylotype IIA sequevar 41, whereas a few others clustered in phylotype IIB, mainly sequevar 4NPB, which is an emergent variant described affecting eucalypt for the first time. Isolates of R. solanacearum phylotype IIB were less aggressive to clone CLR371 (susceptible) whereas the R. pseudosolanacearum isolate tested was the only one pathogenic to the CLR172 (resistant) clone. Isolate aggressiveness varied between the eucalypt clones tested. The results of this study reinforce the importance of conducting molecular and aggressiveness characterization of the pathogen population to develop management strategies aimed at the deployment of host resistance in eucalypt breeding programmes. [ABSTRACT FROM AUTHOR]

Erwinia psidii is the causal agent of bacterial blight of guava, and wilt and dieback of eucalypt in Brazil. Previous studies using repetitive sequence‐based PCR (rep‐PCR) revealed limited genetic diversity in E. psidii populations. Here, the draft genome sequence of the type strain IBSBF435 was probed for variable number of tandem repeats (VNTRs) that could be used to study E. psidii genetic diversity by multilocus variable number of tandem repeat analysis (MLVA). Eleven selected VNTRs were used to assess genetic relatedness among 108 E. psidii strains from guava (36) and eucalypt (72), of different geographic origins and years of collection. A total of 79 haplotypes were detected in the strain collection. The number of alleles per locus ranged from 3 to 15. A minimum spanning tree indicated the occurrence of nine clonal complexes, of which two contained only guava strains, five only eucalypt strains, and two contained guava and eucalypt strains. The three oldest strains collected from guava in the 1980s (IBSBF435, IBSBF454, and IBSBF493) exhibited distinct haplotypes. IBSBF435 was genetically more closely related to some eucalypt strains than to guava strains, which supports previously reported lack of host specificity. IBSBF454 grouped with guava strains more recently collected from different states, suggesting that it could have been disseminated to different Brazilian areas. The implication of the lack of differentiation between guava and eucalypt strains is discussed in relation to the detection of E. psidii affecting eucalypt more than 25 years after the first description of guava bacterial blight. [ABSTRACT FROM AUTHOR]

Erwinia psidii is a gram‐negative bacterium that threatens both guava and eucalypt plantations in several countries. Despite the economic importance of both crops, nothing is currently known about the molecular mechanisms underlying E. psidii pathogenicity and, consequently, how it evolved to infect Eucalyptus species besides its presumed native host Psidium guajava. In this study, we predicted putative type III secretion system effectors that may play important roles during plant–E. psidii interactions and conducted effector structure and phylogenetic analyses to gain important insights into their function and evolution. For that, the whole genomes of four E. psidii strains that exhibit differential aggressiveness towards eucalypt clones were sequenced and their effector repertoires predicted based on sequence identity with known effectors of the model phytopathogen Erwinia amylovora. Only proteins sharing significant sequence identity with the DspE and Eop1 effectors were found. Here, it is shown that these two E. psidii effectors retain all structural characteristics of their corresponding protein superfamilies, but exhibit allelic variations that are consistent with the observed aggressiveness differences between strains. Phylogenetic analyses revealed that whereas E. psidii housekeeping gene sequences are more closely related to those from Erwinia tracheiphila, the effector (either nucleotide or amino acid) sequences are more closely related to their Pantoea agglomerans counterparts, suggesting that dspE and eop1 were both acquired through horizontal gene transfer from the latter bacterial species. The results of this study provide important insights on E. psidii pathogenicity and set the stage for future effector functional studies. [ABSTRACT FROM AUTHOR]

Myrtle rust (MR) caused by Austropuccinia psidii is one of the most important diseases affecting eucalypt (Eucalyptus) plantations in Brazil. Over the years, selection and planting of MR‐resistant clones has been the primary strategy for MR management. In May 2013, young trees of the GG100 hybrid (E. grandis × E. urophylla) clone—widely planted in Brazil and previously classified as resistant to MR—were infected by A. psidii in Minas Gerais, Brazil. In this study, artificial inoculations of a eucalypt clone set with differential reactions to A. psidii races were used to discover a new race of A. psidii (race 5) that was highly aggressive on the majority of eucalypt clones tested. In addition, only this new race successfully infected eucalypt G26 and 847 genotypes, which were formerly classified as resistant to the four previously known races of A. psidii. Since G26 genotype is homozygous for Ppr1 (a major resistance gene against A. psidii), this is the first report of MR resistance breakdown in a eucalypt genotype homozygous for Ppr1. Our findings demonstrate that this new A. psidii race is highly aggressive and capable of infecting a larger number of eucalypt genotypes compared with the previously known A. psidii races 1, 2, 3, and 4. [ABSTRACT FROM AUTHOR]

Kiwifruit (Actinidia spp.) is native to southern China, but was first cultivated in New Zealand and then spread worldwide. Emerging diseases such as ceratocystis wilt have attracted the attention of kiwifruit growers due to the great losses observed in southern Brazil. Effective control can be achieved by screening for resistance, but the genetic variability of the pathogen must be considered. Thus, this study aimed to assess the genetic diversity and variation in aggressiveness of Ceratocystis isolates from kiwifruit in southern Brazil and then evaluate the resistance of kiwifruit cultivars with the most aggressive isolates. A collection of 46 isolates were obtained from southern Brazil and 14 simple‐sequence repeat (SSR) markers was successfully used for genotyping. Out of 14 markers, 13 were polymorphic and identified 26 genotypes. Fourteen distinct genotypes were tested on a susceptible cultivar to select the most aggressive ones. Finally, inoculation with an equal mixture of five of the most aggressive isolates was used to evaluate the resistance of seven kiwifruit cultivars: Red Arguta, Green Arguta, Allison, Chieftain, Hayward, Monty, and Tomury. Cultivars varied in levels of susceptibility, with disease severity ranging from 40% to 100%. Considering the length of stem lesions, Chieftain showed the lowest level of severity at 40%, while no wilt symptoms were observed at 45 days after inoculation. In addition to the seven cultivars, a half‐sibling progeny with 618 plants of the rootstock cv. Bruno was also assessed, but only seven individuals were resistant. These seven plants can be cloned and used as resistant rootstocks in commercial orchards. [ABSTRACT FROM AUTHOR]

Ralstonia solanacearum sensu lato causes bacterial wilt in many agronomic crops and tree species economically important worldwide. It is a species complex that has been divided into phylotypes and sequevars, commonly related to geographic distribution. Knowledge of the phylotype composition and genetic variability in populations of this phytopathogenic bacterium is useful for implementing effective control measures. In a survey conducted in 2019, six bacterial strains were obtained from wilted Eucalyptus urophylla trees in plantations located in the municipality of Dom Eliseu, Pará state, Brazil. Multiplex PCR based on the internal transcribed spacer (ITS) indicated that the bacterial strains belonged to two different species, namely R. pseudosolanacearum (phylotype I) and R. solanacearum (phylotype II). In a phylogenetic analysis, the nucleotide sequence of the endoglucanase (egl) gene from eucalypt strains of phylotype I clustered together with sequevar 18 sequences from GenBank. Separation of the strains into two different species was confirmed by repetitive element palindromic PCR (rep‐PCR). Pathogenicity tests demonstrated that the R. solanacearum and R. pseudosolanacearum strains recovered from E. urophylla cause disease in both tomato and eucalypt plants. Until now, only R. solanacearum (Phylotype II) has been reported causing wilt symptoms on Eucalyptus spp. in Brazil. Therefore, the presence of R. pseudosolanacearum and a need for better understanding of its genetic and aggressiveness variability as well as possible differences between the two species should be considered in breeding programmes aimed at the deployment of host resistance. [ABSTRACT FROM AUTHOR]

Ceratocystis wilt, caused by Ceratocystis fimbriata is one of the most serious limiting factors for mango production in Brazil. Despite efforts in the selection and the identification of mango cultivars resistant to Ceratocystis wilt, the genetic basis of the resistance remains unknown. Therefore, the objective of this study was to understand the inheritance of resistance to C. fimbriata by artificial inoculations of the pathogen in progenies of six commercial varieties of mango using “Tommy Atkins” as the male parent. The cultivars “Keitt”, “Palmer”, “Tommy Atkins” and “Van Dyke” were confirmed as moderately resistant, whereas “Coquinho”, “Espada” and “Haden” were susceptible. The results of the inoculation on the progenies of these cultivars revealed that the resistance in mango is polygenic with a prevalence of genes expressing the effects of dominance and epistasis. The genetic gain with the selection of the 10 more resistant plants was 46%, which indicated a 46% reduction in disease severity. In general, a low frequency of the alleles favorable to disease resistance was observed in the population studied, which suggests the need for the introduction of new sources of genetic materials carrying the genes responsible for resistance. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Mango sudden decline (MSD) caused by Ceratocystis fimbriata is one of the major diseases affecting mango crop in Brazil, Oman, and Pakistan. In Brazil, the main strategy for MSD management has been the use of resistant plants as rootstock for grafting. In this study, we tested the resistance of mango cultivar Ubá to C. fimbriata isolates from different populations. Firstly, we inoculated 2173 seedlings from 129 accessions of mango cv. Ubá using three representative fungal isolates from Brazil. Following the inoculation, the potential resistant plants were challenged against ten C. fimbriata isolates from Brazil and three from Oman. Finally, to confirm its resistance, clonal replicates of the resistant accessions were re-inoculated with the same fungal isolates. In the first selection, 13 accessions were pre-selected as resistant. In subsequent selections, they proved to be resistant to C. fimbriata isolates from populations from Oman/Pakistan and Southeastern Brazil. However, all 13 accessions were susceptible to fungal isolates from populations from Northeastern Brazil and Rio de Janeiro (also in Brazil). Our results reveal that mango cv. Ubá resistance to MSD is isolate specific and depends on the pathogen population. We obtained 13 mango cv. Ubá clones resistant to C. fimbriata , which may be useful as rootstock to MSD management in Oman and specific regions from Brazil. • The resistance of mango cultivar Ubá to mango sudden decline (MSD) is isolate specific. • Thirteen clones of mango cv. Ubá resistant to MSD were obtained. • The resistant clones may be used as rootstock in commercial orchards of mango. [ABSTRACT FROM AUTHOR]

Dieback and wilt, caused by Erwinia psidii (Ep), is one of the most important emergent diseases of Eucalyptus spp. in Brazil. Currently, pathogen detection relies on isolation of bacteria from infected plant tissue and either identification based on morphological, physiological and biochemical tests or DNA amplification using the polymerase chain reaction (PCR), which in many cases is laborious and cumbersome. Considering the need for a simpler and more rapid, yet reliable, method for detecting the pathogen, we obtained a polyclonal antibody (anti‐Ep) and developed an agglutination test for specific detection of E. psidii. The antiserum was produced against the E. psidii strain LPF534 and tested against 101 E. psidii isolates from Eucalyptus spp.; three E. psidii isolates from Psidium guajava; 23 Ralstonia solanacearum and 18 Xanthomonas axonopodis isolates pathogenic to Eucalyptus spp.; and seven endophytic isolates from Eucalyptus spp., three of which are phylogenetically related to the genus Erwinia. Results of direct ELISA indicated that a concentration as low as 3.5 µg/ml of the anti‐Ep antibody was able to detect the E. psidii antigen and that the antibody did not cross‐reacted with other bacteria pathogenic and non‐pathogenic to Eucalyptus spp. In the agglutination test, the anti‐Ep antibody showed positive reaction with all strains of E. psidii tested whereas cross‐reaction with none of the strains that belong to other taxonomic groups was observed. The agglutination test showed a detection limit of 105 colony‐forming units (CFU)/ml, and its specificity was the same as that obtained by PCR amplification using E. psidii‐specific primers. These results demonstrate that the agglutination test developed here is a useful tool for specific, fast and inexpensive detection of E. psidii although only operational on pure bacterial suspensions and not yet directly from infected tissues. [ABSTRACT FROM AUTHOR]

Dieback caused by Erwinia psidii is currently one of the most important emerging diseases in eucalypt plantations in Brazil. However, little is known in terms of the host range of this pathogen or the potential sources of resistance against the disease it causes. In this study, we inoculated plants of species from nine families to gain insight into the host range of E. psidii. Plants of all inoculated species of Myrtaceae except Acca sellowiana exhibited disease symptoms and therefore represent potential hosts for the pathogen under natural conditions. In addition, the response of four Corymbia species, 29 Eucalyptus species and three interspecific Eucalyptus hybrids to inoculation with E. psidii was evaluated. All Corymbia henryi, Corymbia maculata, Eucalyptus thozetiana, Eucalyptus cloeziana, Eucalyptus viminalis, Eucalyptus dalrympleana and Eucalyptus pilularis plants were highly resistant to the pathogen, whereas differential disease resistance was observed in the other species. This study provides important information on sources of resistance to Erwinia psidii with potential use in the development of clones with enhanced resistance in eucalypt species of economic importance. [ABSTRACT FROM AUTHOR]

Podosphaera pannosa is the causal agent of powdery mildew on eucalypt in Brazil. This powdery mildew disease is important in nurseries causing leaf and shoot distortion, shoot discoloration and reduction in growth, which decreases mini‐cutting production. Improved RNA sequencing (RNA‐Seq) technologies have allowed increased information about the transcriptome of several pathogens and hosts, enabling a better understanding of their interaction at the gene level. For this study, we analysed the transcriptome of P. pannosa during leaf infection of Eucalyptus urophylla leaves using RNA‐Seq and de novo transcriptome assembly. The transcriptome was Illumina sequenced and assembled de novo, generating over 178 million RNA‐Seq reads assembled onto 200,473 contigs. After filtering steps, the resulting 12,106 (6%) transcripts were identified as the P. pannosa transcriptome data set. The 10 most abundant transcripts included genes encoding enzymes likely involved in fungal establishment and growth, such as dihydrofolate reductase, putative methyltransferases, acyl‐desaturase, glycoside hydrolase and dehydrogenases. In addition, genes putatively encoding an aquaporin and an orthologue to the effector protein, GoEC2 of Golovinomyces orontii were identified. The predicted secretome consisted of 1,899 translated transcripts, of which 310 exhibited homology to proteins described in the PHI database, 144 of these showing homology to fungal PHI accessions that affected pathogenicity or that are described as effectors. In addition, 81 transcripts encoded secreted proteins homologous to effectors described in the Erysiphales. These results provide a basis for continued studies to better understand the P. pannosa‐eucalypt (Eucalyptus spp.) pathosystem and could parallel studies of the eucalypt transcriptome to help determine host resistance mechanisms. [ABSTRACT FROM AUTHOR]

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 B otrytis pseudocinerea associated with A cca se l lowiana (Myrtaceae). Due to the new phylogenetic positioning of B otrytis pelargonii and B otrytis eucalypti , a taxonomic review of these species was suggested. • Botrytis cinerea is the prevalent Botrytis species in Brazil. • Botrytis pseudocinerea was reported in Brazil associated with Acca sellowiana (Myrtaceae). • Three new plant–pathogen combinations were described. • Eight new hosts to B. cinerea in Brazil were reported. [ABSTRACT FROM AUTHOR]

Abstract 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. [ABSTRACT FROM AUTHOR]

In Brazil the rust caused by Puccinia psidii Winter stands out as the most important disease of eucalyptus. The use of resistant genotypes is the main control method, which makes the detection of markers linked to rust resistance essential to the selection of resistant genotypes. In this study, an F1 progeny of 131 plants from interspecific crossings of Eucalyptus was used to identify markers linked to resistance genes for this pathogen. An integrated map was constructed for linkage group three based on microsatellite markers. For QTL mapping two methodologies based on alleles identical-by-descent (IBD) were used: single marker analysis of Haseman and Elston and the interval mapping procedure of Fulker and Cardon. Both methods showed significant association for the Embra 125 marker.The QTL that explained 42 % of the phenotypic variation was mapped to 0.02 cM of this marker by the Fulker and Cardon. Marker Embra 125 has potential use in assisted selection, thus increasing the efficiency of the selection of resistant genotypes. [ABSTRACT FROM AUTHOR]

• Ceratocystis fimbriata LPF1912 has a compact genome with 43% as coding sequencing. • A set of 4919 orthologous gene clusters represent the minimum quorum for the three pathogens. • Two Ceratocystis pathogens showed a different pathogenicity-related genes compared to Calonectria pseudoreteaudii. • The most of DEGs of C. fimbriata LPF1912 is related to its pathogenicity in Eucalyptus spp. 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. [ABSTRACT FROM AUTHOR]

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., (Copyright © 2019 Neves et al.)

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.

Bacterial leaf blight is a major disease of eucalypt, especially under nursery conditions. Different bacterial species have been associated with the disease in several countries, and despite its importance worldwide, it is not clear to date whether similar disease symptoms are caused by the same or by different etiological agents. In this study, 43 bacterial strains were isolated from blighted eucalypt leaves collected in different geographic areas of Brazil and inoculated onto a susceptible eucalypt clone. Polyphasic taxonomy, including morphological, physiological, biochemical, molecular, and pathogenicity tests showed that only certain strains of Xanthomonas axonopodis caused symptoms of the disease. Strains varied in their aggressiveness, but no correlation with geographic origin was observed. MLSA-based phylogenetic analysis using concatenated dnaK , fyuA , gyrB and rpoD gene sequences allocated the strains in a well-defined clade, corresponding to Rade-marker's group RG 9.6. Inoculation of nineteen plant species belonging to seven botanical families with representative strain LPF 602 showed it to be pathogenic only on Eucalyptus spp, and Corymbia spp. Based on distinct biochemical and pathogenic characteristics that differentiate the eucalypt strains from other pathovars of the X. axonopodis species, here we propose their allocation into the new pathovar X. axonopodis pv. eucalyptorum pv. nov.

Plant growth-promoting rhizobacteria strains from special formulations have been used to optimize eucalyptus cutting production. To undertake quality control for the formulated products, the rhizobacterial strains should be characterized to assess their purity and authentication. In the present study, we characterized nine strains of rhizobacteria, including three Bacillus subtilis (S1, S2 and 3918), two Pseudomonas sp. (MF4 and FL2), P. putida (MF2), P. fulva (Ca), Frateuria aurantia (R1), and Stenotrophomonas maltophilia (CIIb). The strains were differentiated by colony morphology after 24h of incubation in three different solid state culture media (glucose-nutritive agar, 523 medium and yeast extract-mannitol agar), sensitivity to a panel of 28 antibiotics (expressed according to the formation of inhibition halos of bacterial growth in the presence of antibiotics), and PCR-RFLP profiles of the 16S rDNA gene produced using nine restriction enzymes. It was possible to differentiate all nine strains of rhizobacteria using their morphological characteristics and sensitivity to antibiotics. The molecular analysis allowed us to separate the strains CIIb, FL2 and R1 from the strains belonging to the genera Bacillus and Pseudomonas. By using these three methods concomitantly, we were able to determine strain purity and perform the authentication., (Copyright © 2016. Published by Elsevier Editora Ltda.)

Chrysophorte cubensis induced canker occurs in nearly all tropical and subtropical regions where eucalypts are planted, causing losses in both wood quality and volume productivity, especially so in the warmer and more humid regions of Brazil. The wide inter and intra-specific genetic variability of resistance to canker among Eucalyptus species facilitates the selection of resistant plants. In this study, we evaluated resistance to this pathogen in five Eucalyptus grandis (G) and 15 E. urophylla (U) trees, as well as in 495 individuals from 27 progenies derived from crosses between the trees. In the field, six-months-old test seedlings were inoculated with C. cubensis. Lesion length in the xylem and bark was measured eight months later. The results demonstrated that xylem lesions could preferentially be used for the selection of resistant clones. Eight trees (7 U and 1 G) were susceptible, and the remainder (8 U and 4 G) resistant. Individual narrow and broad sense heritability estimates were 17 and 81%, respectively, thereby suggesting that canker resistance is quantitative and highly dependent on dominance and epistasis.