Pathogenic diversity of Didymella rabiei isolates from southern Alberta,Canada

Journal of Plant Diseases and Protection - Sixty-three isolates of Didymella rabiei collected from southern Alberta were analyzed for pathogenic variability using six differential chickpea...     

A molecular marker for the specific detection of new pathotype 5‐like strains of Plasmodiophora brassicae in canola

Clubroot of crucifers, caused by Plasmodiophora brassicae, is managed in canola (Brassica napus) by the deployment of resistant cultivars. Recently, however, new strains of P. brassicae have been detected in Alberta, Canada, that can overcome this resistance. Some of these strains are classified as pathotype 5 on the differential system of Williams, but are distinguished by their ability to overcome host resistance. In order to expedite the identification of these new pathotype 5‐like strains, three primer sets were developed based on the 18S‐ITS region of the pathogen. With primers P5XF3 and P5XR3, a 127 bp product was amplified from all new pathotype 5‐like strains following optimized PCR analysis. A TaqMan probe‐based quantitative assay was also developed. These protocols could be used to detect as little as 0.5 pg P. brassicae DNA, and as few as 10⁴ mL^?1 pathogen resting spores; infection of host tissues could be detected as soon as 4 days after inoculation. The PCR and qPCR assays described in this study represent useful tools for the rapid and reliable diagnosis and quantification of new pathotype 5‐like strains of P. brassicae.     

Occurrence of bacterial rot of onion caused by Bacillus amyloliquefaciens in Korea

In 2008, bacterial rot on onion bulbs (Allium cepa L.) was observed in several low-temperature warehouses in Changnyeong-gun, Korea. The causal pathogen was isolated and identified as Bacillus amyloliquefaciens based on morphological and biochemical characterization and sequence analysis of its genome. The isolated bacteria caused the same rot symptom on inoculated onion bulbs as found in naturally infected onions during storage and was reisolated from these bulbs. This is the first report of bacterial rot of onion caused by B. amyloliquefaciens in Korea.     

Induced resistance againstPhytophthora capsici in pepper plants in response to DL-β-amino-n-butyric acid

Treatment of pepper plants with the nonprotein amino acid, DL-ß-amino-n-butyric acid (BABA) induced resistance to subsequent infection byPhytophthora capsici. In contrast, theα-, andγ-isomers of aminobutyric acid were ineffective as inducers of resistance. A relatively high concentration of BABA at 1,000μg ml^?1, which had no antifungal activityin vitro againstP. capsici, was required to induce resistance against Phytophthora blight with a foliar and stem spray, thus leading to complete control of the disease. About 1 day interval between BABA-treatment and challenge inoculation was sufficient to induce resistance in pepper plants. High inoculum levels ofP. capsici caused Phytophthora development slowly in pepper stems treated with BABA, especially at early plant growth stage, which suggests that the induced resistance in pepper plants may be more quantitative rather than qualitative. BABA applied to the root system also protected pepper stems fromP. capsici infection.     

柑桔黄龙病的接种和预防试验

柑桔黄龙病在福建省从1955年以后逐年增长。大家已一致认为这是一种病毒病害。现在就最近两年在漳州进行的嫁接接种、蚜虫传染和遮荫防病的试验报告如下。在1961年做了病梢皮贴接接种的两个试验。试验地周围400—500米内均无柑园,但接种树和对照树仅距离7—8米。在试验期间经常防治虫害并加强栽培管理。苗木是由病区南靖苗圃选择来的一年生健壮桶柑(即焦柑)嫁接苗(砧木是红桔)。三月间定植后一般生长良好。接种方法系     

Thermal effects on the development of <Emphasis Type="Italic">Bactrocera dorsalis</Emphasis> (Hendel) (Diptera: Tephritidae) and model validation in Taiwan

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a major polyphagous insect pest with a worldwide distribution. The effects of temperature on stage-specific development in B. dorsalis were investigated at eight constant temperatures (13.0 °C, 14.4 °C, 16.2 °C, 19.5 °C, 23.8 °C, 27.7 °C, 31.8 °C and 34.8 °C). B. dorsalis developed successfully from the egg stage to the adult stage at all the tested temperatures, except at the lowest temperatures (13.0 °C and 14.4 °C). Stage-specific lower developmental thresholds and thermal constants were determined using linear regression. The lower and higher temperature threshold (TL and TH, respectively) were estimated using the Sharpe-Schoolfield-Ikemoto model. The lower developmental threshold and thermal constant from egg to adult emergence were 9.8 °C and 325.5 degree-days, respectively. The intrinsic optimum temperatures of the egg, larval, pupal and egg to pupal stage were 20.7 °C, 21.8 °C, 21.1 °C, and 22.4 °C, respectively. The temperature range of the B. dorsalis total immature stage from TL to TH was 20.4 °C (13.8 °C - 34.2 °C). The stage-specific developmental completion of B. dorsalis was determined using a two-parameter Weibull function. The daily adult emergence frequency of B. dorsalis was estimated in relation to adult age and temperature using non-linear developmental rate functions and the Weibull function. The date of cumulative 50% adult emergence estimated using non-linear functions was approximately one day earlier than the experimentally observed date. Thermal performance was compared among B. dorsalis populations from different locations.     

Effect of Prohexadione Calcium on Growth Components and Endogenous Gibberellins Contents of Rice (Oryza sativa L.)

Prohexadione calcium (Pro‐Ca) is a novel plant growth regulator that inhibits the late stages of gibberellins (GAs) biosynthesis in plants, thus reducing the vegetative growth of the plant. Pro‐Ca was applied to field‐grown rice cultivar Ilpumbyeo to evaluate its effect on growth and yield components and endogenous GAs, when applied at different rates and timings. This study illustrated that Pro‐Ca application decreased the internode length, stem length, panicle length, shoots fresh weight and stem lodging index, while stem breaking force was increased in all treatments. The effect of Pro‐Ca was more pronounced in 20 ppm concentration than 10 ppm. The number of panicles m⁻², ripened grain ratio and 1000 grain weight and milled rice yield parameters, increased with the application of Pro‐Ca, though the number of grains per panicle decreased insignificantly. The endogenous bioactive GA₁ contents significantly decreased with the application of Pro‐Ca, as the GA biosynthesis was interrupted at later stages, when GA₂₀ conversion to GA₁ was blocked, thus drastically reducing GA₁ and GA₈ levels, but only insignificant changes were observed for intermediates from GA₁₂ to GA₂₀. The levels of the endogenous GAs in rice shoots were measured by GC‐MS‐SIM using ²H₂‐labelled GAs as internal standards. Present results also illustrated that early application of Pro‐Ca was more effective than its late application for effective control of different growth parameters and thus reducing lodging in rice plants.     

Enzymatic modification of saponins from Platycodon grandiflorum with Aspergillus niger

Platycodon grandiflorum A. DC (Campanulaceae) is a traditional medicinal plant. Its root, Platycodi Radix, contains an abundant amount of saponin glycosides, platycodins, of which platycodin D is one of the major components. The chemical structures of platycodins can be modified by various types of chemical processing, but a modification mediated with microorganisms has been not reported yet. In this study, platycodin D was modified to several partially degraded platycodin glycosides after treatment with a crude enzyme extract from Aspergillus niger (A. niger). The modified platycodin D possessed a shorter sugar side-chain, and presented a remarkably reduced V79-4 cell (Chinese hamster lung fibroblasts) cytotoxicity and erythrocyte hemolytic toxicity, whereas the nitrite-scavenging activity was increased in the modified platycodin D. Sensory scores for pungency, bitterness and after-taste were improved as well in the modified platycodin D. Results suggest that A. niger mediated modification yielded a novel partially degraded platycodin glycoside which possesses increased bioactivities and improved sensory values, yet with reduced toxic profiles.