Sensitivity baseline establishment and resistance risk assessment of Botrytis cinerea from Panax ginseng to prochloraz / 中国中药杂志

This study aimed to establish the baseline sensitivity of Botrytis cinerea from Panax ginseng to prochloraz, and ensure the fitness of prochloraz-resistant mutants and the cross-resistance of B. cinerea to prochloraz and commonly used fungicides for the prevention and control of gray mold including boscalid, pyraclostrobin, iprodione, and pyrimethanil. The sensitivity of B. cinerea from P. ginseng to fungicides was determined by the mycelial growth rate method. The prochloraz-resistant mutants were screened out through fungicide domestication and ultraviolet(UV) induction. The fitness of resistant mutants was determined through the stability of subculture, mycelial growth rate, and pathogenicity test. The cross-resistance between prochloraz and the four fungicides was determined by Person correlation analysis. The results showed that all B. cinerea strains tested were sensitive to prochloraz, and the EC_(50) value ranged from 0.004 8 to 0.062 9 μg·mL~(-1), with an average of 0.022 μg·mL~(-1). The sensitivity frequency distribution diagram showed that 89 B. cinerea strains were located within the main peak with a continuous single peak curve, and the average EC_(50) value of 0.018 μg·mL~(-1) was taken as the baseline sensitivity of B. cinerea to prochloraz. The fungicide domestication and UV induction obtained 6 resistant mutants, among which 2 strains were unstable and the other 2 strains showed decreased resistance after multiple generations of culture. Furthermore, the mycelial growth rate and spore yield of all resistant mutants were lower than those of their parents, and the pathogenicity of most mutants was lower than that of their parents. In addition, prochloraz had no obvious cross-resistance with boscalid, pyraclostrobin, iprodione, and pyrimethanil. In conclusion, prochloraz has great potential for controlling gray mold in P. ginseng, and the resistance risk of B. cinerea to prochloraz is low.

Screening and Evaluation of Yeast Antagonists for Biological Control of Botrytis cinerea on Strawberry Fruits

Gray mold (Botrytis cinerea) is one of the most common diseases of strawberries (Fragaria × ananassa Duchesne) worldwide. Although many chemical fungicides are used for controlling the growth of B. cinerea, the risk of the fungus developing chemical resistance together with consumer demand for reducing the use of chemical fungicides have necessitated an alternative method to control this pathogen. Various naturally occurring microbes aggressively attack plant pathogens and benefit plants by suppressing diseases; these microbes are referred to as biocontrol agents. However, screening of potent biocontrol agents is essential for their further development and commercialization. In this study, 24 strains of yeast with antagonistic ability against gray mold were isolated, and the antifungal activity of the volatile and diffusible metabolites was evaluated. Putative mechanisms of action associated with the biocontrol capacity of yeast strains against B. cinerea were studied through in vitro and in vivo assays. The volatile organic compounds produced by the Galactomyces candidum JYC1146 could be useful in the biological control of plant pathogens and therefore are potential alternative fungicides with low environmental impact.

Antagonistic Effect of Streptomyces sp. BS062 against Botrytis Diseases

The use of microorganisms and their secreted molecules to prevent plant diseases is considered an attractive alternative and way to supplement synthetic fungicides for the management of plant diseases. Strain BS062 was selected based on its ability to inhibit the mycelial growth of Botrytis cinerea, a major causal fungus of postharvest root rot of ginseng and strawberry gray mold disease. Strain BS062 was found to be closely related to Streptomyces hygroscopicus (99% similarity) on the basis of 16S ribosomal DNA sequence analysis. Postharvest root rot of ginseng and strawberry gray mold disease caused by B. cinerea were controlled up to 73.9% and 58%, respectively, upon treatment with culture broth of Streptomyces sp. BS062. These results suggest that strain BS062 may be a potential agent for controlling ginseng postharvest root rot and strawberry gray mold disease.

Bacillus sp. BS061 Suppresses Powdery Mildew and Gray Mold

The use of a microorganism, or its secretions, to prevent plant disease offers an attractive alternative or supplement to synthetic fungicides for the management of plant disease without the negative effects of chemical control mechanisms. During a screening for microorganisms with the potential to be used as microbial fungicides, Bacillus sp. BS061 was isolated from a plant leaf. The strain BS061 potently inhibited the mycelial growth of Botrytis cinerea, and significantly reduced disease incidence of powdery mildew in cucumber and strawberry. We also found that the culture filtrate of BS061 inhibited the mycelial growth of various plant pathogens.

Bacillus sp. BS061 Suppresses Gray Mold and Powdery Mildew through the Secretion of Different Bioactive Substances

A Bacillus sp. BS061 significantly reduced disease incidence of gray mold and powdery mildew. To identify the active principle, the culture filtrate was partitioned between butanol and water. The antifungal activity against B. cinerea was evident in the butanol-soluble portion, and active substances were identified as cyclic lipopeptides, iturin A series, by nuclear magnetic resonance spectrometry (NMR) and mass analysis. Interestingly, antifungal activity against powdery mildew was observed in the water-soluble portion, suggesting that cyclic lipopeptides have no responsibility to suppress powdery mildew. This finding reveals that biocontrol agents of Bacillus origin suppress gray mold and powdery mildew through the secretion of different bioactive substances.

First Report of Botrytis cinerea as a Postharvest Pathogen of Blueberry in Korea

Gray mold of blueberry caused by Botrytis sp. is reported for the first time in Korea. A detailed description of the fungus is given, along with its rDNA internal transcribed spacer sequence. The fungus was identified as Botrytis cinerea based on mycological characteristics and molecular data.

Occurrence of Gray Mold Caused by Botrytis cinerea on Cryptotaenia japonica in Korea

A gray mold disease occurred on Cryptotaenia japonica in Korea. All the isolates of Botrytis sp. from the lesions of the diseased plants were identified to be B. cinerea based on the morphological characteristics. Conidia formed on conidiogenous cells were not in chains, hyaline to pale brown, unicellular, ellipsoidal to obovate with a single hilum at the base, entirely verruculose, and 6.3-11.3~6.3-10.0 microm in size. Pathogenicity of the fungus was proved by artificial inoculation on C. japonica. This is the first record of gray mold on C. japonica caused by B. cinerea in Korea.