Induced resistance in cotton seedlings against fusarium wilt by dried biomass of<Emphasis Type="Italic">Penicillium chrysogenum</Emphasis> and its water extract

Dry mycelium (DM) of killedPenicillium chrysogenum and its water extract (DME) were used to induce resistance in cotton plants againstFusarium oxysporum f.sp.vasinfectum (Fov). Results showed that the efficacy of either DM or DME in controlling the disease depends on both the concentration and the mode of application. DM amended to the soil at 0.25–2% (w/w) provided 32–75% protection againstFov. Soil drench with 2–5% DME (w/v) and pre-sowing seed soakage with 5–10% DME provided 51–77% and 28–35% protection against the wilt disease, respectively, whereas no protection was obtained with foliar sprays of 1–10% DME. DM and its water extract had no direct antifungal activity on growth ofFov in vitro, suggesting that disease control with DM or DME resulted from the induction of natural defense mechanisms in the cotton plants. Soil drench with 5% DME was as effective as 2% DM powder in inducing resistance againstFov, implying that the resistance-inducing substances were mostly water-soluble. Four cotton cultivars with various genetic resistance levels againstFov were tested at the seedling stage: two resistant ‘Pima’ cultivars and two susceptible ‘Acala’ cultivars. The level of protection achieved in the two susceptible cultivars with DME was equal to, or higher than, that of the two resistant cultivars treated with water. Innate and induced peroxidase activity in cotyledons or hypocotyls and roots coincided with the level of genetic resistance and DME-induced resistance, respectively. Based on our results, an integrated control strategy ofFov with both genetic resistance and induced resistance is suggested.     

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.     

黄瓜枯萎病拮抗菌的拮抗促生因子检测及生物效应研究

以黄瓜枯萎病病原菌,尖孢镰刀菌黄瓜专化型(FOC,Fusarium oxysporum f.sp.cucumerinum)为靶标筛选拮抗菌。通过初筛和复筛,获得2株对尖孢镰刀菌黄瓜专化型拮抗效果稳定、拮抗能力较强的细菌QHZ-Yb1和QHZ-Yb2(以下简称,Yb1和Yb2),采用平板对峙法测定其拮抗作用,抑菌带宽度达3.37 mm和3.42 mm,抑菌圈直径2.7 cm,抑菌率分别达到61.9%和62.3%;通过形态学结合生理生化及菌株的16S rDNA序列分析,初步确定这两株菌均为萎缩芽孢杆菌(Bacillus atrophaeus);潜在拮抗促生因子的测定结果表明:菌株Yb1和Yb2具有多种拮抗促生因子,其脂肽类粗提取物的抑菌率分别达到57.4%和58.0%,生长素IAA的分泌量可达1.56 mg·L~(-1)和3.69 mg·L~(-1),溶P量为0.77 mg·L~(-1)和1.19 mg·L~(-1),两个菌株均可产嗜铁素、分泌酪蛋白酶;种子萌发试验结果表明:Yb1和Yb2菌液均可促进黄瓜种子的萌发;菌株生物效应的盆栽试验结果表明:Yb1、Yb2以及Yb1+Yb2菌悬液的处理不仅对黄瓜枯萎病有明显的生防效果,而且可显著增加黄瓜植株的生物量,增加黄瓜植株根际土中细菌和放线菌的数量,减少真菌和尖孢镰刀菌的数量,尤其以Yb1+Yb2菌悬液的处理效果最显著,对黄瓜枯萎病的发病率降低11.11个百分点,植株生物量增加56.7%。结论:菌株Yb1和Yb2具有生防潜力,两菌株配合运用效果更好。     

Regeneration of vascular tissues in relation to Fusarium wilt resistance of carnation

Fusarium wilt-resistant Novada carnations responded both to stem inoculation with a conidial suspension ofFusarium oxysporum f. sp.dianthi orF. oxysporum f. sp.lycopersici and to root inoculation by planting in soil infected withF. oxysporum f.sp.dianthi by means of a localization mechanism comprising gel formation in the xylem vessels and hyperplasia of adjacent parenchyma cells. Dye translocation experiments showed that xylem transport was limited by the presence of vascular gels, although wilting did not occur. Overcapacity of the vascular system apparently allowed for sufficient water transport to compensate for local vascular dysfunction. Also, vascular regeneration in the hyperplastic tissue next to occluded xylem vessels created new pathways for water transport to compensate for those lost by occlusion. Regeneration of xylem vessels was eventually followed by regeneration of xylem fibers, xylem parenchyma, cambium, and phloem cells.Early Sam carnations, susceptible to Fusarium wilt, responded to stem inoculation withF. oxysporum f. sp.lycopersici by similar localization of infection and vascular regeneration. Stem inoculation withF. oxysporum f. sp.dianthi, however, resulted in colonization of the xylem vessels followed by lysis of the vascular tissues. Vascular gelation, hyperplasia of parenchyma cells, and vascular regeneration did generally not occur. However, if some hyperplasia occurred in attempted defence, some differentiation of hyperplastic cells into single xylem vessel elements was observed which only rarely resulted in complete vascular regeneration next to colonized xylem. In the absence of hyperplasia, differentiation of medulla parenchyma cells bordering destroyed vascular tissue into xylem vessel elements was even more exceptional. Apparently, vascular regeneration in carnation is a normal defence reaction to fungal invasion.Samenvatting Novada anjers, resistent tegen Fusarium-verwelkingsziekte, reageerden op stengelinoculatie met een conidiënsuspensie vanFusarium oxysporum f.sp.dianthi of vanF. oxysporum f.sp.lycopersici en op wortelinoculatie door te planten in metF. oxysporumf.sp.dianthi besmette grond met een lokalisatiemechanisme dat onder meer bestond uit vorming van gommen in de houtvaten en hyperplasie van naburige parenchymcellen. Uit proeven over kleurstoftransport bleek dat de sapstroom door de gomvorming beperkt werd, hoewel dit geen verwelkingssymptomen veroorzaakte. Overcapaciteit van het vaatstelsel zorgde kennelijk voor voldoende compensatie aan watertransport om plaatselijke verstoring van de sapstroom op te vangen. Daarnaast werd het verlies aan functionele houtvaten ook opgevangen door vaatweefselregeneratie in het hyperplastische weefsel grenzend aan door gommen verstopte houtvaten. Na verloop van tijd werden behalve houtvaten ook houtvezels, houtparenchymcellen, cambium- en floeemcellen geregenereerd.Early Sam anjers, vatbaar voor Fusarium-verwelkingsziekte, reageerden op stengelinoculatie metF. oxysporum f. sp.lycopersici met eenzelfde lokalisatiemechanisme en ook met vaatweefselregeneratie. Stengelinoculatie metF. oxysporum f.sp.dianthi echter had kolonisatie en vervolgens lysis van het vaatweefsel tot gevolg. Meestal trad er geen gomvorming, hyperplasie van parenchymcellen of vaatweefselregeneratie op. Als echter bij pogingen tot afweer toch enige hyperplasie optrad, bleken sommige hyperplastische cellen wel tot houtvatelementen te differentieren. Dit leidde echter maar zelden tot totale vaatweefselregeneratie parallel aan het gekoloniseerde vaatweefsel. In afwezigheid van hyperplasie differentieerden mergparenchymcellen vlak naast lyserend vaatweefsel slechts bij hoge uitzondering tot houtvatelementen. Vaatweefselregeneratie bij anjer is kennelijk een gewone afweerreactie op besmetting met pathogene schimmels.     

Rootstock resistance to Fusarium wilt and effect on watermelon fruit yield and quality

The potential of grafted watermelon for resistance toFusarium oxysporum f.sp.niveum on some Curcurbitaceae,Lagenaria, Luffa, Benincasa and commercial rootstocks was evaluated. Effects of grafting on yield and quality of diseased plants were evaluated. All grafted plants and rootstocks were resistant to the three known races (0, 1, and 2) ofF. oxysporum f.sp.niveum except watermelon cv. ‘Crimson Tide’, which was susceptible to race 2. Fruit yield was positively (21–112%) affected byLagenaria rootstocks but negatively affected (200–267%) byCucurbita rootstocks when compared with the control. While only minor differences in fruit quality were determined in control and grafted plants onLagenaria rootstocks, the quality parameters for watermelon grafted ontoCucurbita rootstocks were lower than in the control. The reasons for low yield and quality might be due to an incompatibility betweenCucurbita rootstocks and watermelon. These results showed that rootstock influence on disease resistance as well as yield and quality of scion fruit is important in determining the potential use of grafting applications in watermelon. http://www.phytoparasitica.org posting Feb. 2, 2003.     

Fusarium wilt on sweet basil: Cause and sources in southeastern Spain

This study concerned a new disease detected in 1997 in southeastern Spain — Fusarium wilt in basil (Ocimum basilicum L.), caused byFusarium oxysporum f.sp.basilici. Its importance was evaluated at two locations in the Almería area, where 14% of the plants presented symptoms of the disease after 4 months of cropping. The search for sources of the disease inoculum was centered on the health of the seeds and the polypropylene trays that were reused for plant production. Analysis of four lots of seeds from Germany and Italy showed that two of them harboredF. oxysporum f.sp.basilici. This finding was confirmed by the analysis of seeds collected from diseased plants. Furthermore, analysis of three reused trays revealed the presence of the pathogen on them and it was concluded that the trays acted as the source of dispersion of the mycosis. http://www.phytoparasitica.org posting July 14, 2004.     

Fusarium wilt of basil in Greece: Foliar infection and cultivar evaluation for resistance

Fusarium wilt of basil (Ocimum basilicum), caused byFusarium oxysporum f.sp.basilici, is reported for the first time in Greece. Foliage inoculation of young plants resulted in a downward movement of the pathogen to the crown and roots and 20–30% plant mortality. Of 14 commercial basil cultivars evaluated for possible disease resistance using young plants, six out of eight large-leaved cultivars were found resistant, while all six small-leaved ones were susceptible. http://www.phytoparasitica.org posting Feb. 23, 2004.     

Allelism of theFcu-1 andFoc genes conferring resistance to fusarium wilt in cucumber

The inheritance of resistance toFusarium oxysporum f.sp.cucumerinum race 1 was determined in the cucumber cv. WIS-248 by analyzing segregation of F₁, F₂, and BC populations of crosses with the susceptible cv. Straight-8. Resistance was conferred by a single dominant gene. In an allelism test, it was proven that theFcu-1 gene, which confers resistance toF. oxysporum f.sp.cucumerinum races 1 and 2 in cucumber cv. SMR-18 and theFoc gene, which confers resistance toF. oxysporum f.sp.cucumerinum race 2 in cucumber cv. WIS-248, are indistinguishable.     

Suppression of Fusarium wilt of spinach with compost amendments

The effect of different organic composts on the suppression of wilt disease of spinach caused by Fusarium oxysporum f. sp. spinaciae was evaluated in a continuous cropping system in both containers and in microplot field trials. Test soils infested with the pathogen were amended with wheatbran, wheatbran and sawdust, coffee grounds, chicken manure, or mixture of different composts with and without 5% (w/w) crab shell powder either once (5%, w/w) or continuously (2.5%) into the test soils infested with the pathogen. In the container trials, the soil amended with composts became suppressive to disease development on the second and third cropping. The suppressive effect was notable in the soil amended with the mixture of compost with and without crab shell powder. The coffee compost lowered soil pH but became suppressive to the disease after modifying the soil pH. In the field trial using the mixture of the different composts containing 5% crab shell powder, a combination of 5% before the first cropping and 2.5% every second cropping gave stable disease control and promoted plant growth. After compost amendment, populations of fungi, bacteria and actinomycetes as measured by dilution plate counting and the total microbial activity as evaluated by fluorescein diacetate hydrolysis increased and population of the pathogen gradually decreased. These phenomena were especially notable in soils amended with the mixture of different composts. These results indicate that diversity in the organic materials promotes higher microbial activity and population in the soil thereby enhancing disease suppressiveness.     

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.     

Two in vitro assays to evaluate resistance in Linum usitatissimum to Fusarium wilt disease

Two types of in vitro seedling tests were developed to evaluate resistance in flax (Linum usitatissimum) against Fusarium oxysporum f.sp. lini. In the first test a solid medium was used. The second test was based on a liquid medium. Disease severity was assessed after three weeks, using the observed reduction of plant length as a scale. Both methods proved to be useful for screening for resistance, for evaluating race specificity of resistance and for studying symptomatology. The solid medium method proved to be the more accurate for the screening, but the liquid medium method was much less time- and labour-consuming. The results of the tests were significantly correlated with observations under field conditions.     

Comparison of five stem inoculation methods with respect to phytoalexin accumulation and Fusarium wilt development in carnation

Five methods of stem inoculation of carnations with conidial suspensions ofFusarium oxysporum f.sp.dianthi were compared for uptake of the suspension, induction of phytoalexin accumulation and wilt development. Inoculation was performed by incision of the stem across droplets of inoculum placed on leaves, or by injection of droplets into the stem. With both methods, higher inoculum dosages led to higher wilting rates and higher phytoalexin concentrations. Injection was more effective than incision since a lower inoculum dosage was required to obtain the same phytoalexin levels. Injection therefore appears the most promising technique for the development of routine screening methods for resistance based on phytoalexin accumulation.Samenvatting Vijf methoden om anjers via de stengel te inoculeren met een sporensuspensie vanF. oxysporum f.sp.dianthi werden vergeleken wat betreft de opname van de suspensie, de accumulatie van fytoalexinen en het ziekteverloop. Inoculatie vond plaats door de stengel aan te snijden dwars door een druppel inoculum die op een blad was gelegd, of door druppeltjes inoculum te injecteren. Bij beide methoden leidden hogere doses inoculum tot heviger ziektesymptomen en accumulatie van grotere hoeveelheden fytoalexinen. Injectie van inoculum was effectiever dan aansnijden, daar er minder inoculum nodig was voor eenzelfde resultaat. Injectie biedt daarom meer perspectief voor de ontwikkeling van routinematige resistentietoetsen op basis van de accumulatie van fytoalexinen.     

Fusarium wilt of banana: biology,epidemiology and management

Fusarium oxysporum is a soil borne hyphomycete that causes vascular wilts in several crop plants. A variety of remedial measures such as the use of fungicides, soil amendments and biological antagonists have proved insufficient in controlling F. oxysporum. Ever since it was first reported in banana crop, the only effective control strategy known is planting of resistant cultivars. However, presumably due to the high mutation rates and rapid co-evolution with its host, Fusarium wilt has surmounted host defense barriers and has already begun infecting even the resistant Cavendish varieties that dominate export markets worldwide. Transgenic banana plants showing enhanced resistance to Fusarium wilt have been developed in recent past, but they remain largely confined to the laboratory. The importance of banana as source of food and income in developing countries world over and the need to develop Fusarium wilt tolerant cultivars by novel biotechnological approaches is detailed herein. In this communication, we review the biology and management of Fusarium wilt in banana with the aim of providing the baseline of information to encourage much needed research on integrated management of this destructive banana crop disease problem.     

万寿菊根的提取物对西瓜枯萎病反应的抗性研究

 本文研究了万寿菊根的提取物对西瓜枯萎病菌和西瓜幼苗的影响。结果表明,万寿菊根的提取物对供试的西瓜枯萎病菌菌丝生长有明显的抑制作用;同时,经对西瓜幼苗根和叶的酶活性测定和过氧化物同工酶电泳分析的结果表明,该提取物能诱导西瓜保护酶如超氧化物歧化酶(SOD)和过氧化物酶(POD)活性提高,减轻西瓜枯萎病菌粗毒素对西瓜幼苗的毒害作用。     

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.     

Siderophore-mediated competition for iron and induced resistance in the suppression of fusarium wilt of carnation by fluorescent Pseudomonas spp

The mechanisms of suppression of fusarium wilt of carnation by two fluorescentPseudomonas strains were studied.Treatments of carnation roots withPseudomonas sp. WCS417r significantly reduced fusarium wilt caused byFusarium oxysporum f. sp.dianthi (Fod). Mutants of WCS417r defective in siderophore biosynthesis (sid^–) were less effective in disease suppression compared with their wild-type. Treatments of carnation roots withPseudomonas putida WCS358r tended to reduce fusarium wilt, whereas a sid^– mutant of WCS358 did not.Inhibition of conidial germination of Fod in vitro by purified siderophores (pseudobactins) of bothPseudomonas strains was based on competition for iron. The ferrated pseudobactins inhibited germination significantly less than the unferrated pseudobactins. Inhibition of mycelial growth of Fod by bothPseudomonas strains on agar plates was also based on competition for iron: with increasing iron content of the medium, inhibition of Fod by thePseudomonas strains decreased. The sid^– mutant of WCS358 did not inhibit Fod on agar plates, whereas the sid^– mutants of WCS417r still did. This suggests that inhibition of Fod by WCS358r in vitro was only based on siderophore-mediated competition for iron, whereas also a non-siderophore antifungal factor was involved in the inhibition of Fod by strain WCS417r.The ability of thePseudomonas strains to induce resistance against Fod in carnation grown in soil was studied by spatially separating the bacteria (on the roots) and the pathogen (in the stem). Both WCS417r and its sid^– mutant reduced disease incidence significantly in the moderately resistant carnation cultivar Pallas, WCS358r did not.It is concluded that the effective and consistent suppression of fusarium wilt of carnation by strain WCS417r involves multiple mechanisms: induced resistance, siderophore-mediated competition for iron and possibly antibiosis. The less effective suppression of fusarium wilt by WCS358r only depends on siderophore-mediated competition for iron.     

Development of Fusarium Wilt-resistant Genotypes in Safflower (Carthamus tinctorius)

Screening of 51 promising safflower germplasm lines in Fusarium wilt-infested plots resulted in identification of highly wilt-resistant selections viz., 86-93-36A, 237550, VI-92-4-2 and II-13-2A, with some moderate resistance in HUS-305. Progenies from crosses made using these resistant lines were tested for their reaction to wilt. F₁ progenies from 86-93-36A × 237550 and 86-93-36A × II-13-2A recorded zero wilt incidence, while 237550 × 86-93-36A was highly resistant to the Rajendranagar geographical isolate. The reaction for the three progenies showed stability for wilt resistance with no segregation until the F₇ generation. Geographical isolates of Fusarium oxysporum f. sp. carthami (Foc) were collected from different safflower growing regions and tested for their pathogenic variability on six host differentials under glasshouse conditions. Based on the reaction of the differentials, the Foc isolates were grouped into four biotypes. The three resistant progenies were tested for their reaction to the four biotypes. The progeny of cross 86-93-36A × 237550 showed an immune reaction to all the biotypes, except for a highly resistant reaction to biotype 3. The progenies of the two other crosses (86-93-36A × II-13-2A and 237550 × 86-93-36A) exhibited immune reactions to biotypes 2,3 and 1,3, respectively, and were highly to moderately resistant to biotypes 1,4 and 2,4, respectively.     

土壤施加氧化钙对西瓜枯萎病的影响及其机理初探

为探明土壤撒施石灰对西瓜枯萎病发生的影响,本试验设计5个浓度剂量的氧化钙对连作西瓜5年的土壤进行消毒处理,通过栽培感病品种并调查植株生长情况、枯萎病发病率等指标,结合土壤中尖孢镰刀菌西瓜专化型1号小种病原菌孢子量和土壤pH的变化动态,以此评估土壤施加石灰防治西瓜枯萎病的效果,并利用不同浓度的钙对尖孢镰刀菌西瓜专化型菌丝生长和产孢量的影响进行防治机理的初步研究。试验结果表明,当土壤施加氧化钙后,西瓜发病率显著降低,各处理的相对防效分别为14%、57.8%、96.3%、94.7%、94.7%。在定植10d后,各处理均有促进植株生长发育的作用,其中1.34g/kg最显著。而随着氧化钙施加量的增加,土壤pH值也不断提高,30d趋于稳定。对土壤病原菌孢子数量检测表明:各处理土壤中病原菌数量均呈现显著降低的趋势。PDA平板生测结果表明,当钙离子浓度高于80mmol/L时,病原菌的生长及产孢量开始受到抑制,随着浓度的增加,抑制作用加强。土壤施加氧化钙不仅能改善土壤的酸化,还能有效防控西瓜枯萎病,其机理可能是土壤pH值的提高改变了土壤微环境,不利于病原菌侵染;施加的钙离子抑制了病原菌菌丝的生长及孢子的萌发。研究结果对揭示氧化钙防控西瓜枯萎病机制,具有一定的参考价值。     

不同品种香蕉抗枯萎病效果及抗性生理研究

通过盆栽试验研究了向土壤中接种尖孢镰刀菌古巴专化型4号生理小种(FocTR4)后不同抗枯萎病香蕉品种发病率、根际可培养微生物及防御酶活性的变化。结果表明:试验处理中香蕉枯萎病发病率随着FocTR4接种浓度的增加而上升,但在相同浓度处理下,抗病品种发病率显著低于感病品种;各品种香蕉发病率与根际土壤可培养镰刀菌数量均呈显著正相关关系。抗病品种过氧化物酶(POD)、几丁质酶和β-1,3-葡聚糖酶活性高于感病品种,而与多酚氧化酶(PPO)、苯丙氨酸解氨酶(PAL)活性存在一定的相关性。说明香蕉抗病性与香蕉根际土壤微生物群落结构及香蕉本身防御酶活性有关。     

Effect of antagonistic<Emphasis Type="Italic">Fusarium</Emphasis> spp. and of different commercial biofungicide formulations on Fusarium wilt of lettuce

Five experimental trials were carried out to test different biological control agents against Fusarium wilt of lettuce, cause byFusarium oxysporum f.sp.lactucae. In the presence of a very high disease incidence, the best results in terms of disease control as well as increased growth response were shown byTrichoderma harzianum T 22 (RootShield), which, at 3 gl ⁻¹ of substrate, provided very consistent results.F. oxysporum IF 23 gave good disease control but in two out of five trials reduced the biomass produced. Less consistent, but still significant results were provided byF oxysporium MSA 25, at 3 gl ⁻¹ of substrate, and byTrichoderma viride TV 1. The twoF. oxysporum agents Fo 251/2 and Fo 47 and the mixture ofT. harzianum + T. viride (Remedier) partially reduced disease incidence but were less effective than the above mentioned. Less interesting results were offered byStreptomyces griseoviridis (Mycostop). The results obtained show that biological control can play a role in the management of Fusarium wilt of lettuce.