Genetic structure of <Emphasis Type="Italic">Pyrenophora teres</Emphasis> f. <Emphasis Type="Italic">teres</Emphasis> and <Emphasis Type="Italic">P. teres</Emphasis> f. <Emphasis Type="Italic">maculata</Emphasis> populations from western Canada

Infection by Pyrenophora teres f. teres (Ptt) or P. teres f. maculata (Ptm), the causal agents of the net and spot forms of net blotch of barley, respectively, can result in significant yield losses. The genetic structure of a collection of 128 Ptt and 92 Ptm isolates from the western Canadian provinces of Alberta (55 Ptt, 27 Ptm), Saskatchewan (58 Ptt, 46 Ptm) and Manitoba (15 Ptt, 19 Ptm) were analyzed by simple sequence repeat (SSR) marker analysis. Thirteen SSR loci were examined and found to be polymorphic within both Ptt and Ptm populations. In total, 110 distinct alleles were identified, with 19 of these shared between Ptt and Ptm, 75 specific to Ptt, and 16 specific to Ptm. Genotypic diversity was relatively high, with a clonal fraction of approximately 10 % within Ptt and Ptm populations. Significant genetic differentiation (PhiPT = 0.230, P = 0.001) was found among all populations; 77 % of genetic variation occurred within populations and 23 % between populations. Lower, but still significant genetic differentiation (PhiPT = 0.038, P = 0.001) was detected in Ptt, with 96 % of genetic variation occurring within populations. No significant genetic differentiation (PhiPT = 0.010, P = 0.177) was observed among Ptm populations. Isolates clustered in two distinct groups conforming to Ptt or Ptm, with no intermediate cluster. The high number of haplotypes observed, combined with an equal mating type ratio for both forms of the fungus, suggests that P. teres goes through regular cycles of sexual recombination in western Canada.     

Identification and characterization of <Emphasis Type="Italic">Alternaria alternata</Emphasis> (Fr.) Keissler causing <Emphasis Type="Italic">Ceratonia</Emphasis> Blight disease of carob (<Emphasis Type="Italic">Ceratonia siliqua</Emphasis> L.) in Turkey

A new dagger nematode, Xiphinema tica n. sp., is described and illustrated from several populations extracted from soil associated with several crops and wild plants in Costa Rica. The new dagger nematode is characterised by a moderate body size (3276–4240 μm), a rounded lip region, ca 13.5 μm wide, separated from body contour by a shallow depression, amphidial fovea large, stirrup-shaped, a moderately long odontostyle ca 135 μm long, stylet guiding ring located at ca 122 μm from anterior end, vulva almost equatorial (50–54%), well-developed Z-organ, with heavy muscularised wall containing in the most of specimens observed two moderately refractive inclusions variable in shape (from round to star-shaped), with uterine spines and crystalloid bodies; female tail short, dorsally convex-conoid, with rounded end and a small peg, with a c’ ratio ca 0.8, bearing two or three pairs of caudal pores and male absent. The unique and novel uterine differentiation based on the coexistence of a well-developed Z-organ mixed with uterine spines and crystalloid bodies in Xiphinema prompted us to update and include this combination of characters in the polytomous key of Loof and Luc (1990). Integrative diagnosis was completed with molecular data obtained, using D2-D3 expansion segments of 28S rDNA, ITS1-rDNA, partial 18S–rDNA and the partial mitochondrial gene cytochrome c oxidase subunit 1 (coxI). The phylogenetic relationships of this species with other Xiphinema spp. indicated that X. tica n. sp. was monophyletic to the other species from the morphospecies Group 4, Xiphinema oleae.     

Competence of <Emphasis Type="Italic">Frankliniella occidentalis</Emphasis> and <Emphasis Type="Italic">Frankliniella intonsa</Emphasis> strains as vectors for <Emphasis Type="Italic">Chrysanthemum stem necrosis virus</Emphasis>

The vector competence of Frankliniella occidentalis for Chrysanthemum stem necrosis virus (CSNV) was evaluated. Three vector strains with distinct competences for Tomato spotted wilt virus (TSWV) transmission were investigated, including an artificially selected strain (TsH) that has a particularly high competence (>90 %). Newly hatched larvae of F. occidentalis were given an acquisition access period of 5 days on CSNV-infected D. stramonium leaves, and reared to maturity. Their transmission efficiencies were examined using a leaf disk assay using Petunia x hybrida leaves. Following the leaf disk assay, the virus accumulation in the vectors was examined via a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) of their bodies. The results showed that the CSNV acquisition and transmission efficiency of the TsH strain did not differ from those of the others, indicating that the competence of F. occidentalis as a vector for CSNV is not related to that for TSWV. The CSNV transmission and acquisition efficiencies of two F. intonsa strains (Hiroshima and Fukuoka) were also evaluated. In Hiroshima strain, 35 % of adults were viruliferous, but only two transmitters (3 %) were observed. In Fukuoka strain, 6 % were viruliferous, and no transmitters were observed. These results indicate that F. intonsa cannot be a major vector for CSNV. The accumulation of CSNV in the adults of F. occidentalis and F. intonsa evaluated using DAS-ELISA showed a significant difference in ELISA values among transmitter, viruliferous non-transmitter, and non-viruliferous individuals. These results clearly demonstrated that only transmitters that accumulated a threshold quantity of virus can transmit CSNV to plants.     

Rice <Emphasis Type="Italic">terpene synthase 18</Emphasis> (<Emphasis Type="Italic">OsTPS18</Emphasis>) encodes a sesquiterpene synthase that produces an antibacterial (<Emphasis Type="Italic">E</Emphasis>)-nerolidol against a bacterial pathogen of rice

Plant volatile compounds, including terpenes, are known to be involved in the rice defense system. In the present analysis of a terpene synthase, OsTPS18, in rice, we found that OsTPS18 was localized in the cytoplasm and synthesized the sesquiterpenes (E)-nerolidol and (E)-β-farnesene. The amounts of (E)-nerolidol and (E)-β-farnesene increased after jasmonic acid (JA) treatment. (E)-Nerolidol had significant antibacterial activity against Xanthomonas oryzae pv. oryzae (Xoo). These results suggest that (E)-nerolidol plays an important role in JA-induced resistance against Xoo and that it functions as an antibacterial compound in rice.     

Antifungal activity of <Emphasis Type="Italic">Boerhavia diffusa</Emphasis> L. extract against <Emphasis Type="Italic">Phytophthora</Emphasis> spp. in tomato and pepper

A new longidorid nematode, Longidorus persicus n. sp., is described and illustrated from a population extracted from soil associated with wild rose (Rosa sp.) naturally growing in the mountains close to the village of Cheshmeh-e-Nezamei near the city of Gilan-e-Gharb, Kermanshah province, western Iran. The new needle nematode is characterised by a large body size (6550–7763 μm), an anteriorly flattened lip region, ca 13 μm wide, distinctly set off from body contour by a depression, amphidial fovea large, pocket shaped, slightly asymmetrically bilobed, a moderately long and flexible odontostyle ca 86 μm long, stylet guiding ring located at ca 25 μm from anterior end, posterior arrangement of the pharyngeal gland nuclei, vulva almost equatorial (49–54 %), tail short, about 3/4 of its width, dorsally convex-conoid, with rounded terminus, with a c’ ratio ca 1.3, bearing three pairs of caudal pores and male rare (ratio 1:10 females) with spicules ca 46 μm long. Integrative diagnosis was completed with molecular data obtained using D2-D3 expansion segments of 28S rDNA, ITS1-rDNA, and partial 18S-rDNA. The phylogenetic relationships of this species with other Longidorus spp. using D2-D3 expansion segments and partial 18S-rDNA indicated that L. persicus n. sp. clustered together with L. perangustus and L. euonymus: both of them sharing an anteriorly flattened lip region and distinctly set off from body contour by a depression.     

Infection of <Emphasis Type="Italic">Sorghum bicolor</Emphasis>, selected grass species and <Emphasis Type="Italic">Zea mays</Emphasis> by G<Emphasis Type="Italic">loeocercospora sorghi</Emphasis>, causal pathogen of zonate leaf spot

Zonate leaf spot (Gloeocercospora sorghi) is a common disease in Sorghum bicolor producing areas of the U.S., but little is known about its biology, virulence and severity on S. bicolor, Zea mays, and related crop grassweeds. Greenhouse studies were conducted to determine and compare the virulence and severity of G. sorghi on 10 commercially available sorghum hybrids, four Z. mays hybrids and selected grassweed species including Sorghum bicolor (grain sorghum and shattercane biotypes) and Sorghum halepense (Johnsongrass), two of the most problematic arable weeds. Plants from the respective species were inoculated with a local G. sorghi isolate and maintained in a dew-chamber at 24 °C for 24 h and then incubated under greenhouse conditions for 4 weeks. Plants were observed for lesion expression and rated using a modified Horsfall-Barrett scale (0–10). The first symptoms of infection were visible within 24 h following inoculation on shattercane and S. bicolor hybrids. Symptoms consisted of small, non-diagnostic purple lesions on the leaves. Results showed that S. bicolor, S. halepense and shattercane were susceptible to G. sorghi. All other species tested in this study were not infected. More particularly, disease severity, increased from a rating of 3 to 10 on sorghum and from 2 to 7 on S. halepense between 2 and 23 days after inoculation, respectively. However, disease severity on shattercane increased rapidly from 3.5 to 10 between 2 and 8 days after inoculation, respectively. Among the sorghum hybrids tested, FFR-322 appeared to be the most resistant to G. sorghi while Pioneer 83G66 appeared to be the most susceptible. Z. mays hybrids were not infected by the fungus used in this study. G. sorghi could be used effectively to manage shattercane and S. halepense infestations occurring in Z. mays and S. bicolor fields consisting of specific G. sorghi-resistant hybrids.     

Virulence profiling of <Emphasis Type="Italic">Xanthomonas oryzae</Emphasis> pv. <Emphasis Type="Italic">oryzae</Emphasis> isolates,causing bacterial blight of rice in India

Bacterial blight (BB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo), remains a major production constraint in rice cultivation especially in irrigated and rainfed lowland ecosystems in India. The pathogen is highly dynamic in nature and knowledge on pathotype composition among the Xoo population is imperative for designing a scientific resistance breeding program. In this study, four hundred isolates of Xoo collected from diverse rice growing regions of India were analyzed for their virulence and genetic composition. Virulence profiling was carried out on a set of differentials consisting of 22 near isogenic lines (NILs) of IR24 possessing different BB resistance genes and their combinations along with the checks. It was observed that different NILs possessing single BB resistance gene were susceptible to about 59–94% of the Xoo isolates except IRBB 13 (containing BB resistance gene xa13), which showed susceptibility to about 35% of the isolates. Based on the reaction of the Xoo isolates on the differentials, they were categorized into 22 pathotypes. Among the 22 pathotypes, IXoPt-1 and IXoPt-2 were least virulent and IXoPt # 18–22 were highly virulent. Pathotype IXoPt-19 which was virulent on all single BB resistance genes except xa13 constituted the major pathotype (22.5% isolates) and was widely distributed throughout India (16 states). This was followed by pathotype IXoPt-22 (17.25%) which was virulent on all the NILs possessing single BB resistance genes. Molecular analysis was carried out using two outwardly directed primers complementary to sequence of IS1112, a repetitive element of Xoo. A high level of genetic polymorphism was detected among these isolates and the isolates were grouped into 12 major clusters. The data indicated complex nature of evolution of the Xoo pathotypes and there was no strong correlation between pathotypes and genetic clusters as each genetic cluster was composed of Xoo isolates belonging to different pathotypes. The study indicated that none of the single BB resistance genes can provide broad spectrum resistance in India. However, two-gene combinations like xa5 + xa13 and different 3 or 4 genes combination like Xa4 + xa5 + xa13, Xa4 + xa13 + Xa21, xa5 + xa13 + Xa21 and Xa4 + xa5 + xa13 + Xa21 are broadly effective throughout India.     

Host-delivered RNAi-mediated root-knot nematode resistance in <Emphasis Type="Italic">Arabidopsis</Emphasis> by targeting <Emphasis Type="Italic">splicing factor</Emphasis> and <Emphasis Type="Italic">integrase</Emphasis> genes

Root-knot nematodes (RKNs) are one of the most important biotic factors limiting crop productivity in many crop plants. The major RKN control strategies include development of resistant cultivars, application of nematicides and crop rotation, but each has its own limitations. In recent years, RNA interference (RNAi) has become a powerful approach for developing nematode resistance. The two housekeeping genes, splicing factor and integrase, of Meloidogyne incognita were targeted for engineering nematode resistance using a host-delivered RNAi (HD-RNAi) approach. Splicing factor and integrase genes are essential for nematode development as they are involved in RNA metabolism. Stable homozygous transgenic Arabidopsis lines expressing dsRNA for both genes were generated. In RNAi lines of splicing factor gene, the number of galls, females and egg masses was reduced by 71.4, 74.5 and 86.6%, respectively, as compared with the empty vector controls. Similarly, in RNAi lines of the integrase gene, the number of galls, females and egg masses was reduced up to 59.5, 66.8 and 63.4%, respectively, compared with the empty vector controls. Expression analysis revealed a reduction in mRNA abundance of both targeted genes in female nematodes feeding on transgenic plants expressing dsRNA constructs. The silencing of housekeeping genes in the nematodes through HD-RNAi significantly reduced root-knot nematode infectivity and suggests that they will be useful in developing RKN resistance in crop plants.     

Parasitism of <Emphasis Type="Italic">Psytallia concolor</Emphasis> (Hymenoptera: Braconidae) on <Emphasis Type="Italic">Bactrocera oleae</Emphasis> (Diptera: Tephritidae) infesting different olive varieties

Psytallia concolor (Szépligeti) is a koinobiont endoparasitoid of many Tephritidae larvae, including Bactrocera oleae (Rossi), and has been used in Mediterranean areas for biological control of olive fruit fly by inundative release. The present study evaluates the influence of olive fruit variety (Amfissis, Arbequina, Branquita de Elvas, Carolea, Kalamon, Koroneiki, Leccino, Manzanilla, Mastoidis, Moroccan Picholine and Picholine) on P. concolor parasitism efficiency and performance in the field during two successive years. The results showed that the percentage of parasitism was significantly higher (>30%) in Mastoidis and Koroneiki (light-weight varieties <1.5 g) than Leccino which has a medium fruit weight, followed by Amfissis, Moroccan Picholine, Picholine and Branquita de Elvas. Only Manzanilla among large weight varieties, exhibited high percentage of parasitization (42.72%) during 2013. The mean weight of the pupae (>4.21 mg) as well as the length of the developed adult parasitoids (>3.5 cm) in Mastoidis and Manzanilla were significantly higher than these individuals developed from other varieties such as Koroneiki and Kalamon. Finally, the optimal host fruit for P. concolor development seems to be Mastoidis variety with great biological parameters and percentage of parasitism.     

<Emphasis Type="Italic">Aphelenchoides gorganensis</Emphasis> n. sp. (Nematoda: Aphelenchoididae)<Emphasis Type="Italic">,</Emphasis> a new species from Iran

Phytophthora capsici infection of chili pepper seedlings can cause substantial losses due to damping-off and collar rot diseases. Chemical control is no longer effective due to reported resistance development, on top of the related environmental concerns and the consumer demands for reduced use of fungicides. Biological control is a sustainable option, with several agents having been reported to be effective against this pathogen. This research focused on optimizing the application of strain THSW13 of Trichoderma hamatum and a bacterial isolate BJ10–86 with the objectives of improving chili pepper seed germination, reduce damping-off disease incidence, and improve the growth of the seedlings. Bacterial isolate BJ10–86 was subjected to molecular identification and found to be Pseudomonas aeruginosa. Chili pepper seeds treated with the biocontrol agents, individually or in combination, were seeded into commercial nursery media that had been pre-inoculated with P. capsici zoospores. Over a period of 35 days the chili pepper seed treatments significantly (P = 0.008) reduced the disease incidence of seedlings damping-off. Combined application of T. hamatum and P. aeruginosa was the best biocontrol treatment with an area under disease curve of only 36.61 units compared to 92.87 units for the control treatment. Similar results were observed in vitro where T. hamatum and P. aeruginosa synergistically inhibited P. capsici growth by 73.2 %. The inhibition activity of this treatment was similar to mefenoxam treatment, which implies that it is an effective and sustainable alternative for chili pepper seed treatment. The biocontrol seed treatment had no effect on seed germination and seedling growth.     

Rice <Emphasis Type="Italic">OsPBL1</Emphasis> (ORYZA SATIVA ARABIDOPSIS PBS1-LIKE 1) enhanced defense of <Emphasis Type="Italic">Arabidopsis</Emphasis> against <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> DC3000

The receptor-like cytoplasmic kinases (RLCK family VII) are required for plant defense against various pathogens. Previously, OsPBL1 (ORYZA SATIVA ARABIDOPSIS PBS1-LIKE 1) was isolated from rice as a potential RSV (rice stripe virus) resistant factor, but its physiological roles in plant defense are yet to be investigated. In this study, we demonstrated that OsPBL1increased defense against P. syringae in transgenic Arabidopsis. To ascertain the role of OsPBL1 gene in plant defense, OsPBL1 tagged with HA (i.e. Hemagglutinin) was overexpressed in Arabidopsis and examined for the resistance against Pseudomonas syringae pv. tomato DC3000 (i.e. Pst DC3000). At 3 dpi of Pst DC3000, transgenic Arabidopsis lines exhibited the reduced chlorotic lesion and propagation of P. syringae, compared to wild type. Elevated pathogen resistance of transgenic lines was correlated with increased H₂O₂ accumulation and callose deposition on the infected leaves. It was also revealed that expression levels of salicylic acid dependent genes such as PR1, PR2, and PR5, were induced higher in transgenic lines than wild type. Taken together, our data suggested that OsPBL1 exerted the role in defense against pathogen attacks in plant via mainly facilitating salicylic acid dependent pathway.     

Long-term dynamics of causative agents of stem base diseases in winter wheat and reaction of Czech <Emphasis Type="Italic">Oculimacula</Emphasis> spp. and <Emphasis Type="Italic">Microdochium</Emphasis> spp<Emphasis Type="Italic">.</Emphasis> populations to prochloraz

Trichoderma aggressivum is an aggressive contaminant mould in the cultivation of Agaricus bisporus leading to severe reductions in mushroom yields. Production of fully colonised A. bisporus substrate in Europe is commonly carried out in large tunnels (Phase III), after which the substrate undergoes several bulk handling (mixing) operations before ending up on shelves in mushroom growing facilities. The work presented here studied the effect of Trichoderma aggressivum inoculum, substrate mixing and supplementation on Agaricus bisporus yields and evaluated four methods to detect T. aggressivum in bulk handled substrate. Inoculum dilution level was shown to correlate well with mushroom yield (P < 0.0001) with reductions of 2–6 % at the most dilute level (10^?4) and 60–100 % at the most concentrated level (10^?1), depending on the experiment. Supplementation, with or without T. aggressivum, had no significant effect on mushroom yield (P ≥ 0.85) but a high degree of substrate mixing was shown to significantly increase (P < 0.0001) T. aggressivum-associated crop losses. Four T. aggressivum detection methods were evaluated and a quantitative polymerase chain reaction (qPCR) method gave the most consistent and least variable results. Cycle threshold (CT) values ranged from 24 to 40, depending on the experiment and the inoculum dilution level, and false negatives (CT = 40) were reported on one occasion with the most dilute samples. The results indicate that Phase III mushroom substrate is vulnerable to infection by T. aggressivum when the fully colonised substrate is broken up and mixed during bulk handling operations, identifying a previously unidentified risk for Phase III substrate producers.     

Relative potency of culture supernatants of <Emphasis Type="Italic">Xenorhabdus</Emphasis> and <Emphasis Type="Italic">Photorhabdus</Emphasis> spp. on growth of some fungal phytopathogens

In previous research, concentrated metabolites produced by bacteria of the genera Xenorhabdus and Photorhabdus (which are symbionts of entomopathogenic nematodes) were reported to be highly suppressive to fungal and oomycete plant pathogens. Conceivably, application of non-concentrated bacterial filtrates would be more economically feasible compared to using concentrated metabolites. We evaluated the potency of 10 % v/v cell-free supernatants of the bacteria X. bovienii, X. nematophila, X. cabanillasii, X. szentirmaii, P. temperata, P. luminescens (VS) and P. luminescens (K22) against Fusicladium carpophilum (peach scab), F. effusum (pecan scab), Monilinia fructicola (brown rot), Glomerella cingulata (anthracnose) and Armillaria tabescens (root rot). A bioactive compound derived from Photorhabdus bacteria, trans-cinnamic acid (TCA), was also compared with the bacterial filtrates. Fungal colony size based on manual measurements was compared for accuracy to measurements taken by image analysis. Supernatants of Xenorhabdus spp. exhibited stronger suppressive effects on spore germination and vegetative growth when compared with Photorhabdus spp. Overall, TCA was the most effective treatment; vegetative growth was completely inhibited by TCA (1.27 mg/ml). TCA treatments also suppressed spore germination of F. carpophylium and F. effussum by approximately 90 %. The efficacy of supernatants varied among Xenorhabdus species depending on the species tested, but X. szentirmaii filtrates tended to cause greater inhibition relative to the other bacteria supernatants. Manual measurement of colony diameter required at least two replicate estimates of the colony to avoid a type II error. Area measurements were slightly overestimated based on ruler measurements, but did not affect the outcome of the analysis. Supernatants of Xenorhabdus spp., Photorhabdus spp., or TCA, did not cause any phytotoxic effects when applied to various plant species in the greenhouse. Our results indicate the potential of using TCA or Xenorhabdus cell free supernatants as bio-fungicides. Such a product, based on bacterial culture supernatants, would be economically viable, marketable and easily applicable by the end-users in many situations.     

Effect of simultaneous and sequential inoculations of <Emphasis Type="Italic">Meloidogyne incognita</Emphasis>, <Emphasis Type="Italic">Ralstonia solanacearum</Emphasis> and <Emphasis Type="Italic">Phomopsis vexans</Emphasis> on eggplant in sand mix and fly ash mix soil

Effects simultaneous and sequential inoculations of Meloidogyne incognita, Ralstonia solanacearum and Phomopsis vexans were studied on the growth, chlorophyll and carotenoid contents of eggplants grown in 25% fly ash and 25% sand mix soil. Plants grown in 25% fly ash mix soil had lesser plant growth than grown in 25% sand ash mix soil. Inoculation of M. incognita / R. solanacearum or P. vexans caused reduction in plant growth, chlorophyll and carotenoid contents in both types of soils but these pathogens in combination caused a greater reduction in than individual inoculation. Inoculation of M. incognita 20 days prior to R. solanacearum caused a greater reduction in plant growth than inoculation of M. incognita prior to P. vexans. Inoculation of P. vexans prior to R. solanacearum caused a lesser reduction in plant growth, chlorophyll and carotenoid contents than inoculation of P. vexans prior to M. incognita. Inoculation of R. solanacearum 20 days prior to M. incognita caused a greater reduction in plant growth, chlorophyll and carotenoid contents than inoculation of R. solanacearum prior to P. vexans. Galling and multiplication of M. incognita was higher in plants grown in 25% sand amended soil than with 25% fly ash soil. R. solanacearum and P. vexans had adverse effects on galling and nematode multiplication. Wilt and blight indices caused by R. solanacearum and P. vexans were 3 respectively. Wilt and blight indices were 4 when two pathogens were inoculated together.     

Effect of <Emphasis Type="Italic">Metarhizium guizhouense</Emphasis> infection on mating competition and mate choice of <Emphasis Type="Italic">Bactrocera latifrons</Emphasis> (Diptera: Tephritidae)

Metarhizium guizhouense PSUM02 treated males of Bactrocera latifrons were investigated for the mating competition among males and mating choice by female flies to develop an auto-dissemination for the control of B. latifrons. In the present study, on day 1–4 of experiment, M. guizhouense–treated male flies were equally competitive with the normal male flies as we did not observe any differences in mating by treated and normal male flies of B. latifrons. Further, mating competitiveness were found low in treated adult male B. latifrons than normal male B. latifrons from 5th days of treatment until death. Kaplan-Meier survival analysis of treated male flies gave average survival times (AST) of 4.3?±?0.1 days, while the healthy female and male flies in the same cage showed AST of 9.3?±?0.3 and 8.3?±?0.4 days, respectively. The AST of untreated flies in control experiment ranged from 14.2–14.5 days. In mating preference experiment, M. guizhouense–treated male flies were chosen by virgin female than gravid female flies for mating. The treated male flies caused mortality in both virgin and gravid female flies in the same cage with AST of 4.4?±?0.1, 5.6?±?0.1 and 7.4?±?0.2 days, respectively, while untreated flies showed AST ranged from 13.9–14.3 days in control. The treated male flies could transmit the fungus infection to both untreated female and male flies as well as in virgin and gravid female flies by mating and contact. Our experiments showed the potentiality of M. guizhouense PSUM02 in management of B. latifrons by auto-dissemination with treated male flies, which transmit the fungus to a healthy population to reduce insect pest infestations.     

Molecular and morphological characterisation of <Emphasis Type="Italic">Aphelenchoides paraxui</Emphasis> n. sp. (Nematoda: Aphelenchoididae) isolated from <Emphasis Type="Italic">Quercus brantii</Emphasis> in western Iran

Aphelenchoides paraxui n. sp. is described and illustrated from bark samples of an oak tree (Quercus brantii L.) in Kermanshah province, western Iran. The new species is characterized by body length of 500–660 μm (females) and 630–665 μm (males), lip region set off from body contour, lateral fields with four lines, and total stylet 8–9 μm long with small basal swellings. The excretory pore is located ca one body diam. Posterior to metacorpus valve. The spicules are relatively large (29–33 μm in dorsal limb) with apex and rostrum rounded and well developed and the end of the dorsal limb clearly curved ventrad like a hook. The female tail is conical, the terminus having a complicated step-like projection, usually with many tiny nodular protuberances. Male tail bearing six (2 + 2 + 2) caudal papillae and a well-developed mucro. The new species belongs to the Group 2 category of Aphelenchoides species sensu Shahina (1996) in which eight known species among Group 2–4 sensu Shahina namely: A. arcticus, A. asteromucronatus, A. blastophthorus, A. lichenicola, A. saprophilus, A. seiachicus, A. silvester and A. xui, are the most closed species. Molecular analyses of the partial small subunit rDNA gene (SSU), D2/D3 expansion segments of the large subunit rDNA gene (LSU) and internal transcribed spacer (ITS) revealed this as a new species and supported the morphological results.     

Chitinolytic <Emphasis Type="Italic">Streptomyces griseorubens</Emphasis> E44G enhances the biocontrol efficacy against <Emphasis Type="Italic">Fusarium</Emphasis> wilt disease of tomato

Streptomyces griseorubens E44G is a chitinolytic bacterium isolated from cultivated soil in Saudi Arabia (a hot, arid climatic region). In vitro, antifungal potential of S. griseorubens E44G was assessed against the phytopathogenic fungus, Fusarium oxysporum f. sp. lycopersici (the causative agent of the Fusarium wilt disease of tomato). An inhibition zone of 24 mm was recorded. The chitinolytic activity of S. griseorubens E44G was proved when the colloidal chitin agar plate method was used. A thermostable chitinase enzyme of 45 kDa molecular weight was purified using gel filtration chromatography. The optimum activity was obtained at 60 °C and pH 5.5. The purified enzyme has shown a very pronounced activity against the phytopathogenic fungus, F. oxysporum. The molecular characterization of the chitinase gene indicated that it consists of 1218 bp encoding 407 amino acids. The phylogentic analysis based on the nucleotide DNA sequence and the deduced amino acids sequence showed high similarity percentages with other chitinases isolated from different Streptomyces species. In the field evaluation, application of both S. griseorubens E44G treatments significantly increased all tested growth and yield parameters and decreased the disease severity compared with the infected-untreated tomato plants suggesting potential as a biocontrol agent.     

<Emphasis Type="Italic">Bradyrhizobium</Emphasis> isolated from huanglongbing (HLB) affected citrus trees reacts positively with primers for <Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter asiaticus

Bradyrhizobium sp., a slow-growing nitrogen-fixing symbiotic bacterium of legumes and common root endophyte of other plants, is closely related to Candidatus Liberibacter asiaticus (Las), the uncultured putative pathogen associated with citrus huanglongbing (HLB). In attempts to isolate Las on a low-nutrient medium that had been used for the isolation of several uncultured bacteria of the alpha subclass of proteobacteria, slow-growing Bradyrhizobium spp. were isolated and identified by sequencing of 16S rDNA. The individual isolates tested weakly positive (Ct = 31.2–36.0) with the USDA primers commonly used in qPCR assays for Las in foliar tissues. Direct DNA extracts from roots of HLB symptomatic trees that contained sequences of Bradyrhizobium sp. had Ct values ranging from 31.2 to 36.5; sequences of Las were not present in those samples. Potential cross-reaction between DNA of members of the Rhizobiales and sequences amplified by the Las primers were tested in silico with the Primer-BLAST tool in NCBI. Similar to Las, Bradyrhizobium generated predicted 16S rDNA amplicon sizes of 78–79 bp with the qPCR primers and of 1167-1172 bp with the conventional PCR primers. Bradyrhizobium sequences of 16S rDNA had 1–7 mismatches and only 1 mismatch at the 3′ end of qPCR and conventional PCR primers confirming potential cross-reactivity. As Bradyrhizobium is usually not found in foliage, the USDA qPCR primers can be safely used to check leaves for the presence of Las, but a threshold value of 31.0 is recommended for Las detection in roots. Other primers should be tested for potential cross-reaction with members of the Rhizobiales.