AlgU contributes to the virulence of <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">tomato</Emphasis> DC3000 by regulating production of the phytotoxin coronatine

Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), which causes bacterial speck disease of tomato, has been used as a model pathogen to investigate the molecular basis of plant–pathogen interactions. The function of many potential virulence factors encoded in the Pst DC3000 genome and their modes of action are not fully understood. P. syringae is known to produce the exopolysaccharide alginate. Although AlgU, a sigma factor, is known to regulate the expression of genes such as algD related to alginate biosynthesis, the molecular mechanisms of AlgU in the virulence of Pst DC3000 is still unclear. To investigate the function of AlgU and alginate in plant–bacterial pathogen interactions, we generated ΔalgU and ΔalgD mutants. After inoculation with ΔalgU but not ΔalgD, host plants of Pst DC3000 including tomato and Arabidopsis had milder disease symptoms and reduced bacterial populations. Expression profiles of Pst DC3000 genes revealed that AlgU can regulate not only the expression of genes encoding alginate biosynthesis, but also the expression of genes related to type III effectors and the phytotoxin coronatine (COR). We also demonstrated that the ΔalgU mutant showed full virulence in the Arabidopsis fls2 efr1 double mutant, which is compromised in the recognition of PAMPs. Further, the application of COR was able to restore the phenotype of the ΔalgU mutant in the stomatal response. These results suggest that AlgU has an important role in the virulence of Pst DC3000 by regulating COR production.     

Possible function of isoleucine in the methyl jasmonate response of <Emphasis Type="Italic">Arabidopsis</Emphasis> to <Emphasis Type="Italic">Phelipanche aegyptiaca</Emphasis>

Resistance of Arabidopsis thaliana to Phelipanche aegyptiaca (syn. Orobanche aegyptiaca) can be induced by exposure of the host to low concentrations of gaseous methyl jasmonate, in a concentration-dependent fashion. Application of methyl jasmonate at marginal concentrations, 10⁻⁸ M, for 12 h reduced infection by 50%. However, if the host plants were supplied with isoleucine at 10⁻³ M, and the isoleucine removed prior to exposure to methyl jasmonate, infection was reduced to less than 20%. The presence of isoleucine throughout the experiment—before, during and after exposure to methyl jasmonate—reduced infection of the host to almost zero. These results suggest that when Arabidopsis is exposed to methyl jasmonate, full activation of the defense mechanisms, including formation of the isoleucine jasmonic acid conjugate, might be limited by the availability of isoleucine in the host. These findings add another factor to the complex interaction between infecting parasite, and evocation of host defense mechanisms.     

Pathogenicity of <Emphasis Type="Italic">Beauveria bassiana</Emphasis> and <Emphasis Type="Italic">Metarhizium anisopliae</Emphasis> against <Emphasis Type="Italic">Galleria mellonella</Emphasis>

The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) is occasionally found in beehives and is a major pest of stored wax. Entomopathogenic fungi have recently received attention as possible biocontrol elements for certain insect pests. In this study, 90 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae were screened for proteases and lipases production. The results showed significant variations in the enzymatic action between the isolates. In the bioassay, the selected isolates evinced high virulence against the 4th instar of the G. mellonella larvae. The isolates BbaAUMC3076, BbaAUMC3263 and ManAUMC3085 realized 100% mortality at concentrations of 5.5 × 10⁶ conidia ml⁻¹, 5.86 × 10⁵ conidia ml⁻¹, and 4.8 × 10⁶ conidia ml⁻¹, respectively. Strong enzymatic activities in vitro did not necessarily indicate high virulence against the tested insect pest. The cuticle of the infected larvae became dark and black-spotted, indicating direct attack of fungus on the defense system of the insects. The LC₅₀ values were 1.43 × 10³, 1.04 × 10⁵ and 5.06 × 10⁴ for Bba3263AUMC, Bba3076AUMC and Man3085AUMC, respectively, and their slopes were determined by computerized probit analysis program as 0.738 ± 0.008, 0.635 ± 0.007 and 1.120 ± 0.024, respectively.     

Effects of garlic (<Emphasis Type="Italic">Allium sativum</Emphasis>) juice containing allicin on <Emphasis Type="Italic">Phytophthora infestans</Emphasis> and downy mildew of cucumber caused by <Emphasis Type="Italic">Pseudoperonospora cubensis</Emphasis>

The volatile antimicrobial substance allicin (diallylthiosulphinate) is produced in garlic when the tissues are damaged and the substrate allicin (S-allyl-l-cysteine sulphoxide) mixes with the enzyme alliin-lyase (E.C.4.4.1.4). Allicin undergoes thiol-disulphide exchange reactions with free thiol groups in proteins and it is thought that this is the basis of its antimicrobial action. At 50 μg ml^-1, allicin in garlic juice inhibited the germination of sporangia and cysts and subsequent germ tube growth by Phytophthora infestans both in vitro and in vivo on the leaf surface. Disease severity in P. infestans-infected tomato seedlings was also reduced by spraying leaves with garlic juice containing allicin over the range tested (55–110 μg ml⁻¹) with an effectiveness ranging from approximately 45–100%. Similarly, in growth room experiments at concentrations from 50–1,000 μg ml⁻¹, allicin in garlic juice reduced the severity of cucumber downy mildew caused by Pseudoperonospora cubensis by approximately 50–100%. These results suggest a potential for developing preparations from garlic for use in specialised aspects of organic farming, e.g. for reducing pathogen inoculum potential and perhaps for use under glass in horticulture.     

<Emphasis Type="Italic">Tomato chlorotic dwarf viroid</Emphasis> in the ornamental plant <Emphasis Type="Italic">Vinca minor</Emphasis> and its transmission through tomato seed

Two novel aspects of Tomato chlorotic dwarf viroid (TCDVd) are reported, namely that TCDVd was detected in symptomless plants of Vinca minor, a trailing ground cover surviving at subzero temperatures (−12°C); and that TCDVd was seed-borne in tomato and detected in high percentages in tomato seeds and seedlings. Soaking seeds in a low concentration of sodium hypochlorite did not eliminate the viroid. The sequence analysis showed that the TCDVd isolate consists of 360 nucleotides and has sequence identity between 96% to 99% with isolates of TCDVd from other hosts.     

Pymetrozine interferes with transmission of<Emphasis Type="Italic">Tomato yellow leaf curl virus</Emphasis> by the whitefly<Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Pymetrozine, a novel compound belonging to the class pyridine-azomethines, is a feeding inhibitor labeled for use against plant pests in the order Hemiptera. Pymetrozine was evaluated for its ability to interfere with whitefly transmission of the begomovirusTomato yellow leaf curl virus (TYLCV). Pymetrozine was applied as Fulfill ^TM 50 WG at two rates (0.291 and 0.582 g formulationl ⁻¹) to tomato seedlings with four to six true leaves. Viruliferous whiteflies (three to five per plant) were added 1, 4, 7 and 11 d after a single application of pymetrozine, and transmission rates were determined 4 wk after the addition of whiteflies. Pymetrozine provided protection against transmission of TYLCV by viruliferous whiteflies for up to 1 wk after a single apliation. No phytotoxicity was observed on tomato transplants. These results indicate that pymetrozine could be an effective tool for tomato transplant producers to protect susceptible transplants from infection by begomoviruses, such as TYLCV. Pymetrozine might also work well as part of an integrated approach to begomovirus management in greenhouse tomato fruit production. http://www.phytoparasitica.org positing Oct. 20, 2003.     

Functional analysis of the melanin biosynthesis genes <Emphasis Type="Italic">ALM1</Emphasis> and <Emphasis Type="Italic">BRM2</Emphasis>-<Emphasis Type="Italic">1</Emphasis> in the tomato pathotype of <Emphasis Type="Italic">Alternaria alternata</Emphasis>

The tomato pathotype of Alternaria alternata (A. arborescens) produces the dark brown to black pigment melanin, which accumulates in the cell walls of hyphae and conidia. Melanin has been implicated as a pathogenicity factor in some phytopathogenic fungi. Here, two genes of the tomato pathotype for melanin biosynthesis, ALM1 and BRM2-1, which encode a polyketide synthetase and a 1,3,8-trihydroxynaphthalene (THN) reductase, respectively, have been cloned and disrupted in the pathogen. The gene-disrupted mutants, alm1 and brm2-1, had albino and brown phenotypes, respectively. The wild-type and the mutants caused the same necrotic lesions on the leaves after inoculation with spores. These results suggest that melanin is unlikely to play a direct role in pathogenicity in the tomato pathotype A. alternata. Scanning electron microscopy revealed that the conidia of both mutants have much smoother surfaces in comparison to the wild-type. The conidia of those mutants were more sensitive to UV light than those of the wild-type, demonstrating that melanin confers UV tolerance.     

Effects of some fungicides on <Emphasis Type="Italic">Isaria farinosa</Emphasis>, and <Emphasis Type="Italic">in vitro</Emphasis> growth and infection rate on <Emphasis Type="Italic">Planococcus citri</Emphasis>

The effects of some fungicides used against citrus diseases, on mycelial growth and conidial germination of Isaria farinosa (Holmsk.) Fries [Sordariomycetes: Hypocreales] and also on the pathogenicity of the fungus on citrus mealybug, Planococcus citri (Risso), were determined. Systemic fungicides such as tebuconazole, penconazole and nuarimol were the most effective as regards both conidial germination and mycelial growth. Protective fungicides such as captan, chlorothalonil, mancozeb and propineb inhibited conidial germination at between 1 and 5 μg ml⁻¹ concentration, but captan, chlorothalonil and propineb did not inhibit the mycelial growth at 5,000 μg ml⁻¹. Mancozeb inhibited mycelial growth between 2,500 and 5,000 μg ml⁻¹. Sulphur and copper oxychloride did not inhibit the fungus even at very high concentrations. Sulphur, copper oxychloride, fosetyl-al, chlorothalonil and carbendazim did not decrease the mortality percentage caused by I. farinosa. Tebuconazole, penconazole and mancozeb were the most effective and respectively reduced the mortality from 83% to 33%, 28% and 30% in the ovisacs, from 81% to 29%, 27% and 29% in the 1st instar larvae, and from 84% to 34% in the adult females.     

Effect of seed priming with <Emphasis Type="Italic">Serratia plymuthica</Emphasis> and <Emphasis Type="Italic">Pseudomonas chlororaphis</Emphasis> to control <Emphasis Type="Italic">Leptosphaeria maculans</Emphasis> in different oilseed rape cultivars

The efficacy of a seed treatment of oilseed rape (OSR) (Brassica napus) with the rhizobacteria Serratia plymuthica (strain HRO-C48) and Pseudomonas chlororaphis (strain MA 342) applied alone or in combination against the blackleg disease caused by Leptosphaeria maculans was tested with different cultivars. Seeds were soaked in bacterial suspensions (bio-priming) to obtain log₁₀ 6–7 CFU seed⁻¹. Cotyledons were inoculated with a 10 ul droplet of L. maculans spore suspension of log₁₀ 7 spores ml⁻¹ and the disease index (size of lesions) was evaluated 14 days later. A mean disease reduction of 71.6% was recorded for S. plymuthica and of 54% for P. chlororaphis. The combined treatment was not superior to the treatment with S. plymuthica alone. The reduction of the disease caused by S. plymuthica was independent of the cultivar’s susceptibility, whereas the control effect recorded with P. chlororaphis increased with decreasing cultivar resistance to blackleg disease. The bacterial colonization of OSR was restricted to the roots and hypocotyl. No significant difference in bacterial colonization of the rhizosphere was observed between different cultivars, nor between single or combined bacterial seed treatments.     

Pathogenicity,vegetative compatibility and amplified fragment length polymorphism (AFLP) analysis of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">radicis-cucumerinum</Emphasis> isolates from Turkish greenhouses

The objective of the current study was to characterize Fusarium oxysporum f. sp. radicis-cucumerinum isolates from cucumbers in Turkey in terms of pathogenicity, vegetative compatibility and amplified fragment length polymorphism (AFLP) variation. In the 2007 and 2008 greenhouse cucumber-growing seasons, surveys were conducted in Adana, Antalya, Hatay and Mersin provinces of the Mediterranean region of Turkey. Forty-seven fungal isolates of F. oxysporum were recovered from diseased cucumber plants. The pathogenicity of each isolate was tested on cucumber seedlings at the one-true-leaf stage. Forty of the 47 isolates of F. oxysporum were virulent on cucumber seedlings. Based on disease symptoms, the differential effect of temperatures of 17°C and 29°C on disease development, and the virulence on cucumber seedlings, these 40 isolates were identified as F. oxysporum f. sp. radicis-cucumerinum. Nitrate non-utilizing mutants were generated on minimal medium containing 1.5% KClO₃ and their phenotypes were determined. Mutants in different phenotypic classes were paired on minimal medium; of 40 F. oxysporum f. sp. radicis-cucumerinum isolates, thirty-eight were placed into VCG 0260. Remaining two strains were assigned to VCG 0261. The AFLP primers produced a total of 180 fragments between 200 and 500 bp in length for the 30 isolates tested. At a genetic similarity of 0.71, the UPGMA analysis separated the isolates into two distinct clusters. The first cluster, AFLP I, included 28 isolates, of which all belonged to VCG 0260. Two strains in the second AFLP cluster both belonged to VCG 0261.     

Induced resistance to<Emphasis Type="Italic">Cladosporium cucumerinum</Emphasis> in cucumber by pectinases extracted from<Emphasis Type="Italic">Penicillium oxalicum</Emphasis>

Pectinases extract (PE) from the fermentation product ofPenicillium oxalicum BZH-2002 was tested for its ability to induce protection against scab caused byCladosporium cucumerinum on cucumber (Cucumis sativus L.) plants. Seedlings with one true leaf were sprayed with various concentrations of PE (10–200 units ml⁻¹) 3 days before inoculation withC. cucumerinum. Results showed that the induced local protection against the pathogen was dose-dependent when the concentrations of PE were between 20 and 120 units ml⁻¹; systemically induced resistance against the pathogen was not observed. Boiled PE had a slight effect on disease reduction. Commercial pectinases prepared fromAspergillus niger showed lower protection against scab compared with PE when they were used at the same concentration of enzyme activity. No inhibitory activity was observed on conidial germination or germ-tube growth ofC. cucumerinum. PE was further evaluated for its enhancement of defense-related enzymes. Peroxidase (PO), polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) increased in cucumber seedlings after treatment with PE. PO and PPO remained at a higher level in PE-pretreated seedlings throughout the experiment period whether pathogen-inoculated or non-inoculated, whereas PAL activity began to decrease 2 days after PE treatment. http://www.phytoparasitica.org posting July 14, 2004.     

The potential of combining <Emphasis Type="Italic">Pasteuria penetrans</Emphasis> and neem (<Emphasis Type="Italic">Azadirachta indica</Emphasis>) formulations as a management system for root-knot nematodes on tomato

Initial applications of 10⁴ spores g⁻¹ of Pasteuria penetrans, and dried neem cake and leaves at 3 and 2% w:w, respectively, were applied to soil in pots. Juveniles of Meloidogyne javanica were added immediately to the pots (500, 5,000 or 10,000) before planting 6-week-old tomato seedlings. The tomatoes were sampled after 64 days; subsequently a second crop was grown for 59 days and a third crop for 67 days without further applications of P. penetrans and neem. There was significantly less root-galling in the P. penetrans combined with neem cake treatment at the end of the third crop and this treatment also had the greatest effect on the growth of the tomato plants. At the end of the third crop, 30% of the females were infected with P. penetrans in those treatments where spores had been applied at the start of the experiment. The effects of neem leaves and neem cake on the nematode population did not persist through the crop sequences but the potential for combining the amendments with a biological control agent such as P. penetrans is worthy of further evaluation.     

<Emphasis Type="Italic">Agrobacterium</Emphasis>-mediated transformation as a useful tool for the molecular genetic study of the phytopathogen <Emphasis Type="Italic">Curvularia lunata</Emphasis>

In order to explore the molecular mechanisms of virulence and genetic variance of Curvularia lunata in maize, an ATMT (Agrobacterium tumefaciens-mediated transformation) system was established in order to create a wide range of insertional transformants of C. lunata. Our results showed that the germinating conidia were the ideal starting material for transformation. Based on our optimised transformation condition, the transformation efficiency of C. lunata with T-DNA was improved greatly, and the average transformation frequency was as high as 84 ± 5 transformants per 1 × 10⁶ germlings. Southern blotting results of 39 randomly-selected transformants showed a unique hybridisation pattern and predominant single-copy insertions. An ATMT library containing approximate 3000 transformants was generated, and four types of transformants were screened in terms of growth rate, sporulation, mycelial pigmentation, and toxin production in vitro. This library will be used to identify genes involved in the virulence of the pathogen.     

Susceptibility of eggs of <Emphasis Type="Italic">Tribolium confusum</Emphasis>, <Emphasis Type="Italic">Ephestia kuehniella</Emphasis> and <Emphasis Type="Italic">Plodia interpunctella</Emphasis> to four essential oil vapors

Susceptibility of eggs of Tribolium confusum du Val. (Coleoptera: Tenebrionidae), Ephestia kuehniella (Zell.) (Lepidoptera: Phycitidae) and Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) to vapors of essential oil from garlic (Allium sativum L.), birch (Betula lenta L.), cinnamon (Cinnamonum zeylanicum (Blume)) and aniseed (Pimpinella anisum L.) was studied. Preliminary bioassay tests indicated that vapors of the essential oils had a significant effect on the eggs of tested insect species when exposed to a concentration of 20 μl l ⁻¹ air for 24 h. Generally, garlic and birch essential oils were more toxic to the eggs of tested insect species than cinnamon and aniseed essential oils (except for eggs of T. confusum). There was also a significant difference between susceptibility of eggs of T. confusum, E. kuehniella and P. interpunctella to tested essential oils. Toxicity data indicated that eggs of T. confusum were more susceptible to tested essential oils, with LC₉₀ values ranging from 3.11 to 33.49 μl l ⁻¹ air, than those of E. kuehniella and P. interpunctella; eggs of P. interpunctella were the most tolerant to the essential oils, with LC₉₀ values ranging from 22.02 to 72.42 μl l ⁻¹ air. Concentration × time (Ct) products of 0.29, 0.22, 0.13 and 1.37 mg h l ⁻¹ for garlic, birch, cinnamon and aniseed essential oil, respectively, were required to obtain 90% kill of T. confusum eggs. Although cinnamon essential oil had a much closer Ct product value to methyl bromide, garlic and birch essential oils were found to be the most promising ones since they had also high fumigant toxicity on eggs of both E. kuehniella and P. interpunctella.     

Toxigenicity and pathogenicity of <Emphasis Type="Italic">Fusarium poae</Emphasis> and <Emphasis Type="Italic">Fusarium avenaceum</Emphasis> on wheat

In a field experiment between 2004 and 2006, 14 winter wheat varieties were inoculated with either a mixture of three isolates of F. poae or a mixture of three isolates of F. avenaceum. In a subsequent climate chamber experiment, the wheat variety Apogee was inoculated with individual single conidium isolates derived from the original poly conidium isolates used in the field. Disease symptoms on wheat heads were visually assessed, and the yield as well as the fungal incidence on harvested grains (field only) was determined. Furthermore, grains were analysed using LC-MS/MS to determine the content of Fusarium mycotoxins. In samples from field and climate chamber experiments, 60 to 4,860 μg kg⁻¹ nivalenol and 2,400 to 17,000 μg kg⁻¹ moniliformin were detected in grains infected with F. poae and F. avenaceum, respectively. Overall, isolate mixtures and individual isolates of F. avenaceum proved to be more pathogenic than those of F. poae, leading to a higher disease level, yield reductions up to 25%, and greater toxin contamination. For F. poae, all variables except for yield were strongly influenced by variety (field) and by isolate (climate chamber). For F. avenaceum, variety had a strong effect on all variables, but isolate effects on visual disease were not reflected in toxin production. Correlations between visual symptoms, fungal incidence, and toxin accumulation in grains are discussed.     

Mutational analysis of type III effector genes from <Emphasis Type="Italic">Xanthomonas citri</Emphasis> subsp. <Emphasis Type="Italic">citri</Emphasis>

Xanthomonas citri subsp. citri, the causal agent of citrus canker, relies extensively on a type III secretion system for infection by delivering type III effectors into host cells. In the genus Xanthomonas, two major regulators, HrpG and HrpX, are involved in the expression of genes encoding the type III secretion system. Twenty-three candidate type III effectors were identified as targets for analysis. The involvement in pathogenicity of 20 candidate effector genes in X. citri strain 306 (Xcc-306) was investigated using site-directed mutagenesis. Pathogenicity assays in grapefruit of 19 genes using site-directed mutagenesis revealed that none of the mutants demonstrated to have reduced ability to cause canker disease. A mutation in the TAL effector pthA4 ^– resulted in loss of hypertrophy although no changes were observed in bacterial growth in leaves. Mutations in hrpG, hrpX, or hrpA genes displayed a complete loss of pathogenicity. Moreover, all mutants maintained the ability to trigger a hypersensitive response (HR) in non-host tomato. In contrast to previous studies, hrpG ^– , hrpX ^– and hrpA ^– mutants also retained the ability to elicit an HR in tomato, indicating the presence of an Hrp independent elicitor in Xcc-306.     

Assessment of resistance to <Emphasis Type="Italic">Ceratocystis cacaofunesta</Emphasis> in cacao genotypes

Ceratocystis wilt of cacao (caused by Ceratocystis cacaofunesta) is a dangerous disease and results in the death of the plant. This fungus was recently identified in the major cacao-producing regions of Brazil, and was observed to be more aggressive than isolates from other geographical locations. The objective of this study was to develop and test a consistent method to assess cacao genotype response to C. cacaofunesta, based on young plants (seedlings or cuttings). The fungus was inoculated by the deposition of propagule suspensions on cut stems. The parameters to assess disease progress were (a) disease incidence, (b) differences in mortality between the most contrasting cacao genotypes for resistance and susceptibility, (c) disease index, (d) consistency of response over time and (e) relative lesion heights. When seedlings were used for the analyses, the ICS-1 and TSH-1188 genotypes proved to be useful as genetic standards for susceptibility and resistance to C. cacaofunesta, respectively. Inoculum concentrations between 10⁴ and 10⁵ propagules ml⁻¹ and the moment at which the disease incidence stabilized provided appropriate conditions for genotypic comparison. When ten cacao genotypes propagated by cuttings (clones) were assessed, the results confirmed TSH-1188 as the reference genotype for resistance to C. cacaofunesta, while the remaining clones could be grouped as resistant (CEPEC-2008), moderately resistant (CEPEC-2002, CEPEC-2007) and susceptible (CEPEC-2009, CCN-10, CCN-51, HW-25, PH-16, SJ-02). The analytical concepts and results were discussed in terms of their application in breeding programmes aimed at developing genetic resistance to Ceratocystis wilt of cacao.     

A molecular mechanism of resistance to streptomycin in <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pv. <Emphasis Type="Italic">oryzicola</Emphasis>

Xanthomonas oryzae pv. oryzicola, the causal agent of rice leaf streak disease, was found to be sensitive to streptomycin (an aminocyclitol glycoside antibiotic), by inhibition of protein synthesis resulting from interference with translational proofreading. This study aimed to determine the molecular resistance mechanism of X. oryzae pv. oryzicola to streptomycin. Seven streptomycin-resistant mutants were obtained by UV induction or streptomycin selection. These mutants can grow at 100 μg ml⁻¹ of streptomycin while the wild-type strain (RS105) cannot grow at 5 μg ml⁻¹. Sequencing indicated that the rpsL gene encoding ribosomal protein S12 has 375 bp encoding 125 amino acid residues. In all resistant strains, a mutation in which AAG was substituted for AGG (Lys→Arg) occurred either at codon 43 or 88. Two plasmids, pUFRRS and pUFRRX, were constructed by ligating the rpsL gene into the cosmid pUFR034. The plasmids pUFRRS and pUFRRX containing the Lys→Arg mutation of the rpsL gene conferred streptomycin resistance to the sensitive wild-type strain by electroporation. Both transformants, RS1 and RS2, could grow in the medium containing 50 μg ml⁻¹ of streptomycin. A mutation at codon 43 or 88 in rpsL can result in resistance of Xanthomonas oryzae pv. oryzicola to streptomycin.     

<Emphasis Type="Italic">Paecilomyces lilacinus</Emphasis>, a potential biocontrol agent on apple rust mite <Emphasis Type="Italic">Aculus,schlechtendali</Emphasis> and interactions with some fungicides <Emphasis Type="Italic">in vitro</Emphasis>

The apple rust mite Aculus schlechtendali (Nal.) (Acari: Eriophyidae), is a main pest in apple-growing areas in Ankara, Turkey, and chemical control applications have some limitations. Entomopathogenic fungi have a potential for biological control of mites. In this study, an entomopathogenic fungus, Paecilomyces lilacinus (Thom) Samson (Deuteromycota: Hyphomycetes), was first isolated from the mite cadavers on Japanese crab apple leaves and pathogenicity of the fungus was observed in different inoculum densities and relative humidities. The pathogen caused up to 98.22% mortality of the mite population. The effects of some fungicides on the entomopathogenic fungus were determined in in vitro studies. Carbendazim, penconazole and tebuconazole were the most effective fungicides on mycelial growth of P. lilacinus, with EC₅₀ values under 3 μg ml⁻¹. In spore germination tests, captan, mancozeb, propineb were the most effective fungicides, followed by tebuconazole, penconazole, nuarimol and chlorothalonil. Sulphur could not inhibit the conidia germination totally at 5,000 μg ml⁻¹. Copper oxychloride and fosetyl-al prevented conidia formation at concentrations above 1,000 μg ml⁻¹.