Pre-plant bacterisation: a strategy for delivery of beneficial endophytic bacteria and production of disease-free plantlets of black pepper (Pipernigrum L.)

Naturally occurring endophytic bacteria from black pepper vines were found to exhibit strong antagonistic activities against Phytophthora capsici and Radopholus similis. In order to deliver these bacterial strains, as well as to produce disease-free plantlets of black pepper, a pre-plant stem and root bacterisation was standardised. Stem bacterisation with endophytic Pseudomonas spp. was found to suppress P. capsici infection (over 90% reduction in lesion length) on cut shoots. Pre-plant root bacterisation with Pseudomonas aeruginosa, Pseudomonas putida and Bacillus megaterium yielded over 60% of plantlets free from P. capsici infection on roots. Curtobacterium luteum and B. megaterium recorded over 70% reduction of nematode population in soil with concomitant production of over 65% of nematode-free plantlets. Besides protecting the plants from the pathogens, the bacteria were also found to enhance the growth of rooted cuttings. The biocontrol potential of the above endophytic bacteria and their exploitation for disease management in the black pepper nursery are discussed.     

Diversity and activity of biosurfactant-producing Pseudomonas in the rhizosphere of black pepper in Vietnam

Aims: Phytophthora capsici is a major pathogen of black pepper and zoospores play an important role in the infection process. Fluorescent pseudomonads that produce biosurfactants with zoosporicidal activities were isolated from the black pepper rhizosphere in Vietnam, and their genotypic diversity and potential to control Phy. capsici root rot was determined. Methods: Biosurfactant‐producing pseudomonads were genotypically and biochemically characterized by BOX‐polymerase chain reaction (PCR), 16S‐rDNA sequencing, reverse‐phase‐high‐performance liquid chromatography and liquid chromatography‐masss spectrometry analyses. Results: Biosurfactant‐producing fluorescent pseudomonads make up c. 1.3% of the culturable Pseudomonas population in the rhizosphere of black pepper. Although BOX‐PCR revealed substantial genotypic diversity, the isolates were shown to produce the same biosurfactants and were all identified as Pseudomonas putida. When applied to black pepper stem cuttings, several of the biosurfactant‐producing strains provided significant disease control. In absence of the disease, several of the bacterial strains promoted shoot and root growth of black pepper stem cuttings. Conclusions: Biosurfactant‐producing pseudomonads indigenous to the rhizosphere of black pepper plants are genotypically diverse and provide a novel resource for the control of Phy. capsici root rot and growth promotion of black pepper stem cuttings. Significance and Impact of the Study: The results of this study provide a strong basis for further development of supplementary strategies with antagonistic bacteria to control foot and root rot of black pepper and to promote plant growth.     

Susceptibility assessment of bell pepper genotypes to crown and root rot disease

Bell Pepper (Capsicum annuum) is one of the important vegetable crops with valuable food sources, which is used almost around the world. Crown and root rot disease caused by Phytophthora capsici is one of the most important diseases of bell pepper in Iran. The present study was conducted to evaluate the susceptibility of different varieties of bell pepper to crown and root rot disease under glasshouse condition. Fourteen commonly planted genotypes of bell pepper in Iran were evaluated for their susceptibility to infection with the pathogen. For this purpose, disease severity of the chosen genotypes in different growth stages was evaluated. The results indicated that the bell pepper genotypes respond differently to pathogenicity tests. Based on cluster analyses confirmed by the results of SAS analyses, bell pepper cultivars were categorised in five distinct groups.     

Plant-parasitic nematodes and yellowing of leaves associated with black pepper plants in Vietnam

Thirty-five nematode species belonging to 19 genera were extracted from 432 soil and root samples collected in 19 districts in six provinces in the North Central Coast, Central Highlands and Phu Quoc Island. Based on our study, the predominant nematode species associated with black pepper plants in Vietnam is Meloidogyne incognita: almost every soil and root sample examined during our study was infected with this root-knot nematode species. No difference in frequency of occurrence of M. incognita among the three agro-ecological regions surveyed was observed. However, the root population density of M. incognita in black pepper plants was on average about five times higher in the North Central Coast and Central Highlands than in Phu Quoc Island. Large differences in root population density of M. incognita on black pepper plants were observed in different districts within the same agro-ecological region. Black pepper roots infected with M. incognita showed the same type of galls as described in the literature. The percentage of root galling averaged about 40% in all the three agro-ecological regions. The percentage of black pepper plants with yellow leaves was on average about 20–25% in the North Central Coast and Central Highlands, which was somewhat higher compared to Phu Quoc Island (16.9%). Large differences in percentage of black pepper plants with yellow leaves were observed in different districts within the same agro-ecological region. The same type of yellow leaves as described in the literature for black pepper plants infected with Meloidogyne species was observed in our study. In general, a positive relationship between the soil and root population densities of M. incognita on black pepper plants and percentage of plants with yellow leaves was observed. However, in one district (Quang Tri) a relatively low nematode population density was associated with a high percentage of plants with yellow leaves. Five nematode species were recorded for the first time on black pepper plants in Vietnam. Our study reconfirms previous reports that Radopholus similis does not occur in Vietnam.     

Differential induction of chitinase in Piper colubrinum in response to inoculation with Phytophthora capsici,the cause of foot rot in black pepper

Plant chitinases have been of particular interest since they are known to be induced upon pathogen invasion. Inoculation of Piper colubrinum leaves with the foot rot fungus, Phytophthora capsici leads to increase in chitinase activity. A marked increase in chitinase activity in the inoculated leaves was observed, with the maximum activity after 60 h of inoculation and gradually decreased thereafter. Older leaves showed more chitinase activity than young leaves. The level of chitinase in black pepper (Piper nigrum L.) upon inoculation was found to be substantially high when compared to P. colubrinum. RT–PCR using chitinase specific primers revealed differential accumulation of mRNA in P. colubrinum leaves inoculated with P. capsici. However, hyphal extension assays revealed no obvious differences in the ability of the protein extracts to inhibit growth of P. capsici in vitro.     

Population dynamics of Meloidogyne incognita on black pepper plants in two agro-ecological regions in Vietnam

The objective of our study was to examine the effect of local environmental conditions, especially air temperature and rainfall, in two agro-ecological regions in Vietnam on the population dynamics of Meloidogyne incognita on black pepper plants and on percentage root galling. The two study sites were situated in Cam Lo, Quang Tri province (North Central Coast) and Buon Ma Thuot, Dac Lac province (Central Highlands). At the study sites, 13 plant-parasitic nematode taxa belonging to 12 genera were identified. Ten of these taxa were present in both study sites. Helicotylenchus certus, Hemicriconemoides cocophilus and Pratylenchus coffeae were only found in Buon Ma Thuot. Based on nematode population densities, M. incognita was the most abundant taxon present. Rainfall and air temperature differed significantly between the two study sites. The most important climatic difference was rainfall: in Buon Ma Thuot, the rainy season lasted 2 months longer and the monthly rainfall during the rainy season was much higher compared to Cam Lo. Although this difference resulted in some differences in the population dynamics of M. incognita in the soil and roots of the black pepper variety Vinh Linh, the highest root population densities were observed in both study sites during the first half of the dry season. In Cam Lo, the highest percentage root galling was observed during the first half of the dry season. In Buon Ma Thuot, the highest percentage root galling was observed towards the end of the rainy season. Estimating the population densities if M. incognita to decide on the application of a management strategy should be done during the first half of the dry season.     

辣椒疫霉菌侵染模型和侵染条件定量研究

在生长箱内控制条件下分析测定了土壤温度、水分含量对辣椒疫病死苗率的影响.结果表明:土壤温度和水分状况是决定辣椒疫病菌侵染的重要因子,病菌侵染的最适土壤温度为22 ℃～28 ℃,最适土壤含水量为40%,土壤过于干燥和过饱和都不利于病菌侵染发病;辣椒疫病死苗率与土壤温度、水分含量及其互作可用数学模式描述.田间调查发现,辣椒疫病田间流行趋势可用Gompertz模型描述,发病率与初始发病率、土壤温度、水分含量以及空气温度密切相关.建立了田间辣椒疫病发病率预测模型.     

Biological Control of Oomycete Soilborne Diseases Caused by Phytophthora capsici,Phytophthora infestans,and Phytophthora nicotianae in Solanaceous Crops

Oomycete pathogens that belong to the genus Phytophthora cause devastating diseases in solanaceous crops such as pepper, potato, and tobacco, resulting in crop production losses worldwide. Although the application of fungicides efficiently controls these diseases, it has been shown to trigger negative side effects such as environmental pollution, phytotoxicity, and fungicide resistance in plant pathogens. Therefore, biological control of Phytophthora-induced diseases was proposed as an environmentally sound alternative to conventional chemical control. In this review, progress on biological control of the soilborne oomycete plant pathogens, Phytophthora capsici, Phytophthora infestans, and Phytophthora nicotianae, infecting pepper, potato, and tobacco is described. Bacterial (e.g., Acinetobacter, Bacillus, Chryseobacterium, Paenibacillus, Pseudomonas, and Streptomyces) and fungal (e.g., Trichoderma and arbuscular mycorrhizal fungi) agents, and yeasts (e.g., Aureobasidium, Curvibasidium, and Metschnikowia) have been reported as successful biocontrol agents of Phytophthora pathogens. These microorganisms antagonize Phytophthora spp. via antimicrobial compounds with inhibitory activities against mycelial growth, sporulation, and zoospore germination. They also trigger plant immunity-inducing systemic resistance via several pathways, resulting in enhanced defense responses in their hosts. Along with plant protection, some of the microorganisms promote plant growth, thereby enhancing their beneficial relations with host plants. Although the beneficial effects of the biocontrol microorganisms are acceptable, single applications of antagonistic microorganisms tend to lack consistent efficacy compared with chemical analogues. Therefore, strategies to improve the biocontrol performance of these prominent antagonists are also discussed in this review.     

Effect of tissue wounding and time of soil inoculation on pepper root rot development

Five-week-old pepper plants with wounds created on stems and roots were transplanted to soils having inoculum of Phytophthora capsici incorporated for different lengths of time. Disease severity (39.99%) on root trimmed seedlings was not significantly different (P ≤ 0.05) from the severity (36.24%) obtained on stem lacerated seedlings. The wound treatments did not result in significantly different rates of lesion extension per day; stem lacerated seedling had the fastest, 1.99 mm/day lesion extension rate, followed by 1.90 and 1.89 mm/day extension rates obtained on root trimmed and unwounded treatments, respectively. However, time of soil inoculation had significant effect on severity; root trimmed and stem lacerated treatments had 46.3% and 39.8% severities, respectively. Tissue wounding × time of soil inoculation interaction did not have significant effect on disease severity; stem lacerated seedlings transplanted to 1-day and 3-day inoculated soils gave highest severity (49.9%), followed by seedlings inoculated at the time of transplantation. Root trimmed seedlings inoculated at the time of transplantation had highest severity (61.1%), while the lowest severity was obtained on seedlings transplanted to 5-day inoculated soil.     

Endophytic bacterial flora in root and stem tissues of black pepper (Piper nigrum L.) genotype: isolation, identification and evaluation against Phytophthora capsici

Aim:  To isolate and identify black pepper ( Piper nigrum L) associated endophytic bacteria antagonistic to Phytophthora capsici causing foot rot disease.
Methods and Results:  Endophytic bacteria (74) were isolated, characterized and evaluated against P. capsici . Six genera belong to Pseudomonas spp (20 strains), Serratia (1 strain), Bacillus spp. (22 strains), Arthrobacter spp. (15 strains), Micrococcus spp. (7 strains), Curtobacterium sp. (1 strain) and eight unidentified strains were isolated from internal tissues of root and stem. Three isolates, IISRBP 35, IISRBP 25 and IISRBP 17 were found effective for Phytophthora suppression in multilevel screening assays which recorded over 70% disease suppression in green house trials. A species closest match (99% similarity) of IISRBP 35 was established as Pseudomonas aeruginosa ( Pseudomonas EF568931), IISRBP 25 as P. putida ( Pseudomonas EF568932), and IISRBP 17 as Bacillus megaterium ( B. megaterium EU071712) based on 16S rDNA sequencing.
Conclusion:  Black pepper associated P. aeruginosa , P. putida and B. megaterium were identified as effective antagonistic endophytes for biological control of Phytophthora foot rot in black pepper.
Significance and Impact of the Study:  This work provides the first evidence for endophytic bacterial diversity in black pepper stem and roots, with biocontrol potential against P. capsici infection.     

利用辣椒疫霉培养滤液体外筛选胡椒抗瘟病无性系研究

在胡椒（Piper nigrum Linn．)茎尖丛生增殖技术的基础上,以印尼大叶种“Lampong Type”无菌实生苗作外植体源,利用辣椒疫霉(Phytophthora capsici)培养滤液对胡椒茎尖及其增殖形成的丛生芽进行体外选择。辣椒疫霉培养滤液的不同灭菌方法对辣椒疫霉培养滤液的毒性影响显著,过滤灭菌方式可以保持辣椒疫霉培养滤液的毒性,而高温高压灭菌方式则不能。随着辣椒疫霉培养滤液浓度的增加,茎尖和丛生芽的存活率和增殖率都在下降。在存活的茎尖或丛生芽培养中,一部分可正常增殖,其余的形成愈伤组织,或者保持生长停滞的休眠状态。在选择性培养基上继代培养2次后进行生根和移栽,利用离体叶片针刺接种法对温室条件下生长的移栽植株进行抗瘟病测定。以3次抗病检测均无明显症状的植株作为抗病株。随着辣椒疫霉培养滤液浓度的增加,得到的再生植株数量降低,但其中抗病株的比例提高。利用过滤灭菌方式加入选择性培养基的处理中,25％、50％和75％的辣椒疫霉培养滤液分别获得1株、4株和3株抗病株,分别占各处理再生植株总数的1．54％、20．00％和42．86％,共获得8株,占该组处理再生植株总数的8．70％。     

Fungi associated with black pepper plants in Quang Tri province (Vietnam), and interaction between Meloidogyne incognita and Fusarium solani

During a survey of nurseries and plantations of black pepper plants in Quang Tri province in Vietnam during the rainy season of 2007, nine fungal taxa were isolated from the roots of the black pepper plants. Fusarium solani was found in about one out of four black pepper root samples examined but not in the nurseries and also not from black pepper plants younger than five years growing in plantations. Since in these nurseries about one out of two black pepper plants examined had yellow leaves, this observation suggests that another pathogen must be the initial cause of the yellowing of the leaves. A likely pathogenic candidate is M. incognita which was extracted from every single black pepper plant examined in the nurseries. During the same survey, we also observed that F. solani was not isolated from the roots of black pepper plants that did not had yellow leaves and that the percentage of black pepper plants with yellow leaves increased with increased frequency of occurrence of F. solani. This observation indicates that F. solani plays a role in the yellowing of the leaves of black pepper plants in a later stage of the development of the plants. The results of a greenhouse experiment showed the negative effects inoculation with M. incognita alone or in combination with F. solani may have on the percentage of black pepper plants with yellow leaves and on plant growth. No effect of inoculation with F. solani before, at the same time, or two weeks after inoculation with M. incognita on root galling and nematode reproduction was observed.     

Analysis of internal transcribed spacer (ITS) region of Phytophthora tropicalis causing quick wilt disease of black pepper in Vietnam

Phytophthora quick wilt is a devastating disease of black peppers in Vietnam. The internal transcribed spacer (ITS) region of the ribosomal DNA of four Phytophthora samples isolated from the diseased vines in Daknong province of the central highland part of Vietnam was Polymerase chain reaction-amplified, cloned, sequenced and characterised. Database search have showed that they are most closely related to an isolate of Phytophthora tropicalis from Taiwan. Sequence comparisons and phylogenetic analyses based on the ITS region of the four Vietnamese and other GenBank isolates of P. tropicalis and a closely related species, P. capsici, provide strong evidences that the Vietnamese isolates are all different isolates of P. tropicalis.     

Occurrence of symptomless source of Piper yellow mottle virus in black pepper (Piper nigrum L.) varieties and a wild Piper species

Symptomless nature of Piper yellow mottle virus (PYMoV) infection in three varieties of black pepper (Piper nigrum) (Panniyur 1, Panniyur 5 and Panchami) and a wild species of Piper (Piper colubrinum) was confirmed by polymerase chain reaction (PCR) using PYMoV specific primers. The virus could be transmitted from these PYMoV-infected symptomless plants onto symptom producing black pepper cv. Karimunda through mealybug vector, Ferrisia virgata and by graft transmission. About 20–50% seedlings showed typical symptoms of the PYMoV at 30 days after mealybug inoculations while it was 75–94% at 90 days after inoculation. PCR test of the inoculated seedlings confirmed the presence of PYMoV in 50–64%, 76–100% and 80–100% of plants in 30, 60 and 90 days after inoculation, respectively. Similarly, 50–66%, 91–100% and 100% of graft-transmitted plants showed typical symptoms of the disease at 30, 60 and 90 days after grafting. PCR test of the graft-transmitted plants showed 100% PYMoV infection at 60 days after grafting. The results clearly demonstrated the existence of PYMoV-infected symptomless plants that can act as source for secondary spread of the virus in the field.     

Evaluation of fungicides and biocontrol products for the control of Phytophthora root rot of hydrangeas

Abstract

Phytophthora root rot is one of the most important diseases in almost all hydrangeas of nursery production. In this study, the efficacy of fungicides and biocontrol products against Phytophthora root rot of hydrangea was assessed in greenhouse and field experiments. Treatments used in field or greenhouse experiments were RootShield PLUS⁺, MBI110, IT-5103, Grotab, OxiPhos, TerraClean 5.0?+?TerraGrow program, Segovis, Pageant Intrinsic, Empress Intrinsic and Subdue Maxx. Pots/plots were inoculated with Phytophthora nicotianae grown on rice grains, sterilised rice grains were used for negative controls. After the trials, plant growth data (total plant weight, root weight, plant height, plant width) were recorded, and roots were assessed for disease severity using a scale of 0–100%. The treatments most effective in reducing Phytophthora root rot severity were Segovis, Empress Intrinsic, Subdue Maxx, TerraClean 5.0?+?TerraGrow program in both greenhouse and field experiments. This study will help nursery producers make proper management decisions by using recommended fungicides and biocontrol products of this study in a rotation or alone to manage Phytophthora root rot of hydrangea.     

辽宁省辣椒疫病菌多态性及致病力分化研究初探

【目的】明确辽宁省辣椒疫病菌多态性及致病力分化与区域性关系。【方法】利用SRAP技术对辽宁省25个辣椒疫病菌菌株进行了PCR扩增及NTSYS-PC聚类分析,用灌根法进行致病力分化试验并对试验结果进行SPSS 11.5分层聚类分析。【结果】利用筛选出的27组引物对25个菌株进行扩增,得到578条条带,每对引物多态性比率在84%?100%之间,多态性丰富;供试菌株间遗传相似性较高,相似系数0.56?0.91,以相似系数0.68为阈值划分,25个菌株可聚为4组。试验菌株80%为中等致病力,聚类结果较为分散。【结论】供试菌株没有表现出明显的区域性特征,菌株致病力强弱分化区域特征性规律不明显。     

Growth promotion and root colonisation in pepper plants by phosphate‐solubilising Chryseobacterium sp. strain ISE14 that suppresses Phytophthora blight

Previously, we selected bacterial strain ISE14 through a sequential selection procedure that included radicle, seedling, and in planta assays and field tests. This strain not only suppressed a destructive soilborne disease, Phytophthora blight, caused by Phytophthora capsici but also increased fruit yields of pepper plants in the fields. This study was conducted to identify strain ISE14 by 16S rRNA gene sequence analysis and to characterise biocontrol and plant growth promotion activities of the strain in pepper plants. Strain ISE14, identified as Chryseobacterium sp., significantly reduced disease severity in plants inoculated with Ph. capsici and promoted plant growth (lengths and dry weights of shoots and roots) compared with those in plants treated with Escherichia coli DH5α (negative control) or MgSO₄ solution (untreated control). This strain effectively colonised pepper plant roots as assessed by bacterial population analysis and confocal laser scanning microscopy; it enhanced soil microbial activity and biofilm formation, but not the production of indole acetic acid. Strain ISE14 also solubilised organic or inorganic phosphate by production of acid and alkaline phosphatases or reduction in pH, resulting in enhanced pepper plant growth. This strain exhibited similar or greater activity in disease control and plant growth promotion tests compared with positive control strains Paenibacillus polymyxa AC‐1 (biocontrol) and Bacillus vallismortis EXTN‐1 (plant growth). Therefore, Chryseobacterium sp. ISE14 may be a phosphate‐solubilising and plant growth‐promoting rhizobacterium (PGPR) strain that suppresses Phytophthora blight of pepper. To our knowledge, this is the first report of a phosphate‐solubilising PGPR strain of Chryseobacterium sp. that suppresses the pepper disease.     

Capsidiol: Its role in the resistance of Capsicum annuum to Phytophthora capsici

Inoculation of the stems of three Capsicum annuum L. cultivars showing different degrees of sensitivity to the fungal pathogen Phytophthora capsici , resulted in a hypersensitive reaction being expressed along the stems. One of the peppers (cv. Smith-5) showed resistance by total inhibition of fungal growth. Capsidiol, a phytoalexin, which accumulates in the area of necrosis appears to be involved in this resistance. Capsidiol accumulation was analyzed by gas chromatography and was correlated with the restricted growth of P. capsici , in vivo and in vitro, confirming the former's fungistatic and fungitoxic properties. The capacity to inhibit pathogenic growth was evident only when capsidiol production exceeded 1 204 μg ml^-1, a level reached in the resistant variety after 6 days of incubation. Experiments on induced resistance showed that a second inoculation of the stems of the three cultivars also resulted in necrosis and in an accumulation of capsidiol, although to a lesser extent than in the first inoculation. The greater accumulation of capsidiol in the stems of cv. Smith-5 is in accordance with the resistance shown by this cultivar to P. capsici , and confirms the implication of capsidiol in the disease resistance of this cultivar to fungal pathogens. Capsidiol has a fungistatic character at a mean concentration of 3.75 mM, and is fungitoxic at levels above 5 mM. This level must be exceeded and all the growing hyphae must be affected for capsidiol to qualify from being fungistatic to being fungitoxic.     

Phytophthora cryptogea root rot of tomato in rockwool nutrient culture:

The effect of root temperature on growth and yield of rockwool-grown tomato plants infected with Phytophthora cryptogea was investigated. Measurements of shoot and root growth were taken at high (25^oC) and low (15^oC) root temperatures during the generative phase of growth. The growth of roots of healthy and P. cryptogea-infected tomato plants in rockwool blocks was higher in plants grown with roots at 25^oC than at 15^oC after 60 days and a similar effect was found in slabs after 98 days. Under sub-optimal conditions for growth the disease became severe when root temperatures were low. Growth of roots was greatest when roots were maintained at a high temperature in combination with an ambient air temperature of c. 15^oC and the response was greater in cv. Counter than cvs Calypso and Marathon. Water-soluble carbohydrates of roots were higher in those produced in blocks than slabs and were reduced by infection compared to healthy plants with roots at 15^oC and 25^oC. Reduced transpiration rates were found 17 days after inoculation in symptomless plants grown at a root temperature of 25^oC. Infection, regardless of the temperature of the roots or cultivar, led to reduced stem growth. The plants grown at 25^oC were taller than those with a root temperature of 15^oC. After 9 wk of harvest, the cumulative fruit yields in infected cvs Counter and Calypso grown at 25^oC were comparable to that in healthy plants grown at either temperature and cumulative fruit numbers followed a similar pattern. High root temperatures led to delayed fruit ripening between weeks 3–10 and a larger number of unripe fruit. The weight of unripe fruit from infected plants grown at 25^oC at the terminal harvest was higher than from healthy plants with roots maintained at 15^oC.     

Proteomic profile of the plant‐pathogenic oomycete Phytophthora capsici in response to the fungicide pyrimorph

Pyrimorph is a novel fungicide from the carboxylic acid amide (CAA) family used to control plant‐pathogenic oomycetes such as Phytophthora capsici. The proteomic response of P. capsici to pyrimorph was investigated using the iTRAQ technology to determine the target site of the fungicide and potential biomarker candidates of drug efficacy. A total of 1336 unique proteins were identified from the mycelium of wild‐type P. capsici isolate (Hd3) and two pyrimorph‐resistant mutants (R3‐1 and R3‐2) grown in the presence or absence of pyrimorph. Comparative analysis revealed that the three P. capsici isolates Hd3, R3‐1, and R3‐2 produced 163, 77, and 13 unique proteins, respectively, which exhibited altered levels of abundance in response to the pyrimorph treatment. Further investigations, using Cluster of Orthologous Groups of Proteins (COG) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified 35 proteins related to the mode of action of pyrimorph against P. capsici and 62 proteins involved in the stress response of P. capsici to pyrimorph. Many of the proteins with altered expression were associated with glucose and energy metabolism. Biochemical analysis using d ‐[U‐¹⁴C]glucose verified the proteomics data, suggesting that the major mode of action of pyrimorph in P. capsici is the inhibition of cell wall biosynthesis. These results also illustrate that proteomics approaches are useful tools for determining the pathways targeted by novel fungicides as well as for evaluating the tolerance of plant pathogens to environmental challenges, such as the presence of fungicides.