Verticillium Wilt Disease Research Articles

A Phi-Class Glutathione S-Transferase Gene for Verticillium Wilt Resistance in Gossypium arboreum Identified in a Genome-Wide Association Study.

Verticillium wilt disease is one of the most destructive biotic stresses faced by cotton plants. Here, we performed a genome-wide association study (GWAS) in 215 Chinese Gossypium arboreum accessions inoculated as seedlings with Verticillium dahliae to identify candidate loci involved in wilt resistance. We identified 309 loci that had a significant association with Verticillium wilt resistance and - log(P) values >5.0; the highest signal appeared on Ca3 in a 74 kb haplotype block. Five genes were also located within this haplotype block. One of these genes, CG05, was positioned close to the most significant SNP Ca3_23037225 (14 kb); expression of the gene was induced by V. dahliae or by treatment with salicylic acid (SA). Therefore, we suggest that CG05 may respond to invasion by V. dahliae via an SA-related signaling pathway, and we designated this gene as GaGSTF9. We showed that GaGSTF9 was a positive regulator of Verticillium wilt through the use of virus-induced gene silencing (VIGS) and overexpression in Arabidopsis. In addition, the glutathione S-transferase (GST) mutant gstf9 of Arabidopsis was found to be more susceptible to Verticillium wilt than wild-type plants. The levels of endogenous SA and hydrogen peroxide had a significant effect on Arabidopsis plants that overexpressed GaGSTF9, indicating that GST may regulate reactive oxygen species content via catalytic reduction of the tripeptide glutathione (GSH), and then affect SA content. Our data demonstrated that GaGSTF9 was a key regulator mediating cotton responses to V. dahliae and a potential candidate gene for cotton genetic improvement.

Copper complexes of the 1,3,4-thiadiazole derivatives modulate antioxidant defense responses and resistance in tomato plants against fungal and bacterial diseases

The metallic complexes μ-chloro-μ-[2,5-bis (2-pyridyl)-1,3,4-thiadiazole] aqua chlorocopper (II) dichlorocopper (II) (abbreviated 2PTH-Cu2-Cl4); aquabis [2,5-bis (2-pyridyl)-1,3,4-thiadiazole-κ2N2,N3] (trifluoromethane-sulfonato-κO) copper(II) trifluoro metrhanesulfonate (2PTH-Cu-tF) and bis[(2,5-bis(pyridine-2-yl)-1,3,4-thiadiazole-di-azido copper(II)] (2PTH-Cu-Az) were compared for their antimicrobial activities in vitro, and their aptitude to control Verticillium wilt and crown gall diseases development of tomato in the greenhouse. Results showed that the complex 2PTH-Cu-Az inhibited drastically the growth of V. dahliae in vitro. 2PTH-Cu2-Cl4 and 2PTH-Cu-tF did not display any noticeable antimicrobial activity in vitro against all of the pathogens tested. However, in planta evaluation revealed that the three complexes protected tomato against crown gall similarly. They also reduced Verticillium wilt disease severity, although the complex 2PTH-Cu-Az was the most efficient. When compared to other complexes, 2PTH-Cu-Az triggered only a weak oxidative burst as revealed by H2O2 measurement and the activity of ascorbate peroxidase and catalase. These results suggest that the superiority of 2PTH-Cu-Az against V. dahliae rely on its direct antifungal activity and its ability to modulate H2O2 accumulation.

Expression of pathogenesis-related genes in cotton roots in response to Verticillium dahliae PAMP molecules.

Verticillium wilt disease becomes a major threat to many economically important crops. It is unclear whether and how plant immunity takes place during cotton-Verticillium interaction due to the lack of marker genes. Taking advantage of cotton (Gossypium hirsutum) genome, we discovered pathogenesis-related (PR) gene families, which have been widely used as markers of immune responses in plants. To profile the expression of G. hirsutum PR genes in the process of plant immunity, we treated cotton roots with two immunogenic peptides, flg22 and nlp20 known as pathogen-associated molecular patterns, as well as three Verticillium dahliae-derived peptides, nlp20Vd2, nlp23Vd3, and nlp23Vd4 which are highly identical to nlp20. Quantitative real-time PCR results revealed that 14 G. hirsutum PR gene (GhPR) families were induced or suppressed independently in response to flg22, nlp20, nlp20Vd2, nlp23Vd3, and nlp23Vd4. Most GhPR genes are expressed highest at 3 h post incubation of immunogenic peptides. Compared to flg22 and nlp20, nlp20Vd2 is more effective to trigger up-regulated expression of GhPR genes. Notably, both nlp23Vd3 and nlp23Vd4 are able to induce GhPR gene up-regulation, although they do not induce necrosis on cotton leaves. Thus, our results provide marker genes and new immunogenic peptides for further investigation of cotton-V. dahliae interaction.

Epistatic influence in tomato Ve1-mediated resistance.

Resistance to Verticillium wilt disease is associated with the tomato Ve-locus; however, the individual functional roles of Ve1 and Ve2 in host plants remain controversial. As a first step towards Ve mutational analyses in planta, the Ve1 coding region from a resistant tomato near-isoline (cv. Craigella GCR218) was introduced into a susceptible near-isoline (cv. Craigella GCR26). 35S:Ve1 plants segregated into two distinct classes; roughly half were resistant and half were susceptible. Ve1 transcript levels were up-regulated in both classes compared to wild-type plants, showing stable transgenic expression. Expression analysis of Ve2 revealed that mRNA levels were similar between 35S:Ve1 and wild-type tomatoes, demonstrating that Ve1 transgene introduction does not alter endogenous Ve2 expression. Overall, the results of this study confirm the functional role of Ve1 protein in resistance to the vascular fungal pathogen V.dahliae race 1 (Vd1), but suggest that a yet undefined factor exerts an epistatic influence on the Ve1 gene.

Application of host induced gene silencing in crop protection against fungal diseases

Fungal diseases are the main threat to crop yield and quality, often leading to huge economic losses. Chemical fungicides are almost useless to soil-borne and vascular fungal pathogens. The most effective way is crop resistance breeding by using resistance genes. Yet, for plants lacking resistance resources, new approaches are urgently needed for crop protection. Recently, host-induced gene silencing (HIGS) is developed based on the well-known RNA interference, and already effective against viruses and pests. However, it is challenging to validate HIGS in soil-borne fungal pathogens due to uncharacterized and complicated infection processes. Recently, we have made great progresses in revealing the infection structure of Verticillium dahliae, a soil-borne and vascular fungal pathogen that leads to verticillium wilt disease to many crops, including cotton plants. Moreover, we demonstrate that cotton exports endogenous microRNAs to inhibit virulence gene expression in V. dahliae. The most exciting achievement is the successful application of HIGS in cotton plants that confer resistance to V. dahliae. All these results reveal a promising potential for applying HIGS against a wide range of soil-borne fungi.

Potential of Endophytic Fungi Isolated from Cotton Roots for Biological Control against Verticillium Wilt Disease.

Verticillium wilt is a soil-borne disease, and severely limits the development of cotton production. To investigate the role of endophytic fungi on Verticillium wilt, CEF-818 (Penicillium simplicissimum), CEF-714 (Leptosphaeria sp.), CEF-642 (Talaromyces flavus.) and CEF-193 (Acremonium sp.) isolated from cotton roots were used to assess their effects against cotton wilt disease caused by a defoliating V. dahliae strain Vd080. In the greenhouse, all treatments significantly reduced disease incidence and disease index, with the control efficacy ranging from 26% (CEF-642) to 67% (CEF-818) at 25 days (d) after inoculation. In the disease nursery, compared to controls (with disease incidence of 33.8% and disease index of 31), CEF-818, CEF-193, CEF-714 and CEF-642 provided a protection effect of 69.5%, 69.2%, 54.6% and 45.7%, respectively. Especially, CEF-818 and CEF-714 still provided well protection against Verticillium wilt with 46.9% and 56.6% or 14.3% and 33.7% at the first peak of the disease in heavily infected field, respectively (in early July). These results indicated that these endophytes not only delayed but also reduced wilt symptoms on cotton. In the harvest, the available cotton bolls of plant treated with CEF-818 and CEF-714 increased to 13.1, and 12.2, respectively. And the seed cotton yield significantly increased after seed bacterization with CEF-818 (3442.04 kg/ha) compared to untreated control (3207.51 kg/ha) by 7.3%. Furtherly, CEF-818 and CET-714 treatment increased transcript levels for PAL, PPO, POD, which leads to the increase of cotton defense reactions. Our results indicate that seed treatment of cotton plants with CEF-818 and CET-714 can help in the biocontrol of V. dahliae and improve seed cotton yield in cotton fields. This study provided a better understanding of cotton-endophyte interactions which will aid in developing effective biocontrol agents for Verticillium wilt of cotton in futhre.

Cultivar, irrigation, and soil contribution to the enhancement of Verticillium wilt disease in cotton

Verticillium wilt of cotton is incited by Verticillium dahliae Kleb., which colonizes the vascular cylinder of the plant resulting in defoliation, stunting, and yield loss. This project investigated cultivar selection and soil type predisposition for management of this disease to preserve cotton yields. All cotton cultivars planted in this study were susceptible to Verticillium wilt infection and all had some amount of vascular discoloration observed. However, there were varying ranges of tolerance found among different cultivars. ST 4747 GLB2 appeared to the consistently the most tolerant of the cultivars planted and exhibited the highest yields consistently over different seasons. Verticillium wilt disease incidence and severity were increased with irrigation in the controlled microplot test over six soil types. Verticillium wilt symptom severity was greater in the Decatur silt loam and Houston clay soils which have the highest clay and silt content.

Evaluation of the Biocontrol Potential of Purpureocillium lilacinum QLP12 against Verticillium dahliae in Eggplant.

A fungus with broad spectrum antifungal activity was isolated from the soil in Qinling Mountain, Shaanxi Province, in China. The fungus was identified as Purpureocillium lilacinum based on ITS rDNA gene analysis. The strain, coded as QLP12, showed high inhibition activity on fungal mycelium growth in vitro, especially to Mucor piriformis, Trichothecium roseum, Rhizoctonia solani, and Verticillium dahliae, and its potential for biocontrol efficacy of eggplant. Verticillium wilt disease caused by Verticillium dahliae among 10 fungal species tested was explored. In greenhouse experiments, QLP12 showed an excellent growth-promoting effect on eggplant seed germination (76.7%), bud growth (79.4%), chlorophyll content (47.83%), root activity (182.02%), and so on. QLP12 can colonize the eggplant interior and also develop in rhizosphere soil. In greenhouse, the incidence of Verticillium wilt decreased by 83.82% with pretreated QLP12 fermentation broth in the soil. In the field, QLP12 showed prominent biocontrol effects on Verticillium wilt by reducing the disease index over the whole growth period, a decline of 40.1%. This study showed that the strain QLP12 is not only an effective biocontrol agent for controlling Verticillium wilt of eggplant, but also a plant growth-promoting fungus that deserves to be further developed.

Verticillium Wilt on Rose Plants in Minia Governorate and its Control

Nine isolates of Verticillium dahliae, (VD1 -VD9) were isolated from roots and stems of wilted rose plants (1-2 years old) grown in Minia and Abo-Qurqas counties, Minia Governorate during summer, 2012. All isolates were able to induce wilt symptoms with different degrees of vascular discoloration on rose plants through 60 - 90 days after planting. The maximum percentages (100%) of wilted plants were obtained due to using isolates VD1, VD2 and VD3 which were isolated from Minia county, followed by isolate VD8which was isolated from Abo Qurqas county (91.7%). All tested concentrations of Rizolex-T and Topsin-M decreased the linear growth of the four tested isolates. The fungitoxic effect was increased with increasing the fungicide concentration up to 400 ppm; that inhibited completely the growth of the tested fungi. Phos-root X and Formula X-1 stimulated the growth of the four tested isolates at the lowest rates, whereas the highest level, 3 ml/l, decreased the growth than control. Two bioagents, i.e., T. viride and B. subtilis were able to inhibit the mycelial growth of all tested pathogenic isolates. B. subtilis was effective in reducing the growth of the tested isolates where it gave 64.8 and 85.9% inhibition comparing to T. viride. The tested fungicides with different concentrations reduced significantly the percentage of infected plants comparing with control. Rizolex- T was more effective than Topsin-M in their efficiency. The maximum reduction of Verticillium wilt disease was recorded with using 3 ml/l of Phos-Root X and 2ml/l of Formula-X. Addition of the two tested bio agents one week before planting to soil significantly decreased the percentages of infected rose plants and disease severity under artificial infection with any of the tested isolates of Verticillium dahliae.

Host-induced gene silencing compromises Verticillium wilt in tomato and Arabidopsis.

Verticillium wilt, caused by soil-borne fungi of the genus Verticillium, is an economically important disease that affects a wide range of host plants. Unfortunately, host resistance against Verticillium wilts is not available for many plant species, and the disease is notoriously difficult to combat. Host-induced gene silencing (HIGS) is an RNA interference (RNAi)-based process in which small RNAs are produced by the host plant to target parasite transcripts. HIGS has emerged as a promising strategy for the improvement of plant resistance against pathogens by silencing genes that are essential for these pathogens. Here, we assessed whether HIGS can be utilized to suppress Verticillium wilt disease by silencing three previously identified virulence genes of V. dahliae (encoding Ave1, Sge1 and NLP1) through the host plants tomato and Arabidopsis. In transient assays, tomato plants were agroinfiltrated with Tobacco rattle virus (TRV) constructs to target V. dahliae transcripts. Subsequent V. dahliae inoculation revealed the suppression of Verticillium wilt disease on treatment with only one of the three TRV constructs. Next, expression of RNAi constructs targeting transcripts of the same three V. dahliae virulence genes was pursued in stable transgenic Arabidopsis thaliana plants. In this host, V. dahliae inoculation revealed reduced Verticillium wilt disease in two of the three targets. Thus, our study suggests that, depending on the target gene chosen, HIGS against V. dahliae is operational in tomato and A. thaliana plants and may be exploited to engineer resistance in Verticillium wilt-susceptible crops.

The Mitogen-Activated Protein Kinase Kinase VdPbs2 of Verticillium dahliae Regulates Microsclerotia Formation, Stress Response, and Plant Infection.

Verticillium dahliae, a ubiquitous phytopathogenic fungus, forms resting structures, known as microsclerotia that play crucial roles in Verticillium wilt diseases. VdHog1, a mitogen-activated protein kinase (MAPK), controls microsclerotia formation, virulence, and stress response in V. dahliae. In this study, we present detailed evidence that the conserved upstream component of VdHog1, VdPbs2, is a key regulator of microsclerotia formation, oxidative stress and fungicide response and plant virulence in V. dahliae. We identified VdPbs2, homologous to the yeast MAPK kinase Pbs2. Similar to the VdHog1 deletion mutant, VdPbs2 deletion strains exhibited delayed melanin synthesis and reduced formation of microsclerotia. When exposed to stresses, VdPbs2 mutants were more sensitive than the wild type to osmotic agents and peroxide, but more resistant to inhibitors of cell wall synthesis and some fungicides. Finally, VdPbs2 deletion mutants exhibited reduced virulence on smoke tree and tobacco seedlings. When taken together, we implicate that VdPbs2 and VdHog1 function in a cascade that regulates microsclerotia formation and virulence, but not all VdHog1 dependent functions are VdPbs2 regulated. This study thus provides novel insights into the signal transduction mechanisms that regulate microsclerotia formation and pathogenesis in this fungus.

Variation of pathotypes and races and their correlations with clonal lineages in Verticillium dahliae

Understanding pathogenic variation in plant pathogen populations is key for the development and use of host resistance for managing verticillium wilt diseases. A highly virulent defoliating (D) pathotype in Verticillium dahliae has previously been shown to occur only in one clonal lineage (lineage 1A). By contrast, no clear association has yet been shown for race 1 with clonal lineages. Race 1 carries the effector gene Ave1 and is avirulent on hosts that carry resistance gene Ve1 or its homologues. The hypothesis tested was that race 1 arose once in a single clonal lineage, which might be expected if V. dahliae acquired Ave1 by horizontal gene transfer from plants, as hypothesized previously. In a diverse sample of 195 V. dahliae isolates from nine clonal lineages, all race 1 isolates were present only in lineage 2A. Conversely, all lineage 2A isolates displayed the race 1 phenotype. Moreover, 900‐bp nucleotide sequences from Ave1 were identical among 27 lineage 2A isolates and identical to sequences from other V. dahliae race 1 isolates in GenBank. The finding of race 1 in a single clonal lineage, with identical Ave1 sequences, is consistent with the hypothesis that race 1 arose once in V. dahliae. Molecular markers and virulence assays also confirmed the well‐established finding that the D pathotype is found only in lineage 1A. Pathogenicity assays indicated that cotton and olive isolates of the D pathotype (lineage 1A) were highly virulent on cotton and olive, but had low virulence on tomato.

Role of Verticillium dahliae and V. tricorpus naturally infected tubers in causing Verticillium wilt disease, contribution of soil pathogen inoculum and subsequent progeny tuber infection

Colonization of stems, symptom development, yield, progeny tuber infection, quantification of soil inoculum and contribution of soil inoculum on subsequent disease development by Verticillium dahliae, causal agent of Verticillium wilt of potato was evaluated in the glasshouse using naturally infected and non-infected seed tubers of seven cultivars in two trials. Internal seed tuber infection of seven potato cultivars did not contribute to severe disease development although the pathogen was isolated from symptomless plants. Susceptible cultivars Atlantic, Trent and Russet Burbank had the highest incidence of petiole infection while the moderate resistant cv Ranger Russet had the lowest incidence at 65 days after planting. Progeny tuber infection in various cultivars after harvest ranged from 0 (cv Ranger Russet) to 13 % (cv Atlantic). Planting infected tubers contributed to V. dahliae inoculum in the potting soil. Mean levels were highest from cv Russet Burbank (70 pg DNA/g of soil; range from 6 to 149) while the least was recorded in cv Ranger Russet planted soil (11 pg DNA/g of soil; range from 3 to 31). Soil inoculum originating from naturally infected tubers did not contribute to subsequent foliar disease development in Russet Burbank and Shepody cultivars that were grown in this infected soil. However, V. dahliae was isolated from the petiole of some symptomless plants. Progeny tubers were completely free from V. dahliae. Tubers of cv Nicola, infected with Verticillium tricorpus, produced very few Verticillium wilt symptoms but the fungus was re-isolated from the petiole of symptomless plants. Only 4 % of progeny tubers were infected by the pathogen and the level of V. tricorpus inoculum in the soil at maturity was only 1 cfu/g of dry soil. There was no significant difference in the yield of tubers between plants originating from infected and non-infected tubers.

SNP association analysis of resistance to Verticillium wilt (Verticillium dahliae Kleb.) in spinach

Verticillium wilt, caused by Verticillium dahliae Kleb., is an important disease of spinach (Spinacia oleracea L.) and use of genetic resistance is the most economical method of controlling this disease. The objective of this research was to conduct molecular association analysis for Verticillium wilt resistance in spinach. A total of 95 USDA spinach accessions were evaluated for resistance to Verticillium wilt in this study. Phenotyping was conducted using a 0-4 scale of disease severity scores of Verticillium wilt and genotyping was performed using 2,878 SNPs which were postulated from genotyping by sequencing (GBS). STRUCTURE 2.3.4 and MEGA 6 were used for population structure and genetic diversity analysis. The single marker regression (SMR) from QGene, general linear mode (GLM) and mixed linear mode (MLM) from TEASSEL, and compressed mixed linear model (cMLM) and enriched compressed mixed linear model (EcMLM) from GAPIT were used for association analysis of Verticillium wilt resistance. Significant genetic variation of Verticillium wilt disease resistance was observed among the 95 spinach accessions with a wide range from 0.3 to 3.0 on a 0-4 scale. Two well-differentiated genetic populations and admixtures were postulated in the spinach panel. Five SNP markers, AYZV02052595_108, AYZV02112284_14543, AYZV02123399_146, AYZV02164612_331, and AYZV02170942_274 were identified to be associated with Verticillium wilt resistance with R-squared values from 9.3 to 18.2%. These markers may provide a tool utilized in molecular spinach breeding to select Verticillium wilt resistance through marker-assisted selection.

Efficacy of chloropicrin application by drip irrigation in controlling the soil-borne diseases of greenhouse pepper on commercial farms in Poland

Three demonstration experiments were conducted on commercial greenhouse farms to assess the efficacy of chloropicrin (CP), applied by drip irrigation, in controlling Verticillium wilt and root rot disease complex of bell pepper, in comparison with dazomet at 40 g m−2. Chloropicrin was applied through drip irrigation system at 20, 30 and 40 g m−2 of emulsified commercial formulation. The concentration of CP in water was constant, and the required doses were obtained by delivering different amounts of the irrigation water per area unit (from 12.5 to 33 mm). The highest mean efficacy in reducing the inoculum density of Verticillium dahliae in the soil at all locations was obtained after CP application at 30 and 40 g m−2, about 85 and 86%, respectively. The number of viable microsclerotia recovered from the soil on the day of pepper planting was significantly correlated with the final incidence of Verticillium wilt disease (r = 0.962). The highest mean efficacy in controlling Verticillium wilt of pepper (86.4%) was obtained after soil treatment with CP at 40 g m−2, and ranged from 80.2 to 95.6%. The yield was stronger correlated with root rot severity (r = −0.849**) than with progression of Verticillium wilt, expressed by AUDPC (r = −0.651**). The dominant soil-borne pathogen responsible for pepper root rot was Colletotrichum coccodes. All chemical treatments provided a significant reduction in root rot severity compared to the untreated control. On-thefarm evaluation revealed that soil fumigation with drip-applied chloropicrin presents a feasible option for pepper growers.

Enhanced production of microsclerotia in recalcitrant Verticillium dahliae isolates and its use for inoculation of olive plants.

The optimization of a simple protocol for the mass production of viable microsclerotia (MS) of Verticillium spp., even for recalcitrant isolates, to the inoculation of olive cuttings. Four Verticillium spp. isolates were characterized by growth rate and morphology. Then, the production ability and the viability of MS over time were assessed in seven solid culture media and five aqueous media. The best culture medium, according to the quantity and the quality (size) of the MS produced, was the alkaline-modified sodium polipectate (AMSP) aqueous medium. The MS viability was higher in peat moss substrates. Finally, the MS obtained in this work were infective causing 100% incidence of Verticillium wilt (VW) disease in inoculated olive plants. This study demonstrates that the modified sodium polipectate medium amended with 0·1% agar is the most suitable for the production of MS of Verticillium dahliae isolates that have lost the ability to produce MS in standard culture media. Mass production of MS for artificial infestation of soil is critical to the study of epidemiological and control aspects of the VW. To overcome the failure in the production of MS in recalcitrant isolates, a culture media was optimized and a successful plant inoculation experiment was carried out with artificial MS.

A rapid diagnostic assay for detection and quantification of the causal agent of strawberry wilt from field samples

ABSTRACTVerticillium dahliae Kleb, the cause of Verticillium wilt disease, is a destructive pathogen that leads to severe yield losses in strawberry fields and thus considerable economic damages. Although rapid identification and detection methods are becoming available more, pathogen quantification remains one of the main challenges in the disease management. In this study, a real-time polymerase chain reaction (rtPCR) assay was developed to quantitatively assess V. dahliae abundance directly from affected roots and soil collected from different areas in Estonia. A specific primer pair based on the ribosomal DNA (rDNA) internally transcribed spacer was designed for SYBR Green-based assay. Strawberry plant and soil samples were randomly collected from different areas in Estonia and analyzed for V. dahliae by soil plating technique and rtPCR assay. The assay was specific for V. dahliae so that the minimum detection limit was 0.93 pg µl−1 of pathogen DNA and the lowest amount of V. dahliae detected in soil was 10.48 pg µl−1 of target DNA corresponding to one microsclerotia per gram of soil. This technique allowed rapid detection and quantification of the pathogen DNA at the picogram level in soils and even in symptomless plants, facilitating the screening of the pathogen in diverse areas. This is the first study about the rtPCR technique being used successfully to assess populations of V. dahliae with high specificity and sensitivity in Estonia strawberry fields. Results of this research can be useful for growers and agricultural organizations to improve available disease management strategies against Verticillium wilt.

The genes involved in the protective effects of phytohormones in response to Verticillium dahliae infection in Gossypium hirsutum

Verticillium wilt disease caused by soil-borne fungus Verticillium dahliae (V. dahliae), is a serious threats to cotton growth worldwide. Endogenous phytohormones, such as salicylic acid (SA), jasmonic acid (JA), ethylene (ET), and brassinosteroid (BR) have been reported to play important roles in defense response in plants. Based on highthroughput RNA sequencing analysis of resistant Gossypium hirsutum (G. hirsutum) variety Zhongzhimian KV-3, comparing the transcriptome with V. dahliae infection and non-infection, eight differentially expressed candidate genes functions indicated in SA (GhPUB17, GhTGA7 and GhPR1), JA (GhJAZ10 and GhbHLH18), ET (GhEBF1), cytokinine (GhE13L13) and BR (GhBZR1) signal pathways were investigated via virus-induced gene silencing (VIGS) using cotton leaf crumple virus (CLCrV) vector. The expression of eight genes was further validated through quantitative realtime PCR. The result showed that the expression level of GhPUB17, GhJAZ10, GhbHLH18, GhEBF1 and GhE13L13 increased faster in resistant variety Zhongzhimian KV-3 than in susceptible variety 86-1 upon V. dahliae infection. Silencing up-regulated genes GhPUB17, GhJAZ10, GhbHLH18 and GhEBF1 significantly enhanced resistant variety susceptibility to V. dahliae and silencing down-regulated genes GhTGA7 and GhBZR1 significantly increased susceptible variety resistance to V. dahliae. Taken together, these genes are important components in response to V. dahliae infection.

An Analysis of the Roles of Cotton MAPK Family Members in Resistance to Verticillium Wilt Disease

An Analysis of the Roles of Cotton MAPK Family Members in Resistance to Verticillium Wilt Disease

VdCYC8, Encoding CYC8 Glucose Repression Mediator Protein, Is Required for Microsclerotia Formation and Full Virulence in Verticillium dahliae

Verticillium dahliae is the primary causal agent for Verticillium wilt disease on a diverse array of economically important crops, including cotton. In previous research, we obtained the low-pathogenicity mutant T286 from the T-DNA insertional mutant library of the highly virulent isolate Vd080 derived from cotton. In this study, the target disrupted gene VdCYC8 was identified by TAIL-PCR, encoding a homolog of CYC8 proteins involved in glucose repression. The deletion mutant ΔCYC8 exhibited several developmental deficiencies, including reduced microsclerotia formation, reduced sporulation, and slower growth. Moreover, compared with the wild type strain Vd080, the pathogenicity of strain ΔCYC8 was significantly decreased on cotton seedlings. However, the complementary mutants ΔCYC8-C led to restoration of the wild type phenotype or near wild type levels of virulence on cotton. Interestingly, pathogenicity of the strains was correlated with VdCYC8 gene expression levels in complemented mutants. Gene expression analyses in the wild type strain Vd080, the ΔCYC8-45 strain, and complemented strain ΔCYC8-C26 indicated that VdCYC8 regulates the transcription levels of several genes in V. dahliae that have roles in melanin and production.