S OF PRESENTATIONS AT THE 23RD CONGRESS OF THE ISRAELI PHYTOPATHOLOGICAL SOCIETY February 11–12, 2002 The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, Israel

Soilborne pathogens may cause severe reductions in yield and/or damage yield quality, resulting in serious economic losses. Pathogens such as Fusarium oxysporum, Rhizoctonia solani, Verticillium dahliae and Pythium spp. affect various crops (tomato, cucumber and pepper, among others) grown under organic management in greenhouses. These pathogens are difficult to control because of their persistence in the soil and wide host range. Biofumigation refers to the suppression of soilborne pathogens and pests by volatile biocidal compounds (mainly isothiocyanates) released from decomposing Brassica tissues incorporated into the soil when used as green manure crops. We developed a bioassay, in which only the volatile compounds effects are tested, as an efficient tool for the rapid screening of plants for biofumigation, and for the optimization of different aspects of the process (such as green manure concentration and most effective plant organs). The fungicidal effect of cruciferous crops against R. solani was demonstrated in pot and greenhouse experiments: yields were increased and disease was suppressed. The effect of solarization alone on controlling root-knot nematodes was clearly observed, and the combination of solarization with green manure residues or compost resulted in even better disease suppression. In summary, biofumigation can be considered a useful addition to the integrated pest management (IPM) arsenal for the reduction of soilborne pathogens, especially in organic management, where it may be the most promising solution.

This study investigates the possible involvement of serine proteases in interferon-gamma (IFN-gamma) activity on WISH cells. It was observed that inhibition of (3)H-thymidine incorporation induced by IFN-gamma was abrogated by the serine protease inhibitors Nalpha-tosyl-L-lysyl-chloromethane and soybean trypsin inhibitor, both of which act mainly on trypsin. Phenylmethyl sulfonyl fluoride also had a partial inhibitory effect. Other protease inhibitors specific to the cysteine, the aspartic, and the metalloprotease families were not effective. Kinetic analysis revealed that a trypsin-like protease is involved in IFN-gamma activity for up to 7 h. Trypsin-like activity induced by IFN-gamma was detected in the particulate fraction but not in the cytosolic fraction, whereas chymotrypsin activity was not enhanced in either the cytosolic or particulate fractions under similar conditions. Following separation on a gelatin substrate gel, two trypsin-like protease activities located in the particulate fraction were found to increase in response to IFN-gamma treatment. Hence, it seems that a specific membrane-associated trypsin-like protease activity induced by IFN-gamma may play a role in the action of the cytokine on thymidine incorporation in WISH cells.

S OF PRESENTATIONS AT T H E 22ND C O N G R E S S O F T H E I S R A E L I P H Y T O P A T H O L O G I C A L S O C I E T Y February 12-13, 2001 ARO, The Volcani Center, Bet Dagan, Israel Opening Lecture The Contribution of Epidemiological Research to Plant Disease Management D. Shtienberg Dept. of Plant Pathology, ARO, The Volcani Center, Bet Dagan 50250, Israel [e-mail: danish@ netvision.net.il ] Epidemiological research deals with the three components of the disease triangle: the host, the pathogen and the environment. One important goal of epidemiological research is to develop means for rational and cost-effective disease management. In some pathosystems it is possible to identify one (or a few) distinctive factors that govern(s) the occurrence of disease outbreaks. Manipulation of this factor may enable us to prevent the development of an epidemic. However, in most systems the situation is more complicated and many factors, and their interactions, govern the intensity of epidemics. In the 1970s, models based on past (measured) weather and decision rules were used for development of management tools. With the progress in computer science in the 1980s, models that simulated the development of the host and the pathogen were developed. However, simulation models were found inadequate for decision-making. Epidemiological knowledge is currently formulated as relatively simple, hence precise, decision models. These decision models are the frameworks I?y which epidemiological knowledge is transferred to the decision-maker. Nevertheless, the models would not necessarily be suitable in dissimilar environments. (L) A: PHYSIOLOGY AND RESISTANCE Endo-l,4-fl-Giucanase Activity in Isolates ofAlternaria alternata in Relation to Their Virulence in Apple Fruit M. Reuveni, 1 N. Shegalov, 1 D. Shegalov, 1 D. Eshel, 2 Ruth Ben-Arie 3 and D. Prusky 2 1Golan Research Institute, Qazrin 12900 [e-mail: mreuveni@research.haifa.ac.il]; 2Dept. of Postharvest Science, ARO, The Volcani Center, Bet Dagan 50250; and 3Fruit Storage Research Laboratory, Qiryat Shemona 10200, Israel The fungus Alternaria alternata is one of the principal causal agents of moldy core rot of different strains of "Delicious' apples. Disease symptoms generally become apparent after cold storage of the fruit, even though the apple core becomes infected in the orchard. Suitable temperature and humidity conditions in the orchard are evidently conducive to inoculation, but the mode and phenology of infection are not yet clearly understood. Artificial inoculation with fungal spores, of fruits at different stages of development, indicated that the initial blossom (10-30%) and full bloom stages were the most susceptible to infection. Of the 150 A. alternata isolates collected in three orchards in the Golan Heights and Galilee region, three strains with different levels of virulence were chosen for further study. The degree of virulence was based on the level of disease that developed on postharvestinoculated fruit. Inoculation of flowers with strains showing low and high virulence resulted in 30% L = lecture sessions; P = poster (market place) sessions. Phytoparasitica 29:3, 2001 243 and 56% disease incidence, respectively, in harvested fruit. In an attempt to clarify the mode of fungal infection of the fruit, the ability of the three strains to produce two hydrolytic enzymes, endo1,4-/3-glucanase (EG) and polygalacturonase (PG), when grown on apple cell walls, was examined. Thus it was tound that EG production of the virulent strain was twice and six times higher than that of the strains with intermediate and low levels of virulence, respectively. The level of PG production was 2.3 times higher in the highly virulent than in the least virulent strain. Activity gels following electrophoresis of protein extracts from the three strains indicated quantitative, but no qualitative, differences between the strains. A purified EG preparation caused disease symptom development on sensitive apple fruit skin, similar to symptom development following wound inoculation. Disease development in apple fruit following infection with A. ahernata may possibly be related to the ability of the fungus to produce EG and PG enzymes in the core and surrounding fruit tissue. (L) Cotton-Associated Vegetative Compatibility Groups of VerticiUium dahliae in Israel and Their Pathogenicity Nadia Korolev, 1,* J. Katan 2 and Talma Katan 1 1Dept. of Plant Pathology, ARO, The Volcani Center, Bet Dagan 50250 [*e-mail: vpptlg@agri.gov.il]; and 2Dept. of Plant Pathology and Microbiology, The Hebrew Universi~. of Jerusalem, Facul~. of Agricuhural, Food and Environmental Quali~. Sciences, Rehovot 76100, Israel A collection of 351 Verticillium dahliae isolates from cotton, recovered between 1992 and 2000 at 20 sites in Israel, was tested for vegetative compatibility using nitrate-nonutilizing (nit) mutants. Three cotton-associated vegetative compatibility groups (VCGs) were found and identified as VCG1 (34 isolates), VCG2B (218 isolates), and VCG4B (98 isolates). VCG2A was represented by one isolate only, although it was frequently recovered from non-cotton hosts. Three cotton pathotypes were defined among 40 isolates tested, using G. hirsutum cv. 'Acala SJ2' as differential. VCGI isolates induced severe leaf symptoms, stunting and defoliation, and were defined as the previously described cotton-defoliating (D) pathotype; VCG2B isolates also caused severe foliar symptoms, stunting and often death but no-to-partial defoliation, and were defined as cotton-defoliating-like (DL) pathotype; most of the VCG4B isolates induced weak-to-moderate symptoms on cotton and were similar to the previously described cotton-non-defoliating (ND) pathotype. Representatives of each VCG-associated pathotype were tested for their pathogenicity to a range of plant species. The D and DL pathotypes differ in their aggressiveness (D >DL), but the order of hosts (from highly susceptible to resistant) was the same: okra (commercial cultivar), cotton (Acala S J2), watermelon ('Crimson Sweet'), safflower (PI 251264), sunflower (2053), eggplant ('Black Beauty'), tomato ('Rehovot 13'). The ND pathotype formed another sequence differing from the DL pathotype with respect to cotton tolerance and eggplant susceptibility. Tomato was resistant to all tested cotton isolates and pathotypes. (P) Fusarium verticillioides: The Causal Agent of Corn Blight in Israel? A. Sharon, 1'* L. Oren, 1 S. Ezrati 1 and D. Cohen 2 1 Dept. of Plant Sciences, Tel-Aviv Universi~., Tel Aviv 69978 [*e-mail: amirsh @ tauex, tau. ac. il]; and 2Northern R&D, Qiryat Shemona 10200, Israel Corn rots are the most severe diseases of sweet corn in Israel. The incidence of stalk rot and the associated plant blight has increased in recent years, rendering some areas in northern Israel unsuitable for corn. Fusarium verticillioides is known as the causal agent of corn rots, but although previous findings demonstrated that the fungus can be lound in the soil, seeds and plants, it is unclear if this pathogen is indeed the primary cause of plant blight. In the current study we characterized the disease using E verticiUioides-transgenic strains that express the reporter genes green fluorescent

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 by Erwinia carotovora , Streptomyces scabies, Rhizoctonia solani, Fusarium spp. and Spongospora subterranae. The survey was extended until 1998, and included additional pathogens: Ralstonia solanacearum , Helminthosporium solani, Colletotrichum coccodes and Verticillium 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 by Erwinia 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.

The effect of various tyrosine protein kinase inhibitors on processes involved in the antiproliferative effect of interferon-gamma on WISH cells was studied. Following 24 hr treatment interferon-gamma inhibited thymidine incorporation into DNA and thymidine kinase activity, but no significant effect on cell number was observed. The isoflavonoid, genistein, which is a specific inhibitor of tyrosine protein kinase, reversed the inhibition in thymidine incorporation caused by the cytokine in a dose dependent manner. Prunetin, a member of the same group, did not significantly antagonize this effect. N alpha-tosyl-L-lysyl-chloromethane, a serine protease inhibitor which also serves as a tyrosine protein kinase inhibitor, partially reversed the effect of interferon-gamma at a concentration of 100 microM. The bioflavonoid, quercetin, a non-specific tyrosine protein kinase inhibitor, at a concentration of 30 microM completely abolished the action of interferon-gamma on thymidine incorporation. Genistein completely reversed the inhibition of thymidine kinase exerted by interferon, while quercetin had only a slight effect. However, the drugs could not antagonize the antiproliferative effect of interferon following 48 hr incubation, as measured by reduction of cell number. The results indicate that tyrosine protein kinase may play a role in the effects of interferon on thymidine metabolism and thymidine kinase activity. The differential effects of the inhibitors on thymidine metabolism and cell proliferation could support dissociation between the effect of interferon-gamma on these processes. Alternatively, this dissociation of effects could point to the limited use of inhibitors in clarifying modes of action as described.

Potato seed tubers are imported annually to Israel from northern Europe. Although the seed is registered as certified, a survey carried out over a 9-year period indicated that most lots were affected by latent or active bacterial and fungal infections. Latent infection byErwinia carotovora subsp.atroseptica, the causal agent of blackleg, at a level of 103 cells/g peel, was present in 30% of the lots in most years. Black scurf caused byRhizoctonia solani was present in 20–70% of the imported lots, with a moderate to high level of infection in all years except 1985. In contrast, although many lots were affected by powdery scab, common scab, and Fusarium dry rot in most years, disease incidence within lots was generally low. The gangrene pathogen (Phoma exigua) was rarely detected. The survey findings are of marked importance, due to the extensive use of soil fumigation in Israeli agriculture.

This study demonstrates a synergistic effect of IFN gamma and PMA on superoxide generation by human monocytes. A strict correlation was observed between the induction of superoxide production and PK-C activation by PMA alone. No such correlation was evident for IFN gamma. However, exposure of the cells to IFN gamma for 10 to 15 hr prior to PMA treatment enhanced both superoxide production and PK-C activation. Using protein kinase inhibitors, we noticed that while PMA exerted its effect by activating PK-C, IFN gamma operated via activation of calcium/calmodulin-dependent or some other calcium-dependent protein kinases. These kinases appeared to be involved in the effect of IFN gamma on superoxide production, as well as in its potentiation of PMA activity.

The present study describes the use of a new polyacrolein microsphere (acrobead) protein A column. This method enables immunomodulation by the perfusion of whole blood. The efficacy of the column and its adverse effects following perfusion of blood of patients with immune thrombocytopenic purpura (ITP) or malignancies were investigated. Concurrent experiments in which blood was perfused through an acrobead lactoglobulin column were carried out. Cellular blood components were mildly affected during the procedure. A moderate decrease in platelet number, to a nadir of 90 × 10(3) per microL (90 × 10(9)/L), was documented. During the hemoperfusion of ITP patients' blood, plasma hemoglobin reached levels of 25 to 40 mg per dL, a level similar to that found in banked blood during storage. Plasma tumor necrosis factor level, which serves as an indicator of monocytic activation, increased after 90 minutes of hemoperfusion. IgG and immune complexes were removed. The specific activities (removal of mg Ig/mL bead) of acrobead protein A columns, using blood from patients with ITP or malignancies, were 4.9 and 4.5 mg IgG per mL of bead, respectively. The diminution of platelet‐specific IgG in the plasma of patients with ITP was documented as well. There was no activation of the fibrinolytic system as examined by D‐dimers. The use of this new technique, which incorporates the method of direct hemoperfusion, is suggested for future clinical studies.

The present study describes the performance and safety parameters of a novel column composed of protein A linked to acrobeads. Hemoperfusion of anticoagulated whole human blood was carried out in a closed system. Specific adsorption of IgG was documented in whole blood, plasma and IgG diluted in saline. Specific activity of the column was 3.52 mg/ml beads. These studies revealed slight changes in platelet counts and minor hemolysis. The relatively short period needed for maximal hemoperfusion effect and safety may enable the use of this novel therapeutic approach in clinical practice.