Pepper Wilt Research Articles

Occurrence of Fusarium oxysporum causing wilt on pepper in Mexico

A new disease on greenhouse pepper (Capsicum annuum L.) plants in Culiacan, Mexico with symptoms of chlorosis, wilting and vascular necrosis was observed in 2014. Sixty diseased pepper plants were collected from three different areas of the Culiacan Valley to determine the causal agent of the disease and analyse the potential risk presented by this disease in this region. Fusarium oxysporum was recovered consistently (88% of samples collected) and identified based on cultural, morphological and pathogenicity tests, as well as by PCR amplification and DNA sequencing of the TEF-1α gene. Two pathogenicity tests with 10 monoconidial isolates of F. oxysporum, which were selected randomly from diseased tissues, produced disease symptoms similar to those observed on pepper plants in the greenhouses. Symptoms were different from the typical root rot, wilting and necrosis caused by F. solani and F. oxysporum f. sp. radicis-capsici and instead matched those reported for F. oxysporum f. sp. capsici causing pepper wilt. The results suggest that the causal agent of pepper wilt in the samples analysed was F. oxysporum. This is the first report of pepper wilt caused by this fungus in Mexico, and this disease is a potential threat for pepper production in this region.

Management of pepper verticillium wilt by combinations of inducer chemicals for plant resistance, bacterial bioagents and compost

Inducer resistance chemicals (IRCs) Bion (BTH), chitosan and salicylic acid, bacterial bioagents, i.e. Bacillus chitinosporus, B. megaterium, B. pumilus, B. subtilis, B. thuringiensis, Pseudomonas fluorescens and P. putida and compost tea caused a reduction to the linear growth of the fungus Verticillium dahliae, in culture plates. In general, P. fluorescens followed by B. subtilis were the most efficient in reducing the linear growth of V. dahliae. The viability of microsclerotia of V. dahliae was greatly reduced by the tested bacterial bioagents. In addition, B. megaterium, B. subtilis, P. fluorescens and P. putida were the most efficient bioagents, where no microsclerotia germinated three weeks after treatment with these bioagents. In addition, few of microsclerotia germinated when treated with B. chitinosporus, B. pumilus and B. thuringiensis. However, all the microsclerotia of the control treatment were viable even three weeks after treatment with bioagents. The combination and use singly of BTH, B. subtilis, P. fluorescens and compost resulted in a reduction of verticillium wilt in pepper and increase of fruit, photosynthetic pigments, and vitamin-C compared with the control treatment (infested with the causal fungus). Compost was the most efficient of single tactics in disease management. Moreover, no apparent infection was detected when BTH, the two bioagents B. subtilis and P. fluorescens and compost were used together and the fruit yield, photosynthesis pigments and vitamin-C were, similar to the control treatment (un-infested soil). Photosynthesis pigments including chlorophyll a, chlorophyll b and carotenoids as well as free and total ascorbic acid (vitamin-C) were greatly increased due to the tested treatments, i.e. BTH, both bioagents and compost in pepper plants grown in infested soil compared with those of untreated plants (grown in infested soil only). Compost was the best single treatment for minimizing the reduction in photosynthesis pigments in plants grown in infested soil with V. dahliae, as well as free and total ascorbic acid compared with plants grown in soil infested with the causal fungus without any another treatment.

Control of Fusarium Wilt Disease in Pepper Caused by Fusarium oxysporum by using Cabbage (Brassica oleracea var. capitate) Bio fumigation

Fusarium wilt disease one of the most important disease worldwide. This study was carried out to evaluate the effectiveness of cabbage leaves for three concentrations of (2.5, 5 and 10g/ 1kg) in controlling soil fungus Fusarium oxysporum that causes wilting pepper. The results showed that the effectiveness of fresh cabbage leaves in reducing the severity of infection and the percentage of pepper wilt disease with significant differences in comparison with the control treatment. The cabbage leaves added to the soil at concentration of 10 g / 1 kg soil achieved the highest percentage of reduction in the severity of the disease and in at percentage of the disease, amounting to 8.75% and 0.5%, respectively, followed by Cabbage leaves treatment concentration of 5 g / 1 kg soil at 35% and 5%, respectively then followed by treatment with Cabbage leaves a concentration of 2.5 g / 1 kg soil at 55%, 10%, respectively, which all differed significantly from the treatment with pathogenic fungus F. oxysporum showed that the severity of the infection and the percentage of infection were 82% 0.45%, respectively. The results also showed that all Cabbage leaves treatment with concentrations of 2.5, 5 and 10 g / 1 kg soil has not adversely affected the growth standards parameters for Pepper plants length, width of their leaves, and fresh and dry weight of the plants after 40 days of cultivation of pepper seedlings as it did not differ significantly from the control treatment. While the results showed that there were significant differences in the value of vigor index for treatments with Cabbage leaves which ranged from 2663 - 2745 compared to the treatment of pathogenic fungus F. oxysporum, which amounted to 1545 while not significantly differ from the treatment of the control as a vigor index reached in 2574.

Assessment of Wilt Intensity and Identification of Causal Fungal and Bacterial Pathogens on Hot Pepper (Capsicum annuum L.) in Bako Tibbe and Nonno Districts of West Shewa Zone, Ethiopia

Pepper wilt disease intensity was assessed on-farm in Bako Tibbe and Nonno districts of West Shewa Zone, Ethiopia during the main cropping season of October 2012. The wilt causing pathogens were identified from 50 diseased samples collected from the two districts. Of the 120 hot pepper fields surveyed, 116 fields were found to be infected with wilt disease. The overall percent prevalence and incidence of wilt disease was 96.7 and 86.4%, respectively. Identification and pathogenicity tests revealed that Ralstonia solanacearum and four fungal wilt pathogens (Rhizoctonia solani, Fusarium spp., Phytophthora spp. and Verticillium spp.) were detected in the surveyed fields. The percentage of occurrence of Rhizoctonia solani, Fusarium spp., Phytophthora spp. and Verticillium spp. were 45.0, 17.48, 12.59 and 11.89%, respectively; whereas, the frequency of R. solanacearum was 100%. Wilt disease in pepper in these two districts was caused by more than one wilt causing pathogen, thus management strategies should focus on these complex pathogens.

Field evaluation of different application methods of the mixture of Bacillus cereus strain AR156 and Bacillus subtilis strain SM21 on pepper growth and disease resistance

The mixture of Bacillus subtilis strain SM21 and Bacillus cereus strain AR156, referred to as ASB, is a biopesticide in the process of registration in China, which has the capacity of controlling root-knot nematode in cucumber, Phytophthora wilt in pepper and Ralstonia wilt in tomato. In this study, we tested its effects on a range of physiological indicators of plant growth including biomass, yield, chlorophyll content and fruit nutrients of pepper, as well as, its efficacy in controlling bacterial wilt caused by Ralstonia solanacearum under field conditions in 2009 and 2010 by a variety of inoculation methods. Three application methods – soaking seeds, drenching soil around seeds right after sowing and drenching the rhizosphere of transplanted seedling with the aqueous solution (as a soil drench) –and three concentrations of ASB (1.0 × 106 CFU/mL, 1.0 × 107 CFU/mL, and 1.0 × 108 CFU/mL) were employed. The results showed that both soaking seeds with ASB at 1.0 × 107 CFU/mL as well as drenching rhizosphere with ASB at 1.0 × 106 CFU/mL and 1.0 × 107 CFU/mL promoted growth, increased yield and fruit nutrient contents of pepper. The combination of these two inoculation methods led to significant increases in growth and fruit nutrient contents. We found that the most effective way was the combination of soaking seeds with the ASB at 1.0 × 107 CFU/mL and drenching rhizosphere with it at 1.0 × 106 CFU/mL, which is also easy for Chinese farmers to implement.

Management Fusarium Wilt of Sweet Pepper by Bacillus Strains

Isolation trials from the roots of wilted sweet pepper plants yielded Alternaria spp., Fusarium oxysporum, Pythium spp., Rhizontonia solani , Sclerotium rolfsii and Trichoderma spp. The isolates of the fungus F. oxysporum were selected to test their pathogenicity and Kalubia isolate was the most virulent one. The fungus was virulent to sweet pepper and low infection was found in case of the other five tested plants. Therefore, the fungus F. oxysporum named Fusarium oxysporum f.sp. capsici. All the five Bacillus strains, i.e. Bacillus chitinosporus ,B. coagulans , B. humilus ,B.subtilis and B. thuringiensis caused significant reduction to the radial growth of F.o.f.sp.capsici compared with control treatment. In addition, the growth of the tested pathogen was completely inhibited by B.subtilis and B.thuringiensis at the concentration of 60%. Furthermore, B.thuringiensis was the most efficient bioagent in this regard followed by B.subtilis then B.pumilus. Adding the three tested bioagents ,i.e.B.pumilus .B.subtilis and B. Thuringiensis to soil infested with F.o.f.sp.capsici resulted in significant reduction to sweet pepper wilt with significant increase to the plant height as well as the number of pods and their weight / plant compared with control treatment. The symptoms of the disease were obvious both on the foliage growth and the xylem vesicles, but the severity of the disease was more higher on the xylem vesicles than on the foliage growth. In addition, plants grown in soil infested with Bacillus strains were of high values of plant height and fruit yield (number and weight / plant) than that grown in the control (uninfested soil). The total phenolic compounds were greatly increased in the bacterial treated plants as compared to untreated plants with the bioagents and that infested with the pathogen only. These results give a potential of these bacterial strains for use as plant protection agents against Fusarium wilt of sweet pepper. This work was performed to investigate the potential of some bacterial bioagents ,i.e. B. humilus , B.subtilis and B. thuringiensis on management of sweet pepper Fusarium wilt and the formation of phenolic compounds in the plants.

Biocontrol of pepper wilt with three Bacillus species and its effect on growth and yield

Antagonism, Biopesticides, Rhizobacteria, Biological control, Plant growth promoters.

Phytopathogens Causing Wilt in Pepper – Distribution, Symptoms and Identification

In 2012 the evaluation on the development and spread of phytopathogens, causing wilt in pepper was conducted. The observations were carried out under field conditions and natural infectious background in the Plovdiv region. In laboratory conditions were isolated and identified four phytopathogenic fungi of the genus Rhizoctonia, Fusarium, Verticillium and Phytophthora. The results of the analysis showed that the highest percentage of pepper wilt was caused by the fungus - Rhizoctonia solani.

Arbuscular mycorrhizal fungi (AMF) as bioprotector agents against wilt induced by Verticillium spp. in pepper: a review

Verticillium dahliae Kleb. is a vascular pathogen that alters water status and growth of pepper plants and causes drastic reductions in yield. Its control is difficult because it can survive in field soil for several years. The application of arbuscular mycorrhizal fungi (AMF) as bioprotector agents against V. dahliae is an alternative to the use of chemicals which, in addition, is more respectful with the environment. The establishment of the mutualistic association of plant roots and AMF involves a continuous cellular and molecular dialogue between both symbionts that includes the preactivation of plant defense responses that may enhance the resistance or tolerance of mycorrhizal plants to soil-borne pathogens. Some AMF can improve the resistance of Capsicum annuum L. against V. dahliae. This is especially relevant for pepper cultivars (i.e. cv. Piquillo) that exhibit high susceptibility to this pathogen. Compared with non-mycorrhizal plants, mycorrhizal pepper can exhibit more balanced antioxidant metabolism in leaves along the first month after pathogen inoculation, which may contribute to delay both the development of disease symptoms and the decrease of photosynthesis in Verticillium-inoculated plants with the subsequent benefit for yield. In stems, mycorrhizal pepper show earlier and higher deposition of lignin in xylem vessels than nonmycorrhizal plants, even in absence of the pathogen. Moreover, AMF can induce new isoforms of acidic chitinases and superoxide dismutase in roots. Mycorrhizal-specific induction of these enzymatic activities together with enhanced peroxidase and phenylalanine ammonia-lyase in roots may also be involved in the bioprotection of Verticillium-induced wilt in pepper by AMF

Management of chili pepper root rot and wilt (caused by Phytophthora nicotianae) by grafting onto resistant rootstock

Root rot and plant wilting caused by Phytophthora nicotianae is a severe disease of chili pepper ( Capsicum annuum L.) in open fields and under greenhouse production in Tunisia. Chili pepper grafting for disease manage- ment is attracting increased interest in recent years. Using the tube grafting technique, different compatible scion/rootstock combinations were obtained with the wild-type pepper SCM334 and the local chili pepper cultivars ‘Beldi’ and ‘Baker’. SCM334 was resistant to P. nicotianae , while the cultivars Beldi and Baker were susceptible. Plant inoculations were performed with P. nicotianae zoospores, and severity of root rot was rated 30 days post- inoculation using a 0 (healthy plant) to 5 (dead plant) severity score. On SCM334 rootstock and with ‘Beldi’ or ‘Baker’ scions, the intensity of root rot was very low (mean score 0.1–0.2) and plants were healthy. However, with Baker or Beldi rootstocks and SCM334 scions, root rot was severe (mean score 3.1–4.6), leading to high numbers of wilting and dead plants. This severe root rot was similar to that observed on non-grafted plants of ‘Baker’ and ‘Beldi’ inoculated with the pathogen. Under greenhouse conditions, measurements of agronomic characters indicated non-consistent improvement of these features on the scion cultivar when SCM334 was the rootstock. Since plant foliage is not attacked by this pathogen, these results show that susceptible chili pepper scions grafted onto SCM334 rootstocks could be used for root rot management and improvement of pepper yields in P. nicotianae infested soils.

Identification and Evaluation of Resistance to Bacterial Wilt in Pepper

Identification and Evaluation of Resistance to Bacterial Wilt in Pepper

Agentes biocontroladores para manejo de fitopatógenos de suelo y mosca blanca en pimiento. “capsicum annum”

El cultivo de pimiento (Capsicum annum L.), es afectado por fitopatógenos causantes del complejo marchitez e insectos plaga como mosca blanca, Bemisia tabaci, vector de algunos virus por ejemplo los Geminivirus. Los objetivos específicos fueron: 1) Determinar dosis y frecuencias de aplicación de T. asperellum sobre el complejo marchitez del pimiento, y 2) Determinar dosis y frecuencias de aplicación de B. bassiana para el manejo de Bemisia tabaci. En ambos estudios se utilizó un diseño de bloques completamente al azar con tres repeticiones y para la comparación de las medias se utilizó la prueba de rangos múltiples de Duncan p = 0.05. Los causales de la marchitez del pimiento fueron: Fusarium sp., Rhizoctonia sp., Sclerotium rolfsii yRalstonia solanacearum. La menor severidad fue en el tratamiento T. Asperellum 45x106 esporas/L aplicado 7 días después deltransplante. En el estudio de dosis y frecuencias de aplicación de B. bassiana para el manejo de B. tabaci, la dosis 1x106 de B. bassiana aplicado diez días después del transplante mostró la menor presencia de mosca blanca por planta. Los mejores rendimientos se dieron en los tratamientos B. bassiana aplicado 10 días después del transplante en dosis de uno y diez millones de esporas con un promedio de 14 y 13TM en su orden.

RENDIMIENTO Y CALIDAD DE CHILE SECO 'MIRASOL' CULTIVADO BAJO RIEGO PARCIAL DE LA RAÍZ

The efficient use of water resources is mandatory for the dry chili producing area of Zacatecas. The objective of this study was to compare two types of partial rootzone drying (PRD) against commercial irrigation (CI) in relation to yield and fruit quality, irrigation water use efficiency (IWUE), and pepper wilt incidence (WI) of chilli cv. ‘Mirasol’. PRD treatments were PRD50 on which 50% of CI was applied alternately to both sides of the root zone, and PRD50+20 which was similar to PRD50, but additionally 20% of CI was applied to the drying side of the root system. PRD50 and PRD50+20 promoted water savings compared with CI. The fruit quality categories of dry chili and yield were similar among treatments, but yield tended to decrease in PRD50 and PRD50+20 in 2009. The IWUE tended to increase in PRD50 and PRD50+20 relative to CI. In 2008 WI was the same among treatments, but in 2009 it increased in the PRD treatments. Soil water saturation by continuous precipitations after irrigation events partially explained the increase in WI, and therefore the reduction in yield in the 2009. Nevertheless, PRD50 tended to increase IWUE by 28 % and to reduce the volume of water applied by 32 % with respect to CI. Therefore, the RPR is a promising strategy for sustainability of this production system.

The siderophore-producing bacterium, Bacillus subtilis CAS15, has a biocontrol effect on Fusarium wilt and promotes the growth of pepper

In this study, the Chrome Azurol Sulphonate (CAS) agar plate assay for siderophores was used to screen bacteria from the rhizospheric soil of pepper in Hainan, China. As a result, Bacillus subtilis CAS15, which produced a large orange halo, was obtained. A dual-culture test showed that CAS15 strongly antagonized the growth of 15 plant fungal pathogens, with rates of inhibition ranging from 19.26 to 94.07%. Analysis of the siderophore production by the ESI-MS and DHB(G) assays showed that CAS15 produced the catecholic siderophore 2,3-dihydroxybenzoate-glycine-threonine trimeric ester bacillibactin, and that siderophore productivity was inhibited by iron. A pot culture experiment was used to study the effects of B. subtilis CAS15 on pathogen development and plant growth. CAS15 reduced the incidence of Fusarium wilt in pepper significantly, by 12.5–56.9%, which indicated that B. subtilis CAS15 induced systemic resistance to Fusarium wilt in pepper. Iron supplementation reduced this biocontrol effect. There were significant differences in plant height at 14, 21, 28 and 40 days, with treated plants growing 27.24–54.53% taller than controls. B. subtilis CAS15 also enhanced the yield of pepper by shortening the time to 50 percent flowering to 17.26 days, increasing the average fruit weight 36.92%, and increasing the average yield per plant 49.68%. This research showed that B. subtilis CAS15 has great potential for plant growth promotion and biological control.

Possibilities of biological and chemical control of Verticillium wilt in pepper

In pathogen populations in Serbia, the incidence, pathogenic and morphological characters ofVerticillium spp. were studied. Biological and chemical control ofVerticillium was investigated in pepper plants (Capsicum annuum L. cv. ‘Soroksari’) with the biofungicide Polyversum® (Pythium oligandrum) and the conventional fungicides benomyl and propamocarb-hydrochloride. On the basis of macroscopic and microscopic characters of the isolates originating from eight localities in Serbia, it was established that they apparently belong to the speciesVerticillum dahliae. The isolates differed in their pathogenic characters. However, all of them caused marked wilting symptoms on pepper plants 40 days after inoculation, conducted when there were more than nine fully developed leaves on the primary stem. The fungicides were applied either before or after inoculation. Benomyl was the most efficient fungicide in wilt control (88.2% when applied after inoculation and 94.6% when applied before inoculation). Polyversum proved more efficient (66.6%) when applied before rather than after inoculation. Propamocarb-hydrochloride provided sufficient Verticillium wilt control; its efficacy and that of Polyversum were similar, and less efficient than benomyl, but still significantly different from the disease control.

Defence-related Enzymes in Pepper Roots During Interactions with Arbuscular Mycorrhizal Fungi and/or Verticillium dahliae

Previous studies have described that arbuscular mycorrhizal fungi (AMF) can reduce the deleterious effect of Verticillium dahliae Kleb. on pepper growth and yield. In mycorrhizal plants, the bioprotection against soil-borne pathogens can result from the preactivation of defence responses that include some structural modifications and the accumulation of Pathogenesis-Related (PR) proteins. Our first objective was to study if V. dahliae induced defence mechanisms in roots before infected pepper developed visible symptoms of disease. The second aim was to determine if AMF induced defence-related enzymatic activities in pepper roots before or after pathogen’s attack. Results showed that the colonization of pepper roots by Glomus deserticola (Trappe, Bloss and Menge) induced the appearance of new isoforms of acidic chitinases, superoxide dismutase (SOD) and, at early stages, peroxidases. In contrast, V. dahliae neither stimulated the phenylpropanoid pathway nor elicited hydrolytic activities in infected pepper roots. Only in mycorrhizal plants, the inoculation with V. dahliae slightly increased both phenylalanine ammonia-lyase (PAL) and peroxidase activities two weeks later. Mycorrhizal-specific induction of new isoforms of acidic chitinases and SOD together with enhanced peroxidase and PAL activities 2 weeks after pathogen inoculation could be involved in the biocontrol of Verticillium-induced wilt in pepper by AMF.

Verticillium-induced Wilt in Pepper: Physiological Disorders and Perspectives for Controlling the Disease

Verticillium-induced Wilt in Pepper: Physiological Disorders and Perspectives for Controlling the Disease

Partial Resistance of Pepper to Bacterial Wilt Is Oligogenic and Stable Under Tropical Conditions.

Genetic analysis of resistance of pepper to bacterial wilt was performed in the doubled haploid progeny from a cross between a resistant parental line PM 687 and a susceptible cultivar Yolo Wonder. After artificial inoculation with a local isolate of Ralstonia solanacearum, the progeny consisting of 90 lines was transplanted into a naturally infested field in Guadeloupe, Lesser Antilles. The 2 years of experimentation resulted in repeatable results, with a high heritability of the resistance, attesting the reliability of the evaluation procedure and the stability of the resistance over years. Two to five genes with additive effects were estimated to control the resistance, indicating an oligogenic control as observed in tomato sources of resistance. Relationships with resistance to other soilborne or tropical diseases were examined. Susceptibility to Tobacco mosaic virus (TMV) and to nematodes (Meloidogyne spp.) were significantly linked with resistance to bacterial wilt, whereas neither resistance to Phytophthora capsici nor to Leveillula taurica were linked. The similarity of the genetics of resistance to bacterial wilt in pepper and tomato and linkage with TMV resistance locus warrant the comparative mapping of the resistance quantitative trait loci in the genomes of the two species.

Moderate drought influences the effect of arbuscular mycorrhizal fungi as biocontrol agents against Verticillium-induced wilt in pepper

Previous studies have shown that the arbuscular mycorrhizal fungus (AMF) Glomus deserticola (Trappe, Bloss and Menge) can diminish the negative effect of Verticillium dahliae Kleb. on pepper yield. On the other hand, it is known that AMF can be more beneficial for plant growth and physiology under dry conditions than when soil moisture is plentiful. Therefore, our objective was to assess if a moderate water deficit imposed on pepper plants before their inoculation with V. dahliae could improve the effectiveness of G. deserticola as biocontrol agent. In the present experiment, the delay in disease development in Verticillium-inoculated plants associated with AMF did not occur under well watered conditions. In addition, the establishment of mycorrhizal symbiosis and the development of structures by AMF were delayed when both symbiotic and pathogenic fungi infected the same root. Therefore, it is suggested that the equilibrium between pepper plant, G. deserticola and V. dahliae is so complex that small changes in competition between symbiotic and pathogenic fungi for host resources can modify the efficiency of AMF as a biocontrol agent. On the other hand, water deficit enhanced the deleterious effect of V. dahliae on fruit set and yield only when pepper plants were not associated with G. deserticola, which reinforces the idea that AMF may be more important for host plants subjected to stressful conditions. However, comparing well watered non-mycorrhizal and predroughted mycorrhizal plants, we found that moderate water deficit imposed before inoculation with V. dahliae did not improve the effectiveness of G. deserticola as a biocontrol agent.

Changes in stem lignins (monomer composition and crosslinking) and peroxidase are related with the maintenance of leaf photosynthetic integrity during Verticillium wilt in Capsicum annuum.

• Verticillium dahliae is a soilborne pathogen that causes vascular wilt in pepper (Capsicum annuum var. annuum). Here we study to what extent changes in the lignification response of peppers condition tolerance of wilt. • For this, the quantum yield (ΦPSII ), the linear electron transport rate (ETR), and the lignification response (monomer composition and crosslinking) were studied in three C. annuum cultivars differing in degree of tolerance. • The results showed that in tolerant cultivars (Padrón and Yolo Wonder), both ΦPSII and ETR showed significantly higher levels at saturating photosynthetically active radiation values. This was not, however, the case for cv. Luesia, which showed a significant decrease in ΦPSII , ETR and nonphotochemical quenching values, suggesting that photochemical processes are strongly damaged in this cultivar as a consequence of the disease. The analysis of stem lignins in tolerant cultivars revealed that they were mainly composed of p-hydroxyphenyl units, while levels of β-O-4-linked coniferyl and sinapyl alcohols were significantly lower. • It is concluded that through the observed changes in stem lignins (monomer composition and crosslinking) peppers retard, since they maintain leaf photosynthetic integrity, but do not stop (since wilt symptoms are not avoided) V. dahliae fungal hyphae penetration.