Induced resistance in tomato plants against Fusarium wilt invoked by Fusarium oxysporum f.sp. dianthi

Tomato plants, susceptible toFusarium oxysporum f. sp.lycopersici, were inoculated by immersing the roots in a conidial suspension ofF. oxysporum f. sp.lycopersici race 1,F. oxysporum f. sp.dianthi race 2 or a mixture of both fungi. Plants inoculated withF. oxysporum f. sp.lycopersici showed disease symptoms after 2 weeks, whereas plants inoculated withF. oxysporum f. sp.dianthi or a mixture of both fungi remained symptomless for over 7 weeks, the duration of the experiment. In another experiment root systems of plants were split and each half was separately inoculated. One half was firstly inoculated withF. oxysporum f. sp.dianthi or treated with water, followed after a week by a second inoculation of the other half withF. oxysporum f. sp.lycopersici or by a water treatment. The disease symptoms in the half firstly inoculated withF. oxysporum f. sp.dianthi were significantly delayed, compared to plants of which that half had been treated with water. BecauseF. oxysporum f. sp.dianthi reduced disease symptoms caused byF. oxysporum f. sp.lycopersici without any direct interaction with this pathogen, it is concluded thatF. oxysporum f. sp.dianthi is able to induce resistance againstF. oxysporum f. sp.lycopersici in tomato plants.     

Predictive factors for the suppression of fusarium wilt of tomato in plant growth media

ABSTRACT Fusarium wilts are economically important diseases for which there are no effective chemical control measures. However, biological control and fertility management are becoming efficient alternatives for controlling this disease. Growth media formulated with composts that are able to suppress Fusarium wilt of tomato provide a control system that integrates both strategies. The aim of this study was to predict Fusarium wilt suppression of growth media using abiotic and biotic variables. Grape marc compost was the most effective medium used to suppress Fusarium wilt. Cork compost was intermediate, and light peat and expanded vermiculite were the most conducive growth media. The growth media evaluated were in a pH range of 6.26 to 7.97. Both composts had high beta-glucosidase activity. When pH and beta-glucosidase activity were taken into account as predictive variables, more than 91% of the variation in severity of Fusarium wilt was explained. This relationship illustrates the effect of nutrient availability and the degree of microbiostasis, two key factors in this pathosystem. Microbial populations involved in suppressiveness were cellulolytic and oligotrophic actinomycetes, fungi, and the ratios cellulolytic actinomycetes/cellulolytic bacteria, oligotrophic bacteria/copiotrophic bacteria, and oligotrophic actinomycetes/oligotrophic bacteria. Based on community level physiological profiles, different community structures were evident among growth media evaluated.     

A rapid laboratory method for assessing the biological control potential of Penicillium oxalicum against Fusarium wilt of tomato

A rapid, simple and reliable procedure was developed to evaluate biological control of Fusarium wilt of tomato by Penicillium oxalicum . The method consists in growing tomato plants in flasks with nutrient solution in a growth chamber. Plants were previously treated in the seedbed with a conidial suspension (10⁷ conidia mL⁻¹) of P. oxalicum 7 days before transplanting. Fusarium oxysporum f.sp. lycopersici (race 2) was added to the Hoagland solution just before transplanting. Different concentrations and several isolates of F. oxysporum f.sp. lycopersici were tested. Using this method, plants showed typical symptoms of the disease and the effect of the biocontrol agent was clear. Consumption of nutrient solution was reduced in diseased plants, and this reduction was diminished by treatment with P.oxalicum . Consumption of nutrient solution was correlated with other disease-related parameters (AUDPC, weight of aerial parts, stunting) and was an easy and objective parameter to measure.     

Extracts of killedPenicillium chrysogenum Induce resistance against Fusarium wilt of melon

Dry fungal biomass ofPenicillium chrysogenum (dry mycelium), a waste product of the pharmaceutical industry, was extracted with water and applied to the roots of melon plants before or after inoculation withFusarium oxysporum f.sp.melonis (Font). Seedlings (4–6 days after emergence) treated with either acidic dry mycelium extract (DME) or neutralized dry mycelium extract (NDME) were protected against challenge infection withFom. A single drench with 2–5% DME applied 12–72 h before inoculation provided significant control of the disease compared with water-drenched, challenged seedlings. No protection was seen in plants treated 0–6 h before inoculation or 0–48 h after inoculation. Neither DME nor NDME (0.5–5%) had any effect on fungal growthin vitro, which implied that disease controlin vivo was mediated by induced resistance. The resistance induced by DME protected melon plants not only against race 1,2, but also against the three other races of the pathogen, indicating a race-non-specific resistance againstFom. Both DME and NDME significantly increased peroxidase activity and free L-proline content in seedlings 12 h and 48 h after soil drench, respectively. Resistance to Fusarium wilt was significantly associated with elevated levels of peroxidase activity but not with free L-proline content. Thus, peroxidase might be involved in the defense mechanisms activated by DME or NDME. http://www.phytoparasitica.org posting Aug. 31, 2001.     

An electron microscope study of tomato spotted wilt virus in the plant cell

Characteristic particles of about 70 m diameter were found in tomato spotted wilt virus (TSWV) infected cells of roots, stems, leaves and petals of several plant species. These particles were similar in size and form to those found in the pellets of partially purified infective TSWV.     

Efficacy of bacterial antagonists and different commercial products against Fusarium wilt on rocket

Seven experimental trials were carried out to evaluate the efficacy of the bacterial strains Achromobacter xylosoxydans AM1 and Serratia sp. DM1 obtained from suppressive soils and from soilless used rockwool substrates (Pseudomonas putida FC6B, Pseudomonas sp. FC7B, Pseudomonas putida FC8B, Pseudomonas sp. FC9B and Pseudomonas sp. FC24B) against Fusarium wilt on rocket caused by Fusarium oxysporum ff. spp. raphani and conglutinans. Along with these strains, two commercial bioproducts (RootShield—Trichoderma harzianum T22; Cedomon—Pseudomonas chlororaphis MA342) were also tested. Different application strategies such as soil treatment (trials I to VI; 10⁷ and 10⁸ CFU ml⁻¹) and root dipping (trial VII; 10⁸ and 10⁹ CFU ml⁻¹) were performed in a glasshouse in order to test the efficacy of the bacterial strains against Fusarium oxysporum ff. spp. raphani and conglutinans. The lowest disease incidence (16.7%) was observed with the application of Achromobacter sp. AM1, Serratia sp. DM1 at 10⁸ CFU ml⁻¹ and Pseudomonas sp. FC9B at 10⁷ CFU ml⁻¹ against F. oxysporum f. sp. conglutinans (experiment I). Maximum plant biomass (5.0 g/plant) was registered in Serratia sp. DM1 at 10⁸ CFU ml⁻¹ treated plants in trial IV. The trials against F. oxysporum f. sp. raphani (experiment II) showed that the application of Pseudomonas sp. FC7B, P. putida FC8B at 10⁸ CFU ml⁻¹ and P. chlororaphis MA342 at 7.5 × 10⁶ CFU ml⁻¹ significantly reduced disease incidence to values ranging between 87% and 92%. The highest plant biomass was recorded with the application of Achromobacter sp. AM1 and P. putida FC6B at 10⁷ CFU ml⁻¹ (3.9 to 4.2 g) carried out 7 days before the artificial inoculation of the pathogens (trial IV). The present study showed the potential biocontrol activity of the bacterial strains Achromobacter sp. AM1, Serratia sp. DM1 and Pseudomonas sp. FC9B against F. oxysporum f. sp. conglutinans and of Pseudomonas sp. FC7B, P. putida FC8B, P. chlororaphis MA342, Achromobacter sp. AM1 and P. putida FC6B against F. oxysporum f. sp. raphani. Growth-promoting activity of biocontrol bacteria used during the trials was observed.     

Suppressive effect of secondary metabolites from Streptomyces plumbeus isolate F31D against Fusarium oxysporum f. sp. lycopersici,the causal agent of Fusarium wilt of tomato

Journal of General Plant Pathology - Fusarium wilt of tomato, a disease caused by the soilborne fungus Fusarium oxysporum f. sp. lycopersici, causes major losses to tomato production. Chemical...     

Carnation Fusarium wilt suppression in four composts

Fusarium wilt is now a major disease of carnation crops worldwide. Methyl bromide, which is used to remedy it, is environmentally unsafe. An alternative approach integrated into biological control is to grow crops in suppressive media. Suppressiveness of seven plant growth media to Fusarium oxysporum f. sp. dianthi was evaluated in bioassays with carnation (Dianthus cariophyllus) cv. Medea. These media were: (1) grape marc compost, (2) cork compost, (3) olive oil husk + cotton gin trash composted and mixed with rice husk, (4) spent mushroom compost mixed with peat, (5) coir fibre, (6) light peat and (7) vermiculite. In order to look for carnation Fusarium wilt suppressiveness indicators, growth medium pH and β-glucosidase activity were evaluated. Furthermore, F. oxysporum populations were measured in plant growth media at the beginning and end of bioassays. The compost media showed a range of suppressiveness in comparison with peat. Grape marc compost was the most effective plant growth medium in suppressing carnation Fusarium wilt. On the other hand coir fibre, peat and vermiculite were conducive for this disease. β-glucosidase activity and pH were positively correlated with disease severity as in other reports for tomato. Therefore, these two parameters are good indicators for carnation Fusarium wilt suppressiveness, and possibly for other F. oxysporum pathosystems. All composts showed similar F. oxysporum populations at the end of the bioassays to peat and vermiculite.     

Activation of tomato plant defence responses against bacterial wilt caused by Ralstonia solanacearum using DL-3-aminobutyric acid (BABA)

In this study, we investigated the ability of DL-3-aminobutyric acid (BABA) to protect tomato against bacterial wilt caused by Ralstonia solanacearum. This was combined with studies of accumulation of total phenolic compounds, free and total salicylic acid (SA), and activity of enzymes related to plant defence, i.e., polyphenol oxidase (PPO) and catalase (CAT). Under greenhouse conditions, tomato plants pre-treated by soil drenching with BABA profoundly reduced disease severity of bacterial wilt compared to plants receiving a soil drench with water. Thus, BABA reduced leaf wilting index by 75.3 % and vascular browning index by 69.9 %, without any in vitro inhibitory activity on the pathogen. BABA treatment significantly reduced the population of R. solanacearum in stems of tomato plants and additionally also significantly increased both fresh and dry weight of roots and shoots of tomato plants compared with the inoculated control. Application of BABA resulted in a high increase in PPO activity both in plants with and without inoculation. Compared to water-treated plants, treatment with BABA also induced a significant increase of total phenolic compounds as well as of free and total SA in leaves of both inoculated and non-inoculated tomato plants at all sampling times. CAT activity decreased in tomato plants treated with BABA in comparison with the water-treated control plants and the decrease in activity correlated with an increasing total SA accumulation. These findings suggest that BABA treatment resulted in induction of resistance to bacterial wilt in tomato.     

北京辣椒和番茄上番茄斑萎病毒的鉴定

北京大兴区某蔬菜种植基地的辣椒和番茄发现疑似病毒感染,造成较大经济损失.经症状分析和RT-PCR检测,证实其感染番茄斑萎病毒(tomato spotted wilt virus,TSWV).基于TSWV序列特征对该地区TSWV进化及来源进行分析,结果显示其与北京顺义区已经报道TSWV毒株进化关系较近,但较国内其他地区株...     

Resistance-breaking tomato spotted wilt orthotospovirus isolates on resistant tomato in Serbia

Journal of Plant Diseases and Protection - The most effective management strategy for tomato spotted wilt orthotospovirus (TSWV) has been the use of resistant tomato (Sw-5b+) cultivars....     

Bacillus subtilis as an alternative biologically based strategy for controlling Fusarium wilt disease in tomato: A histological study

The employment of formulateBacillus subtilis as a biocontrol agent successfully controlledFusarium oxysporum f.sp.lycopersici within tomato seedlings (in vivo). B. subtilis was able to proted cortex and vascular tissues of tomato against progression of the wilt pathogen. No changes were observed in tomato tissues due to application ofB. subtilis except for hypertrophy and elongation of cortex tissues, which indicates the production of plant growth hormones byB. subtilis.     

Effects of timing and method of application of Penicillium oxalicum on efficacy and duration of control of Fusarium wilt of tomato

The effects of timing and method of application of Penicillium oxalicum on the control of fusarium wilt of tomato were investigated. Application of P. oxalicum to tomato seedlings in seedbeds reduced disease caused by Fusarium oxysporum f.sp. lycopersici in a growth chamber by 45–49% and in glasshouse experiments by 22–69%. Disease suppression was maintained for 60–100 days after inoculation with the pathogen in the glasshouse. No disease reduction was observed in tomato plants where P. oxalicum was applied to seeds. Treatment with P. oxalicum did not affect the population of F. oxysporum f.sp. lycopersici in the rhizosphere.     

Control of Fusarium wilt in banana with Chinese leek

The inhibitory effects of Chinese leek (Allium tuberosum) on Fusarium oxysporum f. sp. cubense (Foc) and on Fusarium wilt incidence were studied in order to identify a potential efficient way to control the disease. Adopting the rotation system of Chinese leek-banana reduced the Fusarium wilt incidence and disease severity index by 88?C97?% and 91?C96?%, respectively, and improved the crop value by 36?C86?%, in an area heavily infested by Foc between 2007 and 2009. As a result of inoculation in the greenhouse, Chinese leek treatment reduced disease incidence and the disease severity index by 58?% and 62?%, respectively in the variety Baxi (AAA) and by 79?% and 81?%, respectively in the variety Guangfen NO.1 (ABB). Crude extracts of Chinese leek completely inhibited the growth of Foc race 4 on Petri dishes, suppressed the proliferation of the spores by 91?% and caused 87?% spore mortality. The findings of this study suggest that Chinese leek has the potential to inhibit Foc growth and Fusarium wilt incidence. This potential may be developed into an environmentally friendly treatment to control Fusarium wilt of banana.     

Effect of calcium nutrition on resistance of tomato against bacterial wilt induced by Ralstonia solanacearum

This study investigated the effect of calcium nutrition on tomato bacterial wilt caused by Ralstonia solanacearum and the regulation of resistance mechanisms. Plants cultured in nutrient solution with calcium concentrations of 0.5, 5.0, and 25.0 mM, were inoculated with R. solanacearum by the root dip method. Severity of disease development, Ca concentration in tomato root and shoot tissues, hydrogen peroxide (H₂O₂) concentration, peroxidase (POD, EC 1.11.1.7) and polyphenol oxidase (PPO, EC 1.10.3.2) in tomato leaves were analyzed. Disease severities of low, medium and high Ca treatments were 100 %, 77.1 % and 56.8 % respectively. Plant growth in high Ca treatment was significantly better than those in low Ca treatment in height, stem diameter and biomass. Tomato plants absorbed significantly more Ca in roots and shoots as the level of Ca in the nutrient solution increased. In addition, H₂O₂ level in high Ca treatment rose faster and reached a higher peak with 10.86 μM gFW^?1(31.32 % greater than medium Ca plants). The activities of POD and PPO also have a greater increase in high Ca treatment with 99.09 U gFW^?1 and 107.24 U gFW^?1 compared to 40.70 U gFW^?1 and 77.45 U gFW^?1 in low Ca treatment. A negative correlation was found between Ca concentration, level of H₂O₂, POD, PPO in tomato, and disease severity, indicating that they played an important role in resistance of tomato to this disease. These results suggested that Ca was involved in the regulation of H₂O₂ concentration, and activity of POD and PPO in tomato.     

Effect of ammonium/nitrate ratio in nutrient solution on control of Fusarium wilt of tomato by Trichoderma asperellum T34

The behaviour of Fusarium oxysporum f.sp. lycopersici (Fol) and the effectiveness of the microbial control agent Trichoderma asperellum strain T34 were examined in hydroponically grown tomato plants under five ammonium/nitrate ratios. The results showed that disease severity was reduced by the action of T34 under increasing concentrations of ammonia. Furthermore, rhizosphere F. oxysporum populations decreased with T34 application. The presence of T34 augmented leaf nitrogen concentration in treatments infested with Fol. In addition, T34 application reduced iron concentration in tomato leaves at high ammonium/nitrate ratios and reduced the severity of Fusarium wilt at high iron and nitrogen leaf concentrations.     

Epidemiology of Fusarium wilt in cyclamen in an ebb and flow system

Introduction ofFusarium oxysporum f. sp.cyclaminis either into the nutrient solution or into the potting soil, did not result in noticeable spread of disease in a cyclamen crop grown in pots on tables of an ebb and flow system. Immediately after its introduction, only a small amount of the inoculum was detected in the soil in the pots and in the nutrient solution flowing onto the tables.Study of the epidemiology of the disease, after introduction of the pathogen into the system, revealed a mechanical process. Within 24 hours the amount of cfu found in the out-flowing nutrient solution and halfway down the container was sharply reduced. After 5–7 days few cfu could be detected. On the contrary on the bottom of the containers the fungus was observed in increasing amounts. In the system used the spores of the fungus settled down and were not transported during floods.Samenvatting Bij cyclamenteelt op een eb-vloed-systeem werd, na introductie vanF. oxysporum f.sp.cyclaminis via de voedingsoplossing of via de grond in de potten, vrijwel geen verspreiding van het pathogeen gevonden. In vrij korte tijd na de introductie werd in de uitstromende voedingsoplossing en in de potgrond slechts een zeer gering gedeelte van de oorspronkelijk geïntroduceerde hoeveelheidFusarium teruggevonden.Bij onderzoek omtrent de epidemiologie van de ziekte na introductie in het syssteem waren op verschillende plaatsen na 24 uren slechts zeer geringe hoeveelheden en na 5–7 dagen vrijwel geenFusarium aantoonbaar. Daarentegen werden op de bodem van de voorraadtanks in toenemende mate grote hoeveelhedenFusarium aangetroffen. In het gebruikte systeem bezonken de sporen en werden niet meegevoerd tijdens de vloed.Seconded to the Research Station for Floriculture (PBN), Linnaeuslaan 2A, 1431 JV Aalsmeer, the Netherlands.