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1.
Mycologia ; : 1-15, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31750788

RESUMO

Corynespora cassiicola (Burk. & M.A. Curtis) C.T. Wei. is an anamorphic fungus that affects more than 530 plant species, including economically important crops. Several lineages of this pathogen have been recognized, but the classification of isolates into clades is time-consuming and still sometimes leads to unclear results. In this work, eight major phylogenetic clades (PhL1-PhL8) including 245 isolates of C. cassiicola from 44 plant species were established based on a Bayesian inference analysis of four combined C. cassiicola genomic loci retrieved from GenBank, i.e., rDNA internal transcribed spacer (ITS), actin-1,ga4, and caa5. The existence of PhL1-PhL5 and PhL7 as clonal lineages was further confirmed through the analysis of full-genome single-nucleotide polymorphisms of 39 isolates. Haplotypes of the caa5 locus were PhL specific and encode isoforms of the LDB19 domain of a putative α-arrestin N-terminal-like protein. Evolution of the Caa5 arrestin is in correspondence with the PhLs. ga4 and caa5 PhL consensus sequences and a cleaved amplified polymorphic sequence (CAPS) procedure were generated based on the conserved nucleotide sequences and enzyme restriction patterns observed among isolates from the same lineage, respectively. The CAPS method was validated in silico, and its practical use allowed us to differentiate between tomato and papaya isolates, as well as to reveal the prevalence of PhL1 among isolates infecting soybean in Brazil. This novel approach could be useful in the efforts to control the diseases associated with C. cassiicola.

2.
Plant Dis ; 103(9): 2212-2220, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31306094

RESUMO

White mold, caused by Sclerotinia sclerotiorum, is a yield-limiting disease of soybean in Brazil. Uniform fungicide trials have been conducted annually since 2009. Data from 74 cooperative field trials conducted over a 10-year period were assembled. We selected five fungicides applied two times around flowering: dimoxystrobin plus boscalid (DIMO+BOSC), carbendazim plus procymidone (CARB+PROC), fluazinam (FLUZ), fluopyram (FLUO), and procymidone (PROC). For comparison, thiophanate-methyl (TMET) applied four times was also included as a low-cost treatment. Network models were fitted to the log of white mold incidence (percentages) and log of sclerotia mass data (grams/hectare) and to the nontransformed yield data (kilograms/hectare) for each treatment, including the untreated check. Back-transformation of the meta-analytic estimates indicated that the lowest and highest mean (95% confidence interval [CI]) percent reductions in incidence and sclerotia mass were 54.2 (49.3 to 58.7) and 51.6% (43.7 to 58.3) for TMET and 83.8 (79.1 to 87.5) and 87% (81.9 to 91.6) for CARB+PROC, respectively. The overall mean (95% CI) yield responses ranged from 323 kg/ha (247.4 to 400.3) for TMET to 626 kg/ha (521.7 to 731.7) for DIMO+BOSC, but the variance was significantly reduced by a binary variable (30% threshold) describing disease incidence in the untreated check. On average, an increment of 352 kg/ha was estimated for trials where the incidence was >30% compared with the low-disease scenario. Hence, the probability of breaking even on fungicide costs for the high-disease scenario was >65% for the more effective, but more expensive fungicide (FLUZ) than TMET. For the low-disease scenario, profitability was less likely and depended more on variations in fungicide cost and soybean price.


Assuntos
Ascomicetos , Fungicidas Industriais , Doenças das Plantas , Soja , Agricultura , Ascomicetos/efeitos dos fármacos , Brasil , Fungicidas Industriais/economia , Fungicidas Industriais/farmacologia , Fungicidas Industriais/normas , Doenças das Plantas/prevenção & controle , Soja/microbiologia
3.
Plant Dis ; 102(4): 807-817, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30673410

RESUMO

An apparent decline of fungicide performance for the control of soybean rust in Brazil has been reported but the rate at which it has occurred has not been formally quantified. Control efficacy and yield response to three fungicides applied as single active ingredients (a.i.)-azoxystrobin (AZOX), cyproconazole (CYPR), and tebuconazole (TEBU)-and four applied as mixtures-AZOX+CYPR, picoxystrobin + CYPR, pyraclostrobin + epoxiconazole, and trifloxystrobin + prothioconazole (TRIF+PROT)-were summarized using network meta-analytic models fitted to mean severity and yield data from 250 trials (10-year period). The effect of year was tested on both variables in a meta-regression model. Overall control efficacy ranged from 56 to 84%; the three single-a.i. fungicides performed the poorest (56 to 62%). Yield increase for single-a.i. fungicides was as low as 30% but ranged from 47 to 65% for the premixes. Significant declines in both variables were detected for all fungicides except TRIF+PROT. For TEBU, control efficacy (yield response) declined the most: 78% (18%) to 54% (8%) from 2004-05 to 2013-14. The recent surge of resistant populations of Phakopsora pachyrhizi to both demethylation inhibitor and quinone outside inhibitor fungicides is likely the driving force behind a significant decline after 4 years of fungicide use.


Assuntos
Basidiomycota/efeitos dos fármacos , Farmacorresistência Fúngica , Fungicidas Industriais/farmacologia , Doenças das Plantas/prevenção & controle , Soja/microbiologia , Brasil , Modelos Biológicos , Doenças das Plantas/microbiologia , Fatores de Tempo
4.
Phytopathology ; 105(3): 307-15, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25244347

RESUMO

Meta-analytic models were used to summarize and assess the heterogeneity in the relationship between soybean yield (Y, kg/ha) and rust severity (S, %) data from uniform fungicide trials (study, k) conducted over nine growing seasons in Brazil. For each selected study, correlation (k=231) and regression (k=210) analysis for the Y-S relationship were conducted and three effect-sizes were obtained from these analysis: Fisher's transformation of the Pearson's correlation coefficient (Zr) and the intercept (ß0) and slope (ß1) coefficients. These effect-sizes were summarized through random-effect and mixed-effect models, with the latter incorporating study-specific categorical moderators such as disease onset time (DOT) (70%, moderate=>40 and ≤70%, and low=≤40% S the check treatment), and growing season. The overall mean for r- (back-transformed Z-r) was -0.61, based on the random-effects model. DOT and DP explained 14 and 25%, respectively, of the variability in Z-r. Stronger associations (r-=-0.87 and -0.90) were estimated by mixed-effects models for the Zr data from studies with highest DP (DP>70%) and earliest rust onset (DOT0.73 pp/%(-1)) were estimated for studies with DOT70%; the latter possibly due to high fungicide efficacy when DP is low, thus leading to higher yield differences between fungicide-protected and nontreated plots. The critical-point meta-analytic models can provide general estimates of yield loss based on a composite measure of disease severity. They can also be useful for crop loss assessments and economic analysis under scenarios of varying DOT and weather favorableness for epidemic development.


Assuntos
Basidiomycota/fisiologia , Interações Hospedeiro-Patógeno , Soja/microbiologia , Biomassa , Análise de Regressão , Soja/crescimento & desenvolvimento
5.
BMC Biotechnol ; 11: 14, 2011 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-21299880

RESUMO

BACKGROUND: Asian rust (Phakopsora pachyrhizi) is a common disease in Brazilian soybean fields and it is difficult to control. To identify a biochemical candidate with potential to combat this disease, a new chitinase-like xylanase inhibitor protein (XIP) from coffee (Coffea arabica) (CaclXIP) leaves was cloned into the pGAPZα-B vector for expression in Pichia pastoris. RESULTS: A cDNA encoding a chitinase-like xylanase inhibitor protein (XIP) from coffee (Coffea arabica) (CaclXIP), was isolated from leaves. The amino acid sequence predicts a (ß/α)8 topology common to Class III Chitinases (glycoside hydrolase family 18 proteins; GH18), and shares similarity with other GH18 members, although it lacks the glutamic acid residue essential for catalysis, which is replaced by glutamine. CaclXIP was expressed as a recombinant protein in Pichia pastoris. Enzymatic assay showed that purified recombinant CaclXIP had only residual chitinolytic activity. However, it inhibited xylanases from Acrophialophora nainiana by approx. 60% when present at 12:1 (w/w) enzyme:inhibitor ratio. Additionally, CaclXIP at 1.5 µg/µL inhibited the germination of spores of Phakopsora pachyrhizi by 45%. CONCLUSIONS: Our data suggests that CaclXIP belongs to a class of naturally inactive chitinases that have evolved to act in plant cell defence as xylanase inhibitors. Its role on inhibiting germination of fungal spores makes it an eligible candidate gene for the control of Asian rust.


Assuntos
Basidiomycota/efeitos dos fármacos , Quitinases/farmacologia , Café/enzimologia , Xilosidases/antagonistas & inibidores , Sequência de Aminoácidos , Basidiomycota/fisiologia , Quitinases/química , Quitinases/genética , Quitinases/metabolismo , Clonagem Molecular , Café/genética , Eletroforese em Gel de Poliacrilamida , Germinação/efeitos dos fármacos , Anotação de Sequência Molecular , Dados de Sequência Molecular , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteínas de Plantas/farmacologia , Alinhamento de Sequência , Soja/microbiologia , Esporos Fúngicos/efeitos dos fármacos
6.
Mol Plant Microbe Interact ; 20(8): 887-99, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17722693

RESUMO

Asian soybean rust (ASR), caused by Phakopsora pachyrhizi, is now established in all major soybean-producing countries. Currently, there is little information about the molecular basis of ASR-soybean interactions, which will be needed to assist future efforts to develop effective resistance. Toward this end, abundance changes of soybean mRNAs were measured over a 7-day ASR infection time course in mock-inoculated and infected leaves of a soybean accession (PI230970) carrying the Rpp2 resistance gene and a susceptible genotype (Embrapa-48). The expression profiles of differentially expressed genes (ASR-infected compared with the mock-inoculated control) revealed a biphasic response to ASR in each genotype. Within the first 12 h after inoculation (hai), which corresponds to fungal germination and penetration of the epidermal cells, differential gene expression changes were evident in both genotypes. mRNA expression of these genes mostly returned to levels found in mock-inoculated plants by 24 hai. In the susceptible genotype, gene expression remained unaffected by rust infection until 96 hai, a time period when rapid fungal growth began. In contrast, gene expression in the resistant genotype diverged from the mock-inoculated control earlier, at 72 h, demonstrating that Rpp2-mediated defenses were initiated prior to this time. These data suggest that ASR initially induces a nonspecific response that is transient or is suppressed when early steps in colonization are completed in both soybean genotypes. The race-specific resistance phenotype of Rpp2 is manifested in massive gene expression changes after the initial response prior to the onset of rapid fungal growth that occurs in the susceptible genotype.


Assuntos
Basidiomycota/fisiologia , Doenças das Plantas/genética , RNA Mensageiro/metabolismo , Soja/microbiologia , Análise por Conglomerados , Perfilação da Expressão Gênica , Genótipo , Imunidade Inata/genética , Análise de Sequência com Séries de Oligonucleotídeos , Soja/genética , Soja/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
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