Determination of seedborne fungi and detection of aflatoxins in sudanese fenugreek seeds

Following incubation of fenugreek(Trigonella foenum- graecum L.) seeds on potato dextrose agar and moist filter papers at 28±2°C, 59 species and 11 varieties belonging to 21 genera of fungi were determined as seedborne in fenugreek crops. Among these isolates, 45 species and 9 varieties are new records for this crop; and two species are new to the mycoflora of Sudan:Aspergillus stellifer andEmericella variecolor. The genusAspergillus (15 species and 8 varieties) is the most prevalent, followed byDrechslera (3 species),Rhizopus (3 species),Alternaria andFusarium (6 species each),Emericella (4 species and 2 varieties)Cladosporium andPenicillium (4 species each),Chaetomium (3 species) andCurvularia (3 species and one variety). The remaining 11 genera displayed low level of infection. Of the common pathogens of fenugreek plants,Fusarium oxysporum (2.13%) was recovered from the seeds of this crop. Thin layer Chromatographic analysis of chloroform extracts of 13 seed samples showed that two samples were naturally contaminated with aflatoxins B₁, B₂, G₁ and G₂ (7.5–35.2 μg/kg). http://www.phytoparasitica.org posting Nov. 4, 2001.     

Seed mycoflora ofLens esculenta and their biocontrol by chitosan

Thirty-two fungal species belonging to 17 genera were recorded on 45 seed samples of lentil (Lens esculenta) collected from different governorates in Egypt. The prevalent genera wereAlternaria, Aspergillus, Cladosporium, Fusarium andPenicillium. Chitosan enhanced suppression of seedborne mycoflora, as estimated using either agar plates or a blotter test of lentil seed samples. These results suggested an alternative non-toxic means for controlling seedborne fungi. Furthermore, pretreatment of lentil seeds with chitosan significantly reduced the natural contamination with mycotoxins — aflatoxins, ochratoxin A, citrinin and zearalenone — under storage conditions for 6 months.     

Species presence and density of tetranychid and phytoseiid mites in unsprayed and sprayed apple orchards in Northern Israel

Species presence and density of mixed populations of phytophagous tetranychid and predacious phytoseiid mites were studied in sprayed and unsprayed apple orchards in northern Israel during three growing seasons. Two species of phytophagous tetranychids, namely,Tetranychus cinnabarinus Boisduval andT. Urticae Koch, and two species of predatory phytoseiid mites —Typhlodromus athiasae Porath and Swirski andAmblyseius swirskii Athias-Henriot — were found. Predator density was lower than herbivore density in sprayed commercial orchards, but the reverse was true in unsprayed orchards. Contribution from the Agricultural Research Organization. No. 2855-E, 1989 series.     

Natural occurrence of citrinin in rice grains and its biocontrol byTrichoderma hamatum

Paddy rice was sampled from El-Sharkia, El-Gharbia, El-Dakahlia and Kafr El-Shekh governorates, Egypt. Of the 30 samples taken, ten were contaminated with the mycotoxin citrinin. An average of 6.79 × 10⁴ fungal spores per gram rice was found. The isolated fungi represented 47 species and 28 genera. The predominant genera wereAspergillus, Cladosporium andPenicillium. Aspergilli were represented by 22 species;Aspergillus niger andA. flavus had the highest occurrence.Penicillium viridicatum produced the highest amount of citrinin on glucose ammonium nitrate salts broth and rice grains, and hence this isolate was selected as a good producer of citrinin in this study. The presence ofTrichoderma hamatum reduced the amount of citrinin produced byP. viridicatum compared with its respective control. The excessive growth ofT. hamatum onP. viridicatum was increased with time. Viability ofP. viridicatum conidia decreased byT. hamatum with an increase in the incubation period. Chitinases and 1,3-β-glucanase enzyme activity ofT. hamatum increased with extending the incubation period onP. viridicatum mycelia up to maximum values at 72 and 84 h, respectively.T. hamatum led to a decrease in the production of citrinin byP. viridicatum on rice grains compared with the respective control values. http://www.phytoparasitica.org posting Dec. 19, 2004.     

Note:Cnaemidophorus rhododactyla, a NewRosa spp. Pest for Turkey, and its new parasitoids, a NewRosa spp. Pest for Turkey, and its new parasitoids

In the present study,Cnaemidophorus rhododactyla (Denis & Schiffermüller) (Lepo Pterophoridae) was noted for the first time as a pest ofRosa spp. in Turkey. The larva ofC. rhododactyla makes a cavity by feeding in the flower-bud and destroys at least 60% of the mass of the flower-bud. There are approximately 12 species ofRosa in Erzurum and Kars provinces, butRosa dumalis Bechst. andR. subcanina L. suffered more damage than the otherRosa species. One species of Tachinidae (Diptera) —Pseudoperichaeta palesoidea (Robineau-Desvoidy), and two species of Ichneumonidae (Hymenoptera) —Sinophorus turionus (Ratz.) andScambus brevicornis Gravenhorst, were reared as larval parasitoids ofC. rhododactyla. C. rhododactyla is a new host record for these parasitoids. Additionally,S. turionus is a new record for the Turkish fauna.     

New Ichneumonidae (Hymenoptera) parasitoids of forest insect pests in Bulgaria

During the period 1989–1998 investigations were carried out on the parasitoids of some forest insect pests in Bulgaria. Twenty-one ichneumonid species are reported for the first time in Bulgaria as parasitoids of different coleopteran, lepidopteran, and hymenopteran hosts. From these, 6 parasitoids are new records for the parasitoid complexes of the hosts:Exochus decoratus Holmgr. onEudemis profundana (Den. & Schiff.) andGelechia turpella (Den. & Schiff.);Lissonota culiciformis Grav.—onParanthrene tabaniformis (Rott.);Lissonota unicincta Holmgr.—onG. turpella; Xorides gracilicornis (Grav.)—onXylotrechus sp.; andEriborus terebrator Aubert—onClostera anastomosis (L.). Most parasitoids developed as primary parasitoids in the hosts.Itoplectis alternans (Grav.) is a primary parasitoid ofNycteola asiatica (Krul.) and a hyperparasitoid ofE. terebrator: Acropimpla pictipes (Grav.) is secondary parasitoid onAnacampsis populella (Cl.). With the exception of two species ofOlesicampes genus, which destroyed over 50% ofStauronematus compressicornis (F.) andPristophora conjugata (Dahlm.) larvae, andE. terebrator which killed 15.4% ofC. anastomosis population, the rest of the parasitoids occurred in low densities, and did not play an important role in reducing the number of their hosts.     

Characterization of two races of the stem and bulb nematode (Ditylenchus dipsaci) in Israel

Two distinct races ofDitylenchus dipsaci in Israel were identified: one, which infects and damages onion and garlic, reproduces on pea, but does not infect phalaris grass; and a second, which infects and damages phalaris—and, probably, also ‘Saia’ oats—but fails to infect onion and garlic. A new ‘garlic’ race of the nematode does not appear to have been introduced into Israel together with the ‘Lavinia’ garlic cultivar, as previously speculated, but rather the introduced Lavinia clone is highly susceptible to the existing ‘onion and garlic’ race ofD. dipsaci.     

Resistance to fusarium basal rot of onion in greenhouse and field and associated expression of antifungal compounds

Greenhouse and field evaluations of onion for resistance to Fusarium basal rot caused byFusarium oxysporum f.sp.cepae were conducted on cultivars ‘Akgün 12’ and ‘Rossa Savonese’ previously described as resistant at the seedling stage. In the greenhouse experiments inoculations were carried out on seeds or soil; in the field experiments evaluation was performed on onion sets from plants grown in naturally infested soils. Akgün 12 and to a lesser extent Rossa Savonese were resistant to the disease at the bulb stage in all experiments. Results were also consistent with those obtained from a previous screening at the seedling stage. Onion sets were also extracted and fractionated by thin layer chromatography to determine their content of antifungal compounds. Extracts were characterized by the expression of distinct antifungal components, which may be involved in resistance to the pathogen. http://www.phytoparasitica.org posting July 14, 2004.     

Weed hosts ofVerticillium dahliae in crete: Susceptibility, symptomatology and significance

A survey of common and uncommon weed species usually showing Verticillium wilt symptoms was carried out during 1992–2000 in Crete, Greece.Verticillium dahliae was isolated in 48 out of 182 sampled fields, in which several weed species were grown, from several locations in Oropedio, Lasithi. Altogether, 124 isolates ofV. dahliae were recovered from the vascular stem-tissue of 19 weed species, belonging to ten botanical families. Pathogenicity trials with 13 out of 19 weed species that have never been reported as hosts of the fungus, using for inoculation isolates which originated from the same weed species, resulted in infection of all of them, showing various disease symptoms. Seven weed species (Anthemis melanolepis, Cardaria draba, Convolvulus arvensis, Erodium sp.,Euphorbia helioscopia, Helminthotheca echioides andSinapis alba) are new hosts worldwide, and six additional species (Euphorbia sp.,Lactuca serriola, Raphanus raphanistrum, Sinapis arvensis, Sonchus oleraceus andTrifolium sp.) are new hosts for Greece. The most susceptible (isolation frequency: 27.9–52.8%, moderate disease severity) species were:Capsella bursa-pastoris, C. draba, Chenopodium album, Senecio vulgaris andSolanum nigrum. Less susceptible (isolation frequency: 4.8–17.8%, slight disease severity) were:Amaranthus sp.,A. melanolepis, C. arvensis, Erodium sp.,Euphorbia sp.,E. helioscopia, H. echioides, L. serriola, Malva sylvestris, R. raphanistrum, S. alba, S. arvensis, S. oleraceus andTrifolium sp. Some species —C. draba, C. album, L. serriola andS. nigrum L. — that usually showed external and vascular wilt symptoms, occasionally exhibited only reduced growth. Visible symptoms under natural field conditions in all 13 weed species that had never been reported as hosts ofV. dahliae were similar to those observed after their artificial inoculation. The fungus was not isolated fromFoeniculum vulgare ssp.piperitum, Oxalis corniculata andStellaria media, among other species. http://www.phytoparasitica.org posting Sept. 18, 2002.     

Storability of onion bulbs contaminated by<Emphasis Type="Italic">Aspergillus niger</Emphasis> mold

In the course of pre- and postharvest epidemiological studies on bulbs contamination byAspergillus niger, two Sudanese onion cultivars were tested: ‘Saggai Red’ and ‘El-Hilo White’.A. niger spores, whether seedborne, soilborne or airborne, were avirulent to the healthy growing onion plants. The fungus heavily contaminated the dead onion tissues, mainly the dead leaves followed by the dry scales, the dead roots and, to a lesser extent, the bulb necks, preferring the red-skinned cultivar to the white one. The initial spores carried from naturally contaminated field soil on the dead tissues could germinate and produce massive numbers of new spores on bulbs stored at average climatic conditions of Sudan (23–39°C, 29–93% relative humidity). Under laboratory-controlled conditions, optimal growth occurred at 75–85% r.h. on bulbs with dry scales and maximum losses occurred at 100% r.h. and ambient temperature. Underin vitro conditions, the optimal growth and sporulation temperature forA. niger was in the range of 30–35°C. Early harvesting and removal of the dead onion tissues improved bulb storability in aseptic stores under low temperature and relative humidity conditions. http://www.phytoparasitica.org posting Oct. 20, 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.     

The anthocoridae of Israel (heteroptera)

Data are presented on the 26 species of Anthocoridae of Israel, five of which are new to this country. Five species are abundant; two of them (both monophagous) reduce significantly the populations of their preys —Elatophilus hebraicus Per. feeding onMatsucoccus josephi (Coccoidea: Margarodidae), a destructive pest of Aleppo pine, andMontandoniola moraguesi (Put.) feeding onGynaikothrips ficorum (Thysanoptera), deforming the leaves ofFicus microcarpa; the three other abundant species areAnthocoris nemoralis (F.) — preying mostly on psyllids and aphids,Scoloposcelis pulchella (Zett.) — destroying the young stages of pine bark beetles, andCardiastethus nazarenas Reut. — feeding on many groups of small arthropods. Contribution from the Agricultural Research Organization. No. 2621-E, 1989 series.     

Phytotoxic effects of fumonisin B1 on cowpea seed

The cultivation of cowpea (Vigna unguiculata) plays a vital role in the livelihood of many subsistence farmers and rural communities in tropical and subtropical countries. The seeds are prone to fungal infestation and mycotoxin contamination during sub-optimal storage conditions. Fumonisin B₁ (FB₁), produced byFusarium proliferatum, has been detected in cowpea seeds. Surface-disinfected seeds were imbibed in sterile distilled water amended with FB₁ at various concentrations. Percentage germination was determined according to the International Seed Testing Association rules. All the toxin concentrations significantly decreased seed germination and the two highest concentrations — 50 and 100μg ml⁻¹ FB₁ — inhibited root and shoot elongation. FB₁-treated embryonic tissues evinced compaction of the protoplasm and separation of the plasmalemma from the cell wall. Lipid bodies accumulated, which seemed to be lining the cell wall. This is the first study to demonstrate the phytotoxic effects of FB₁ on cowpea seeds.     

Biological control ofBotrytis cinerea in residues and flowers of Rose (Rosa hybrida)

Microbial isolates from living petals, petal residues and leaf residues of rose, and from laboratory collections, were evaluated for control ofBotrytis cinerea in rose. In leaf residues artificially infested withB. cinerea, isolates of the filamentous fungiGliocladium roseum, FR136 (unidentified) andTrichoderma inhamatum reduced sporulation of the pathogen by >90%, other filamentous fungi were 25–90% effective, and those of yeasts and bacteria were <50% effective. In artificially inoculated petal residues, no microbe reduced sporulation ofB. cinerea by >75%, but isolates ofCladosporium oxysporum and four yeasts were 51–75% effective, and three filamentous fungi, eight yeasts andBacillus subtilis isolates were 26–50% effective. Isolates ofT. inhamatum, C. oxysporum andG. roseum performed best againstB. cinerea among isolates evaluated in leaf residues naturally infested with the pathogen and indigenous microorganisms. Totals of ten isolates of filamentous fungi (includingC. oxysporum andC. cladosporioides), two of yeasts and five ofBacillus subtilis completely prevented lesion production byB. cinerea in detached petals, and a further six isolates of filamentous fungi (includingG. roseum) and six yeasts were 90–99% effective. Isolates ofC. oxysporum, C. cladosporioides andB. subtilis, the most effective microorganisms againstB. cinerea in flower buds, reduced number of lesions in the range of 42–65% compared with 59–89% for à standard fungicide (vinclozolin). It is suggested that application of leading antagonists Jo living rose leaves and flowers should optimize control of inoculum production byB. cinerea when the tissues die. Optimal biocontrol of lesion production in flower buds requires a better understanding of the microenvironment of petals.     

Histological study of giant cells formed by the root-knot nematodeMeloidogyne artiellia as compared withM. hapla andM. javanica in cabbage, turnip and barley

Feeding sites induced by the root-knot nematodeMeloidogyne artiellia in turnip (Brassica rapa), cabbage (Brassica oleracea) and barley (Hordeum vulgare) were examined by light and electron transmission microscopy, and compared with those formed byM. javanica andM. hapla. The feeding cells ofM. artiellia in turnip and cabbage showed hypertrophy, hyperplasia and vacuolization, and became multinucleate giant cells. In contrast to the typical simple-shaped giant cells ofM. javanica andM. hapla, those ofM. artiellia had an amoeboid structure containing ‘protuberances’, which are distinct from previously reported ‘projects’ of giant cells induced byM. incognita in other plants. Protuberances expanding between vascular cells were observed in young and developed giant cells. Since no cell-wall fragments were found at the bases of the protuberances, either by light or electron microscopy, it is strongly indicated that these structures were caused by local expansion of the giant cells rather than by fusion with adjacent cells. The giant cells ofM. artiellia in barley had regular shapes of giant cells without protuberances, and resembled those induced byM. javanica orM. hapla in turnip and cabbage. http://www.phytoparasitica.org posting Sept. 17, 2006.     

Fungal infection and mycotoxin contamination of maize in the Humid forest and the western highlands of Cameroon

Fungal incidence and mycotoxin contamination of farm-stored maize were assessed and compared in grain samples from three villages each in two agroecological zones over time. Maize samples were collected at 2 and 4 months after stocking from 72 farmers’ stores in 1996 and 1997 in the Humid Forest (HF) and Western Highlands (WHL) of Cameroon. Mycological assays of these samples revealed several fungal species.Nigrospora spp. were the most prevalent fungi in HF (32%) and WHL (30%) in 1996,Fusarium verticillioides (22%) andF. graminearum (27%) were also isolated from these samples. In the WHL in 1996, no significant difference in fungal incidence was found among villages for samples collected 2 months after harvest, but at 4 months incidence was significantly higherP<0.05). In 1997 the levels of fungal contamination were lower than in 1996. The incidence ofAspergillus spp. was low in general, ranging from 0.0 to 5.9% infected kernels. Analysis with thin layer chromatography detected low levels of aflatoxins in a few samples.F. verticillioides mycotoxin fumonisin Bi (300-26,000 ng/g) andF. graminearum metabolites deoxynivalenol (<100–l,300 ng/g) and zearalenone (<50–110 ng/g) were determined by means of polyclonal antibody competitive direct enzyme-linked immunosorbent assay. A significant correlation (r=0.72; P=0.0001) was found between the incidence ofF. graminearum and the contamination with deoxynivalenol. Storage time (2vs 4 months after stocking) had a significant positive effect (r=0.39; P=0.013) on the level of fumonisin B₁. This is the first report of the natural occurrence of these mycotoxins in maize in Cameroon.     

Pathogenicity and mycotoxin production by <Emphasis Type="Italic">Fusarium proliferatum</Emphasis> isolated from onion and garlic in Serbia

Fusarium proliferatum can occur on a wide range of economically important vegetable plants but its role in disease is not always well established. In 2000 and 2001, from forty-one field samples of wilting onion and garlic plants in Serbia, F. proliferatum as the predominant fungal species was isolated from root and bulbs. Seventy isolates were firstly characterized for their sexual fertility and were shown to be mostly members of Gibberella intermedia (sixty-seven of seventy isolates, the remaining three isolates were unfertile), the sexual stage of F. proliferatum (syn. mating population D of G. fujikuroi complex). A selected set of eleven F. proliferatum isolates from both hosts were also tested for their pathogenicity and toxigenicity. Although onion and garlic plants were susceptible to all isolates, onion plants showed a significantly higher disease severity index. Six of the eleven isolates of F. proliferatum produced fumonisin B₁ from 25 to 3000 μg g⁻¹, and beauvericin from 400 to 550 μg g⁻¹; ten isolates produced fusaric acid from 80 to 950 μg g⁻¹ and moniliformin from 50 to 520 μg g⁻¹. Finally, all isolates produced fusaproliferin up to 400 μg g⁻¹. These results confirm F. proliferatum as an important pathogen of garlic and onion in Europe and that there is a potential mycotoxin accumulation risk in contaminated plants of both garlic and onion.     

Neem (Azadirachta indica) seed kernel extracts and azadirachtin as oviposition deterrents against the melon fly (Bactrocera cucurbitae) and the oriental fruit fly (Bactrocera dorsalis)

Neem(Azadirachta indica A. Juss.) seed kernel (NSK) extracts,viz., NSK aqueous suspension (NSKS), ethanolic extract of NSK (EtOH. NSK), hexane extract of NSK (neem oil), ethanolic extract of the hexane extract (EtOH. oil) and acetone extract of deoiled NSK powder (Acet. DNSKP) at 1.25-20% concentrations, and pure azadirachtin at 1.25-10 ppm, were evaluated as oviposition deterrents toBactrocera cucurbitae (Coq.) andB. dorsalis Hendel. NSKS at ≥5% under choice test conditions, and at all concentrations (≥1.25%) in no-choice tests significantly deterred oviposition in both species. Similarly, EtOH. NSK was significantly active at all the concentrations tested for both species in choice and no-choice tests. However, with neem oil and EtOH. oil sensitivities of the two species differed considerably. Both extracts deterred oviposition byB. cucurbitae at all the concentrations tested under both choice and no-choice test conditions. On the other hand, withB. dorsalis, neem oil was significantly deterrent only at 20% in both test regimes and at 5% and 20% for EtOH. oil under choice and no-choice test conditions, respectively. Acet. DNSKP significantly deterred oviposition by both species at all concentrations tested. Azadirachtin failed to deter oviposition in either species.     

Further studies on the role of monoterpenes in pine host selection and oviposition ofThaumetopoea pityocampa

In a young mixed pine plantation (Pinus nigra andP. pinea) in central Italy, the influence of the pine needle monoterpenes (R)-(+)-limonene, (S)-(−)-limonene and (1S)-(−)-β-pinene on the oviposition activity of the pine processionary moth,Thaumetopoea pityocampa (Denis et Schiffermüller), was assessed. Two application methods were compared: spraying the trees with the substances emulsified with water, and setting up polyethylene dispensers from which the monoterpenes evaporated. During the moth’s flight period weekly treatments (at 500 mg of monoterpene /l water) were carried out and the evaporation from the polyethylene dispensers (each with 5 g of a single monoterpene) was checked on each occasion by weighing the dispensers. The GLM analysis did not uncover any difference between the methods of application or between the pine species.T. pityocampa laid a significantly (P=0.01) lower number of egg masses on the trees treated with (1S)-(−)-β-pinene than on those treated with the other substances and on the control trees. A ∼45% reduction in egg mass number was obtained on the pines treated with (1S)-(−)-β-pinene, independent of the level of infestation, method of application or pine species. (R)-(+)-limonene and (S)-(−)-limonene were not effective. http://www.phytoparasitica.org posting July 29, 2008.     

Survey of Bacterial and Fungal Seedborne Diseases in Imported and Domestic Potato Seed Tubers

Potato seed tubers are imported to Israel from northern Europe and planted in spring; tubers harvested early from the spring crop are used as seed for the autumn crop. Although only seed lots registered as certified are imported, a previous survey (1984–1994) indicated that most imported lots were affected by latent or active infections caused byErwinia carotovora,Streptomyces scabies, Rhizoctonia solani, Fusarium spp. andSpongospora subterranae. The survey was extended until 1998, and included additional pathogens:Ralstonia solanacearum,Helminthosporium solani, Colletotrichum coccodes andVerticillium dahliae. Most of these pathogens were also monitored in domestic seed tubers, and are reported for the first time. Brown rot was not observed in any of the imported lots. Blackleg and soft rot caused byErwinia spp. were detected in most of the imported lots; however, less than 7% of the lots were contaminated at high levels, while approximately 65% were contaminated at moderate levels. Common scab was detected in most of the imported lots; 51% of the imported lots were contaminated at moderate or high levels, whereas only 6.5% of the domestic seed lots were contaminated at these levels. Black scurf was detected in most of the imported lots; on average, 47.3%, 44.2% and 1.4% of the lots were contaminated at low, moderate and high levels, respectively, and only 7.1% were disease-free. In contrast, most of the domestic lots were either disease-free (45.4%) or had a low disease incidence (37.3%). Only 16.7% of the lots were moderately infected and 0.2% were highly contaminated. Silver scurf was observed in most of the imported lots during all years of the survey, with no differences among the producing countries; on average, 22.7%, 66.1% and 7.5% of the lots were contaminated at low, moderate and high levels, respectively, and only 3.7% were disease-free. Most of the domestic lots (76%) were disease-free and only 6.6% were infected at moderate or high levels. Black dot was observed in a considerable portion of the shipments from Holland during all years of the survey, particularly in 1998, when 34% of the lots were infected. The shipments from France and Germany were infected at low levels, except in 1998, when 19% and 11% of the lots, respectively, arrived infected. In shipments from Scotland and Ireland low incidences of the disease were observed in 1994 and 1995. In the domestic lots, black dot incidence was low (<2.4%) except in 1996, when 11% of the lots were infected.V. dahliae was monitored only in domestic seed tubers. The incidence of disease-free lots was 56–64%, whereas in 20–30% of the lots the level of infection was <5%, and in 6–16% of the lots the level was >5%. The survey findings demonstrate transmission of seedborne pathogens; most of these pathogens can become established in the soil and eventually cause severe outbreaks of disease in potatoes grown in Israel. http://www.phytoparasitica.org posting May 16, 1999.