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Biological control agent Bacillus subtilis formulated as Theia is registered for control of fungal and bacterial diseases of fruit crops. Combinations of Theia and strategic concentrations of two demethylation inhibitor (DMI) fungicides were investigated to explore potential synergisms. Bacteria were cultured in nutrient broth and combined with technical grades and two formulations of propiconazole (emulsifiable concentrate [EC] and wettable powder) and metconazole (EC and water-dispersible granule) at 0, IO, 50, 100, and 150 ug/ml of active ingredient. After cocultivation, the optical density (OD«x)) and colony forming units (CFU/ml) were evaluated. In contrast to EC formulations, the wettable powder or water-dispersible granule formulations at 10 or 50 pg/ml of both DMIs did not affect vegetative cell growth. The mixture of Theia and each formulated DMI at 50 ug/ml of active ingredient resulted in a significant reduction of Moniliniafructicola lesion development on apple, Colletotrichum siamense lesion development on cherry, and Botrytis cinerea lesion development on cherry. The combination of Theia with EC formulations showed weaker disease reduction due to antagonism. Only Theia plus non-EC formulated propiconazole and metconazole significantly reduced brown rot disease incidence of apple compared with the respective solo treatments and anthracnose disease incidence of cherry compared with the untreated control. Our results indicated that at least some DMI fungicides possess bactericidal effects depending on the formulation and concentration. The combination of Theia with a lower-than-label-rateconcentration (50 ug/ml) of the DMI fungicides propiconazole and metconazole showed potential for synergistic effects, especially when non-EC formulations were used. [ABSTRACT FROM AUTHOR]

Fungal diseases, including downy mildew (caused by Plasmopara viticola) and gray mold (caused by Botrytis cinerea), significantly impact the marketable yield of grapes produced worldwide. Cytochrome b of the mitochondrial respiratory chain of these two fungi is a key target for Quinone outside inhibitor (QoI)-based fungicide development. Since the mode of action (MOA) of QoI fungicides is restricted to a single site, the extensive usage of these fungicides has resulted in fungicide resistance. The use of fungicide combinations with multiple targets is an effective way to counter and slow down the development of fungicide resistance. Due to the high cost of in planta trials, in silico techniques can be used for the rapid screening of potential fungicides. In this study, a combination of in silico simulations that include Schrödinger Glide docking, molecular dynamics, and Molecular Mechanism-Generalized Born Surface Area calculation were used to screen the most potent QoI and non-QoI-based fungicide combinations to wild-type, G143A-mutated, F129L-mutated, and double-mutated versions that had both G143A and F129L mutations of fungal cytochrome b. In silico docking studies indicated that mandestrobin, famoxadone, captan, and thiram have a high affinity toward WT cytochrome b of Botrytis cinerea. Although the QoIs mandestrobin and famoxadone were effective for WT based on in vitro results, they were not broadly effective against G143A-mutated isolates. Famoxadone was only effective against one isolate with G143A-mutated cytochrome b. The non-QoI fungicides thiram and captan were effective against both WT and isolates with G143A-mutated cytochrome b. Follow-up in silico docking and molecular dynamics studies suggested that fungicide combinations consisting of famoxadone, mandestrobin, fenamidone, and thiram should be considered in field testing targeting Plasmopara viticola and Botrytis cinerea fungicide resistance. [ABSTRACT FROM AUTHOR]

Armillaria root rot (ARR) poses a significant threat to the long-term productivity of stone-fruit and nut crops in the predominant production area of the United States. To mitigate this issue, the development of ARR-resistant and horticulturally-acceptable rootstocks is a crucial step towards the maintenance of production sustainability. To date, genetic resistance to ARR has been found in exotic plum germplasm and a peach/plum hybrid rootstock, 'MP-29'. However, the widely-used peach rootstock Guardian® is susceptible to the pathogen. To understand the molecular defense mechanisms involved in ARR resistance in Prunus rootstocks, transcriptomic analyses of one susceptible and two resistant Prunus spp. were performed using two causal agents of ARR, including Armillaria mellea and Desarmillaria tabescens. The results of in vitro co-culture experiments revealed that the two resistant genotypes showed different temporal response dynamics and fungus-specific responses, as seen in the genetic response. Gene expression analysis over time indicated an enrichment of defense-related ontologies, including glucosyltransferase activity, monooxygenase activity, glutathione transferase activity, and peroxidase activity. Differential gene expression and co-expression network analysis highlighted key hub genes involved in the sensing and enzymatic degradation of chitin, GSTs, oxidoreductases, transcription factors, and biochemical pathways likely involved in Armillaria resistance. These data provide valuable resources for the improvement of ARR resistance in Prunus rootstocks through breeding. [ABSTRACT FROM AUTHOR]

Isoprothiolane (IPT) resistance has emerged in Magnaporthe oryzae, due to the long-term usage of IPT to control rice blast in China, yet the mechanisms of the resistance remain largely unknown. Through IPT adaptation on PDA medium, we obtained a variety of IPT-resistant mutants. Based on their EC50 values to IPT, the resistant mutants were mainly divided into three distinct categories, i.e., low resistance (LR, 6.5 ≤ EC50 < 13.0 μg/mL), moderate resistance 1 (MR-1, 13.0 ≤ EC50 < 25.0 μg/mL), and moderate resistance 2 (MR-2, 25.0 ≤ EC50 < 35.0 μg/mL). Molecular analysis of MoIRR (Magnaporthe oryzae isoprothiolane resistance related) gene demonstrated that it was associated only with the moderate resistance in MR-2 mutants, indicating that other mechanisms were associated with resistance in LR and MR-1 mutants. In this study, we mainly focused on the characterization of low resistance to IPT in M. oryzae. Mycelial growth and conidial germination were significantly reduced, indicating fitness penalties in LR mutants. Based on the differences of whole genome sequences between parental isolate and LR mutants, we identified a conserved MoVelB gene, encoding the velvet family transcription factor, and genetic transformation of wild type isolate verified that MoVelB gene was associated with the low resistance. Based on molecular analysis, we further demonstrated that the velvet family proteins VelB and VeA were indispensable for IPT toxicity and the deformation of the VelB-VeA-LaeA complex played a vital role for the low IPT-resistance in M. oryzae, most likely through the down-regulation of the secondary metabolism-related genes or CYP450 genes to reduce the toxicity of IPT. Author summary: Isoprothiolane (IPT) resistance has emerged in Magnaporthe oryzae, due to the long-term usage of IPT to control rice blast in China, yet the mechanisms of the resistance remain largely unknown. Here, we explored the mechanisms of low IPT resistance in M. oryzae. Combining the whole genome sequencing and genetic transformation, we identified a conserved MoVelB gene, encoding the velvet family transcription factor to be a determinant for IPT toxicity. We further demonstrated that the deformation of the VelB-VeA-LaeA complex conferred the low IPT-resistance in M. oryzae, most likely through down-regulating the secondary metabolism-related genes or CYP450 genes to reduce the toxicity of IPT. This study improved our understanding of the resistance mechanism as well as the mode of action of IPT which will be helpful for making suitable strategies to manage the emerging resistance of IPT in M. oryzae. [ABSTRACT FROM AUTHOR]

Cut roses are highly valuable ornamentals and their profitability depends on the flower postharvest performance. Bent neck symptoms in roses make them unmarketable and are typically related to physiological disorders, bacteria accumulation in the vase solution, and Botrytis cinerea infection. Unusual bent neck symptoms were observed in 4.7% of 'Orange Crush' roses from two commercial shipments, resulting in complete flower collapse. This research was aimed to determine the causal agent of the bent neck symptoms. Following incubation in a humid chamber, symptomatic roses evolved in water-soaked lesions with the presence of white mycelium and sclerotia development. Fungal isolations and molecular characterization were performed and Sclerotinia sclerotiorum was identified as the causal agent of rose bent neck. Therefore, when bent neck symptoms are observed, S. sclerotiorum incidence should be considered to avoid possible outbreaks. [ABSTRACT FROM AUTHOR]

Peach is a popular and important tree fruit widely produced in the world, and the production of high-quality peach fruit does require management of pests and diseases. In this review, major peach diseases from China, Spain, and USA are described in detail for the benefit of producers, consultants, researchers, and other interested parties. Minor diseases of concern in these countries are also described. Current progress on pathogen resistance to major chemical classes of fungicides as well as current resistance management practices are discussed. Specific cultural practices applied in China, Spain, and USA are also described to provide an overview of peach disease management. A ‘Future Outlook’ section is included at the end of this review to highlight the challenges and opportunities for disease management in the future. [ABSTRACT FROM AUTHOR]

Colletotrichum is regarded as one of the 10 most important genera of plant pathogens in the world. It causes diseases in a wide range of economically important plants, including peaches. China is the largest producer of peaches in the world but little is known about the Colletotrichum spp. affecting the crop. In 2017 and 2018, a total of 286 Colletotrichum isolates were isolated from symptomatic fruit and leaves in 11 peach production provinces of China. Based on multilocus phylogenetic analyses (ITS, ACT, CAL, CHS-1, GAPDH, TUB2, and HIS3) and morphological characterization, the isolates were identified to be C. nymphaeae, C. fioriniae, and C. godetiae of the C. acutatum species complex, C. fructicola and C. siamense of the C. gloeosporioides species complex, C. karsti of the C. boninense species complex, and one newly identified species, C. folicola sp. nov. This study is the first report of C. karsti and C. godetiae in peaches, and the first report of C. nymphaeae, C. fioriniae, C. fructicola, and C. siamense in peaches in China. C. nymphaeae is the most prevalent species of Colletotrichum in peaches in China, which may be the result of fungicide selection. Pathogenicity tests revealed that all species found in this study were pathogenic on both the leaves and fruit of peaches, except for C. folicola, which only infected the leaves. The present study substantially improves our understanding of the causal agents of anthracnose on peaches in China. [ABSTRACT FROM AUTHOR]

Xanthomonas arboricola pv. pruni (Xap) causes bacterial spot, a major worldwide disease of Prunus species. Very few chemical management options are available for this disease and frequent applications of oxytetracycline (OTC) in the United States peach orchards have raised concerns about resistance development. During 2017–2020, 430 Xap strains were collected from ten peach orchards in South Carolina. Seven OTC-resistant (OTC R) Xap strains were found in 2017 and 2020 from four orchards about 20–270 km apart. Interestingly, the seven strains were also resistant to streptomycin (STR). Six strains grew on media amended with ≤100 μg/mL OTC, while one strain, R1, grew on ≤250 μg/mL OTC. Genome sequence analysis of four representative OTC R strains revealed a 14–20 kb plasmid carrying tetC , tetR , and strAB in each strain. These three genes were transferable to Xanthomonas perforans via conjugation, and they were PCR confirmed in all seven OTC R Xap strains. When tetC and tetR were cloned and expressed together in a sensitive strain, the transconjugants showed resistance to ≤100 μg/mL OTC. When tetC was cloned and expressed alone in a sensitive strain, the transconjugants showed resistance to ≤250 μg/mL OTC. TetC and tetR expression was inducible by OTC in all six wild-type strains resistant to ≤100 μg/mL OTC. However, in the R1 strain resistant to ≤250 μg/mL OTC, tetR was not expressed, possibly due to the presence of Tn 3 in the tetR gene, and in this case tetC was constitutively expressed. These data suggest that tetC confers OTC resistance in Xap strains, and tetR regulates the level of OTC resistance conferred by tetC. To our knowledge, this is the first report of OTC resistance in plant pathogenic xanthomonads. [ABSTRACT FROM AUTHOR]

Horticultural performance of eleven blackberry cultivars, including two primocane-fruiting cultivars, was evaluated over three years after fruiting began at the Musser Fruit Research Center in South Carolina, United States. Results showed differences in yield between cultivars for each year of the study. 'Natchez' had the highest cumulative yield after three years, followed by 'Navaho', 'Von', and 'Osage', whereas 'Prime-Ark® Traveler' produced significantly less than these four cultivars. Yield steadily declined for all cultivars over the three years, except for 'Osage', which remained consistent. 'Prime-Ark® Freedom' always had the largest fruit, although it had the greatest yield reduction after the second year. Multiple factors may explain yield decline for the majority of the cultivars studied, including freeze damage and tip dieback. Tip dieback was observed in 2016 in multiple cultivars, but dieback incidence was highest on 'Prime-Ark® Traveler'. The dieback was associated with an outbreak of broad mites and thrips in the experimental block and with secondary pathogens isolated from the decaying tissues primarily Fusarium spp. and Alternaria spp. Cultivar differences in susceptibility to Alternaria spp. were confirmed in laboratory studies. [ABSTRACT FROM AUTHOR]

Potato Alternaria leaf blight is one of the economically most important disease in potato production worldwide. A recent study reported a quick method to distinguish main Alternaria pathogens A. tenuissima, A. alternata, and A. solani using partial histone H3 gene sequences. Using this method, our collection of 79 isolates from 8 provinces in China were presumably separated into A. tenussima and A. alternata. But in depth morphological and genetic analysis casted doubt on this identification. Culture morphologies of six presumed A. alternata isolates (PresA_alt) and six presumed A. tenuissima isolates (PresA_ten) were not significantly different. PresA_ten isolates also produced conidia in branched chains which supposed to be A. aternata. Phylogenetic analyses were conducted using internal transcribed spacer region (ITS) and five genes commonly used for species identification including glyceraldehyde-3-phosphate dehydrogenase (GPDH), translation elongation factor 1-alpha (TEF1), β-tubulin, plasma membrane ATPase (ATPase), and calmodulin genes. The results showed that GPDH and TEF1 sequences of PresA_alt and PresA_ten isolates were identical. The 12 isolates did not cluster by presumed species neither by individual or concatenated sequence comparisons. The phylogeny–trait association analysis confirmed that the two group isolates were undistinguishable by those molecular markers. Analysis of histone H3 gene sequences revealed variable intron sequences between PresA_ten and PresA_alt isolates, but the amino acid sequences were identical. Our results indicate that the previously published method to distinguish Alternaria species based on histone H3 gene sequence variation is inaccurate and that the prevalence of A. tenuissima isolates in China was likely overestimated. [ABSTRACT FROM AUTHOR]

BACKGROUND: Stem‐end rot caused by Lasiodiplodia theobromae is one of the most important diseases of papaya in northeastern Brazil. It can be controlled effectively by demethylation inhibitor (DMI) fungicides, but the occurrence of DMI resistance may decrease fungicide efficacy. RESULTS: Detached fruit studies revealed that isolates with EC50 values of 6.07 and 6.28 μg mL−1 were not controlled effectively, but reduced virulence and ability to grow at temperatures ranging from 12 to 32 °C suggesting fitness penalties were observed. Cross‐resistance was observed only between difenoconazole and propiconazole. The entire cytochrome P450 sterol 14α‐demethylase (LtCYP51) gene and its flanking regions were cloned. The gene was 1746 bp in length and contained three introns. The predicted protein contained 525 amino acids. Phylogenetic tree analysis showed that the LtCYP51 belongs to the CYP51B clade. No amino acid variation was found between sensitive and resistant isolates; however, the gene was constitutively more highly expressed in resistant isolates. CONCLUSION: Resistance to DMI fungicides in L. theobromae is based on LtCYP51 gene overexpression and fitness penalties may be present in difenoconazole‐resistant isolates. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Botrytis cinerea isolates with multi-fungicide resistance have frequently been isolated from small fruit fields such as strawberries and blackberries. Individual B. cinerea isolates have been found resistant to up to seven chemical classes of fungicides. Fitness costs and less competitiveness have been observed in multi-fungicide resistant isolates, but this has not been examined under field conditions. In the spring of 2016, flowers of field-grown blackberries were either not inoculated or inoculated with B. cinerea isolates sensitive (0CCR), resistant to five or six chemical classes excluding phenylpyrroles (5CCR), or resistant to six or seven chemical classes including phenylpyrroles (6CCR/MDR1h). The experimental field was left unsprayed for the duration of this study and isolates of B. cinerea were collected from flowers and/or fruit in each of the three experimental years. Isolates collected in summer of 2016 revealed resistance phenotypes in each plot closely matching those of the respective inoculum, with 95% 0CCR, 55% 5CCR, and 91% 6CCR/MDR1h isolates recovered from 0CCR, 5CCR, and 6CCR/MDR1h inoculation plots, respectively. In the 2017 and 2018 isolate collections, 6CCR/MDR1h resistance phenotypes were found in plots inoculated and non-inoculated with this phenotype, indicating their persistence and movement between plots. Resistance phenotypes different from the inoculum were also recovered each year, indicating that the inoculum was successfully competing with a native Botrytis population. Despite the competition, 6CCR/MDR1h isolates were recovered in high frequency from all inoculated plots in 2018. G3pdh and mrr1 sequences of 6CCR/MDR1h isolates collected in 2018 were identical to the sequences of the inoculum, indicating that these isolates likely descended from the inoculum. This study demonstrates that isolates carrying multi-fungicide resistant phenotypes, specifically 6CCR/MDR1h, are competitive in the absence of fungicide selection pressure. Unlabelled Image • Multi-fungicide resistant Botrytis cinerea inocula competed with native population. • 6CCR/MDR1h phenotype was recovered frequently in third year amidst dry weather. • Recovered isolates were genotypically and phenotypically identical to the inoculum. [ABSTRACT FROM AUTHOR]

Gray mold and anthracnose fruit rot are two of the most important diseases threatening strawberry production in the United States. Managing these diseases is critical, but difficult without understanding how the fungus causing each disease operates. Improvements in design technology and computer processing power have enabled us to create a new generation of informational resources that explain disease development in a new and exciting way. High-definition photos and time-lapse videos help us recognize and diagnose diseases from their first appearance in the field. Through illustrations and animations, concepts, such as disease cycles, can be explained more effectively. Free availability of these materials on websites and social media makes them accessible to growers, agents, and specialists. Through these materials we can clarify and justify current management practices so that growers can more effectively combat diseases in the field. Using gray mold and anthracnose fruit rot as an example, we created photo galleries and updated, visually stimulating disease cycles for continued and improved grower training. [ABSTRACT FROM AUTHOR]

The role of the 14[alpha]-demethylase gene (MfCYP51) and the ATP-binding cassette transporter gene MFABC1in conferring demethylation inhibitor (DMI) fungicide resistance in field isolates with resistance to propiconazole is examined. The results have shown that overexpression of the MfCYP51 gene is very important in conferring DMI fungicide resistance in Monilinia fructicola field isolates from Georgia and that this overexpression is correlated with Mona located upstream of the MfCYP51 gene.

BACKGROUND: The increasing use of demethylation inhibitor (DMI) fungicides for the control of peach brown rot has resulted in resistance in Monilinia fructicola. Resistance in the southeastern USA is caused by overexpression of the MfCYP51 gene due to the presence of a 65‐bp inserted element 'Mona' located in the upstream regulatory region of MfCYP51. A rapid diagnostic assay would be useful to detect the presence and monitor further spread of this resistance mechanism. RESULTS: A loop‐mediated isothermal amplification (LAMP) method was developed for rapid detection of 'Mona'‐based DMI resistance. The assay was optimized for specificity and sensitivity, and was shown to detect the presence of 10 fg of purified target DNA per reaction within 85 min. Only DNA isolated from DMI‐resistant isolates containing 'Mona' resulted in a fluorescent signal after LAMP assay amplification. DNA from sensitive isolates from China and the USA and six other common fungal species of peach did not yield a signal. The method also positively identified 'Mona' from crude DNA extracts (using Lyse and Go reagents heated to 100 °C for 10 min) obtained from the mycelium and conidia of symptomatic fruit. CONCLUSION: Considering its specificity, stability and repeatability, the LAMP assay could be a valuable tool for rapid on‐site diagnosis of M. fructicola isolates resistant to DMI fungicides in the southeastern USA. © 2018 Society of Chemical Industry This article presents the development of a LAMP method to on‐site detect DMI fungicide resistance in Monilinia fructicola. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Metalaxyl is a phenylamide fungicide, introduced for oomycete management in the 1970s. RPA190 gene has been reported to be associated with metalaxyl resistance, although other genes may also be involved in the process. This study assessed the evolutionary association of amino acid (AA) mutations in RPA190 with metalaxyl resistance in Phytophthora infestans. RESULTS: All isolates from Yunnan were resistant to metalaxyl with multiple AA mutations in RPA190. Two main evolutionary pathways were found in metalaxyl resistance: in one pathway, RPA190 from sensitive isolates (SAA) underwent a single type AA mutation at position 1476, changing from valine to glycine (V1476G); the second pathway involved multiple steps of point mutations. In a phylogenetic tree, nucleotide sequences of the gene clustered into six clades largely corresponding to AA isoform groups. Among the clusters, sequences carrying mutations V1476G and P980S formed two independent clades; other clades shared a common mutation of F382Y. All three mutations together with another two were shown to be under positive selection and the number of AA mutations in an isolate was positively correlated with EC50 values. CONCLUSION: Multiple mutations such as V1476G, P980S, and F382Y in RPA190 contribute to metalaxyl resistance, and resistance to metalaxyl can emerge in at least two independent pathways in P. infestans. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Monilinia fructicola is a diverse pathogen of pome and stone fruits that causes severe economic losses each year. However, little is known about inoculum flow within or between orchards and pathogen establishment in an orchard, because few methods exist for detecting diversity or tracking isolates over time. SSR loci are an effective option, but may be confounded by a high degree of mutability and potential sensitivity to abiotic stress. RESULTS Through transcriptome analysis, we identified novel markers mrr1, DHFR and MfCYP01 and validated stability of these markers under fungicide stress in natural infection sites. Nucleotide variation within mrr1, DHFR and MfCYP01 sequences differentiated isolates at all spatial scales: within the same infection site, between trees and between two farms. Sequenced regions were also effective for matching isolates collected from blossoms at the beginning of the season to progeny in cankers obtained at the end of the season. CONCLUSIONS Collectively, results show that mrr1, DHFR and MfCYP01 are able to accurately differentiate M. fructicola isolates at the population level, can be used to track isolates over time, and are more stable than SSRs under external stresses. Either by themselves or combined with SSR markers, these gene-encoding regions are a much-needed tool for better understanding M. fructicola population dynamics. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The genetic element 'Mona' has been shown previously to be associated with resistance to demethylation inhibitors (DMIs) in Monilinia fructicola. In this study, the promoter activity of the 'Mona' element was demonstrated genetically and the activity was narrowed down to a 20-bp active region through a series of deletions. 'Mona' knockout transformants (ΔMona) were generated from DMI-resistant isolate Bmpc7, and EC50 values and expression of the MfCYP51 gene were found to be reduced in transformants compared with the parental isolate. When the 'Mona' element was inserted into the upstream region of the MfCYP51 gene of the DMI-sensitive isolate HG3, the EC50 values and expression of the MfCYP51 gene increased in the transformants compared with the parental sensitive isolate. These results indicate that the 'Mona' element determines the DMI fungicide resistance through the up-regulation of the expression of the downstream MfCYP51 gene. No fitness penalty was observed in knockout and insertion transformants, i.e. transformants showed similar mycelial growth rate, sporulation and ability to cause lesions on fruit compared with their parental isolates, suggesting that the 'Mona' element does not affect basal life activities. [ABSTRACT FROM AUTHOR]

Rice false smut disease is an increasing threat to rice production in the world. Despite of best efforts, research for the infection of the fungus has yielded equivocal and conflicting results about where and how the infection is initiated and developed. Here we show a stepwise infection pattern and sophisticated regulation during this process. Initial infection occurred on the filaments, which prevented the production of mature pollen thus blocked the pollination. In the following days, the pathogen invaded the stigmas and styles, occasionally the ovaries. Expression analysis indicated that the fungus mimicked a successful fertilization process and enabled the continuous supply of nutrients for fungus to produce false smut balls. The stepwise infection of flower organs and mimicry of ovary fertilization unveiled in this study guided the rice plant into supplying nutrients for false smut ball development and represents a new and unique biological process of host pathogen interactions. [ABSTRACT FROM AUTHOR]

BACKGROUND Colletotrichum species cause anthracnose diseases on many plants and crops. A new generation of succinate dehydrogenase inhibitors (SDHIs) was developed recently. The inhibitory activity of the five SDHI fungicides against Colletotrichum species was determined in this study. RESULTS Isolates of C. gloeosporioides, C. acutatum, C. cereale and C. orbiculare were insensitive (naturally resistant) to boscalid, fluxapyroxad and fluopyram on YBA agar medium. In contrast, these isolates were relatively sensitive to penthiopyrad, except for C. orbiculare. Most interestingly, benzovindiflupyr showed highest inhibitory activity against all of these four species. Benzovindiflupyr was effective against C. gloeosporioides and C. acutatum on apple and peach fruit, as well as on cucumber plants inoculated with C. orbiculare. The sdhB, sdhC and sdhD genes encoding the subunits of fungicide-targeted succinate dehydrogenase were sequenced, but, despite high polymorphisms, no apparent resistance mutations were found in Colletotrichum species. CONCLUSIONS This is the first report on the activity of benzovindiflupyr against Colletotrichum species. The broad-spectrum efficacy of benzovindiflupyr within the Colletotrichum genus might be exploited when designing disease management strategies against various pathogens on a wide range of crops. Other mechanism(s) than fungicide target-site modification may be responsible for differential sensitivity of Colletotrichum species to SDHI fungicides. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Evolved resistance to fungicides is a major problem limiting our ability to control agricultural, medical and veterinary pathogens and is frequently associated with substitutions in the amino acid sequence of the target protein. The convention for describing amino acid substitutions is to cite the wild-type amino acid, the codon number and the new amino acid, using the one-letter amino acid code. It has frequently been observed that orthologous amino acid mutations have been selected in different species by fungicides from the same mode of action class, but the amino acids have different numbers. These differences in numbering arise from the different lengths of the proteins in each species. The purpose of the present paper is to propose a system for unifying the labelling of amino acids in fungicide target proteins. To do this we have produced alignments between fungicide target proteins of relevant species fitted to a well-studied 'archetype' species. Orthologous amino acids in all species are then assigned numerical 'labels' based on the position of the amino acid in the archetype protein. © 2016 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND The dicarboximide fungicide dimethachlone has been widely used in China for more than 12 years to control the Sclerotinia stem rot caused by Sclerotinia sclerotiorum disease. First signs of resistance in the field are reported at low frequency. In this study, four resistant isolate/mutants were used to explore still unknown mechanisms leading to dimethachlone resistance. RESULTS The resistant isolate/mutants had significantly higher EC50 values compared with the sensitive control isolates. Cross-resistance was confirmed between dimethachlone and procymidone, iprodione and fludioxonil. The resistant isolate/mutants revealed a decreased mycelial growth rate, were less pathogenic on leaves of oilseed rape, were more sensitive to osmotic pressure and oxidative stress and released more electrolytes compared with the sensitive isolates. Only in one lab mutant did we find a point mutation ( V238A) in the SsOs1 gene of the high-osmolarity glycerol ( HOG) signalling pathway. The expression of this gene was lost in the field resistant isolate HN456-1- JBJ and decreased in mycelium that was subjected to either high osmotic pressure or dimethachlone; however, another key gene in the HOG pathway, SsHog1, could be induced in the resistant isolate and mutants with NaCl treatment. CONCLUSION This study demonstrates that resistance to dicarboximide fungicide dimethachlone in S. sclerotiorum is emerging in China. Several fitness parameters, including mycelial growth rate, sclerotia formed in vitro, aggressiveness on leaves and osmotic and H2O2 sensitivity, indicate that the resistant strains may not effectively compete with sensitive isolates in the field in the absence of selection pressure. Lost expression or the V238A point mutation in the SsOs1 gene may confer resistance to dicarboximide fungicide dimethachlone in S. sclerotiorum, but this study illustrates that other, yet unknown mechanisms also exist. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Oak root rot is responsible for considerable tree losses in commercial peach production in the southeastern United States, including South Carolina. The presence of a distinct mycelial fan formation at [...]

Monilia yunnanensis was recently identified as a new species causing brown rot of peach in China. Sterol 14α-demethylase inhibitors (DMIs) continue to be important in the management of brown rot of Monilinia spp. worldwide. Tebuconazole and triadimefon are two kinds of DMI fungicides that may be used for brown rot control in China. To establish the baseline sensitivity of M. yunnanensis to these two DMI fungicides, 203 M. yunnanensis single spore isolates were collected. Measurements of sensitivity to the two fungicides were based on inhibition of mycelial growth. For both fungicides, the sensitivity distribution was a unimodal curve, with an EC range (the effective concentration to inhibit mycelial growth by 50 %) of 0.0001-0.0644 μg/ml for tebuconazole and 0.2311-1.7477 μg/ml for triadimefon. The M. yunnanensis isolates were obtained from orchards where DMI fungicides have not been used for peach brown rot control, thus the fungicide sensitivity distribution established in this study can be considered as the baseline for monitoring the resistance development in M. yunnanensis once the DMI fungicides are used to control peach brown rot. [ABSTRACT FROM AUTHOR]

In this study, all available cytochrome b (Cyt b) genes from the GOBASE database were compiled and the evolutionary dynamics of the Cyt b gene introns was assessed. Cyt b gene introns were frequently present in the fungal kingdom and some lower plants, but generally absent or rare in Chromista, Protozoa, and Animalia. Fungal Cyt b introns were found at 35 positions in Cyt b genes and the number of introns varied at individual positions from a single representative to 32 different introns at position 131, showing a wide and patchy distribution. Many homologous introns were present at the same position in distantly related species but absent in closely related species, suggesting that introns of the Cyt b genes were frequently lost. On the other hand, highly similar intron sequences were observed in some distantly related species rather than in closely related species, suggesting that these introns were gained independently, likely through lateral transfers. The intron loss-and-gain events could be mediated by transpositions that might have occurred between nuclear and mitochondria. Southern hybridization analysis confirmed that some introns contained repetitive sequences and might be transposable elements. An intron gain in Botryotinia fuckeliana prevented the development of QoI fungicide resistance, suggesting that intron loss-and-gain events were not necessarily beneficial to their host organisms. [ABSTRACT FROM AUTHOR]

Trunk infusion of peach with propiconazole has been suggested as a potential strategy to protect roots from colonization by Armillaria species. In the present study, we investigated the persistence of propiconazole in peach roots following fall infusions and its potential for Armillaria root rot control in a commercial peach orchard. Four 12-year-old trees were infused with either 2 liters of a propiconazole solution at 0.4 mg ml-1 or water in September 2007. Bark tissue collected from primary roots of propiconazole-infused trees 48 hr and 6 and 12 months after infusion and analyzed using gas chromatography-mass spectroscopy contained 6.4, 1.4, and 0.9 μg propiconazole per gram fresh bark, respectively. Asymptomatic trees adjacent to trees that had died from Armillaria root rot (protective treatment) and symptomatic but alive trees (curative treatment) were infused with 1 liter of a propiconazole solution (0.4 mg ml-1) in spring and fall of 2008 and 2009 at a commercial peach orchard planted in 2005. Trees were rated for Armillaria root rot severity 6, 12, 24, and 36 months post-infusion. In the protective treatment, the survival rate in both non-infused and infused trees was 80% 36 months post-infusion. However, more (60%) of the propiconazole-infused trees remained asymptomatic compared to the control trees (30%). A significant difference was observed between the non-infused and propiconazole-infused trees following curative treatment. None of the control trees were alive after 36 months compared to 40% of propiconazole-infused trees. We conclude that fall infusion of peripheral trees of infection centers with propiconazole can slow the expansion of Armillaria root rot infection centers in commercial peach orchards. [ABSTRACT FROM AUTHOR]

BACKGROUND: The long-term preservation of interesting phenotypes in plant pathogenic fungi allows for follow-up studies in the future. Twelve storage approaches were investigated to determine their effects on instability of propiconazole resistance for three demethylation inhibitor (DMI) fungicide-resistant and two DMI-sensitive isolates of Monilinia fructicola. They included mycelium in PDA slants under mineral oil, in PDA plugs under 10% glycerol, on dried filter paper and conidia on silica gel, each stored for 36 weeks at 4, − 20, and − 80 °C. RESULTS: None of the storage approaches prevented the rapid decline of EC50 values for propiconazole in the three resistant isolates, and no significant differences were found among storage approaches ( P = 0.787) or between storage approaches and consecutive transfers ( P = 0.053). Most of the decline in resistance occurred during the first 4 weeks of storage. The DMI resistance-associated genetic element Mona, located in the immediate upstream region of the Mf CYP51 gene, was still present in the three resistant isolates after 36 weeks of storage and weekly transfers. Furthermore, the Mona element and a portion of the Mf CYP51 gene, which encodes the target enzyme for DMIs, did not reveal signs of DNA methylation. Resistance to propiconazole was partially regained in resistant isolates after two growth cycles on fresh peach fruit. CONCLUSIONS: Obtained data indicate that the decline of DMI resistance in M. fructicola cannot be prevented using commonly employed storage methods at various temperatures. The number of consecutive transfers and the storage duration prior to fungicide sensitivity tests in M. fructicola should be indicated in scientific papers. Copyright © 2011 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Succinate dehydrogenase inhibitor (SDHI) fungicides are important tools to control preharvest and postharvest brown rot of stone fruits. In this study we determined the mycelial growth rate of Monilinia fructicola isolates on various media and picked the three that allowed the fastest growth to assess the sensitivity of mycelium to SDHI fungicides boscalid, fluopyram, and penthiopyrad. Minimal medium (MM) supported mycelial growth the best and yielded lowest EC50 values for three SDHI fungicides. EC50 values corresponded with disease incidence data obtained from detached fruit assays. Penthiopyrad had significantly greater intrinsic activity in vitro compared to fluopyram at the α = 0.05 level and compared to boscalid at the α = 0.1 level. However, detached fruit assays revealed that this 'advantage' did not carry over in vivo. In conclusion, MM appears to be the best medium currently available to assess the sensitivity of M. fructicola mycelium in vitro. [ABSTRACT FROM AUTHOR]

In this study, 145 peaches and nectarines displaying typical brown rot symptoms were collected from multiple provinces in China. A subsample of 26 single-spore isolates were characterized phylogenetically and morphologically to ascertain species. Phylogenetic analysis of internal transcribed spacer (ITS) regions 1 and 2, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), b-tubulin (TUB2) revealed the presence of three distinct Monilinia species. These species included Monilinia fructicola, Monilia mumecola, and a previously undescribed species designated Monilia yunnanensis sp. nov. While M. fructicola is a well-documented pathogen of Prunus persica in China, M. mumecola had primarily only been isolated from mume fruit in Japan. Koch's postulates for M. mumecola and M. yunnanensis were fulfilled confirming pathogenicity of the two species on peach. Phylogenetic analysis of ITS, G3PDH, and TUB2 sequences indicated that M. yunnanensis is most closely related to M. fructigena, a species widely prevalent in Europe. Interestingly, there were considerable differences in the exon/intron structure of the cytochrome b (Cyt b) gene between the two species. Morphological characteristics, including spore size, colony morphology, lesion growth rate, and sporulation, support the phylogenetic evidence suggesting the designation of M. yunnanensis as a new species. A new multiplex PCR method was developed to facilitate the detection of M. yunnanensis and differentiation of Monilinia spp. causing brown rot of peach in China. [ABSTRACT FROM AUTHOR]

The Gastrodia antifungal protein (GAFP-1) is a mannose-binding lectin that can confer increased disease resistance in transgenic tobacco and plum. In all previously generated, transgenic lines, the gene was under the control of the 35SCaMV promoter. In this study, transgenic plum lines were created from seeds derived from open pollination of the cultivar Bluebyrd (BB-OP) with gafp-1 under the control of the polyubiquitin promoter bul409 and evaluated for Phytophthora root rot (PRR) and Root knot nematode (RKN) susceptibility. One of nine transgenic lines synthesizing GAFP-1 exhibited increased tolerance to PRR caused by P. cinnamomi. The same line (BB-OP-1) was also significantly more tolerant to RKN infection caused by Meloidogyne incognita. BB-OP-1 was more resistant to PRR and equally resistant to RKN compared with the cultivar Stanley-derived 4J line, which expresses gafp-1 under the control of the 35SCaMV promoter. GAFP-1 synthesis in BB-OP-1 was not elevated by pathogen infection, suggesting that the bul409 promoter is not inducible in the plum/GAFP-1 system. This study confirms the usefulness of the gafp-1 gene in various cultivars of transgenic plum and establishes that the bul409 promoter is at least equal in effectiveness to the 35SCaMV promoter for gafp-1 expression in transgenic lines of woody plants. [ABSTRACT FROM AUTHOR]

The article focuses on research which aimed at sequencing and cloning of the cytochrome b (Cyt b) gene from Monilinia fructicola (M. fructicola). It reveals that the 1166 bp intron downstream of the G143 codon and Cyt b gene area covering the location of G143 and the adjoining 1166 bp intron was polymerase chain reaction (PCR) amplified. It notes that the study was the first complete sequence of Cyt b gene for M. fructicola.

The Gastrodia antifungal protein (GAFP) is a monocot mannose-binding lectin isolated from the Asiatic orchid Gastrodia elata. This lectin has previously been shown to provide increased resistance in transgenic Nicotiana tabacum against taxonomically unrelated root pathogens Phytophthora nicotianae, Rhizoctonia solani, and Meloidogyne incognita, but its potential to confer disease resistance in tree species is not known. Agrobacterium tumefaciens-mediated transformation yielded three gafp-1 expressing plum lines (Prunus domestica) designated 4J, 4I, and 5D. These lines possessed one, two, and four copies of the gafp-I gene, respectively, as demonstrated by DNA blotting. Lines 4J and 4I were not phenotypically different from the nontransformed control line, but line 5D showed significant divergence in leaf morphology and growth habit. Compared with the inoculated control line, lines 4J and 4I exhibited increased tolerance to Phytophthora root rot (PRR) caused by P. chlnamomi. When inoculated with the root-knot nematode, Meloidogyne incognita, the 4J and 4I lines showed a significantly lower degree of root galling than the inoculated control line. Nematode reproduction, as measured by the presence of egg masses and the number of eggs produced per gram fresh root, was significantly reduced in line 4J compared with the inoculated control line. The results of this study suggest that the expression of gafp-I in the roots of a woody plant may confer some level of resistance to PRR and root-knot nematode. Long-term field trials will be necessary to confirm this hypothesis. [ABSTRACT FROM AUTHOR]

The ability to develop fungicide resistance was assessed in Monilinia fructicola isolates with different fungicide sensitivity phenotypes by adapting mycelium and conidia to increasing concentrations of selective fungicides and UV mutagenesis. Results showed that adaptation to Quinone outside inhibitor (QoI) fungicide azoxystrobin and sterol demethylation inhibitor (DMI) fungicide propiconazole was more effective in conidial-transfer experiments compared to mycelial-transfer experiments. DMI- resistant (DMI-R) isolates adapted to significantly higher doses of azoxystrobin in both, mycelial- and conidial-transfer experiments compared to benzimidazole-resistant (BZI-R) and sensitive (S) isolates. Adaptation to propiconazole in conidial-transfer experiments was accelerated in BZI-R isolates when a stable, nonlethal dose of 50 µg/ml thiophanatemethyl was added to the selection medium. One of two azoxystrobin-resistant mutants from DMI-R isolates did not show any fitness penalties; the other isolate expired before further tests could be carried out. The viable mutant caused larger lesions on detached peach fruit sprayed with azoxystrobin compared to the parental isolate. The azoxystrobin sensitivity of the viable mutant returned to baseline levels after the mutant was transferred to unamended medium. However, azoxystrobin resistance recovered quicker in the mutant compared to the corresponding parental isolate after renewed subculturing on medium amended with 0.2 and 1 µg/ml azoxystrobin; only the mutant but not the parental isolate was able to adapt to 5 µg/ml azoxystrobin. In UV mutagenesis experiments, the DMI-R isolates produced significantly more mutants compared to S isolates. All of the UV-induced mutants showed stable fungicide resistance with little fitness penalty. This study indicates the potential for Qol fungicide resistance development in M. fructicola in the absence of a mutagen and provides evidence for increased mutability and predisposition to accelerated adaptation to azoxystrobin in M. fructicola isolates resistant to DMI fungicides. [ABSTRACT FROM AUTHOR]

The article presents a study which investigates the potential benefits of a sulfur/propiconazole mixture for the control of propiconazole-resistant isolates. A disease was developed by propiconazole-resistant isolates on detached fruit after protective or curative applications of propiconazole or its mixture with sulfur. According to the result, additive to slightly synergistic effects were observed for the mixture in protective treatments of peaches inoculated with propiconazole-resistant isolates. The addition of elemental sulfur to demethylation inhibitor (DMI) fungicide is likely to be a relatively inexpensive means to improve brown rot control in peach production area where reduced sensitivity to DMI fungicides is suspected.

Abstract: Demethylation-inhibitor fungicides (DMIs) are key components for managing Monilinia fructicola populations, even those with demonstrated reduced DMI sensitivity because few effective alternatives are available. Rotational fungicide programs that include DMIs would therefore benefit from selection of the most effective DMI. The goal of this study was to investigate the in vitro efficacy and in vivo potential of three triazole fungicides to reduce brown rot disease caused by M. fructicola isolates sensitive or with reduced sensitivity to DMIs. Baseline isolate SCDL71.01 was sensitive to propiconazole, tebuconazole, and fenbuconazole with mean EC50 values ranging from 0.018 to 0.023 μlml−1. Single spore isolates collected from an orchard in middle Georgia (GADL) were significantly less sensitive to all three triazoles compared to SCDL71.01; however, tebuconazole and fenbuconazole were significantly more effective compared to propiconazole in vitro. Protective and curative applications of each triazole on SCDL71.01 inoculated fruit prevented disease development. However, there were significant differences in efficacy of these triazoles when fruit were inoculated with GADL isolates. In protective applications, fenbuconazole and tebuconazole were significantly (P<0.05) more effective compared to propiconazole in reducing important disease measurements of GADL isolates. In curative applications, tebuconazole alone was most effective (P<0.05) in reducing disease measurements of GADL isolates. Both, in vitro and in vivo results indicate differential performances among triazoles against isolates with reduced sensitivity to DMIs. [Copyright &y& Elsevier]

Single-spore isolates of Monilinia fructicola were collected from commercial orchards in South Carolina and Georgia with prolonged past exposure to demethylation inhibitor (DMI) fungicides and from an orchard with no DMI history (baseline population). Sensitivity to propiconazole was determined using the concentration in agar media required to suppress radial growth of mycelium by 50% (EC50). Mean EC50 values from six South Carolina populations were not different from the baseline population (P < 0.05). Two of five populations from Georgia revealed significantly higher mean EC50 values compared with the baseline population (P < 0.05). Isolates with high (AP5 and AP6) and low (DL71 and DL72) EC50 values were selected to determine disease incidence on peach fruit after protective or curative applications of propiconazole at 0.15 or 0.3 liter/ha (half and full label rate, respectively). Disease incidence was significantly greater on peaches inoculated with AP5 and AP6 after curative treatment with propiconazole at 0.15 liter/ha (P < 0.05). Following protective or curative treatments at 0.3 liter/ha, disease incidence was significantly greater for AP6 but not for AP5. These results suggest that a shift toward reduced sensitivity has developed in some M. fructicola populations from Georgia, and that isolates with reduced sensitivity to propiconazole are more difficult to control in the field. Field testing of DMI fungicides, captan, Q0I fungicides, and fenhexamid in experimental orchards indicated that the DMI fungicides are still among the most efficacious products for brown rot control, and that new products containing Q0I fungicides may be viable disease control alternatives or rotation partners. [ABSTRACT FROM AUTHOR]

The costs of two reduced-fungicide programs (5 applications each) and two micronized wettable-sulfur programs (6 or 11 applications each) and their impact on scab control and fruit quality were evaluated on 'Contender' and 'Cresthaven' peach over two growing seasons. The reduced-fungicide programs consisted of applications of chlorothalonil and captan or chlorothalonil, azoxystrobin, and captan. All programs provided excellent scab control when disease pressure was low to moderate; however, six sulfur applications did not adequately control scab under high disease pressure. The product cost of the reduced-fungicide chemicals was higher, but comparable with six applications of micronized wettable sulfur or nine hypothetical applications of nonmicronized wettable sulfur per season. The reduced-fungicide programs were preferable to weekly applications of sulfur (11 applications) because they equally controlled scab at a reduced cost and have greater potential to protect against other summer diseases. The fungicide program effects on fruit quality were inconsistent. A more detailed study is needed to determine if a relationship between fungicide programs and fruit quality exists. [ABSTRACT FROM AUTHOR]

The cytochrome P450 sterol 14α-demethylase gene (MfCYP51) from Monilinia fructicola (G. Wint.) Honey was cloned and sequenced. The gene was 1680 bp in length (including introns) and was predicted to have two introns of 54 and 57 bp. The nucleotide sequence was 82.1, 53.4, 47.1, 45.1, and 33.6% and the amino acid sequence was 89.7, 76.1, 76.1, 71.8, and 66.9% identical to the CYP51 genes from Botrytis cinerea, Tapesia yallundae, T. acuformis, Erysiphe graminis, and Uncinula necator, respectively. Expression of MfCYP51 in PDR5::TN5 deficient Saccharomyces cerevisiae resulted in reduced sensitivity of the yeast transformants to myclobutanil but not to propiconazole, fenbuconazole or tebuconazole. A wildtype population of 33 M. fructicola isolates was significantly less sensitive to myclobutanil than to propiconazole, fenbuconazole, and tebuconazole. The sensitivity of the isolates to myclobutanil and the three other DMI fungicides included in this study was correlated positively, suggesting a similar or identical mode of action. The low sensitivity in M. fructicola wildtype isolates to myclobutanil could result from a less effective binding potential of the fungicide to the 14α-demethylase. [Copyright &y& Elsevier]

Brown rot, caused by Monilinia fructicola (G Wint) Honey, is a serious disease of peach in all commercial peach production areas in the USA, including South Carolina where it has been primarily controlled by pre-harvest application of 14-α demethylation (DMI) fungicides for more than 15 years. Recently, the Qo fungicide azoxystrobin was registered for brown rot control and is currently being investigated for its potential as a DMI fungicide rotation partner because of its different mode of action. In an effort to investigate molecular mechanisms of DMI and Qo fungicide resistance in M fructicola, the ABC transporter gene MfABC1 and the alternative oxidase gene MfAOX1 were cloned to study their potential role in conferring fungicide resistance. The MfABC1 gene was 4380 bp in length and contained one intron of 71 bp. The gene revealed high amino acid homologies with atrB from Aspergillus nidulans (Eidam) Winter, an ABC transporter conferring resistance to many fungicides, including DMI fungicides. MfABC1 gene expression was induced after myclobutanil and propiconazole treatment in isolates with low sensitivity to the same fungicides, and in an isolate with high sensitivity to propiconazole. The results suggest that the MfABC1 gene may be a DMI fungicide resistance determinant in M fructicola. [ABSTRACT FROM AUTHOR]

The rapid emergence of resistance in plant pathogens to the limited number of chemical classes of fungicides challenges sustainability and profitability of crop production worldwide. Understanding mechanisms underlying fungicide resistance facilitates monitoring of resistant populations at large-scale, and can guide and accelerate the development of novel fungicides. A majority of modern fungicides act to disrupt a biochemical function via binding a specific target protein in the pathway. While target-site based mechanisms such as alternation and overexpression of target genes have been commonly found to confer resistance across many fungal species, it is not uncommon to encounter resistant phenotypes without altered or overexpressed target sites. However, such non-target site mechanisms are relatively understudied, due in part to the complexity of the fungal genome network. This type of resistance can oftentimes be transient and noninheritable, further hindering research efforts. In this review, we focused on crop pathogens and summarized reported mechanisms of resistance that are otherwise related to target-sites, including increased activity of efflux pumps, metabolic circumvention, detoxification, standing genetic variations, regulation of stress response pathways, and single nucleotide polymorphisms (SNPs) or mutations. In addition, novel mechanisms of drug resistance recently characterized in human pathogens are reviewed in the context of nontarget-directed resistance. [ABSTRACT FROM AUTHOR]

Colletotrichum spp. cause devastating diseases in agricultural crops, including fruit crops. They can differ in host plant and plant organ specificity and even in fungicide sensitivity. In strawberry, members of the C. gloeosporioides species complex (referred to as C. gloeosporioides) primarily cause crown rot and those of the C. acutatum species complex (referred to as C. acutatum) primarily cause fruit rot. Fludioxonil is registered for use (in combination with cyprodinil; Switch 62.5WG in the US) in strawberry against anthracnose disease caused by Colletotrichum spp. In this study we examined the sensitivity of C. gloeosporioides (C. fructicola and C. siamense) and C. acutatum (C. nymphaeae and C. fioriniae) isolates from different hosts and different geographical locations in the US to fludioxonil and examined possible mechanisms of inherent fungicide tolerance. The dose response to fludioxonil of C. gloeosporioides isolates (including 4 isolates of C. theobromicola) revealed about 70% inhibition of mycelial growth at 1 mg/L that was maintained at 10 mg/L and 100 mg/L and lead to minimum inhibitory concentration (MIC) values >100 mg/L. In contrast, mycelial growth of C. acutatum isolates was completely inhibited at 1 mg/L. C. gloeosporioides isolates were also significantly less sensitive to iprodione. An investigation into possible mechanisms of C. gloeosporioides isolates tolerance to fludioxonil and iprodione revealed no evidence of OS-1 gene involvement. Isolates of both species complexes were equally sensitive to salt stress based on mycelial growth inhibition on potato dextrose agar amended with 2%, 4%, and 6% NaCl. In addition, orthologous amino acid alterations in OS-1 previously linked to fludioxonil resistance in Botrytis cinerea were not found in C. gloeosporioides or C. acutatum isolates. This study also showed limited in vitro inhibitory activity of cyprodinil against isolates of both species complexes (MIC values >100 mg/L) and unveils a potential weakness of the fludioxonil+cyprodinil premixture marketed as Switch 62.5WG against C. gloeosporioides species complexes. Unlabelled Image • C. gloeosporioides species complex isolates were inherently tolerant to fludioxonil. • Fludioxonil strongly inhibited C. acutatum species complex isolates. • No evidence of os-1 gene involvement in C. gloeosporioides tolerance to fludioxonil. [ABSTRACT FROM AUTHOR]

Abstract: Biofumigation of peaches in shipping cartons with pads containing culture of the volatile-producing fungus Muscodor albus was investigated for the control of brown rot caused by Monilinia fructicola. Biofumigation during cold storage (1–2°C) with 50 or 200g of M. albus per plastic bag and enclosed carton containing 14kg of fruit reduced the incidence of brown rot significantly (P <0.05) with ‘Coronet’ and ‘Red Globe’ peaches and disease incidence was comparable or lower (P <0.05) than decay in fungicide-treated peaches. Biofumigation was not as effective in non-bagged cartons, although significant brown rot control was observed in ‘Red Globe’ peaches with the 200-g treatment. Containment of volatile compounds in the cartons is thus important for the efficacy of this treatment in cold storage. [Copyright &y& Elsevier]

Although Botrytis fragariae was only recently identified as a new Botrytis species that causes strawberry gray mold, its prevalence extends to many states of the eastern United States. Compared with B. cinerea, which is known to be the causal agent of gray mold on many crop plants including strawberry, B fragariae appears to have specifically adapted to strawberry and exhibits distinct fungicide sensitivity. This is the first presentation of a high-quality genome assembly of B fragariae with gene annotation based on sequence homology and deep transcriptome data. The genome sequence information from B. fragariae is expected to help reveal genomic features underlying its host specialization and evolution of distinct fungicide resistance and other novel pathogenicity mechanisms. [ABSTRACT FROM AUTHOR]

Colletotrichum spp. isolates contain two paralogous CYP51 genes that encode sterol 14-demethylase enzymes; however, their role in sensitivity to demethylation inhibitor (DMI) fungicides is yet to be determined. In this study, each of the two genes from Colletotrichum fioriniae and C. nymphaeae was able to rescue the function of CYP51 in the yeast Saccharomyces cerevisiae, demonstrating their independent function. Deletion of CYP51A led to increased sensitivity to propiconazole, diniconazole, prothioconazole, cyproconazole, epoxiconazole, flutriafol, prochloraz, and difenoconazole in C. fioriniae, and to the same fungicides and tebuconazole in C. nymphaeae, with the exception of prochloraz. Deletion of CYP51B in C. fioriniae and CYP51B in C. nymphaeae made mutants increasingly sensitive to five of nine DMI fungicides tested. The results suggest species-specific, differential binding of DMI fungicides onto the two CYP51 enzymes. Pairing DMIs with different effects on CYP51A and -B deletion mutants resulted in synergistic effects, as determined in mycelial growth inhibition experiments. Deletion mutants showed no fitness penalty in terms of mycelial growth, sporulation, and virulence. Our study elucidates the effect of CYP51A and CYP51B of Colletotrichum spp. on DMI sensitivity, suggesting that using a mixture of DMIs may improve the efficacy for anthracnose management. [ABSTRACT FROM AUTHOR]