The adaptive potential of a plant pathogenic fungus, Rhizoctonia solani AG-3, under heat and fungicide stress

The ability to improve fitness via adaptive evolution may be affected by environmental change. We tested this hypothesis in an in vitro experiment with the plant pathogen Rhizoctonia solani Anastomosis Group 3 (AG-3), assessing genetic and environmental variances under two temperatures (optimal and higher than optimal) and three fungicide concentrations (no fungicide, low and high concentration of a copper-based fungicide). We measured the mean daily growth rate, the coefficient of variation for genotypic (I G) and environmental variance (I E) in growth, and broad-sense heritability in growth. Both higher temperature and increased fungicide concentration caused a decline in growth, confirming their potential as stressors for the pathogen. All types of standardized variances in growth—I G, phenotypic variance, and I E as a trend—increased with elevated stress. However, heritability was not significantly higher under enhanced stress because the increase in I G was counterbalanced by somewhat increased I E. The results illustrate that predictions for adaptation under environmental stress may depend on the type of short-term evolvability measure. Because mycelial growth is linked to fitness, I G reflects short-term evolvability better than heritability, and it indicates that the evolutionary potential of R. solani is positively affected by stres

Intraspecific Evolution of Rhizoctonia solani AG-1 IA Associated with Soybean and Rice in Brazil based on Polymorphisms at the ITS-5.8S rDNA Operon

Rhizoctonia solani AG-1 IA causes leaf blight on soybean and rice. Despite the fact that R. solani AG-1 IA is a major pathogen affecting soybean and rice in Brazil and elsewhere in the world, little information is available on its genetic diversity and evolution. This study was an attempt to reveal the origin, and the patterns of movement and amplification of epidemiologically significant genotypes of R.solani AG-1 IA from soybean and rice in Brazil. For inferring intraspecific evolution of R. solani AG-1 IA sampled from soybean and rice, networks of ITS-5.8S rDNA sequencing haplotypes were built using the statistical parsimony algorithm from Clement et al. (2000) Molecular Ecology 9: 1657-1660. Higher haplotype diversity (Nei M 1987, Molecular Evolutionary Genetics Columbia University Press, New york: 512p.) was observed for the Brazilian soybean sample of R. solani AG-1 IA (0.827) in comparison with the rest of the world sample (0.431). Within the south-central American clade (3-2), four haplotypes of R.solani AG-1 IA from Mato Grosso, one from Tocantins, one from Maranhão, and one from Cuba occupied the tips of the network, indicating recent origin. The putative ancestral haplotypes had probably originated either from Mato Grosso or Maranhão States. While 16 distinct haplotypes were found in a sample of 32 soybean isolates of the pathogen, the entire rice sample (n=20) was represented by a single haplotype (haplotype 5), with a worldwide distribution. The results from nested-cladistic analysis indicated restricted gene flow with isolation by distance (or restricted dispersal by distance in nonsexual species) for the south-central American clade (3-2), mainly composed by soybean haplotype

Phylogeography of the Solanaceae-infecting Basidiomycota fungus Rhizoctonia solani AG-3 based on sequence analysis of two nuclear DNA loci

<p>Abstract</p> <p>Background</p> <p>The soil fungus <it>Rhizoctonia solani </it>anastomosis group 3 (AG-3) is an important pathogen of cultivated plants in the family Solanaceae. Isolates of <it>R. solani </it>AG-3 are taxonomically related based on the composition of cellular fatty acids, phylogenetic analysis of nuclear ribosomal DNA (rDNA) and beta-tubulin gene sequences, and somatic hyphal interactions. Despite the close genetic relationship among isolates of <it>R. solani </it>AG-3, field populations from potato and tobacco exhibit comparative differences in their disease biology, dispersal ecology, host specialization, genetic diversity and population structure. However, little information is available on how field populations of <it>R. solani </it>AG-3 on potato and tobacco are shaped by population genetic processes. In this study, two field populations of <it>R. solani </it>AG-3 from potato in North Carolina (NC) and the Northern USA; and two field populations from tobacco in NC and Southern Brazil were examined using sequence analysis of two cloned regions of nuclear DNA (pP42F and pP89).</p> <p>Results</p> <p>Populations of <it>R. solani </it>AG-3 from potato were genetically diverse with a high frequency of heterozygosity, while limited or no genetic diversity was observed within the highly homozygous tobacco populations from NC and Brazil. Except for one isolate (TBR24), all NC and Brazilian isolates from tobacco shared the same alleles. No alleles were shared between potato and tobacco populations of <it>R. solani </it>AG-3, indicating no gene flow between them. To infer historical events that influenced current geographical patterns observed for populations of <it>R. solani </it>AG-3 from potato, we performed an analysis of molecular variance (AMOVA) and a nested clade analysis (NCA). Population differentiation was detected for locus pP89 (Φ_{<it>ST </it>}= 0.257, significant at P < 0.05) but not for locus pP42F (Φ_{<it>ST </it>}= 0.034, not significant). Results based on NCA of the pP89 locus suggest that historical restricted gene flow is a plausible explanation for the geographical association of clades. Coalescent-based simulations of genealogical relationships between populations of <it>R. solani </it>AG-3 from potato and tobacco were used to estimate the amount and directionality of historical migration patterns in time, and the ages of mutations of populations. Low rates of historical movement of genes were observed between the potato and tobacco populations of <it>R. solani </it>AG-3.</p> <p>Conclusion</p> <p>The two sisters populations of the basidiomycete fungus <it>R. solani </it>AG-3 from potato and tobacco represent two genetically distinct and historically divergent lineages that have probably evolved within the range of their particular related Solanaceae hosts as sympatric species.</p

Sensibilidade de populações de Mycosphaerella fijienses e M. Musicola a triazóis em bananais de regiões produtoras no Estado de São Paulo / Sensitivity of Mycosphaerella fijienses and M. Musicola populations to triazoles in banana plantations in producing regions in São Paulo State

As sigatokas negra (Mycosphaerella fijiensis, Mf) e amarela (M. musicola, Mm) são as doenças foliares mais destrutivas da bananeira no Brasil. Os fungos produzem grande quantidade de esporos sexuados e assexuados, com alta variabilidade genética e alta capacidade evolucionária nas populações. Os fungicidas Inibidores de desmetilação de esterol (DMIs) estão entre os mais comumente utilizados para o controle destas doenças, e a pressão de seleção pelo uso contínuo tem levado à seleção de populações resistentes. Devido à importância destas doenças para as regiões produtoras de banana no Brasil, é urgentemente necessário o conhecimento sobre o nível de sensibilidade de Mf e Mm a fungicidas inibidores de desmetilação de esterol (DMIs). O conhecimento prévio dos cenários de resistência a fungicidas em regiões e áreas produtoras de banana do país poderá ser usados para orientar os produtores a adotarem estratégias anti-resistência. Dessa forma, o objetivo do presente trabalho foi analisar a sensibilidade de populações de Mycosphaerella spp. a fungicidas DMIs. A resistência dos isolados foi determinada com base nos valores de EC50 para o fungicidas DMI/triazóis amplamente utilizados: tebuconazol e propiconazol. As populações de patógenos utilizadas em nosso estudo são oriundas do Vale do Ribeira e do Noroeste de São Paulo. O Vale do Ribeira representa a maior produção de banana do estado, predominando o plantio das variedades Prata e Nanica, onde são feitas em torno de 8 a 12 aplicações anuais de fungicidas, principalmente azoles. No Noroeste paulista foi coletada uma área plantada de agricultura familiar, sem aplicação de fungicidas. A região de maior aplicação de fungicida (Vale do Ribeira) apresentou maior quantidade de isolados resistentes, tanto para propiconazol quanto para tebuconazol. Quanto à amostragem de espécies, a Mycosphaerella fijiensis foi encontrada apenas no Vale do Ribeira e a M. musicola apenas no Noroeste Paulista. No entanto, em ambas as populações apresentam elevado risco de se tornarem insensíveis aos DMIs avaliados

Divergência genética entre linhagens de milho utilizando microssatélites e correlação com desempenho de híbridos simples

O sucesso nos programas de melhoramento genético de milho depende da identificação de genitores com boa capacidade de combinação para a produção de híbridos e na conservação da variabilidade genética do germoplasma. O emprego de marcadores moleculares pode auxiliar na avaliação da diversidade genética e na predição de híbridos, por meio da estimativa da distância genética. Com esse objetivo foram genotipadas, por marcadores microssatélites, 40 linhagens oriundas dos compostos Dentado e Flintisa e investigada a correlação do desempenho dos híbridos simples interpopulacionais com as distâncias genéticas entre suas linhagens. Verificou-se diversidade genética nos dois grupos de linhagens, permitindo a separação em grupos heteróticos distintos, mas sem concordância total com os dados de genealogia. As correlações entre performance dos híbridos e distância genética das linhagens foram baixas, indicando que altos níveis de distância genética entre linhagens é condição necessária, mas não suficiente para que seus híbridos exibam as melhores performances

Controle biológico da cigarrinha (Dalbulus aidis) e da lagarta-do-cartucho (Spodoptera frugiperda) do milho com Beauveria SSP / Biological control of corn leafhopper (Dalbulus maidis) and corn borer caterpillar (Spodoptera frugiperda) with Beauveria SSP

O controle de diversas pragas de importância agrícola vem se tornando cada vez mais difícil pelo uso de inseticidas, o qual se dá possivelmente em função da emergência de populações de insetos pragas e vetores resistentes a diversos princípios ativos. Sendo assim a utilização de métodos alternativos vem ganhando cada vez mais força e dentro esses medos um em destaque e o controle biológico, o qual utiliza microrganismos, como no caso a Beauveria spp., para o controle de divessar pragas agrícolas, como no caso da lagarta do cartucho e da cigarrinha do milho. Dessa forma o objetivo deste trabalho foi de determinar, em condições de campo, o potencial do fungo Beauveria spp como agente de controle biológico da cigarrinha (Dalbulus maidis), diminuindo os sintomas do complexo enfezamento, e da lagarta-do-cartucho (Spodoptera frugiperda) em milho. O fungo isolado no laboratório de Fitopatologia Molecular da UNESP de Ilha Solteira e multiplicado em milheto para posteriormente inoculado em campo. A resposta desse fungo entomopatogênico foi negativo para essas pragas do milho.O controle de diversas pragas de importância agrícola vem se tornando cada vez mais difícil pelo uso de inseticidas, o qual se dá possivelmente em função da emergência de populações de insetos pragas e vetores resistentes a diversos princípios ativos. Sendo assim a utilização de métodos alternativos vem ganhando cada vez mais força e dentro esses medos um em destaque e o controle biológico, o qual utiliza microrganismos, como no caso a Beauveria spp., para o controle de divessar pragas agrícolas, como no caso da lagarta do cartucho e da cigarrinha do milho. Dessa forma o objetivo deste trabalho foi de determinar, em condições de campo, o potencial do fungo Beauveria spp como agente de controle biológico da cigarrinha (Dalbulus maidis), diminuindo os sintomas do complexo enfezamento, e da lagarta-do-cartucho (Spodoptera frugiperda) em milho. O fungo isolado no laboratório de Fitopatologia Molecular da UNESP de Ilha Solteira e multiplicado em milheto para posteriormente inoculado em campo. A resposta desse fungo entomopatogênico foi negativo para essas pragas do milho

Ancient dispersal of the human fungal pathogen Cryptococcus gattii from the Amazon rainforest.

Over the past two decades, several fungal outbreaks have occurred, including the high-profile 'Vancouver Island' and 'Pacific Northwest' outbreaks, caused by Cryptococcus gattii, which has affected hundreds of otherwise healthy humans and animals. Over the same time period, C. gattii was the cause of several additional case clusters at localities outside of the tropical and subtropical climate zones where the species normally occurs. In every case, the causative agent belongs to a previously rare genotype of C. gattii called AFLP6/VGII, but the origin of the outbreak clades remains enigmatic. Here we used phylogenetic and recombination analyses, based on AFLP and multiple MLST datasets, and coalescence gene genealogy to demonstrate that these outbreaks have arisen from a highly-recombining C. gattii population in the native rainforest of Northern Brazil. Thus the modern virulent C. gattii AFLP6/VGII outbreak lineages derived from mating events in South America and then dispersed to temperate regions where they cause serious infections in humans and animals

Advancing Eucalyptus genomics: identification and sequencing of lignin biosynthesis genes from deep-coverage BAC libraries

<p>Abstract</p> <p>Background</p> <p><it>Eucalyptus </it>species are among the most planted hardwoods in the world because of their rapid growth, adaptability and valuable wood properties. The development and integration of genomic resources into breeding practice will be increasingly important in the decades to come. Bacterial artificial chromosome (BAC) libraries are key genomic tools that enable positional cloning of important traits, synteny evaluation, and the development of genome framework physical maps for genetic linkage and genome sequencing.</p> <p>Results</p> <p>We describe the construction and characterization of two deep-coverage BAC libraries EG_Ba and EG_Bb obtained from nuclear DNA fragments of <it>E. grandis </it>(clone BRASUZ1) digested with <it>Hind</it>III and <it>BstY</it>I, respectively. Genome coverages of 17 and 15 haploid genome equivalents were estimated for EG_Ba and EG_Bb, respectively. Both libraries contained large inserts, with average sizes ranging from 135 Kb (Eg_Bb) to 157 Kb (Eg_Ba), very low extra-nuclear genome contamination providing a probability of finding a single copy gene ≥ 99.99%. Libraries were screened for the presence of several genes of interest <it>via </it>hybridizations to high-density BAC filters followed by PCR validation. Five selected BAC clones were sequenced and assembled using the Roche GS FLX technology providing the whole sequence of the <it>E. grandis </it>chloroplast genome, and complete genomic sequences of important lignin biosynthesis genes.</p> <p>Conclusions</p> <p>The two <it>E. grandis </it>BAC libraries described in this study represent an important milestone for the advancement of <it>Eucalyptus </it>genomics and forest tree research. These BAC resources have a highly redundant genome coverage (> 15×), contain large average inserts and have a very low percentage of clones with organellar DNA or empty vectors. These publicly available BAC libraries are thus suitable for a broad range of applications in genetic and genomic research in <it>Eucalyptus </it>and possibly in related species of <it>Myrtaceae</it>, including genome sequencing, gene isolation, functional and comparative genomics. Because they have been constructed using the same tree (<it>E. grandis </it>BRASUZ1) whose full genome is being sequenced, they should prove instrumental for assembly and gap filling of the upcoming <it>Eucalyptus </it>reference genome sequence.</p