Papers by Acelino Alfenas
Forest Pathology, Jan 19, 2018
terveinal and anphighenous lesions, distributed over the limb or just on one half of the leaf bla... more terveinal and anphighenous lesions, distributed over the limb or just on one half of the leaf blade, particularly along the main vein and on leaf margins, ultimately leading to defoliation (Gonçalves et al., 2008) (Figure 1). The disease occurs mainly in forest nurseries, but also affects young plants in the field (Alfenas, Zauza, Mafia, & Assis, 2009). Problems with this disease are more frequent in the growing and hardening areas of forest nurseries, where sprinkler irrigation systems or rainwater provide prolonged periods of leaf wetness exacerbate the spread, multiplication and penetration of X. axonopodis. Diseased eucalypt cuttings are unsuitable for planting in the field due to the reduced photosynthetic area and potential for the spread of the pathogen into previously unaffected areas (Neves, Guimarães, Ferraz, & Alfenas, 2014). Control of bacterial leaf blight includes practices that reduce inoculum sources and favourable conditions for infection, such as removal of infected leaves and plants, propagation of susceptible clones in seasons unfavourable for disease development (cold and dry weather), drip irrigation or subirrigation, suspended and covered nurseries, and disinfested tools (Alfenas et al., 2009). All of these techniques are very costly; thus, alternative measures are required to maintain profitability. Nutrients are essential for the growth and development of plants and are important factors in responses to pathogens, affecting disease development by changing plant physiology and/or by affecting the pathogen (Huber & Haneklaus, 2007). The effects of nutrients have been demonstrated in various pathosystems (Bécot, Pajot,
Forest Pathology, Oct 6, 2019
Due to the great adaptability of many eucalypt genotypes to different edaphoclimatic conditions, ... more Due to the great adaptability of many eucalypt genotypes to different edaphoclimatic conditions, eucalypt plantations are established in many parts of the world and currently represent one of the most important sources of fibre for the pulp and paper industries (Wingfield et al., 2009). With the expansion of eucalypt plantations, there has been an increase in the occurrence of new pests and diseases (Alfenas, Zauza, Mafia, & Assis, 2009; Wingfield et al., 2009). Calonectria leaf blight (CLB) is a main fungal leaf disease that occurs in cuttings and eucalypt plantations, especially in hot and humid regions (Alfenas et al.
DOAJ (DOAJ: Directory of Open Access Journals), Aug 1, 2012
Leaf blight and defoliation caused by Teratosphaeria species is one of the most important leaf di... more Leaf blight and defoliation caused by Teratosphaeria species is one of the most important leaf diseases of Eucalyptus globulus. Due to the importance of this tree species for the production of pulp and paper, and recent reports of severe leaf disease symptoms in Brazil, the present study was conducted to identify the pathogen(s) involved. Symptomatic leaves were collected in the Brazilian states of Paraná and Rio Grande do Sul, single ascospore cultures established, and isolates were investigated using DNA-based molecular tools. A species-specific PCR and sequence data from the nuclear ribosomal DNA operon were used for species identification. The following seven species were identified: Mycosphaerella scytalidii, Dissoconium dekkeri (=M. lateralis), Teratosphaeria ohnowa, T. perpendicularis, T. pseudafricana, T. flexuosa and T.nubilosa. Of the recorded species, T. nubilosa is regarded as the most serious threat to the cultivation of E. globulus in the states surveyed.
Microbiology Resource Announcements
Here, we report the draft genome sequence of Calonectria pteridis , the causal agent of Calonectr... more Here, we report the draft genome sequence of Calonectria pteridis , the causal agent of Calonectria leaf blight in eucalyptus plantations in Brazil. The 58,373,473-bp genome assembly consists of 1,167 scaffolds, with a GC content of 50.21%. These genomic data can contribute to future studies involving the biology, adaptability, and pathogenicity of C. pteridis .
In: Reynolds, Gregory J.; Wilhelmi, Nicholas P.; Palacios, Patsy, compilers. Proceeding of the 66th Western International Forest Disease Work Conference; 3-7 June 2019; Estes Park, CO. WIFDWC: www.wifdwc.org. p. 213-214, 2020
Fitopatologia Brasileira, 1998
Plant Molecular Biology, 2020
Key MessageA resistantE. grandisgenotype showed a constitutive overexpression of genes related to... more Key MessageA resistantE. grandisgenotype showed a constitutive overexpression of genes related to resistance to myrtle rust caused byA. 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.
Microbiology Resource Announcements, 2019
Here, we report the annotated draft genome sequence of Xanthomonas axonopodis pv. eucalyptorum pa... more 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.
Microbiology Resource Announcements, 2019
Here, we present a draft genome sequence of the type strain IBSBF 435 of Erwinia psidii ( Enterob... more 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.
Forest Pathology, 2017
Since the myrtle rust pathogen (Austropuccinia psidii) was first reported (as Puccinia psidii) in... more Since the myrtle rust pathogen (Austropuccinia psidii) was first reported (as Puccinia psidii) in Brazil on guava (Psidium guajava) in 1884, it has been found infecting diverse myrtaceous species. Because A. psidii has recently spread rapidly worldwide with an extensive host range, genetic and genotypic diversities were evaluated within and among A. psidii populations in its putative native range and other areas of myrtle rust emergence in the Americas and Hawaii. Microsatellite markers revealed several unique multilocus genotypes (MLGs), which grouped isolates into nine distinct genetic clusters [C1-C9 comprising C1: from diverse hosts from Costa Rica, Jamaica, Mexico, Puerto Rico, and USA-Hawaii, and USA-California; C2: from eucalypts (Eucalyptus spp.) in Brazil/Uruguay and rose apple (Syzygium jambos) in Brazil; C3: from eucalypts in Brazil; C4: from diverse hosts in USA-Florida; C5: from Java plum (Syzygium cumini) in Brazil; C6: from guava and Brazilian guava (Psidium guineense) in Brazil; C7: from pitanga (Eugenia uniflora) in Brazil; C8: from allspice (Pimenta dioica) in Jamaica and sweet flower (Myrrhinium atropurpureum) in Uruguay; C9: from jabuticaba (Myrciaria cauliflora) in Brazil]. The C1 cluster, which included a single MLG infecting diverse host in many geographic regions, and the closely related C4 cluster are considered as a "Pandemic biotype," associated with myrtle rust emergence in
Scientia Horticulturae, 2016
Ceratocystis wilt, caused by Ceratocystis fimbriata is one of the most serious limiting factors f... more 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.
PloS one, 2016
The Mango Sudden Decline (MSD), also referred to as Mango Wilt, is an important disease of mango ... more The Mango Sudden Decline (MSD), also referred to as Mango Wilt, is an important disease of mango in Brazil, Oman and Pakistan. This fungus is mainly disseminated by the mango bark beetle, Hypocryphalus mangiferae (Stebbing), by infected plant material, and the infested soils where it is able to survive for long periods. The best way to avoid losses due to MSD is to prevent its establishment in mango production areas. Our objectives in this study were to: (1) predict the global potential distribution of MSD, (2) identify the mango growing areas that are under potential risk of MSD establishment, and (3) identify climatic factors associated with MSD distribution. Occurrence records were collected from Brazil, Oman and Pakistan where the disease is currently known to occur in mango. We used the correlative maximum entropy based model (MaxEnt) algorithm to assess the global potential distribution of MSD. The MaxEnt model predicted suitable areas in countries where the disease does not a...
Fitopatologia Brasileira, 2007
European Journal of Plant Pathology, 2016
Mango is amongst the most exported fruits worldwide and the mango tree has been cultivated in man... more Mango is amongst the most exported fruits worldwide and the mango tree has been cultivated in many countries with tropical and subtropical climates. Currently, Ceratocystis wilt caused by Ceratocystis fimbriata is among the most important diseases on mango tree. Planting of resistant genotypes is the best strategy for disease control. In the selection of resistant plants a highly aggressive isolate should be used in inoculations under controlled conditions. Thus, the objective of this study was to evaluate whether there are differences in aggressiveness among isolates of C. fimbriata obtained from diseased mango trees in Brazil. Before inoculation, five randomly selected isolates were tested for sporulation and mycelial growth in different culture media in order to select the best conditions for inoculum production. Twenty-four isolates from the States of São Paulo, Rio de Janeiro, Minas Gerais and Mato Grosso do Sul were inoculated in the susceptible mango cultivar Espada. Subsequently, the four most aggressive isolates were inoculated in other five different mango cultivars. The culture media MEA provided the best levels of sporulation and mycelial growth for four of the five tested isolates. Isolates SEMG1-1 from Minas Gerais and SESP8-3 from São Paulo were the most aggressive. The response of cultivars to the most aggressive isolates tested in the present work varied from highly resistant to highly susceptible, ‘Ubá’ being the most resistant regardless of the isolate tested. These results demonstrate that there are significant differences in aggressiveness among C. fimbriata isolates from mango in Brazil, as well as cultivar × isolate interaction.
Forest Pathology, 2015
Summary The dieback and wilting caused by Erwinia psidii are emerging eucalypt diseases that have... more Summary The dieback and wilting caused by Erwinia psidii are emerging eucalypt diseases that have been observed since 2014 in the south and central-south regions of Brazil. Field observations have shown variability in disease severity resistance among Eucalyptus spp. clones and species. It is hypothesized that this variability is due to genetic resistance. To confirm this hypothesis, inoculations in genetically distinct eucalypt plants are necessary. However, lack of an inoculation method and disease assessment makes difficult to select resistant genotypes for use in commercial plantations or genetic breeding programmes. Three inoculation methods were tested on eight clones of Eucalyptus spp. Among them, inoculum deposition with bacteria-impregnated toothpick on the axillary buds was the simplest and most effective, capable to reproduce the disease symptoms observed under conditions of natural infection. We also developed a rating scale for disease assessment. Among eight clones tested, only Clone 1 (Eucalyptus saligna) and Clone 2 (Eucalyptus urophylla) were resistant.
Tropical Plant Pathology, 2015
The variation in disease incidence of bacterial wilt caused by Ralstonia solanacearum among eucal... more The variation in disease incidence of bacterial wilt caused by Ralstonia solanacearum among eucalypt clones (Eucalyptus spp.) in the field indicates that the disease may be controlled by planting resistant material. However, efficient inoculation methods for bacterial wilt on eucalypt are scarce and have low replicability. In this work, we developed an effective protocol for inoculation of R. solanacearum, which was subsequently validated on different eucalypt clones. Three methods were tested: (i) soil infestation with bacterial cell suspension; (ii) immersion of wounded roots in the bacterial cell suspension; and (iii) injection of bacterial cell suspension in the base of the stem. The injection method proved to be the most efficient for inoculating eucalypt with R. solanacearum. Differentiation between resistant and susceptible clones was observed 30 days after inoculation in independent assays. Base stem inoculation of 21 eucalypt clones showed that four clones, classified as resistant, did not exhibit wilt symptoms or bacterial ooze at the end of the experiment. Although no wilting symptoms were observed, four other clones were considered susceptible because at least one plant showed bacterial ooze from the inoculated tissue. The remaining 13 clones were highly susceptible, presenting typical wilt symptoms and bacterial ooze.
Fitopatologia Brasileira
ABSTRACT
Tropical Plant Pathology, 2015
Your article is protected by copyright and all rights are held exclusively by Sociedade Brasileir... more Your article is protected by copyright and all rights are held exclusively by Sociedade Brasileira de Fitopatologia. This e-offprint is for personal use only and shall not be selfarchived in electronic repositories. If you wish to self-archive your article, please use the accepted manuscript version for posting on your own website. You may further deposit the accepted manuscript version in any repository, provided it is only made publicly available 12 months after official publication or later and provided acknowledgement is given to the original source of publication and a link is inserted to the published article on Springer's website. The link must be accompanied by the following text: "The final publication is available at link.springer.com".
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Papers by Acelino Alfenas