玉米线虫矮化病病原鉴定

为明确东华北春玉米区暴发的一种危害严重、引起玉米植株矮化的新病害病原,从病区采集大量病株及其根际土壤,采用室内人工接种的方法对分离频率最高的3种镰孢菌,即亚粘团镰孢菌Fusarium subglutinans、拟轮枝镰孢菌F.verticillioides和层出镰孢菌F.proliferatum及线虫(群体)进行致病性测定。结果表明:有线虫(群体)的处理能够引起该病害典型症状,即植株矮化,叶片上有沿叶脉方向的黄色或白色失绿条纹,茎基部组织从内向外呈纵向或横向开裂,推断该病的发生和线虫有关。将回接发病植株病土中分离的矮化线虫属Tylenchorhynchus sp.、短体线虫属Pratylenchus sp.、发垫刃线虫属Trichotylenchus sp.、拟盘旋线虫属Pararotylenchus sp.、小环线虫属Criconemella sp.、垫刃线虫属Tylenchus sp.、丝尾垫刃线虫属Filenchus sp.、螺旋线虫属Helicotylenchus sp.和真滑刃线虫属Aphelenchus sp.进行分属后再回接,只有发垫刃属线虫的处理出现与田间发病症状一致的植株。综合形态特征、致病力和分子序列分析结果,确定该病病原为长岭发垫刃线虫T.changlingensis,并将该病害称为玉米线虫矮化病(maize nematode stunt disease)。     

A solar collector for soil disinfestation

A solar collector to be used for disinfestation of substrates for plant propagation is described. At a high solar radiation intensity (more than 1 cal cm^–2 min^–1), one day of treatment was sufficient for disinfestation of soil infested withSclerotium rolfsii, Sclerotinia sclerotiorum, Fusarium solani f.sp.phaseoli orPythium aphanidermatum.Treatment of soil in the solar collector strongly reduced the total numbers of fungi, bacteria and actinomycetes. The nutrient status of the soil was only slightly changed and did not result in an effect on plant growth.     

Evaluation of several antagonists and different methods of application against fusarium wilt of carnation1

Saprophytic Fusarium strains, isolated from Fusarium-suppressive soils, have been tested in pot and glasshouse experiments in order to reduce soil colonization by Fusarium oxysporum f.sp. dianthi. The highest amount of antagonist inoculum tested (200 g m^-2) showed the best results in controlling carnation wilt. The antagonistic Fusarium strains showed good efficacy when applied by dipping rooted cuttings in conidial suspensions of the antagonists or by mixing inoculated wheat kernels or perlite + wheat bran with the soil. The effectiveness of the antagonistic Fusarium strains in reducing incidence of F.o. f.sp. dianthi was improved by combining chemical (benomyl, 20 g m^-2) with biological measures.     

药剂和森林腐殖土防治落叶松幼苗立枯病的效果分析

本文报道了在辽阳地区土壤条件下,用化学药剂防治松苗立枯病(Rhizoctonia solaniKühn,Fusarium sp.)效果不明显、而施入森林腐殖土防治该病取得了极显著效果。方法是将森林腐殖土按每平方米苗床10千克用量与苗床10公分表上掺拌均匀。防病原因是:1.腐殖土中含有大量菌根菌,该菌与苗根形成菌根,有利于水分及无机盐类的吸收、利用。菌根菌又有抑制立枯病菌的作用;2.增加了土壤中有机质及N、P、K的含量,苗木生长健壮,提高了抗病能力。     

芝麻枯萎病病原菌致病力室内鉴定方法

 芝麻枯萎病(Sesame Fusarium wilt, SFW)是由尖孢镰刀菌芝麻专化型(Fusarium oxysporum Schl. f. sp. sesami (Zap.), FOS)引起的一种土传真菌病害, 是世界芝麻生产上的主要病害之一。为测定FOS致病力, 本文选用郑芝98N09等4个芝麻品种, 在苗期对15个FOS菌株的致病力强弱进行了室内鉴定和评价。结果表明, 采用1×10⁶个/mL分生孢子悬浮液与无菌蛭石和无菌土壤按V1∶V2∶V6比例混合接菌(即最终接菌浓度为1.4×10⁵孢子/g土壤), 在接菌后第7 d幼苗开始出现枯萎病症状, 调查菌株致病性的最佳时间为接菌后第25 d~28 d;在供试15个FOS菌株中, 对4个品种均表现为强致病力的菌株有8个(DI>50), 均表现为弱致病力的菌株有5个(DI<20);不同芝麻品种对不同菌株的抗性有一定差异。该方法可应用于芝麻枯萎病病原菌致病性测定和芝麻种质抗枯萎病特性评价, 并为后续的机理研究提供了技术支持。     

Differential interactions between strains of Rhizorhapis,Sphingobium, Sphingopyxis or Rhizorhabdus and accessions of Lactuca spp. with respect to severity of corky root disease

Over 100 isolates of Rhizorhapis suberifaciens, Sphingobium (Sb.) sp., Sb. mellinum, Sb. xanthum, Rhizorhabdus sp., and Sphingopyxis sp. (Sphingomonodaceae) were tested for pathogenicity on lettuce (Lactuca sativa) cultivars Salinas and Green Lakes, susceptible and resistant, respectively, or their resistant descendent breeding line (B.L.) 440‐8, to R. suberifaciens type strain CA1^T. Rhizorhabdus sp. CA15 and NL2, R. suberifaciens CA3, and Sphingopyxis CA32 were equally virulent to Green Lakes or B.L. 440‐8 and Salinas. Over 40 accessions from four Lactuca species were tested for resistance to R. suberifaciens CA1^T/CA3 or Rhizorhabdus sp. CA15/NL2. All lettuce accessions with resistance to CA1^T were susceptible to isolates CA15, NL2 and/or CA3. None of the Lactuca lines were highly resistant to all four isolates. There was a significant differential interaction between eight Lactuca lines and ten isolates of Rhizorhapis and related genera with respect to corky root severity. Three strains of isolates were distinguished: (i) isolates with a similar virulence pattern as R. suberifaciens CA1^T, (ii) isolates with a virulence pattern similar to that of R. suberifaciens CA3 and Sphingopyxis sp. CA32, and (iii) isolates of Rhizorhabdus being moderately aggressive to all Lactuca lines. Thus, strains belonging to several genera can cause similar symptoms (a rare phenomenon) but have different virulence patterns on Lactuca species and cultivars.     

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.     

Soil receptivity toFusarium solani f. sp.pisi and biological control of root rot of pea

Potential antagonists ofFusarium solani f. sp.pisi (Fsp) were selected from soil samples with varying degrees of receptivity to this pathogen. They were tested against Fsp isolate 48 (Fs48), in increasingly complex systems. Most species testedin vitro were able to antagonize Fs48. No relation could be establishedin vitro between the receptivity of the soil from which an isolate originated and its antagonism to Fs48. In soils naturally infested with pea root rot pathogens, which were stored humid at 4°C for a period longer than a year, various isolates ofFusarium, Gliocladium andPenicillium spp. were able to reduce root rot. After sterilization of these soils, onlyGliocladium roseum isolates, added at 10⁵ conidia g^–1 dry soil, significantly reduced disease severity and prevented root weight losses caused by Fs48 at 10⁴ conidia g^–1 dry soil. In soils in which the biota were activated by growing peas before the assays, doses of 10⁶ and 10⁷ ofG. roseum were required to reduce root rot. In these soils, the antagonistic effects of fluorescent pseudomonad strains from soil of low receptivity to Fsp were variable. Some strains of fluorescent pseudomonads, from soil moderately receptive to Fsp and from highly infested soils, were also able to reduce root rot. Disease suppression by pseudomonad strains was more evident in the absence than in the presence ofAphanomyces euteiches in the root rot pathogen complex. The role of receptiveness of the soil with regard to potential antagonists is discussed.     

Control of Fusarium oxysporum f. sp. cucumerinum of cucumbers by soil solarization with impermeable plastics and/or reduced doses of methyl bromide*

Soil solarization is not broadly adopted as a soil deinfestation method mainly because of its long duration (4–6 weeks). We present evidence showing that the duration of solarization can be reduced to nearly half using impermeable plastics and/or low doses of methyl bromide, while still ensuring effective control of Fusarium oxysporum f. sp. cucumerinum. Chlamydospores of a pathogenic isolate of F. o. cucumerinum, formed in sterile soil, were inserted into nylon mesh envelopes and incorporated into the soil prior to treatment at 20‐ and 30‐cm soil depths. Soil treatments included untreated control, soil solarization with polyethylene or impermeable plastics (LMG), and soil solarization with polyethylene or impermeable plastics plus 20 g m^?2 methyl bromide. According to the effects on artificial inocula of F. o. cucumerinum checked at weekly intervals for 4 weeks, soil solarization with impermeable plastics was most effective in destroying pathogen populations even two weeks after soil covering.     

Effect of solarization and fumigant applications on soilborne pathogens and root-knot nematodes in greenhouse-grown tomato in Turkey

A study was conducted in two greenhouses with a history of Fusarium crown and root rot (Fusarium oxysporum f.sp.radicis-lycopersici, Forl) and root-knot nematodes (Meloidogyne javanica andM. incognita). During the 2005–06 growing season, the effectiveness of soil disinfestation by solarization in combination with low doses of metham-sodium (500, 750, 1000 and 1250l ha⁻¹) or dazomet (400 g ha⁻¹), was tested against soilborne pathogens and nematodes in an attempt to find a suitable alternative to methyl bromide, which is soon to be phased out. Solarization alone was not effective in the greenhouse with a high incidence ofForl. In the greenhouse with a low level ofForl, all the treatments tested reduced disease incidence, and were therefore considered to be applicable for soil disinfestation. In addition, root-knot nematode density decreased with all the treatments tested in both of the greenhouses.     

A case study of infection of rice roots by deleterious fungi and minor pathogenic<Emphasis Type="Italic"> Pythium</Emphasis> species in a paddy field

Roots of rice plants grown in paddy fields in a transplant culture system were collected seven times between 8 and 22 weeks after transplanting, for two crop seasons. Rice seedlings grown in a potting medium amended with the collected roots were significantly shorter than those grown in the same medium either without the addition of the roots or amended with pasteurized, collected roots indicating that seedlings were inhibited by heat-labile microorganisms on the collected rice roots. Ninety-five and 172 pure cultures of Pythium spp. and fungi, respectively, were isolated from the rice roots collected 5 or 7.5 weeks after transplanting in the fields. Among these microorganisms, Pythium aristosporum inhibited seedling growth in greenhouse experiments, and Acremonium sp., Alternaria sp., Epicoccum nigrum, Fusarium sp., Massarina sp., Penicillium spp., Rhinocladiella sp., Stemphylium sp., Trichocladium sp., and several unidentified fungi inhibited seminal root growth in in vitro experiments. These microorganisms might be involved in the inhibition of seedling growth in soils amended with the rice roots collected from the paddy field. Thus, roots of rice plants at the middle stage of growth transplanted into paddy fields can harbor pathogenic or deleterious fungi or Pythium sp(p). The effects of these microorganisms on rice growth in paddy fields are discussed.     

Laboratory evaluation of steinernematid and heterorhabditid nematodes for control of the beetleMaladera matrida

The potential use of steinernematid and heterorhabditid nematodes against the beetleMaladera matrida Argaman (Coleoptera: Scarabaeidae) was determined under laboratory and greenhouse conditions. Infective juveniles (IJ’s) of the nematodeHeterorhabditis sp., Hp88 strain, mixed with soil at a concentration as low as 50 IJ’s/cm³ soil, resulted in 86% control. No increase in control was obtained with higher nematode concentrations. Soil surface application of the nematodes at concentrations of 160 and 640 IJ’s/cm² was sufficient to obtain 87% and 86% mortality, respectively, even at a depth of 40 cm below the soil surface. TheHeterorhabditis sp. Hp88 strain was found to be the most pathogenic to the beetle grubs at 25°C. Lower control levels of 30-47% were achieved byHeterorhabditis sp. HL81 strain,S. feltiae ‘All’ strain and 5.bibionis CR strain. The nematodeHeterorhabditis sp. BS strain did not have any effect on insect mortality. However, at a temperature of 16°C, the HL81 strain ofHeterorhabditis sp. was the most effective. Grubs 3-5 wk old were found to be the most susceptible developmental stage of infection ofHeterorhabditis sp. Hp88 strain. Pupae, which were exposed to the nematodes in the same experimental regime, were not affected. The results obtained in the present study suggest thatM. matrida is an attractive candidate for biological control by entomoparasitic nematodes.     

Mixtures of organic amendments and biochar promote beneficial soil microbiota and affect Fusarium oxysporum f. sp. lactucae,Rhizoctonia solani and Sclerotinia minor disease suppression

The use of soil fumigants and fungicides to control soilborne pathogens is reduced due to awareness of their negative drawbacks. Long-term application of such agrochemicals negatively affects soil microbiota and reduces natural soil suppressiveness. We investigated long-term impacts of biochar and not-pyrogenic organic amendment (OAs: manure, alfalfa straw and glucose), on disease suppression compared with conventional management in three pathosystems: Fusarium oxysporum f. sp. lactucae (FOL)–lettuce, Rhizoctonia solani–tomato and Sclerotinia sclerotiorum–lettuce, by conditioning soil for 2 years. Soil analyses included pH, electrical conductivity, organic carbon, total nitrogen, C:N ratio, N-NO₃⁻, N-NH₄⁺, cation exchange capacity, available phosphorus, Ca²⁺, Mg²⁺, K⁺, Na⁺, fluorescein diacetate (FDA), and total and active limestone. Soil microbiota was characterized by combining BIOLOG EcoPlates with next-generation sequencing of 16S and 18S rRNA genes. Soil amended with OAs generally suppressed disease by S. sclerotiorum and FOL compared to fumigants and synthetic fertilizers. However, the incidence of R. solani infection was lower in soil treated with synthetic fertilizers than soil amended with OAs. EC, pH, C:N, N-NO₃⁻, N-NH₄⁺, FDA and BIOLOG were significantly correlated with disease, depending on pathosystem. Bacterial richness and diversity, presence of some genera like Acidobacteria, Chloracidobacteria, Solibacteres, Anaerolineae, Nitrospira and Deltaproteobacteria were negatively related to disease incidence of FOL and S. sclerotiorum, whereas damping-off caused by R. solani was negatively affected by the presence of Flavobacterium and Chitinofagha. Therefore, we concluded that long-term application of OAs can effectively improve soil suppressiveness and reduce disease incidence against root pathogens, although the effects vary considerably depending upon pathosystem.     

Development of a real‐time PCR method for the detection of the dagger nematodes Xiphinema index,X. diversicaudatum,X. vuittenezi and X. italiae,and for the quantification of X. index numbers

The ectoparasitic dagger nematodes Xiphinema index and Xiphinema diversicaudatum, often at low numbers in the soil, are vectors of grapevine nepoviruses, which cause huge agronomical problems for the vineyard industry. This study reports a method, based on real‐time PCR, for the specific detection of these species and of the closely related non‐vector species Xiphinema vuittenezi and Xiphinema italiae. Specific primers and TaqMan probes were designed from the ribosomal DNA internal transcribed spacer 1 (ITS1), enabling the specific detection of single individuals of each of the X. index, X. diversicaudatum, X. italiae and X. vuittenezi species whatever the nematode population. The specificity of detection and absence of false positive reaction were confirmed in samples of each species mixed with the three other Xiphinema species or mixed with nematodes representative from other genera (non‐plant‐parasitic Dorylaimida, Longidorus sp., Meloidogyne spp., Globodera spp. and Pratylenchus sp.). The method was shown to be valid for the relative quantification of X. index numbers through its use, from crude nematode extracts of soil samples, in a greenhouse assay of grapevine accessions ranging from highly susceptible to resistant. As an alternative to time‐consuming microscopic identification and counting, this real‐time PCR method will provide a fast, sensitive and reliable diagnostic and relative quantification technique for X. index nematodes extracted from fields or controlled conditions.     

黄龙病对柑橘叶际微生物组的影响

为明确柑橘叶际微生物组对黄龙病发生的响应规律，采用荧光定量PCR技术检测采集柑橘叶片感染黄龙病菌的情况，通过扩增子测序分析法对PCR检测结果为阴性和阳性叶片的微生物群落进行比较，并通过相关性分析和网络分析对黄龙病菌和叶际微生物的相关性进行解析。结果显示，夏季采集的柑橘叶片中黄龙病菌的检出率为7.5%，而到秋季黄龙病菌的检出率上升到32.3%。黄龙病的发生显著改变了柑橘叶际细菌群落的组成和结构，对于细菌类群的丰度也有一定影响；而对叶际真菌群落的组成和结构无显著影响。黄龙病菌与叶际细菌存在普遍的负相关关系，正相关关系相对较少但相关性更强。黄龙病菌可能通过与厌氧棍状菌Anaerotruncus sp.、梭菌Clostridiales sp.、假单胞菌Pseudomonas sp.、鞘脂单胞菌Sphingomonas sp.、毛螺菌Lachnospiraceae sp.和链球菌Streptococcus sp.的负向互作对柑橘叶际整个细菌群落产生负影响。表明黄龙病发生对柑橘叶际真菌和细菌群落的影响规律不同，同时黄龙病菌可能通过与几种主要细菌的负向互作来实现对叶际微生物组的影响。     

Effect of fungicides on the complex of <Emphasis Type="Italic">Fusarium</Emphasis> species and saprophytic fungi colonizing wheat kernels

Fusarium head blight of wheat, often associated with mycotoxin contamination of food and feed is caused by various Fusarium species. The efficacy of fungicide sprays for the control of the disease and mycotoxins varies from being highly effective to even increasing mycotoxin levels. The potential role of antagonistic fungi in this variability was investigated assessing sensitivity of Fusarium species and saprophytic fungi colonizing wheat kernels to fungicides. Saprophytes were tested for their antagonistic activity to the prevalent Fusarium species Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, and Fusarium poae. Fungal isolates from mature winter wheat kernels were Alternaria alternata, Arthrinium sp., Aspergillus niger, Epicoccum sp., Microdochium spp., Rhizopus oryzae and Trichoderma sp. In dual culture A. niger, R. oryzae and Trichoderma hamatum were more effective in reducing mycelial growth of Fusarium species than Microdochium majus; A. alternata and Epicoccum sp. were ineffective because of slow growth rates. Saprophytic fungi were sensitive to triazoles; however, prothioconazole and tebuconazole had stronger effects on mycelial growth of Fusarium species. ED₅₀ values also indicated significant differences in the sensitivity of Fusarium species to triazoles (range 0.1–1.7 mg l⁻¹). Azoxystrobin and fluoxastrobin were largely ineffective in inhibiting in vitro growth of Fusarium spp.; sensitivity of the other fungi was generally lower, except for M. majus which was highly sensitive. Due to differences in fungicide sensitivity among Fusarium spp. and ear-colonizing fungi antagonistic to Fusarium spp. fungicides are likely to modify the balance within the mycoflora of wheat ears which may also affect the mycotoxin contamination of grain.     

Steinernematid and heterorhabditid nematodes for biological control of the giant looper,Boarmia selenaria

The pathogenicity of steinernematid and heterorhabditid nematodes to caterpillars of the giant looper,Boarmia selenaria (Schiffermüller) (Lepidoptera: Geometridae), was determined under laboratory conditions. High mortality (over 80%) was achieved, in a petri dish bioassay, with a minimum of 20,000 infective juveniles (IJ) ofSteinernema carpocapsae (Filipjev) (=Neoaplectana carpocapsae Weiser), strain ‘All’. The LD₅₀ was 4250 IJ per caterpillar. Similar results were obtained withS. carpocapsae, strain ‘Mexican’,Steinernema sp., strain ‘CR’;Heterorhabditis bacteriophora, strain ‘HP88’; andHeterorhabditis sp., strain ‘IS’. The first and second instars were the most susceptible stages to nematode infection. A laboratory model assay indicated that 80–90% of the caterpillars were killed when they migrated to the soil to pupate; this occurred when IJ were applied to sandy and heavy soils at a concentration of 400 IJ/cm³ soil. A greenhouse test reconfirmed the effectiveness of utilizing the entomopathogenic nematodes in an “ambush” system against caterpillars migrating to the soil.     

A new ‘forma specialis’ of Fusarium solani causing leaf yellowing of Phalaenopsis

The pathogenicity of 35 Fusarium solani isolates obtained from diseased leaves of greenhouse‐grown Phalaenopsis plants in Taiwan was tested on different orchids, including Phalaenopsis sp., Cymbidium spp., Oncidium sp., Dendrobium sp. and Cattleya sp., plus pea (Pisum sativum), chrysanthemum (Chrysanthemum indicum) and cucurbit [melon (Cucumis melo) and cucmber (C. sativus)] plants. Isolates of F. solani from Phalaenopsis spp. caused severe leaf yellowing on Phalaenopsis and mild symptoms on Cymbidium spp., but no visual symptoms on Oncidium sp., Dendrobium sp., Cattleya sp., pea, chrysanthemum or melon. Fusarium solani isolates collected from Phalaenopsis, pea and cucurbits were molecularly characterized by internal transcribed spacer (ITS), intergenic spacer (IGS) and β‐tubulin gene analyses. Phylogenetic trees constructed by distance and parsimony methods indicated that isolates from Phalaenopsis were grouped into one type based on ITS, IGS and β‐tubulin sequences with high bootstrap value (> 84%) support, compared to ‘formae speciales’ of F. solani from the other hosts. These analyses show that isolates of F. solani from Phalaenopsis are distinct from F. solani isolates from other hosts in Taiwan. Therefore, it is proposed that F. solani isolates that incite Phalaenopsis leaf yellowing be designated F. solani f. sp. phalaenopsis.     

Mucor Species in Orchard Soil – Population Dynamics and Pathogenicity on Pear Fruit

Strains of Mucor piriformis were isolated from orchard soils and from packinghouse dump-tank waters. Pathogen propagules were not found in fruit sample washings. M. piriformis was the most prevalent of the Mucor isolates, only one of 67 isolates was a different Mucor sp., possibly M. racemosus. The population of the pathogen propagules fluctuated in an annual cyclic pattern, declining in warm months and increasing after harvest. The viability of sporangiospores was markedly affected by rain. There was a good correlation (r=0.88) between the number of recovered propagules in the soil and the amount of rainfall. M. piriformis isolates caused decay on pear at 0°C after 14 days.     

The potential for Fusarium oxysporum f. sp. fragariae,cause of fusarium wilt of strawberry,to colonize organic matter in soil and persist through anaerobic soil disinfestation

Fusarium wilt of strawberry, caused by Fusarium oxysporum f. sp. fragariae, is a disease of primary concern for strawberry production in many countries. Crop rotation and anaerobic soil disinfestation (ASD) have gained recent interest for their potential to contribute to management of this disease. Both techniques involve incorporation of organic matter into soil, which may be utilized by strains of Fusarium that are competitive saprophytes. We show that F. oxysporum f. sp. fragariae can colonize strawberry, lettuce, raspberry, and broccoli leaf tissues, which are sources of organic matter generated during crop rotation. This pathogen increased in soil population density during ASD treatments that did not become anaerobic, possibly as a result of growth on the organic amendment. However, significant population decreases were observed after ASD treatment when at least 100,000 cumulative reduced mV hours occurred in a 14-day experiment. Post-ASD abundance of F. oxysporum f. sp. fragariae in soil was negatively correlated with cumulative reduced mV hours. The only treatment that consistently caused disinfestation was exposed to a maximum temperature of 22 °C, which indicates there is potential for developing effective ASD treatments in the cool climates where strawberries are grown. Awareness that F. oxysporum f. sp. fragariae can act as a competitive soil saprophyte should be further investigated for its potential to alter disease outcomes where organic amendments are applied.