Differing susceptibility to<Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> formulations of<Emphasis Type="Italic">Thaumetopoea wilkinsoni</Emphasis> populations between forests with different<Emphasis Type="Italic">Bt</Emphasis> management in Israel

The susceptibility ofThaumetopoea wilkinsoni larvae toBacillus thuringiensis (Bt) formulations was screened in 2003 and 2004. Eggs and larvae were collected from pine forests in 11 geographical locations in Israel. Larval mortality bioassays were conducted with commercial formulations (Delfin WG, Dipel DF and Foray 48B) at concentrations ranging from 0.001% to 0.1%. Significant differences in susceptibility toBt were recorded among populations that were treated withBt intensively, frequently, or never. The mortality recorded in a population that was never treated withBt was twice that in an intensivelyBt-treated population. The correlation between susceptibility toBt and the possible resistance to the microbe is discussed. http://www.phytoparasitica.org posting Jan. 31, 2007.     

Virulence and diversity of <Emphasis Type="Italic">Blumeria graminis</Emphasis> f.sp. <Emphasis Type="Italic">hordei</Emphasis> in East China

Four hundred and sixty-one isolates of Blumeria graminis f.sp. hordei were obtained from eight populations occurring on cultivated barley (Hordeum vulgare) at four geographically distant locations in China during 2003 and 2004. Their virulence frequency was determined on 30 differential lines. No isolate was virulent on differential lines possessing the resistance genes Mla1, Mla3, Mla6, Mla7, Mla9, Mla12, Mla13, Mlat, Mlg, Mla10, Mla22, Mla23, Mlp1, Ml(N81) and Mlmw. Virulences to the first nine resistance genes are prevalent in Europe and constitute the main part of genetic distance between Chinese and European populations. Conversely, no isolate was avirulent on the differential lines possessing the genes Mla8 and Ml(Ch). The frequencies of isolates overcoming the genes Mla2, Mla11, Mlk1 and Mlk2 were .4–9.3%, and frequencies of isolates overcoming the genes Mlh, MlLa, Ml(Bw), Mlra, Ml(Ru2), mlw, MlGa, MlWo and Mlnn ranged from 18.2% to 98.7%. Based on reactions of differential lines possessing the genes Mlk1, Mlh, MlLa, Ml(Bw), Mlra and Ml(Ru2), pathotypes were identified and diversity parameters calculated. Eleven of 22 detected pathotypes were found in both years and comprised 94.6% of isolates. Generally, the populations from different locations in 1 year were more closely related than populations collected from the same locations in different years. Complete effectiveness of the resistance genes, for which no corresponding virulences were found, will allow Chinese breeders to access many modern European barley cultivars that are fully resistant to powdery mildew in China, including those possessing the non-host resistance gene mlo.     

Is the parasitization rate of<Emphasis Type="Italic">Diaeretiella rapae</Emphasis> influenced when<Emphasis Type="Italic">Brevicoryne brassicae</Emphasis> feeds on<Emphasis Type="Italic">brassica</Emphasis> plants?

The development time and parasitization rate ofDiaeretiella rapae (M’Intosh) onBrevicoryne brassicae (L.) feeding on differentBrassica cultivars was studied in the laboratory at 20°C. The shortest development time from egg to adult parasitoid was 11.6 days on cabbage cv. ‘Yalova 1’ and the longest was 12.1 days on turnip cv. ‘Antep’ and rapeseed cv. local variety. Females lived significantly longer than males on the host plants used in the study. Females and males had the shortest longevity on rapeseed at 11.1 and 5.1 days, respectively. The highest percent parasitism ofB. brassicae byD. rapae was found on cabbage (40.20%), and the lowest was recorded on turnip (32.64%). Our results demonstrate that parasitism rate could be influenced by the plant quality, probably due to the nutritional status of the aphids or to toxic compounds ingested through the plant. Cabbage, cauliflower and broccoli were found to be suitable plants for the parasitoid, considering the development time of pre-adults, and the parasitization rate ofD. rapae onB. brassicae. http://www.phytoparasitica.org posting Jan. 23, 2007.     

Use of sclerotia of<Emphasis Type="Italic">Sclerotinia sclerotiorum</Emphasis> for efficient production of conidia of<Emphasis Type="Italic">Coniothyrium minitans</Emphasis> in liquid culture

A study was conducted to determine the feasibility of using sclerotia ofSclerotinia sclerotiorum for producing conidia ofConiothyrium minitans in liquid culture. The medium (SST) was made of water containing 2.0, 1.5, 1.0 or 0.5% (w/v) ground sclerotia ofS. sclerotiorum and 100 μgl ⁻¹ thiamine hydrochloride (HCl). One ml of conidial suspension (2 × 10⁷ conidia ml⁻¹) ofC. minitans LRC 2534 was inoculated into 100 ml of SST medium or control (thiamine HCl in water) and incubated at 20 ± 2°C on a shaker at 200 rpm. Subsamples were removed periodically and examined under a compound microscope. Conidia in the SST media germinated within 24 h, developed into branched hyphae within 48 h, produced pycnidia after 3–4 days, and the pycnidia released mature conidia after 7 days. Production of conidia varied with the concentration of sclerotia in the SST medium. It was lower (3.6 × 10⁶ conidia ml⁻¹) at 0.5% but higher (1.2 × 10⁸ conidia ml⁻¹) at 2%. The new conidia were viable and the colonies developing from them showed the original morphological characteristics. It was concluded that using SST liquid medium as a substrate for mass production of conidia ofC. minitans has potential for use in commercial development of this mycoparasite as a biocontrol product. http:www.phytoparasitica.org posting Jan. 23, 2007.     

Effect of seed treatment of<Emphasis Type="Italic">Arachis hypogaea</Emphasis> with<Emphasis Type="Italic">Bacillus subtilis</Emphasis> on nodulation in biocontrol of southern blight (<Emphasis Type="Italic">Sclerotium rolfsii</Emphasis>) disease

The employment of formulatedBacillus subtilis for peanut seeds (Arachis hypogaea cv. ‘Shulamit’) counteracted the destructive effects of the seedborne pathogenSclerotium (Athelia)rolfsii on the nodulation, leghemoglobin and nitrogenase activity of peanuts. Moreover, the changes in crop vigor index, total nitrogen content and survivability of bothRhizobium spp. andB. subtilis have been related to compatibility and even an occasional synergism between them. http://www.phytoparasitica.org posting Nov. 12, 2006.     

Characteristics of a <Emphasis Type="Italic">Plasmopara angustiterminalis</Emphasis> isolate from <Emphasis Type="Italic">Xanthium strumarium</Emphasis>

Leaves of Xanthium strumarium infected with downy mildew were collected in the vicinity of a sunflower field in southern Hungary in 2003. Based on phenotypic characteristics of sporangiophores, sporangia and oospores as well as host preference the pathogen was classified as Plasmopara angustiterminalis. Additional phenotypic characters were investigated such as the size of sporangia, the number of zoospores per sporangium and the time-course of their release. Infection studies revealed infectivity of the P. angustiterminalis isolate to both X. strumarium and Helianthus annuus. Inoculation of the sunflower inbred line, HA-335 with resistance to all known P. halstedii pathotypes, resulted in profuse sporulation on cotyledons and formation of oospores in the bases of hypocotyls. Infections of sunflower differential lines often led to damping-off. Molecular genetic analysis using simple sequence repeat primers and nuclear rDNA sequences revealed clear differences to Plasmopara halstedii, the downy mildew pathogen of sunflower.     

Environmental persistence of<Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> products tested under natural conditions against<Emphasis Type="Italic">Thaumetopoea wilkinsoni</Emphasis>

Information on persistence ofBacillus thuringiensis (Bt) is needed to improve the microbial pest management programs against the pine processionary mothThaumetopoea wilkinsoni in pine forests in Israel. The persistence of the microbe under natural conditions of rain and sunlight was evaluated and is documented here for the first time. Pine saplings were sprayed with three commercialBt products, Foray 48B, Delfin WG and Dipel DF, all used at 32,000 IU mg⁻¹ in a formulation with 1% (w/v) of condensed milk. In experiments conducted in November and December of 2004, the saplings were either exposed to rain and sunlight or were sheltered to avoid these environmental factors. The lowest rainfall recorded in the 8-day experiments was 16.5 mm (test 2) and the heaviest was 71.1 mm (test 1). Solar irradiation ranged from 9.4 to 10.9 MJ m⁻². The minimum temperature was close to 10°C and the maximum was less than 23°C. Needles of the treated saplings and their controls were sampled after 0, 1, 5 and 8 days, and were fed to 1 ^st or 2 ^nd instar larvae. Dipel DF persisted better than Delfin WG and still retained its initial activity of 80–100% mortality on day 8 at low rainfall (test 2). Dripping ofBt from upper to lower branches was quantified with the larval bioassays. The milk formulation proved to be an effective rain-fasting adjuvant. http://www.phytoparasitica.org posting May 4, 2007.     

<Emphasis Type="Italic">Physalis ixocarpa</Emphasis> and <Emphasis Type="Italic">P. peruviana</Emphasis>, new natural hosts of <Emphasis Type="Italic">Tomato chlorosis virus</Emphasis>

Tomato chlorosis virus causes yellow leaf disorder epidemics in many countries worldwide. Plants of Physalis ixocarpa showing abnormal interveinal yellowing and plants of Physalis peruviana showing mild yellowing collected in the vicinity of tomato crops in Portugal were found naturally infected with ToCV. Physalis ixocarpa and P. peruviana were tested for susceptibility to ToCV by inoculation with Bemisia tabaci, Q biotype. Results confirmed that ToCV is readily transmissible to both species. The infection was expressed in P. ixocarpa by conspicuous interveinal yellow areas on leaves that developed into red or brown necrotic flecks, while P. peruviana test plants remained asymptomatic. Infected plants of both P. ixocarpa and P. peruviana served as ToCV sources for tomato infection via B. tabaci transmission. This is the first report of P. ixocarpa and P. peruviana as natural hosts of ToCV.     

A survey of the genera of<Emphasis Type="Italic">Microgaster</Emphasis> latreille and<Emphasis Type="Italic">Hygroplitis</Emphasis> thomson (Hymenoptera: Braconidae: Microgastrinae) from China

The genera ofMicrogaster Latreille 1804 andHygroplitis Thomson 1895 from China are presented systematically in this paper. Thirty-two species ofMicrogaster and three species ofHygroplitis are known in China. Diagnosis, character variation, distribution and host of each species among the two genera are presented, including its host and distribution. Keys to the species ofMicrogaster andHygroplitis are given. http://www.phytoparasitica.org posting Dec. 19, 2006.     

Isolation of pathogenicity- and gregatin-deficient mutants of <Emphasis Type="Italic">Phialophora gregata</Emphasis> f. sp. <Emphasis Type="Italic">adzukicola</Emphasis> through <Emphasis Type="Italic">Agrobacterium tumefaciens</Emphasis>-mediated transformation

Phialophora gregata f. sp. adzukicola, a causal agent of brown stem rot in adzuki beans, produces phytotoxic compounds: gregatins A, B, C, D, and E. Gregatins A, C, and D cause wilting and vascular browning in adzuki beans, which resemble the disease symptoms. Thus, gregatins are considered to be involved in pathogenicity. However, molecular analyses have not been conducted, and little is known about other pathogenic factors. We sought to isolate nonpathogenic and gregatin-deficient mutants through Agrobacterium tumefaciens-mediated transformation (ATMT) for cloning of pathogenicity-related genes. The co-cultivation of P. gregata and A. tumefaciens for 48 h at 20°C with 200 μM acetosyringone resulted in approximately 80 transformants per 10⁶ conidia. The presence of acetosyringone in the A. tumefaciens pre-cultivation period led to an increase in T-DNA copy number per genome. Of 420 and 110 transformants tested for their pathogenicity and productivity of gregatins, one nonpathogenic and three gregatin-deficient mutants were obtained, respectively. The nonpathogenic mutant produced gregatins, whereas the gregatin-deficient mutants had pathogenicity comparable to the wild-type strain. This is the first report of ATMT of P. gregata. Further analysis of these mutants will help reveal the nature of the pathogenicity of this fungus including the role of gregatin in pathogenesis.     

Incidence of viruses in <Emphasis Type="Italic">Alstroemeria</Emphasis> plants cultivated in Japan and characterization of <Emphasis Type="Italic">Broad bean wilt virus-2, Cucumber mosaic virus</Emphasis> and <Emphasis Type="Italic">Youcai mosaic virus</Emphasis>

Alstroemeria plants were surveyed for viruses in Japan from 2002 to 2004. Seventy-two Alstroemeria plants were collected from Aichi, Nagano, and Hokkaido prefectures and 54.2% were infected with some species of virus. The predominant virus was Alstroemeria mosaic virus, followed by Tomato spotted wilt virus, Youcai mosaic virus (YoMV), Cucumber mosaic virus (CMV), Alstroemeria virus X and Broad bean wilt virus-2 (BBWV-2). On the basis of nucleotide sequence of the coat protein genes, all four CMV isolates belong to subgroup IA. CMV isolates induced mosaic and/or necrosis on Alstroemeria. YoMV and BBWV-2 were newly identified by traits such as host range, particle morphology, and nucleotide sequence as viruses infecting Alstroemeria. A BBWV-2 isolate also induced mosaic symptoms on Alstroemeria seedlings.     

Characterization of biotin-autotrophic isolates derived from naturally occurring auxotrophic race 2 isolates of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">lactucae</Emphasis>

Race 2 isolates of Fusarium oxysporum f. sp. lactucae have been recognized as biotin auxotrophs and consequently have restricted growth on Puhalla's minimal medium (MM), which contains no biotin. Biotin-autotrophic isolates were raised from race 2 isolates through cultural mutation that grew as well on MM as they did on MM supplemented with biotin. These autotrophs were identical to the parental isolates in pathogenicity on race differential cultivars of lettuce (Patriot, Banchu Red Fire, and Costa Rica No. 4), and thus were designated as race 2. A vegetative compatibility test indicated that the autotrophic isolates fell into the same vegetative compatibility group as the parents. Culture filtrates of the autotrophs allowed abundant growth of the parental auxotroph on MM, and, through a competitive enzyme-binding assay, biotin was detected in the culture filtrates. These results suggest that biotin auxotrophy in the natural race 2 isolates has no direct relation to pathogenicity, qualitatively defined as physiological race, or to vegetative compatibility.     

Susceptibility and resistance of <Emphasis Type="Italic">Beta vulgaris</Emphasis> subsp. <Emphasis Type="Italic">maritima</Emphasis> to foliar rub-inoculation with <Emphasis Type="Italic">Beet necrotic yellow vein virus</Emphasis>

Four lines (designated MR0, MR1, MR2, and M8) from 13 accessions of Beta vulgaris subsp. maritima were selected on the basis of phenotypes produced after foliar rub-inoculation with Beet necrotic yellow vein virus (BNYVV). The susceptible phenotype developed bright yellow local lesions, whereas the resistant phenotype had symptoms ranging from no visible lesions to necrotic lesions at the inoculation site. MR1 and MR2 lines had a resistant phenotype depending on the isolate and the MR0 line was susceptible to all isolates of BNYVV tested. The M8 line was highly susceptible; the virus spread systemically and caused severe stunting. These plant lines will be useful for distinguishing BNYVV isolates having different pathogenicities, especially those controlled by RNA3 and/or RNA5.     

Biofilm formation and resistance to bactericides of <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">theae</Emphasis>

Biofilm-grown cells of Pseudomonas syringae pv. theae (P.s.theae) wild-type strain K9301 on abiotic surface had remarkable resistance to kasugamycin in comparison to planktonically grown cells; however, the biofilm-grown cells of K9301 had the same sensitivity to copper sulfate. Because both the lesser biofilm-forming strain K9301S3 and enhanced biofilm-forming strain K9301-6 also had remarkable biofilm resistance to kasugamycin just as K9301 did and because epigallocatechin gallate, which enhanced biofilm formation of P.s.theae, had no effect on biofilm resistance to kasugamaycin, the degree of biofilm formation was not correlated with the antibiotic susceptibilities. In addition, K9301 and K9301S3 had less sensitivity to kasugamycin but had high sensitivity to copper sulfate on nonwounded leaf surfaces. These results indicate a possibility that the mechanism of P.s.theae biofilm resistance to bactericide functions on both abiotic and nonwounded leaf surfaces.     

Behavior and mutation of <Emphasis Type="Italic">Ralstonia solanacearum</Emphasis> in <Emphasis Type="Italic">Solanum toxicarium</Emphasis> grown in aseptic culture

To study the behavior and mutation of Ralstonia solanacearum in Solanum toxicarium, which is resistant to bacterial wilt, S. toxicarium was grown in aseptic culture and inoculated with R. solanacearum. Although 60%–80% of the inoculated plants were wilting after 2 to 3 days, most wilted plants had recovered by 20 days after inoculation. The pathogen was reisolated from over 98% of inoculated plant stems, but the percentage of recovery decreased the closer the isolation sites were toward the upper stem sections. Three colony types, characterized as fluidal white, nonfluidal red, and a mixture of fluidal white and nonfluidal red, were reisolated from the stems. Nonfluidal red colonies were less virulent on tomato plants than fluidal white colonies.     

Genetic diversity of <Emphasis Type="Italic">Fusarium oxysporum</Emphasis> f. sp. <Emphasis Type="Italic">spinaciae</Emphasis> in Japan based on phylogenetic analyses of rDNA-IGS and <Emphasis Type="Italic">MAT1</Emphasis> sequences

Twenty-eight isolates of Fusarium oxysporum f. sp. spinaciae (FOS; the causal agent of spinach wilt) collected from Japan were assessed for mating type and subjected to phylogenetic analysis. Mating type analysis revealed all isolates to be MAT1-2, suggesting that there is no sexual recombination within the population. Phylogenetic analyses based on nucleotide sequences of the ribosomal DNA intergenic spacer (IGS) and the mating type locus (MAT1) suggested that FOS is polyphyletic. The cluster analysis based on IGS showed four phylogenetic groups (S1–S4) among the isolates. Two distinct lineages, S1 and S3, included FOS isolates both of the vegetative compatibility group (VCG) types, 0330 and 0331, demonstrating that VCG differentiation in FOS may not necessarily reflect the phylogenetic relationships based on IGS and MAT1-2-1.     

A new <Emphasis Type="Italic">Rhizoctonia</Emphasis> sp. closely related to <Emphasis Type="Italic">Waitea circinata</Emphasis> causes a new disease of creeping bentgrass

Isolates of an unidentified Rhizoctonia sp. (UR isolates) were obtained from creeping bentgrass and Kentucky bluegrass with reddish brown sheath and foliar rots. Because the UR isolates anastomosed with isolates of three varieties of Waitea circinata (var. oryzae, var. zeae, and var. circinata), colony morphology, hyphal growth rate at different temperatures, pathogenicity, sequence analysis of the internal transcribed spacers (ITS) region of ribosomal RNA genes (rDNA) were compared. The colony color of mature UR isolates was distinct from isolates of the other three varieties of W. circinata. In pathogenicity tests on creeping bentgrass, the severity of the disease caused by UR isolates was significantly higher than that caused by the three varieties of W. circinata. Sequence similarities of the rDNA-ITS region between UR isolates and between isolates within each variety were high (97–100%), but they were lower among isolates from UR and the varieties of W. circinata (88–94%). In a phylogenetic tree based on the rDNA-ITS sequences, UR isolates formed a cluster separate from each of the clusters formed by the three varieties of W. circinata. These results indicate that the UR isolates clearly differ from the three varieties of W. circinata. We therefore propose that the UR isolates be classified as new Rhizoctonia sp. that are closely related to W. circinata and that the disease on creeping bentgrass should be called Waitea reddish-brown patch disease (Sekikasshoku-hagusare-byo in Japanese).     

<Emphasis Type="Italic">Pythium</Emphasis> and <Emphasis Type="Italic">Phytophthora</Emphasis> species associated with root and stem rots of kalanchoe

Pythium and Phytophthora species were isolated from kalanchoe plants with root and stem rots. Phytophthora isolates were identified as Phytophthora nicotianae on the basis of morphological characteristics and restriction fragment length polymorphism (RFLP) analysis of the rDNA-internal transcribed spacer regions. Similarly, the Pythium isolates were identified as Pythium myriotylum and Pythium helicoides. In pathogenicity tests, isolates of the three species caused root and stem rots. Disease severity caused by the Pythium spp. and Ph. nicotianae was the greatest at 35°–40°C and 30°–40°C, respectively. Ph. nicotianae induced stem rot at two different relative humidities (60% and >95%) at 30°C. P. myriotylum and P. helicoides caused root and stem rots at high humidity (>95%), but only root rot at low humidity (60%).     

Gummy stem blight of balsam pear caused by <Emphasis Type="Italic">Didymella bryoniae</Emphasis> and its anamorph <Emphasis Type="Italic">Phoma cucurbitacearum</Emphasis>

Gummy stem blight of balsam pear found in the Kanto district and in the Hokkaido Prefecture was demonstrated to be caused by Didymella bryoniae (Auerswald) Rehm based on inoculation experiments, molecular analysis, and morphological identification of the pathogenic fungus. This fungus was also pathogenic to related plants belonging to Cucurbitaceae. The imperfect stage of the fungus was identified as Phoma cucurbitacearum (Fr.: Fr.) Sacc. based on morphological similarities.