Diagnosis and Integrated Management of Fruit Rot in Cucurbita argyrosperma, Caused by Sclerotium rolfsii.
ABSTRACT: Fruit rot is the principal phytopathological problem of pipiana pumpkin (Cucurbita argyrosperma Huber) in the state of Guerrero. The aims of this research were to 1) identify the causal agent of southern blight on pumpkin fruits by morphological, pathogenic, and molecular analysis (ITS1, 5.8S, ITS2); 2) evaluate in vitro Trichoderma spp. strains and chemical fungicides; and 3) evaluate under rainfed field conditions, the strains that obtained the best results in vitro, combined with fungicides during two crop cycles. Number of commercial and non-commercial fruits at harvest, and seed yield (kg ha-1) were registered. Morphological, pathogenic and molecular characterization identified Sclerotium rolfsii as the causal agent of rot in pipiana pumpkin fruits. Now, in vitro conditions, the highest inhibition of S. rolfsii were obtained by Trichoderma virens strain G-41 (70.72%), T. asperellum strain CSAEGro-1 (69%), and the fungicides metalaxyl (100%), pyraclostrobin (100%), quintozene (100%), cyprodinil + fludioxonil (100%), and prochloraz (100%). Thiophanate-methyl only delayed growth (4.17%). In field conditions, during the spring-summer 2015 cycle, T. asperellum strain CSAEGro-1 + metalaxyl, and T. asperellum + cyprodinil + fludioxonil, favored the highest number of fruits and seed yield in the crop.
Project description:We studied the effect of two commonly used fungicides on the epiphytic yeast community of strawberry. Greenhouse and field experiments were conducted applying Switch (cyprodinil plus fludioxonil) or Signum (boscalid plus pyraclostrobin) to strawberry plants. Yeasts on leaves and fruits were assessed on treated and untreated plants at several time points via plating and denaturing gradient gel electrophoresis (DGGE) analysis. The yeast counts on plates of the treated plants were similar to the control plants. Unripe fruits had 10 times larger yeast concentrations than ripe fruits or leaves. Some dominant yeast types were isolated and in vitro tests showed that they were at least 10 times less sensitive to Switch and Signum as compared with two important fungal strawberry pathogens Botrytis cinerea and Colletotrichum acutatum, which are the targets for the fungicide control. DGGE analysis showed that the applied fungicides had no effect on the composition of the yeast communities, while the growing system, strawberry tissue, and sampling time did affect the yeast communities. The yeast species most commonly identified were Cryptococcus, Rhodotorula, and Sporobolomyces. These results point toward the potential applicability of natural occurring yeast antagonists into an integrated disease control strategy for strawberry diseases.
Project description:This study investigated if the use of the pesticides cyprodinil and fludioxonil produced an inhibitory effect on the bovine liver catalase (CAT) activity. It was documented that the activity of the enzyme decreased with increasing concentrations of cyprodinil and fludioxonil from 0 to 500 ppm. At pesticide concentrations of 250 and 500 ppm, the activity of CAT remained unchanged and passed to a steady state. The exposure to cyprodinil in concentrations of 10, 50, 100, 250 and 500 ppm, led to a decrease in the per cent of the CAT enzyme activity calculated as 45.4, 68.0, 73.0, 77.8 and 77.4, respectively. Similarly, the exposure to fludioxonil in concentrations of 10, 50, 100, 250 and 500 ppm, produced the following percentage decrease in the CAT enzyme activity: 20.0, 30.8, 42.8, 46.3 and 45.9, respectively. Cyprodinil inhibited CAT competitively, whereas the mechanism of fludioxonil inhibition over the enzyme was non-competitive.
Project description:Greenhouse studies were conducted to evaluate the dissipation rate kinetics and estimate the behavior of selected pesticides after washing, peeling, simmering, and canning of tomato expressed as processing factor (PF). Two varieties (Marissa and Harzfeuer) were treated by six fungicides: azoxystrobin, boscalid, chlorothalonil, cyprodinil, fludioxonil, and pyraclostrobin at single and double dose and risk assessment defined as hazard quotient was performed. The QuEChERS method was used for sample preparation followed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The dissipation of fungicides approximately fitted to a first-order kinetic model, with half-life values ranging from 2.49 and 2.67 days (cyprodinil) to 5.00 and 5.32 days (chlorothalonil) for Marissa and Harzfeuer variety, respectively. Results from processing studies showed that treatments have significant effects on the removal of the studied fungicides for both varieties. The PFs were generally less than 1 (between 0.01 and 0.90) and did not depend on variety. The dietary exposure assessed based on initial deposits of application at single and double dose on tomatoes and concentration after each process with PF correction showed no concern to consumer health. Our results would be a useful tool for monitoring of fungicides in tomatoes and provide more understanding of residue behavior and risk posed by these fungicides.
Project description:Postharvest application of fungicides is commonly applied in order to reduce food loss. Prochloraz is currently the only postharvest fungicide registered in Israel and Europe in avocado fruits. Due to its unfavorable toxicological properties, prochloraz will be banned from the end of 2020 for future postharvest usage and therefore a substitute candidate is urgently warranted. Fludioxonil, a relatively safe, wide spectrum fungicide, is approved in Europe and Israel for postharvest use in various fruits, but not avocado. Hence, fludioxonil has been evaluated in the present study as a potential substitute for prochloraz in avocado. The objectives of the present study were to determine fludioxonil efficacy against common fungal infestations in avocado and distribution kinetics between peel and pulp in comparison to prochloraz. At the same concentration range (75-300 µg/L), fludioxonil was as effective as prochloraz in inhibiting postharvest decay, while in the early season cultivars, suffering mainly from stem-end rot, it exhibited a better decay control than prochloraz. Fludioxonil and prochloraz displayed negligible and undetected pulp levels, respectively, due to low peel penetrability. Taken altogether, fludioxonil was found to be a suitable candidate for replacing prochloraz as a postharvest fungicide in avocado.
Project description:The role of a mitogen-activated protein kinase (MAPK) TmkA in inducing systemic resistance in cucumber against the bacterial pathogen Pseudomonas syringae pv. lacrymans was investigated by using tmkA loss-of-function mutants of Trichoderma virens. In an assay where Trichoderma spores were germinated in proximity to cucumber roots, the mutants were able to colonize the plant roots as effectively as the wild-type strain but failed to induce full systemic resistance against the leaf pathogen. Interactions with the plant roots enhanced the level of tmkA transcript in T. virens and its homologue in Trichoderma asperellum. At the protein level, we could detect the activation of two forms reacting to the phospho-p44/42 MAPK antibody. Biocontrol experiments demonstrated that the tmkA mutants retain their biocontrol potential against Rhizoctonia solani in soil but are not effective against Sclerotium rolfsii in reducing disease incidence. Our results show that, unlike in many plant-pathogen interactions, Trichoderma TmkA MAPK is not involved in limited root colonization. Trichoderma, however, needs MAPK signaling in order to induce full systemic resistance in the plant.
Project description:Fusarium wilt (FW) caused by Fusarium oxysporum f. sp. niveum (FON) is a soil-borne disease that seriously limits watermelon production. In the present study, Trichoderma asperellum (T. asperellum) M45a was shown to be an effective biocontrol agent against FW. In a pot experiment, the application of 105 cfu/g of T. asperellum M45a granules had an improved control effect on FW during the blooming period (up to 67.44%) in soils subjected to five years of continuous cropping with watermelon, while the average length of watermelon vines was also significantly improved (P?<?0.05). Additionally, the acid phosphatase (ACP), cellulase (CL), catalase (CAT), and sucrase (SC) activities in the M45a-inoculation group were significantly higher than those in the control (CK) group, and transformation of the soil nutrients (total N, NO3-N, and available P) was significantly increased. Moreover, T. asperellum M45a inoculation reduced fungal diversity, increased bacterial diversity and especially enhanced the relative abundance of plant growth-promoting rhizobacteria (PGPR), such as Trichoderma, Sphingomonas, Pseudomonas, Actinomadura, and Rhodanobacter. Through functional prediction, the relative abundance of ectomycorrhiza, endophytes, animal pathotrophs, and saprotrophs in the fungal community was determined to be significantly lower than that observed in the M45a-treated soil. Correlation analysis revealed that Sphingomonas, Pseudomonas, and Trichoderma had the most differences in terms of microorganism abundance, and these differences were positively correlated with ACP, CL, CAT, and SC. These findings provide guidance for the use of fungicides to achieve microecological control of FW in continuously cropped watermelon plots.
Project description:Aloe vera (L.) Burm.f. is a highly important and extensively cultivated medicinal plant and that is also extensively used in the cosmetic industry. It has been frequently reported to suffer from Alternaria leaf spot disease in various parts of the world. Various fungicides used to combat this disease, have deleterious effects on the environment and on pharmacologically important constituents of Aloe vera. To avoid the harmful effects of fungicides an ecofriendly approach has been adopted here. A weekly survey was conducted during 2013-2015 in and around North 24 Parganas (West Bengal) to obtain the percentage of disease index (PDI). For biological control of the disease, screening of the antagonistic efficacy of biocontrol agents was carried out through the in vitro dual-culture-plate method and scanning electron microscopy (SEM) was used to study the mechanism. The in vitro effects of fungicides on the radial growth of the pathogen were evaluated through the poison food method and were compared with potent antagonistic fungi. Field application of potent antagonistic fungi was conducted through the dip-and-spray method. The results showed that, the PDI peaked during the hot and humid conditions of May to September (76.57%-98.57%) but decreased during the winter, December-January (35.71-46.66%). Trichoderma asperellum exerted the greatest inhibition of the radial growth of A. brassicae acting through non volatile (70.39%) and volatile metabolites (72.17%). A SEM study confirmed the hyperparasitic nature of T. asperellum through hyphal coiling-T. asperellum was similar to 2% blitox-50 (73.92%) and better than 2% bavistin (59.77%) (in vitro). In agricultural field trials (2013-15), Trichoderma application restricted the disease to the smallest area (PDI 24.00-29.33%) in comparison to untreated plots (73.33%). In conclusion, saplings treated with the dip method (108 spores / mL) and sprayed 4 times with a spore suspension of biocontrol agents such as T. asperellum, T. viride and T. harzianum, standardized at a rate of 2.5 L / plot (36 sq ft) (108 spores/ mL) are suggested for the ecofriendly management of this epidemic leaf spot disease of Aloe vera in agricultural fields.
Project description:Biological control plays a crucial role in grapevine pathogens disease management. The cell-wall degrading enzymes chitinase, cellulase and β-glucanase have been suggested to be essential for the mycoparasitism activity of Trichoderma species against grapevine fungal pathogens. In order to develop a useful strain as a single source of these vital enzymes, it was intended to incorporate the characteristics of two parental fungicides tolerant mutants of Trichoderma belonging to the high chitinase producing species T. harzianum and the high cellulase producing species T. viride, by fusing their protoplasts. The phylogeny of the parental strains was carried out using a sequence of the 5.8S-ITS region. The BLAST of the obtained sequence identified these isolates as T. harzianum and T. viride. Protoplasts were isolated using lysing enzymes and were fused using polyethylene glycol. The fused protoplasts have been regenerated on protoplast regeneration minimal medium supplemented with two selective fungicides. Among the 40 fast growing fusants, 17 fusants were selected based on their enhanced growth on selective media for further studies. The fusant strains were growing 60%-70% faster than the parents up to third generation. All the 17 selected fusants exhibited morphological variations. Some fusant strains displayed threefold increased chitinase enzyme activity and twofold increase in β-glucanase enzyme activity compared to the parent strains. Most fusants showed powerful antagonistic activity against Macrophomin aphaseolina, Pythium ultimum and Sclerotium rolfsii pathogens. Fusant number 15 showed the highest inhibition percentage (92.8%) against M. phaseolina and P. ultimum, while fusant number 9 showed the highest inhibition percentage (98.2%) against the growth of S. rolfsii. A hyphal intertwining and degradation phenomenon was observed by scanning electron microscope. The Trichoderma antagonistic effect against pathogenic fungal mycelia was due to the mycoparasitism effect of the extracellular enzymes.
Project description:The gray mold fungus Botrytis cinerea is a major threat to fruit and vegetable production. Strawberry fields usually receive several fungicide treatments against Botrytis per season. Gray mold isolates from several German strawberry-growing regions were analyzed to determine their sensitivity against botryticides. Fungicide resistance was commonly observed, with many isolates possessing resistance to multiple (up to six) fungicides. A stronger variant of the previously described multidrug resistance (MDR) phenotype MDR1, called MDR1h, was found to be widely distributed, conferring increased partial resistance to two important botryticides, cyprodinil and fludioxonil. A 3-bp deletion mutation in a transcription factor-encoding gene, mrr1, was found to be correlated with MDR1h. All MDR1h isolates and the majority of isolates with resistance to multiple fungicides were found to be genetically distinct. Multiple-gene sequencing confirmed that they belong to a novel clade, called Botrytis group S, which is closely related to B. cinerea and the host-specific species B. fabae. Isolates of Botrytis group S genotypes were found to be widespread in all German strawberry-growing regions but almost absent from vineyards. Our data indicate a clear subdivision of gray mold populations, which are differentially distributed according to their host preference and adaptation to chemical treatments.
Project description:We report the application of RNA sequencing technology for transcriptome profiling of Trichoderma asperellum challenged with Organophosphorus Pesticide Dichlorvos. Based on RNA-seq analysis, in T. asperellum TJ01 treated with 100 μg/mL, 500 μg/mL, and 1000 μg/mL dichlorvos, 204, 490, and 872 genes were significantly upregulated, respectively, while 37, 177, and 383 genes were significantly downregulated, respectively. This study provides a framework for the application of transcriptome profiling towards characterization of trichoderma under stress of Organophosphorus Pesticide. Overall design: Examination of differential response of Trichoderma in Dichlorvos treated group or control .