Botrytis polyphyllae: A New Botrytis Species Causing Gray Mold on Paris polyphylla.

Paris polyphylla is an important perennial medicinal plant in China. A disease similar to gray mold on P. polyphylla occurred at the seedling stage in March 2016 and 2017 in Tengchong city, Yunnan Province of China. The disease resulted in up to 50% mortality in serious cases. Isolates from diseased plants grew 10.6 mm/day at 20°C on PDA. After 21 days, sclerotia were spherical to elliptical (0.4-2.5 × 0.3-1.8 mm). Conidia from diseased tissues were hyaline to pale brown, long, ovoid, unicellular, and measured 15.1-24.5 × 8.8-13.4 µm; conidiophores were 526-1,064 ×12-15 µm. Isolates did not form conidiophores or conidia on PDA or MYA. A phylogenetic analysis based on G3PDH, RPB2, and HSP60 sequence data supported assignment of three representative isolates as a new species of Botrytis. Based on morphological, phylogenetic characteristics and Koch's Postulates, the causal agent of gray mold on P. polyphylla was identified as a novel species, Botrytis polyphyllae.

Talaromyces pinophilus strain AUN-1 as a novel mycoparasite of Botrytis cinerea, the pathogen of onion scape and umbel blights.

This study aimed to investigate the mycoparasitism of Botrytis cinerea, the pathogen of scape and umbel blights of onion seed crops, by endophytic Talaromyces pinophilus. The dual culture test showed that the antagonistic potentiality of T. pinophilus against B. cinerea depend on the mycoparasitism that was morphologically detected by the formation of mycelial overgrowth. Moreover, the light micrograph of the mycelia at the contact zone exhibited that the hyphae of T. pinophilus penetrated and grew intracellularly inside the hyphae of B. cinerea. A more illustrative figure of the establishment of coiled hyphae as well as the conformation of the penetration process was assayed by SEM and TEM analyses. SEM micrograph revealed that the hyphae of T. pinophilus grew along hyphae of B. cinerea, attached, coiled around the host hypha and generated pseudoappressorium. A clear disintegration of cell wall of the host hypha was observed at the penetration site. The micrographs of TEM exhibited the ability of T. pinophilus to produce pseudoappressorium, penetrate and then entere a hypha of B. cinerea causing distinct cytoplasmic disorganization. High activities of cell wall degrading enzymes (chitinase, lipase and protease) involved in the mycoparasitism were evaluated by the endophytic T. pinophilus. In conclusion, this study demonstrated that the endophytic T. pinophilus may be a promising biocontrol agent against phytopathogenic fungi instead of chemical fungicides.

Synthesis and antifungal activity of 2-allylphenol derivatives against fungal plant pathogens.

2-Allylphenol (2-AP) is an effective fungicide against a number of plant pathogens, which can be metabolized and bio-transformed to four chemical compounds by Rhizoctonia cerealis. To determine if its degradation affects antifungal activity, two major metabolites derived from 2-AP including 2-(2-hydroxypropyl) phenol and 2-(3-hydroxypropyl) phenol were synthesized. Inhibition of mycelial growth of several plant pathogens by the metabolites was evaluated, and structures of two metabolites were determined by hydrogen nuclear magnetic resonance (1H NMR). Among these metabolites, only 2-(2-hydroxypropyl) phenol inhibited test pathogens effectively. EC50 values of 2-(2-hydroxypropyl) phenol for inhibition of mycelial growth of R. cerealis, Pythium aphanidermatum, Valsa mali and Botrytis cinerea ranged from 1.0 to 23.5µg/ml, which were lower than the parental fungicide 2-AP that ranged from 8.2 to 48.8µg/ml. Hyphae of R. cerealis and P. aphanidermatum treated with 2-(2-hydroxypropyl) phenol were twisted. Newly developed hyphae were slender, twisted and swollen on the tip, while old hyphae were hollow and ruptured. This is the first report indicating the formation of 2-(2-hydroxypropyl) phenol may have contributed to toxicity of 2-allylphenol in control of plant pathogens.

A gapless genome sequence of the fungus Botrytis cinerea.

Following earlier incomplete and fragmented versions of a genome sequence for the grey mould Botrytis cinerea, a gapless, near-finished genome sequence for B. cinerea strain B05.10 is reported. The assembly comprised 18 chromosomes and was confirmed by an optical map and a genetic map based on approximately 75 000 single nucleotide polymorphism (SNP) markers. All chromosomes contained fully assembled centromeric regions, and 10 chromosomes had telomeres on both ends. The genetic map consisted of 4153 cM and a comparison of the genetic distances with the physical distances identified 40 recombination hotspots. The linkage map also identified two mutations, located in the previously described genes Bos1 and BcsdhB, that conferred resistance to the fungicides boscalid and iprodione. The genome was predicted to encode 11 701 proteins. RNAseq data from >20 different samples were used to validate and improve gene models. Manual curation of chromosome 1 revealed interesting features, such as the occurrence of a dicistronic transcript and fully overlapping genes in opposite orientations, as well as many spliced antisense transcripts. Manual curation also revealed that the untranslated regions (UTRs) of genes can be complex and long, with many UTRs exceeding lengths of 1 kb and possessing multiple introns. Community annotation is in progress.

Antifungal activity of ß-carbolines on Penicillium digitatum and Botrytis cinerea.

ß-carbolines (ßCs) are alkaloids widely distributed in nature that have demonstrated antimicrobial properties. Here, we tested in vitro six ßCs against Penicillium digitatum and Botrytis cinerea, causal agents of postharvest diseases on fruit and vegetables. Full aromatic ßCs (harmine, harmol, norharmane and harmane) exhibited a marked inhibitory effect on conidia germination at concentrations between 0.5 and 1 mM, while dihydro-ßCs (harmalina and harmalol) only caused germination delay. Harmol showed the highest inhibitory effect on both fungal pathogens. After 24 h of exposure to 1 mM harmol, conidia revealed a severe cellular damage, exhibiting disorganized cytoplasm and thickened cell wall. Harmol antimicrobial effect was fungicidal on B. cinerea, while it was fungistatic on P. digitatum. Conidia membrane permeabilization was detected in treatments with harmol at sub-inhibitory and inhibitory concentrations, for both pathogens. In addition, residual infectivity of P. digitatum on lemons and B. cinerea on blueberries was significantly reduced after exposure to this alkaloid. It also inhibited mycelial growth, preventing sporulation at the highest concentration tested. These results indicate that harmol might be a promising candidate as a new antifungal molecule to control causal agents of fruit diseases.

Chasing stress signals - Exposure to extracellular stimuli differentially affects the redox state of cell compartments in the wild type and signaling mutants of Botrytis cinerea.

Reactive oxygen species (ROS) are important molecules influencing intracellular developmental processes as well as plant pathogen interactions. They are produced at the infection site and affect the intracellular redox homeostasis. However, knowledge of ROS signaling pathways, their connection to other signaling cascades, and tools for the visualization of intra- and extracellular ROS levels and their impact on the redox state are scarce. By using the genetically encoded biosensor roGFP2 we studied for the first time the differences between the redox states of the cytosol, the intermembrane space of mitochondria and the ER in the filamentous fungus Botrytis cinerea. We showed that the ratio of oxidized to reduced glutathione inside of the cellular compartments differ and that the addition of hydrogen peroxide (H2O2), calcium chloride (CaCl2) and the fluorescent dye calcofluor white (CFW) have a direct impact on the cellular redox states. Dependent on the type of stress agents applied, the redox states were affected in the different cellular compartments in a temporally shifted manner. By integrating the biosensor in deletion mutants of bcnoxA, bcnoxB, bctrx1 and bcltf1 we further elucidated the putative roles of the different proteins in distinct stress-response pathways. We showed that the redox states of ΔbcnoxA and ΔbcnoxB display a wild-type pattern upon exposure to H2O2, but appear to be strongly affected by CaCl2 and CFW. Moreover, we demonstrated the involvement of the light-responsive transcription factor BcLtf1 in the maintenance of the redox state in the intermembrane space of the mitochondria. Finally, we report that CaCl2 as well as cell wall stress-inducing agents stimulate ROS production and that ΔbcnoxB produces significantly less ROS than the wild type and ΔbcnoxA.

Translocation from nuclei to cytoplasm is necessary for anti A-PCD activity and turnover of the Type II IAP BcBir1.

Type II inhibitors of apoptosis (IAPs) belong to a subgroup of IAP-related proteins. While IAPs are restricted to animals, Type II IAPs are found in other phyla, including fungi. BcBir1, a Type II IAP from Botrytis cinerea has anti apoptotic-like programmed cell death (A-PCD) activity, which is important for pathogenicity of this fungus. Here we report on the role of sub-cellular localization of BcBir1 in protein turnover and anti A-PCD activity. Expression of BcBir1 in Saccharomyces cerevisiae had no effect on sensitivity of the yeast cells to A-PCD-inducing conditions, whereas expression of a truncated N' part reduced sensitivity of the cells to these conditions. The full-length BcBir1 protein was detected only in the yeast nucleus, whereas the N' part was observed both in the nucleus and cytoplasm. In B. cinerea, BcBir1 was mainly nuclear under optimal conditions, whereas under A-PCD-inducing conditions it shuttled to the cytoplasm and then it was completely degraded. Collectively, our results show that anti A-PCD activity of BcBir1 occurs in the cytoplasm, the C' end mediates regulation of steady state level of BcBir1 in the nucleus, and the N' end mediates anti A-PCD activity as well as fast degradation of BcBir1 in the cytoplasm.

Aquaporin8 regulates cellular development and reactive oxygen species production, a critical component of virulence in Botrytis cinerea.

Aquaporins (AQPs) are ubiquitous in nearly all organisms, mediating selective and rapid flux of water across biological membranes. The role of AQPs in phytopathogenic fungi is poorly understood. Orthologs of AQP genes in Botrytis cinerea were identified and knocked out. The effects of AQPs on hyphal growth and conidiation, formation of infection structures and virulence on plant hosts were examined. The role of AQP8 in reactive oxygen species (ROS) production, distribution and transport were further determined. Among eight AQPs, only AQP8 was essential for the ability of B. cinerea to infect plants. AQP8 was demonstrated to be an intrinsic plasma membrane protein, which may function as a channel and mediate hydrogen peroxide uptake. Deletion of AQP8 in B. cinerea completely inhibited the development of conidia and infection structures, and significantly affected noxR expression. Further observations revealed that both AQP8 and noxR impacted ROS distribution in the hyphal tips of B. cinerea. Moreover, AQP8 affected the expression of a mitochondrial protein, NQO1. A knockout mutant of NQO1 was observed to display reduced virulence. These data lead to a better understanding of the important role of AQP8 in the development and pathogenesis of plant pathogens.

Identification and Characterization of Botrytis Blossom Blight of Japanese Plums Caused by Botrytis cinerea and B. prunorum sp. nov. in Chile.

Blossom blight is a destructive disease of plums (Prunus salicina) when humid and temperate weather conditions occur in Chile. Disease incidence ranging from 4 to 53% has been observed. Symptoms include light brown petal necrosis, starting as light brown mottles or V-shaped necrosis at the margins of the petals, progressing to the stamen and pistils. In this study, the etiology of blossom blight of plums was determined. High- and low-sporulating isolates of Botrytis were obtained consistently from blighted blossoms and apparently healthy flowers of plums. Based on colony morphology, conidial production and molecular phylogenetic analysis, these high- and low-sporulating isolates were identified as B. cinerea and B. prunorum sp. nov., respectively. Phylogenetic analysis of the genes glyceraldehyde 3-phosphate dehydrogenase (G3PDH), heat-shock protein 60 (HSP60), and DNA-dependent RNA polymerase subunit II (RPB2) grouped B. prunorum isolates in a single cluster, distantly from B. cinerea and other Botrytis species. The phylogenetic analysis of necrosis and ethylene-inducing protein (NEP1 and NEP2) genes corroborated these results. Analysis of the internal transcribed spacer region and large-subunit (26S) ribosomal DNA and detection of Boty and Flipper transposable elements, were not useful to differentiate between these Botrytis species. Both species were pathogenic on plum flowers and the fruit of plums, apples, and kiwifruits. However, B. prunorum was less virulent than B. cinerea. These pathogens were re-isolated from inoculated and diseased tissues; thus, Koch's postulates were fulfilled, confirming its role in blossom blight of plums. B. cinerea was predominant, suggesting that B. prunorum may play a secondary role in the epidemiology of blossom blight in plums in Chile. This study clearly demonstrated that the etiology of blossom blight of plums is caused by B. cinerea and B. prunorum, which constitute a species complex living in sympatry on plums and possibly on other stone fruit trees.

Loss of bcbrn1 and bcpks13 in Botrytis cinerea Not Only Blocks Melanization But Also Increases Vegetative Growth and Virulence.

Botrytis cinerea is a necrotrophic pathogen that causes gray mold disease in a broad range of plants. Dihydroxynaphthalene (DHN) melanin is a major component of the extracellular matrix of B. cinerea, but knowledge of the exact role of melanin biosynthesis in this pathogen is unclear. In this study, we characterize two genes in B. cinerea, bcpks13 and bcbrn1, encoding polyketide synthase and tetrahydroxynaphthalene (THN) reductases, respectively, and both have predicted roles in DHN melanin biosynthesis. The ∆bcpks13 and ∆bcbrn1 mutants show white and orange pigmentation, respectively, and the mutants are also deficient in conidiation in vitro but show enhanced growth rates and virulence on hosts. Moreover, the mutants display elevated acidification of the complete medium (CM), probably due to oxalic acid secretion and secretion of cell wall-degrading enzymes, and preferably utilize plant cell-wall components as carbon sources for mycelium growth in vitro. In contrast, overexpression of bcbrn1 (OE::bcbrn1 strain) results in attenuated hydrolytic enzyme secretion, acidification ability, and virulence. Taken together, these results indicate that bcpks13 and bcbrn1 participate in diverse cellular and developmental processes, such as melanization and conidiation in B. cinerea in vitro, but they negatively regulate the virulence of this pathogen.

Redox systems in Botrytis cinerea: impact on development and virulence.

The thioredoxin system is of great importance for maintenance of cellular redox homeostasis. Here, we show that it has a severe influence on virulence of Botrytis cinerea, demonstrating that redox processes are important for host-pathogen interactions in this necrotrophic plant pathogen. The thioredoxin system is composed of two enzymes, the thioredoxin and the thioredoxin reductase. We identified two genes encoding for thioredoxins (bctrx1, bctrx2) and one gene encoding for a thioredoxin reductase (bctrr1) in the genome of B. cinerea. Knockout mutants of bctrx1 and bctrr1 were severely impaired in virulence and more sensitive to oxidative stress. Additionally, Δbctrr1 showed enhanced H2O2 production and retarded growth. To investigate the impact of the second major cellular redox system, glutathione, we generated deletion mutants for two glutathione reductase genes. The effects were only marginal; deletion of bcglr1 resulted in reduced germination and, correspondingly, to retarded infection as well as reduced growth on minimal medium, whereas bcglr2 deletion had no distinctive phenotype. In summary, we showed that the balanced redox status maintained by the thioredoxin system is essential for development and pathogenesis of B. cinerea, whereas the second major cellular redox system, the glutathione system, seems to have only minor impact on these processes.

Inhibition of agronomically relevant fungal phytopathogens by tyrocidines, cyclic antimicrobial peptides isolated from Bacillus aneurinolyticus.

The tyrocidines, a complex of analogous cyclic decapeptides produced by Bacillus aneurinolyticus, exhibited noteworthy activity against a range of phytopathogenic fungi, including Fusarium verticillioides, Fusarium solani and Botrytis cinerea. The activity of the tyrocidine peptide complex (Trc mixture) and purified tyrocidines exhibited minimum inhibition concentrations below 13 µg ml(-1) (~10 µM) and was significantly more potent than that of the commercial imidazole fungicide, bifonazole. Although the tyrocidines' activity was negatively influenced by the presence of Ca(2+), it remained unaffected by the presence of Mg(2+), Na(+) and K(+). Microscopic analysis revealed significant impact on the morphology of F. solani and Bot. cinerea including retarded germination and hyperbranching of hyphae. Studies with membrane-impermeable dyes, SYTOX green and propidium iodide suggested that the main mode of action of tyrocidines involves the disruption of fungal membrane integrity. Because of the tyrocidines' broad spectrum and potent antifungal activity, possible multiple targets reducing the risk of overt resistance and general salt tolerance, they are promising candidates that warrant further investigation as bio-fungicides.

A novel partitivirus that confers hypovirulence on plant pathogenic fungi.

UNLABELLED: Members of the family Partitiviridae have bisegmented double-stranded RNA (dsRNA) genomes and are not generally known to cause obvious symptoms in their natural hosts. An unusual partitivirus, Sclerotinia sclerotiorum partitivirus 1 (SsPV1/WF-1), conferred hypovirulence on its natural plant-pathogenic fungal host, Sclerotinia sclerotiorum strain WF-1. Cellular organelles, including mitochondria, were severely damaged. Hypovirulence and associated traits of strain WF-1 and SsPV1/WF-1 were readily cotransmitted horizontally via hyphal contact to different vegetative compatibility groups of S. sclerotiorum and interspecifically to Sclerotinia nivalis and Sclerotinia minor. S. sclerotiorum strain 1980 transfected with purified SsPV1/WF-1 virions also exhibited hypovirulence and associated traits similar to those of strain WF-1. Moreover, introduction of purified SsPV1/WF-1 virions into strain KY-1 of Botrytis cinerea also resulted in reductions in virulence and mycelial growth and, unexpectedly, enhanced conidial production. However, virus infection suppressed hyphal growth of most germinating conidia of B. cinerea and was eventually lethal to infected hyphae, since very few new colonies could develop following germ tube formation. Taken together, our results support the conclusion that SsPV1/WF-1 causes hypovirulence in Sclerotinia spp. and B. cinerea. Cryo-EM (cryo-electron microscopy) reconstruction of the SsPV1 particle shows that it has a distinct structure with similarity to the closely related partitiviruses Fusarium poae virus 1 and Penicillium stoloniferum virus F. These findings provide new insights into partitivirus biological activities and clues about molecular interactions between partitiviruses and their hosts. IMPORTANCE: Members of the Partitiviridae are believed to occur commonly in their phytopathogenic fungal and plant hosts. However, most partitiviruses examined so far appear to be associated with latent infections. Here we report a partitivirus, SsPV1/WF-1, that was isolated from a hypovirulent strain of Sclerotinia sclerotiorum and describe its biological and molecular features. We have demonstrated that SsPV1 confers hypovirulence. Furthermore, SsPV1 can infect and cause hypovirulence in Botrytis cinerea. Our study also suggests that SsPV1 has a vigorous ability to proliferate and spread via hyphal contact. SsPV1 can overcome vegetative incompatibility barriers and can be transmitted horizontally among different vegetative compatibility groups of S. sclerotiorum, even interspecifically. Cryo-EM reconstruction of SsPV1 shows that it has a distinct structure with similarity to closely related partitiviruses. Our studies exploit a novel system, SsPV1 and its hosts, which can provide the means to explore the mechanisms by which partitiviruses interact with their hosts.

A novel Botrytis species is associated with a newly emergent foliar disease in cultivated Hemerocallis.

Foliar tissue samples of cultivated daylilies (Hemerocallis hybrids) showing the symptoms of a newly emergent foliar disease known as 'spring sickness' were investigated for associated fungi. The cause(s) of this disease remain obscure. We isolated repeatedly a fungal species which proved to be member of the genus Botrytis, based on immunological tests. DNA sequence analysis of these isolates, using several different phyogenetically informative genes, indicated that they represent a new Botrytis species, most closely related to B. elliptica (lily blight, fire blight) which is a major pathogen of cultivated Lilium. The distinction of the isolates was confirmed by morphological analysis of asexual sporulating cultures. Pathogenicity tests on Hemerocallis tissues in vitro demonstrated that this new species was able to induce lesions and rapid tissue necrosis. Based on this data, we infer that this new species, described here as B. deweyae, is likely to be an important contributor to the development of 'spring sickness' symptoms. Pathogenesis may be promoted by developmental and environmental factors that favour assault by this necrotrophic pathogen. The emergence of this disease is suggested to have been triggered by breeding-related changes in cultivated hybrids, particularly the erosion of genetic diversity. Our investigation confirms that emergent plant diseases are important and deserve close monitoring, especially in intensively in-bred plants.

The high-affinity phosphodiesterase BcPde2 has impact on growth, differentiation and virulence of the phytopathogenic ascomycete Botrytis cinerea.

Components of the cAMP signaling pathway, such as the adenylate cyclase Bac and the protein kinase A (PKA) were shown to affect growth, morphogenesis and differentiation as well as virulence of the phytopathogenic fungus Botrytis cinerea. While loss of Bac caused drastically reduced intracellular cAMP levels, deletion of the PKA resulted in extremely increased cAMP concentrations. To regulate the intracellular level of the second messenger cAMP, a balance between its biosynthesis through adenylate cyclase activity and its hydrolysis by phosphodiesterases (PDEs) is crucial. Here, we report the functional characterization of the two PDEs in the ascomycete B. cinerea, BcPde1 and BcPde2. While deletion of bcpde2 resulted in severely affected vegetative growth, conidiation, germination and virulence, the bcpde1 deletion strain displayed a wild-type-like phenotype. However, the double bcpde1/2 deletion mutant exhibited an even stronger phenotype. Localization studies revealed that BcPde2 accumulates at the plasma membrane, but is also localized in the cytoplasm. BcPde1 was shown to be distributed in the cytoplasm as well, but also accumulates in so far unknown mobile vesicles. Overexpression of bcpde1 in the Δbcpde2 background rescued the deletion phenotype, and in addition an increased transcript level of bcpde1 in the Δbcpde2 strain was observed, indicating redundant functions of both PDEs and an interdependent gene expression.

Involvement of Botrytis cinerea small GTPases BcRAS1 and BcRAC in differentiation, virulence, and the cell cycle.

Small GTPases of the Ras superfamily are highly conserved proteins that are involved in various cellular processes, in particular morphogenesis, differentiation, and polar growth. Here we report on the analysis of RAS1 and RAC homologues from the gray mold fungus Botrytis cinerea. We show that these small GTPases are individually necessary for polar growth, reproduction, and pathogenicity, required for cell cycle progression through mitosis (BcRAC), and may lie upstream of the stress-related mitogen-activated protein kinase (MAPK) signaling pathway. bcras1 and bcrac deletion strains had reduced growth rates, and their hyphae were hyperbranched and deformed. In addition, both strains were vegetatively sterile and nonpathogenic. A strain expressing a constitutively active (CA) allele of the BcRAC protein had partially similar but milder phenotypes. Similar to the deletion strains, the CA-BcRAC strain did not produce any conidia and had swollen hyphae. In contrast to the two deletion strains, however, the growth rate of the CA-BcRAC strain was normal, and it caused delayed but well-developed disease symptoms. Microscopic examination revealed an increased number of nuclei and disturbance of actin localization in the CA-BcRAC strain. Further work with cell cycle- and RAC-specific inhibitory compounds associated the BcRAC protein with progression of the cell cycle through mitosis, possibly via an effect on microtubules. Together, these results show that the multinucleate phenotype of the CA-BcRAC strain could result from at least two defects: disruption of polar growth through disturbed actin localization and uncontrolled nuclear division due to constitutive activity of BcRAC.

Interaction with Penicillium expansum enhances Botrytis cinerea growth in grape juice medium and prevents patulin accumulation in vitro.

Interactions between fungi occur when they grow on the same host plant. This is the case of Botrytis cinerea and Penicillium expansum on grape. P. expansum is also responsible for production of the mycotoxin patulin. In this study, the influence of the interaction between both fungi on fungal growth parameters was studied as well as the effect on the accumulation of patulin by P. expansum. For that purpose, spores of B. cinerea and P. expansum were inoculated together (mixed inoculum), and the parameters growth rate, time for growth and patulin accumulation were assessed. The presence of P. expansum conidia shortened the time for growth of mixed inoculum colonies which, at the end of incubation, were B. cinerea-like. Although some P. expansum growth was observed in mixed inoculum colonies, very low levels of patulin were observed. In assays carried out in patulin-spiked medium, B. cinerea was capable to metabolize the mycotoxin. The capabilities of B. cinerea to shorten time for growth and prevent patulin accumulation are competing abilities that facilitate grape colonization.

Farnesol induces apoptosis-like phenotype in the phytopathogenic fungus Botrytis cinerea.

This study demonstrates that the isoprenoid farnesol produces a toxic effect on the phytopathogenic fungus Botrytis cinerea in solid and liquid media. In solid media farnesol retarded 72 h the beginning of mycelial growth. Also, it was demonstrated that the toxic effect is due to farnesol triggers apoptosis in B. cinerea because ROS accumulation, DNA fragmentation and phosphatidylserine externalization were detected in farnesol-treated mycelium. Therefore, compounds that increase the intracellular farnesol or induce apoptosis could have a potential application as fungicide against B. cinerea.

Involvement of BcVeA and BcVelB in regulating conidiation, pigmentation and virulence in Botrytis cinerea.

The heterotrimeric velvet complex VeA/VelB/LaeA is involved in the regulation of diverse cellular processes in Aspergillus nidulans. In this work, we investigated functions of two velvet-like genes BcVEA and BcVELB in Botrytis cinerea. Morphological characterization of BcVEA and BcVELB deletion mutants showed that the deletion of BcVEA and BcVELB led to increased conidiation and melanin biosynthesis. BcVEA and BcVELB deletion mutants also showed increased sensitivity to oxidative stress. Pathogenicity assays revealed that both BcVeA and BcVelB were essential for full virulence of B. cinerea. Yeast two-hybrid assay displayed the interaction of BcVeA with BcVelB. Results of this study indicate that BcVeA and BcVelB coordinate similar processes in the regulation of fungal development, oxidative stress response, and virulence in B. cinerea.

Antagonistic effects of Bacillus cereus strain B-02 on morphology, ultrastructure and cytophysiology of Botrytis cinerea.

The study on antagonistic mechanism of biocontrol strains gives the premise and basis for efficient and stable biological control. This study aimes to overcome of biocontrol agent in aspects of complicated and diversified mode of action, short-lasting and unstable efficacy in the production processes. This study elucidated the antagonistic mechanism of Bacillus cereus strain B-02 on Botrytis cinerea by detecting changes in morphology, ultrastructure and physiology in affected hyphae of Botrytis cinerea. Which provided certain theoretical and practical significance for biological control of gray mould caused by B. cinerea. B. cereus strain B-02 isolated from tomato rhizosphere mightily suppressed gray mold in tomato caused by B. cinerea. Spore germination and hyphal growth of B. cinerea were inhibited by B. cereus strain B-02. Changes of cell morphology such as distortion, shrinking and swelling were observed by SEM. TEM observation further indicated the ultrastructural alterations of hyphae, including mitochondrion reduction, un-membranous inclusion in cytoplasm, considerable thickening of cell walls, and electronic density enhancement. LSCM observation revealed the fluorescence intensity of nucleus DNA, mitochondrion DNA and reactive oxygen radical in treated hyphae were all stronger than control and the difference was significant (P < 0.01). These results indicated that the antagonistic effects of B. cereus strain B-02 on B. cinerea were likely due to a combination of abnormal synthesis of nucleus DNA and mitochondrion DNA and multifarious ultrastructural alterations in hyphal cell.