Destructive Fungal Pathogen Research Articles

Morphological, genetic and pathogenic variability among Botrytis cinerea species complex causing gray mold of strawberry

The necrotrophic fungus Botrytis cinerea is capable of infecting more than 1400 plant species, encompassing both dicotyledons and monocotyledons. Recognized as the world's second most destructive fungal pathogen, B. cinerea is responsible for significant pre- and postharvest diseases, especially gray mold on a variety of economically important crops, vegetables, and fruits. This study focused on characterizing the variability of ten B. cinerea isolates from strawberry fruits harvested across various regions in Egypt. The differentiation among these isolates was evaluated through morphological, genetic, pathogenic, and biochemical methods. The isolates exhibited variation in cultural development, colony color, shape, margin, and texture. The study highlighted morphological differences in conidiophores, variations in conidia size, and sclerotia production on three different media. The ten Botrytis isolates have differed in mycelial growth rate and pathogenicity on strawberry fruits and positively correlated with oxalic acid production. Isolate B3 of B. cinerea was the most aggressive, while isolate B5 demonstrated the lowest. Two isolates of Botrytis represented the first occurrence of Botrytis species in Egypt, B. californica and B. eucalypti, which were identified using ITS sequencing and combined with morphological characteristics. They were also responsible for causing gray mold on strawberry fruits. These results are expected to greatly contribute to the knowledge of morphological and genetic variability in B. cinerea isolates, as well as offer valuable insights for the development of disease management strategies.

Antifungal mechanism of nanosilver biosynthesized with Trichoderma longibrachiatum and its potential to control muskmelon Fusarium wilt

Fusarium oxysporum (Schl.) f.sp. melonis, which causes muskmelon wilt disease, is a destructive filamentous fungal pathogen, attracting more attention to the search for effective fungicides against this pathogen. In particular, Silver nanoparticles (AgNPs) have strong antimicrobial properties and they are not easy to develop drug resistance, which provides new ideas for the prevention and control of muskmelon Fusarium wilt (MFW). This paper studied the effects of AgNPs on the growth and development of muskmelon, the control efficacy on Fusarium wilt of muskmelon and the antifungal mechanism of AgNPs to F. oxysporum. The results showed that AgNPs could inhibit the growth of F. oxysporum on the PDA and in the PDB medium at 100–200 mg/L and the low concentration of 25 mg/L AgNPs could promote the seed germination and growth of muskmelon seedlings and reduce the incidence of muskmelon Fusarium wilt. Further studies on the antifungal mechanism showed that AgNPs could impair the development, damage cell structure, and interrupt cellular metabolism pathways of this fungus. TEM observation revealed that AgNPs treatment led to damage to the cell wall and membrane and accumulation of vacuoles and vessels, causing the leakage of intracellular contents. AgNPs treatment significantly hampered the growth of mycelia in the PDB medium, even causing a decrease in biomass. Biochemical properties showed that AgNPs treatment stimulated the generation of reactive oxygen species (ROS) in 6 h, subsequently producing malondialdehyde (MDA) and increasing protective enzyme activity. After 6 h, the protective enzyme activity decreased. These results indicated that AgNPs destroy the cell structure and affect the metabolisms, eventually leading to the death of fungus.

2-Phenylethanol biocontrol postharvest tomato gray mold and its effect on tomato quality

Botrytis cinerea is a highly destructive fungal pathogen responsible for substantial economic losses in fruit and vegetable production. Volatile organic compounds (VOCs) emitted by plants or microorganisms show promise as sources for novel biocontrol strategies. This study evaluated the effect of 2-phenylethanol (2-PE) on the quality of tomatoes and its antifungal efficacy against B. cinerea, alongside exploring possible mechanisms of action. The results showed that 2-PE notably increased the soluble sugar content in postharvest tomatoes without adversely affecting other quality parameters. Moreover, 2-PE markedly suppressed the growth of B. cinerea mycelium and reduced the incidence of infection in tomatoes in a dose-dependent manner. It also increased the activity of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), phenylalanine ammonia-lyase (PAL), β-1,3-glucanase (GLU), chitinase (CHI), and their corresponding gene expression, enhancing the host defense capability of tomatoes. Treatment with 2-PE led to the downregulation of genes linked with the pathogenicity of the fungus. Concurrently, 2-PE triggered the expression of autophagy-related genes and provoked the accumulation of reactive oxygen species (ROS) in B. cinerea. The resulting ROS-induced oxidative stress compromised membrane integrity, which facilitated the leakage of cellular components and culminated in the death of B. cinerea cells. Collectively, these outcomes suggest significant potential for 2-PE in the development of a novel biocontrol agent.

Fine-tuning of the dual-role transcription factor WRKY8 via differential phosphorylation for robust broad-spectrum plant immunity

Plants perceive pathogen-associated molecular patterns (PAMPs) using plasma-membrane-localized pattern recognition receptors (PRRs) to activate broad-spectrum pattern-triggered immunity. However, the regulatory mechanisms that ensure robust broad-spectrum plant immunity remain largely unknown. Here, we reveal that the transcription factor WRKY8 has a dual role in the transcriptional regulation of PRR genes: repressing expression of the nlp20/nlp24 receptor gene RLP23 while promoting that of the chitin receptor gene CERK1. SsNLP1 and SsNLP2, two nlp24-type PAMPs from the destructive fungal pathogen Sclerotinia sclerotiorum, activate two calcium-elicited kinases, CPK4 and CPK11, which phosphorylate WRKY8 and thus release its inhibition on RLP23 to promote accumulation of RLP23 transcripts. Meanwhile, SsNLPs activate the RLCK-type kinase PBL19, which phosphorylates WRKY8 and thus enhances accumulation of CERK1 transcripts. Intriguingly, RLP23 is repressed at later stage by PBL19-mediated phosphorylation of WRKY8, thus avoiding excessive immunity and enabling normal growth. Our findings unveil a plant strategy of “killing two birds with one stone” to elicit robust broad-spectrum immunity. This strategy is based on PAMP-triggered fine-tuning of a dual-role transcription factor to simultaneously amplify two PRRs that recognize PAMPs conserved across a wide range of pathogens. Moreover, our results reveal a novel plant strategy for balancing the trade-off between growth and immunity by fine-tuning the expression of multiple PRR genes.

Antifungal efficacy of Bacillus amyloliquefaciens ZK-9 against Fusarium graminearum and analysis of the potential mechanism of its lipopeptides

Fusarium graminearum is a destructive fungal pathogen that seriously threatens wheat production and quality. In the management of fungal infections, biological control is an environmentally friendly and sustainable approach. Here, the antagonistic strain ZK-9 with a broad antifungal activity was identified as Bacillus amyloliquefaciens. ZK-9 could produce extracellular enzymes such as pectinase, protease, cellulase, and amylase, as well as plant growth-promoting substances including IAA and siderophore. Lipopeptides extracted from strain ZK-9 had the high inhibitory effects on the mycelia of F. graminearum with the minimum inhibitory concentration (MIC) of 0.8 mg/mL. Investigation on the action mechanism of lipopeptides showed they could change the morphology of mycelia, damage the cell membrane, lower the content of ergosterol and increase the relative conductivity of membrane, cause nucleic acid and proteins leaking out from the cells, and disrupt the cell membrane permeability. Furthermore, metabolomic analysis of F. graminearum revealed the significant differences in the expression of 100 metabolites between the lipopeptides treatment group and the control group, which were associated with various metabolic pathways, mainly including amino acid biosynthesis, pentose, glucuronate and glycerophospholipid metabolism. In addition, strain ZK-9 inhibited Fusarium crown rot (FCR) with a biocontrol efficacy of 82.14 % and increased the plant height and root length by 24.23 % and 93.25 %, respectively. Moreover, the field control efficacy of strain ZK-9 on Fusarium head blight (FHB) was 71.76 %, and the DON content in wheat grains was significantly reduced by 69.9 %. This study puts valuable insights into the antifungal mechanism of lipopeptides against F. graminearum, and provides a promising biocontrol agent for controlling F. graminearum.

CsSNF1 kinase plays important roles in fungal development and virulence of the pepper anthracnose fungus Colletotrichum scovillei

AbstractPepper is a vegetable that is used and cultivated worldwide. The quality and production of pepper are reduced by fruit anthracnose disease caused by Colletotrichum scovillei. The highly conserved fungal sucrose non‐fermenting 1 (SNF1)‐related AMPK protein kinases are implicated in the pathogenicity and differentiation of several destructive foliar fungal pathogens; in addition, they affect fungal growth in the presence of glucose at different concentrations and under different environmental stresses. However, the function of SNF1 in C. scovillei is unclear. We functionally characterized SNF1 of C. scovillei using a targeted deletion mutant (ΔCssnf1) generated by homology‐dependent replacement. ΔCssnf1 was severely impaired in mycelial growth under glucose‐limited conditions; multiple defects in conidiation, conidial germination, appressorium formation, lipid degradation and vacuole formation were also observed. Compared to the wild type, ΔCssnf1 caused anthracnose disease of reduced severity on intact and wounded pepper fruits. These defects were recovered in the complemented strain (Cssnf1c). Taken together, our findings implicate CsSNF1 in the growth, development and virulence of C. scovillei.

Resistance risk assessment for benzovindiflupyr in Sclerotium rolfsii and transmission of resistance genes among population.

Sclerotium rolfsii is a destructive soil-borne fungal pathogen which is distributed worldwide. In previous study, the succinate dehydrogenase inhibitor (SDHI) fungicide benzovindiflupyr has been identified for its great antifungal activity against Sclerotium rolfsii. This study is aimed to investigate the resistance risk and mechanism of benzovindiflupyr in Sclerotium rolfsii. Eight stable benzovindiflupyr-resistant isolates were generated by fungicide adaptation. Although the obtained eight resistant isolates have a stronger pathogenicity than the parental sensitive isolate, they have a fitness penalty in the mycelial growth and sclerotia formation compared to the parental isolate. A positive cross-resistance existed in the resistant isolates between benzovindiflupyr and thifluzamide, carboxin, boscalid and isopyrazam. Three-point mutations, including SdhBN180D, SdhCQ68E and SdhDH103Y, were identified in the benzovindiflupyr-resistant isolates. However, molecular docking analysis indicated that only SdhDH103Y could influence the sensitivity of Sclerotium rolfsii to benzovindiflupyr. After mycelial co-incubation of resistant isolates and the sensitive isolate, resistance genes may be transmitted to the sensitive isolate. The in vivo efficacy of benzovindiflupyr and thifluzamide against benzovindiflupyr-resistant isolates was a little lower than that against the sensitive isolate but with no significant difference. The results suggested a low to medium resistance risk of Sclerotium rolfsii to benzovindiflupyr. However, once resistance occurs, it is possible to spread in the population of Sclerotium rolfsii. This study is helpful to understanding the risk and mechanism of resistance to benzovindiflupyr in multinucleate pathogens such as Sclerotium rolfsii. © 2024 Society of Chemical Industry.

The role of VdSti1 in Verticillium dahliae: insights into pathogenicity and stress responses.

Sti1/Hop, a stress-induced co-chaperone protein, serves as a crucial link between Hsp70 and Hsp90 during cellular stress responses. Despite its importance in stress defense mechanisms, the biological role of Sti1 in Verticillium dahliae, a destructive fungal pathogen, remains largely unexplored. This study focused on identifying and characterizing Sti1 homologues in V. dahliae by comparing them to those found in Saccharomyces cerevisiae. The results indicated that the VdSti1-deficient mutant displayed increased sensitivity to drugs targeting the ergosterol synthesis pathway, leading to a notable inhibition of ergosterol biosynthesis. Moreover, the mutant exhibited reduced production of microsclerotia and melanin, accompanied by decreased expression of microsclerotia and melanin-related genes VDH1, Vayg1, and VaflM. Additionally, the mutant's conidia showed more severe damage under heat shock conditions and displayed growth defects under various stressors such as temperature, SDS, and CR stress, as well as increased sensitivity to H2O2, while osmotic stress did not impact its growth. Importantly, the VdSti1-deficient mutant demonstrated significantly diminished pathogenicity compared to the wild-type strain. This study sheds light on the functional conservation and divergence of Sti1 homologues in fungal biology and underscores the critical role of VdSti1 in microsclerotia development, stress response, and pathogenicity of V. dahliae.

An In-Depth Evaluation of Powdery Mildew Hosts Reveals One of the World's Most Common and Widespread Groups of Fungal Plant Pathogens.

Powdery mildews are highly destructive fungal plant pathogens that have a significant economic impact on both agricultural and ecological systems worldwide. The intricate relationship between powdery mildews and their host plants has led to cospeciation. In this study, we conducted an extensive evaluation of powdery mildew hosts to provide an updated understanding of the host ranges and distributions of these fungi. The "United States National Fungus Collections Fungus-Host Dataset" is the primary source of information for our analyses. The analysis of the dataset demonstrated the worldwide prevalence of powdery mildews; the data contained over 72,000 reports of powdery mildews, representing ∼8.7% of all host-fungal records. We have updated the taxonomy and nomenclature of powdery mildews. In total, powdery mildews infect ∼10,125 host taxa belonging to 205 families of flowering plants, which accounts for 1,970 genera in 200 countries across six continents. Furthermore, we estimate that powdery mildews infect approximately 2.9% of described angiosperm species. Our study underscores the need for regular updates on powdery mildew host information due to the continuously evolving taxonomy and the discovery of new host taxa. Since 1986, we estimate an additional 1,866 host taxa, 353 genera, and 36 families have been reported. Additionally, the identification of powdery mildew hosts provides valuable insights into the coevolutionary dynamics between the fungi and their plant hosts. Overall, this updated list provides valuable insights into the taxonomy and geographic distribution of powdery mildew species, which builds upon the previous work of Amano in 1986. Discerning the geographic spread and host range of economically significant plant pathogens is vital for biosecurity measures and identifying the origins and expansion of potentially harmful pathogens.

Long-Read Sequencing Genome Assembly of Ceratocystis fimbriata Enables Development of Molecular Diagnostics for Sweetpotato Black Rot.

Ceratocystis fimbriata is a destructive fungal pathogen of sweetpotato (Ipomoea batatas) that leads to losses at all stages of sweetpotato production. Accurate detection of C. fimbriata would allow for more efficient deployment of management tactics in sweetpotato production. To develop a diagnostic assay, a hybrid genome assembly of C. fimbriata isolate AS236 was generated. The resulting 31.7-MB assembly was near-chromosome level, with 18 contigs, 6,481 predicted genes, and a BUSCO completion score of 98.4% when compared with the fungus-specific lineage database. Additional Illumina DNA reads from C. manginecans, C. platani, and a second C. fimbriata isolate (C1421) were then mapped to the assembled genome using BOWTIE2 and counted using HTSeq, which identified 148 genes present only within C. fimbriata as molecular diagnostic candidates; 6 single-copy and 35 highly multi-copy (>40 BLAST hits), as determined through a self-BLAST-P alignment. Primers for PCR were designed in the 200-bp flanking region of the first exon for each candidate, and the candidates were validated against a diverse DNA panel containing Ceratocystis species, sweetpotato pathogens, and plants. After validation, two diagnostic candidates amplified only C. fimbriata DNA and were considered to be highly specific to the species. These genetic markers will serve as valuable diagnostic tools with multiple applications including the detection of C. fimbriata in seed, soil, and wash water in sweetpotato production.

Unveiling mechanisms for induced systemic resistance, resistance breeding and molecular marker‐assisted breeding against Phomopsis blight of Solanum melongena

AbstractPhomopsis vexans is one of the most destructive fungal pathogens associated with eggplant and currently poses a significant threat to eggplant production worldwide. The detrimental impact of P. vexans on eggplant yield has been extensively explored by various mycologists who have conducted thorough studies on the diversity, pathology and biological aspects of the pathogen. However, achieving enduring resistance or effective management has proven to be a challenge thus far. PCR‐based detection and molecular association of Phomopsis resistance use molecular markers to examine the potential for heterosis in various crosses, aiming for premium hybrids with genetic resistance and high‐yielding capabilities. The latest genome sequencing methods and availability of a wider range of genetic diversity has enabled the breeding of resistant varieties of eggplant. This review provides a detailed description on P. vexans including its epidemiology, dispersal methods, symptomology, colony characteristics, taxonomy and evolution of its strains. Different resistance breeding techniques including heterosis breeding, host plant resistance, identification of resistant sources, inheritance pattern for Phomopsis resistance, importance of grafting to impart resistance, significance of induced resistance, PCR‐based detection and molecular association of Phomopsis resistance are explained. Future approaches include molecular marker techniques such as genome‐wide association studies, sequence‐characterized amplified regions (SCAR), role of biotic inducers, pathogenesis‐related proteins and plant growth‐promoting rhizobacteria against Phomopsis blight of eggplant.

Microbial Interactions in the Management of Groundnut Stem Rot

Groundnut (Arachis hypogaea L.) is an important oil seed crop in the world belonging to the Leguminosae family. It is one of the essential food and cash crops of our country. In India, a large number of diseases attack groundnut [1]. Among soil borne diseases, stem rot or white mold caused by Sclerotium rolfsii Sacc. [2] is an important disease causing significant yield losses in several groundnut growing countries (Mehan et al., 1994). Sclerotium rolfsii Sacc. is a destructive soil borne fungal pathogen of oil seed crop in India. Different practices are recommended for management of groundnut stem rot such as deep summer ploughing, destruction of plant debris, crop rotation with jowar and bajra, seed treatment with carbendazim or captan or mancozeb or tebuconazole, soil drenching with hexaconazole, application of ammonium sulphate or calcium ammonium nitrate instead of urea and application of gypsum at flowering stage. Further, no single treatment is full proof and disease continues to cause losses in farmers’ fields. Biological control offers an interesting alternative to fungicides for sustainable management of soil borne diseases. Biocontrol is a non-chemical measure, could be effective as chemical control by various techniques. Among the techniques, the mixture of antagonists was studied to enchance the control efficacy. In most studies, the involvement of only mechanism of biological control is demonstrated. Involvement of more than one mechanism has been reported in only a few systems. Use of several biocontrol agents with several mechanisms of control fits in well with the concepts of integrated disease management, in which several means of disease suppression are applied concurrently. When single or more means of mechanisms are not effective, the others may compensate for the former absence. The present study, involved three major bacterial antagonists viz., Streptomyces violaceusniger, Streptomyces exfoliatus and Pseudomonas fluorescens to find out the effective dose of mixtures. The different doses from 10-1 to 10-5 were studied, the dose 10-1 of Streptomyces violaceusniger have more efficiency of 86.70, than S. exfoliatus. The efficacy of Streptomyces violaceusniger with combination of other antagonists were tested and found that, the mixture of Streptomyces violaceusniger and P. fluorescens have synergistic activity than any other combinations which have synergistic factor greater than one.

Sulfur metabolism-mediated fungal glutathione biosynthesis is essential for oxidative stress resistance and pathogenicity in the plant pathogenic fungus Fusarium graminearum.

Fusarium graminearum is a destructive fungal pathogen that causes Fusarium head blight (FHB) on a wide range of cereal crops. To control fungal diseases, it is essential to comprehend the pathogenic mechanisms that enable fungi to overcome host defenses during infection. Pathogens require an oxidative stress response to overcome host-derived oxidative stress. Here, we identify the underlying mechanisms of the Fgbzip007-mediated oxidative stress response in F. graminearum. ChIP-seq and subsequent genetic analyses revealed that the role of glutathione in pathogenesis is not dependent on antioxidant functions in F. graminearum. Altogether, this study establishes a comprehensive framework for the Fgbzip007 regulon on pathogenicity and oxidative stress responses, offering a new perspective on the role of glutathione in pathogenicity.

Ferrous Sulfate-Mediated Control of Phytophthora capsici Pathogenesis and Its Impact on Pepper Plant.

Phytophthora capsici, a destructive fungal pathogen, poses a severe threat to pepper (Capsicum annuum L.) crops worldwide, causing blights that can result in substantial yield losses. Traditional control methods often come with environmental concerns or entail substantial time investments. In this research, we investigate an alternative approach involving ferrous sulfate (FeSO4) application to combat P. capsici and promote pepper growth. We found that FeSO4 effectively inhibits the growth of P. capsici in a dose-dependent manner, disrupting mycelial development and diminishing pathogenicity. Importantly, FeSO4 treatment enhances the biomass and resistance of pepper plants, mitigating P. capsici-induced damage. Microbiome analysis demonstrates that FeSO4 significantly influences soil microbial communities, particularly fungi, within the pepper root. Metabolomics data reveal extensive alterations in the redox metabolic processes of P. capsici under FeSO4 treatment, leading to compromised cell membrane permeability and oxidative stress in the pathogen. Our study presents FeSO4 as a promising and cost-effective solution for controlling P. capsici in pepper cultivation while simultaneously promoting plant growth. These findings contribute to a deeper understanding of the intricate interactions between iron, pathogen control, and plant health, offering a potential tool for sustainable pepper production.

Phenotype and genotype characterization of Botrytis cinerea isolates from cut roses in Yunnan, China

AbstractBotrytis cinerea is considered to be the second most destructive fungal pathogen worldwide, causing severe pre‐ and postharvest losses in cut roses. However, to date, no systematic research on its characteristics in cut roses has been reported. In our study, a total of 100 isolates from cut roses from Yunnan, China, were analysed. A combination of morphological characteristics and phylogenetic analysis of RPB2 revealed that 100 isolates were of the species B. cinerea. These isolates were pathogenic on unwounded detached rose petals. Pathogenicity was evaluated according to the size of petal spots and categorized into grades 0–5, from weak to strong. The inhibition rate varied greatly following the addition of procymidone (21.9%–100%) and cyprodinil (25.0%–92.3%). Analysis of Bc‐hch sequences revealed all isolates belong to phylogenetic Group II. According to the presence or absence of transposable elements, 87, 5, 4 and 4 isolates were identified as transposa, vacuma, Boty‐only and Flipper‐only types, respectively. Detection of mating type indicated that all isolates were heterothallic with 45% belonging to MAT1‐1 and 55% to MAT1‐2. Isolates were divided into four subpopulations when analysing single‐nucleotide polymorphisms at the genomic level, with a significant difference in pathogenicity between subpopulations 1 and 4. The evolutionary tree indicated that isolates AN‐02, AN‐22 and SM‐C18 were clustered in the root, suggesting an earlier evolutionary time than other isolates; moreover, they all exhibited low pathogenicity (grade 1). This systematic study of the characteristics of B. cinerea will provide significant support for grey mould control and further research.

De Novo RNA Sequencing and Transcriptome Analysis of Sclerotium rolfsii Gene Expression during Sclerotium Development.

Sclerotium rolfsii is a destructive soil-borne fungal pathogen that causes stem rot in cultivated plants. However, little is known about the genetic basis of sclerotium development. In this study, we conducted de novo sequencing of genes from three different stages of S. rolfsii (mycelia, early sclerotium formation, and late sclerotium formation) using Illumina HiSeqTM 4000. We then determined differentially expressed genes (DEGs) across the three stages and annotated gene functions. STEM and weighted gene-co-expression network analysis were used to cluster DEGs with similar expression patterns. Our analysis yielded an average of 25,957,621 clean reads per sample (22,913,500-28,988,848). We identified 8929, 8453, and 3744 DEGs between sclerotium developmental stages 1 versus 2, 1 versus 3, and 2 versus 3, respectively. Additionally, four significantly altered gene expression profiles involved 220 genes related to sclerotium formation, and two modules were positively correlated with early and late sclerotium formation. These results were supported by the outcomes of qPCR and RNA-sequencing conducted on six genes. This is the first study to provide a gene expression map during sclerotial development in S. rolfsii, which can be used to reduce the re-infection ability of this pathogen and provide new insights into the scientific prevention and control of the disease. This study also provides a useful resource for further research on the genomics of S. rolfsii.

Genetic breakthroughs in the Brassica napus–Sclerotinia sclerotiorum interactions

Sclerotinia sclerotiorum (Lib.) de Bary is a highly destructive fungal pathogen that seriously damages the yield and quality of Brassica napus worldwide. The complex interaction between the B. napus and S. sclerotiorum system has presented significant challenges in researching rapeseed defense strategies. Here, we focus on the infection process of S. sclerotiorum, the defense mechanisms of rapeseed, and recent research progress in this system. The response of rapeseed to S. sclerotiorum is multifaceted; this review aims to provide a theoretical basis for rapeseed defense strategies.

Development and validation of allele-specific PCR-based SNP typing in a gene on chromosome D03 conferring resistance to Fusarium wilt race 4 in Upland cotton (Gossypium hirsutum).

Upland cotton (Gossypium hirsutum) is the most important fiber crop for the global textile industry. Fusarium oxysporum f. sp. vasinfectum (FOV) is one of the most destructive soil-borne fungal pathogens in cotton. Among eight pathogenic races and other strains, FOV race 4 (FOV4) is the most virulent race in US cotton production. A single nucleotide polymorphism (SNP) in a glutamate receptor-like gene (GhGLR4.8) on chromosome D03 was previously identified and validated to confer resistance to FOV race 7, and targeted genome sequencing demonstrated that it was also associated with resistance to FOV4. The objective of this study was to develop an easy and convenient PCR-based marker assay. To target the resistance SNP, a forward primer for the SNP with a mismatch in the 3rd position was designed for both the resistance (R) and susceptibility (S) alleles, respectively, with addition of 20-mer T7 promoter primer to the 5' end of the forward primer for the R allele. The two forward primers, in combination with each of five common reverse primers, were targeted to amplify amplicons of 50-260bp in size with R and S alleles differing in 20bp. Results showed that each of three common reverse primers in combination with the two forward primers produced polymorphic markers between R and S plants that were consistent with the targeted genome sequencing results. The polymorphism was distinctly resolved using both polyacrylamide and agarose gel electrophoreses. In addition, a sequence comparative analysis between the resistance gene and homologous sequences in sequenced tetraploid and diploid A and D genome species showed that none of the species possessed the resistance gene allele, suggesting its recent origin from a natural point mutation. The allele-specific PCR-based SNP typing method based on a three-primer combination provides a fast and convenient marker-assisted selection method to search and select for FOV4-resistant Upland cotton.

RVE2, a new regulatory factor in jasmonic acid pathway, orchestrates resistance to Verticillium wilt.

Verticillium dahliae, one of the most destructive fungal pathogens of several crops, challenges the sustainability of cotton productivity worldwide because very few widely-cultivated Upland cotton varieties are resistant to Verticillium wilt (VW). Here, we report that REVEILLE2 (RVE2), the Myb-like transcription factor, confers the novel function in resistance to VW by regulating the jasmonic acid (JA) pathway in cotton. RVE2 expression was essentially required for the activation of JA-mediated disease-resistance response. RVE2 physically interacted with TPL/TPRs and disturbed JAZ proteins to recruit TPL and TPR1 in NINJA-dependent manner, which regulated JA response by relieving inhibited-MYC2 activity. The MYC2 then bound to RVE2 promoter for the activation of its transcription, forming feedback loop. Interestingly, a unique truncated RVE2 widely existing in D-subgenome (GhRVE2D) of natural Upland cotton represses the ability of the MYC2 to activate GhRVE2A promoter but not GausRVE2 or GbRVE2. The result could partially explain why Gossypium barbadense popularly shows higher resistance than Gossypium hirsutum. Furthermore, disturbing the JA-signalling pathway resulted into the loss of RVE2-mediated disease-resistance in various plants (Arabidopsis, tobacco and cotton). RVE2 overexpression significantly enhanced the resistance to VW. Collectively, we conclude that RVE2, a new regulatory factor, plays a pivotal role in fine-tuning JA-signalling, which would improve our understanding the mechanisms underlying the resistance to VW.

Wood Coloration and Decay Capabilities of Mycoparasite Scytalidium ganodermophthorum.

Scytalidium ganodermophthorum (telomorph: Xylogone ganodermopthora) Kang, Sigler, Lee & Yun is a destructive fungal pathogen that produces a yellow pigment that is used in sustainable product development. Similar pigmenting ascomycetes cause soft rot in woody substrates, however, the decay capabilities of S. ganodermophthorum have not been assessed or related to pigment production. A wood block decay test showed highly variable production of the expected bright yellow pigment and a secondary darker pigment when tested against multiple wood species and nutrient conditions. Microscopic examination showed cell wall erosion typical of type-2 soft rot in wood, although enzymatic analysis did not show detectible levels of endocellulase. Chitinase was detected in plate cultures but not wood cultures, indicating adaption of the fungus to a variety of environmental growth conditions. The high variability of pigmentation in wood cultures suggests that growth of S. ganodermophthorum on liquid media and use of extracted pigment is a superior method for obtaining consistent yellow coloration.