Neopestalotiopsis clavispora and Pseudopestalotiopsis camelliae-sinensis causing grey blight disease of tea (Camellia sinensis) in Malaysia

European Journal of Plant Pathology - Tea (Camellia sinensis) is a popular and extensively consumed beverage in Malaysia along with many other countries around the world. Grey blight is one of the...     

新疆真藓属(Bryum Hedw.)新资料

通过经典分类学方法,对采自新疆各地的185号真藓属植物标本进行了整理、鉴定,报道新疆新记录2种:毛状真藓(Bryum apiculatum Schwaegr.)与近高山真藓(Bryum paradoxum Schwaegr.)。重新确定了曾有文献记载,但未见现存标本因而未加入新疆苔藓植物名录的:狭网真藓(Bryum algovicum Sendt.ex C.Müll.)与红蒴真藓(Bryum atrovirens Brid.)。并对新记录种的识别特征、生境及其地理分布作了阐述。根据识别特征绘制了狭网真藓、红蒴真藓与近高山真藓的墨线图。     

新疆喀纳斯国家级自然保护区土壤螨类群落特征

为研究喀纳斯自然保护区土壤螨类群落特征,2011年7月和9月对该保护区针叶林、混交林、阔叶林、灌木林、草甸草原、林间草地、沼泽地7种生境进行了取样调查。结果表明:1)共获得土壤螨类7268只,隶属于3亚目51科58属。其中甲螨亚目3819只,38科44属,占总数的93.34%;中气门亚目264只,9科11属,占总数的6.45%;前气门亚目7只3科3属,占总数的0.21%。整个研究区域中奥甲螨属Oppia、盖头甲螨属Tectocepheus、钉棱甲螨属Passalozetes、菌甲螨属Scheloribates为优势类群,占总数的60.05%;阿斯甲螨属、短甲螨属、大翼甲螨属等13属为常见类群,占总数的29.43%;其余的41属为稀有类群,占总数的10.52%。2)在不同生境条件下土壤螨类个体数和类群数均有显著差异(P<0.05),其中个体数依次为阔叶林>针叶林>林间草地>混交林>沼泽地>草甸草原>灌木林;而类群数依次为阔叶林>草甸草原>沼泽地>针叶林>灌木林>混交林>林间草地。3)垂直分布具有明显的表聚性特征,其中0~5cm土层最多,其次为5~10cm,而10~15cm最少。4)在该保护区不同生境土壤螨类的群落组成和结构差异与植被类型、土壤环境因素及人为干扰程度有关。     

Organic Seed-treatment as a Substitute for Chemical Seed-treatment to Control Common Bunt of Wheat

Common bunt of wheat, caused by Tilletia laevis and T. tritici, is a major seed and soil-borne disease in West Asia and North Africa. The use of resistant cultivars and chemical seed-treatments are the current control measures used to combat this disease. The aim of this study was to investigate alternative control measures to chemical seed-treatments that are environmentally friendly to support cultivar resistance. Several organic nutrients [skimmed milk powder, hucket (local skimmed milk) and wheat flour] at a concentration of 160g per kg of seeds were used as seed-treatments on two susceptible bread and durum wheat cultivars (Bau and Sebou, respectively) to examine their effectiveness in controlling the disease. Field trials over four years showed that skimmed milk powder, hucket, and wheat flour reduced common bunt infection levels by 96%, 93% and 62%, respectively. In most cases, the effectiveness of the skimmed milk powder and hucket was equal to the chemical seed-treatment; thus, these organic nutrients offer an effective and environmentally safe alternative to chemical treatments. However, a study of their economic value as well as of their effect on seed germination, and field emergence is needed.     

Phenylalanine ammonia lyase activity in chilli CM-334 infected by Phytophthora capsici and Nacobbus aberrans

We tested the hypothesis that PAL activity in chilli plants CM-334 inoculated with Nacobbus aberrans (Na) alone or in combination with Phytophthora capsici (Pc), is lower than in those inoculated only with Pc. At 21 days after nematode inoculation, inoculated plants showed a significant (P < 0.01) reduction of 48% in PAL activity compared to those non-inoculated in two separate experiments. In two other tests, where plants were inoculated with the oomycete 21 days after inoculation with the nematode, PAL activity at 2, 4, 6, 8 and 24 h after inoculation with Pc was significantly higher (Tukey, P < 0.01) in plants inoculated only with Pc than in plants inoculated only with Na or both pathogens (Na+Pc).     

<Emphasis Type="Italic">Cucurbit aphid-borne yellows virus</Emphasis> in Egypt

During 2010, yellowing symptoms were frequently observed in cultivated squash fields in Egypt. A total of 717 symptomatic squash leaf samples were collected from four regions where squash cultivation is of economic importance for the country: Kafrelsheikh, El-Behira, El-Sharkia and El-Ismailia. Serological analysis showed that 95.6% of the symptomatic squash samples were infected by Cucurbit aphid-borne yellows virus (CABYV), and visual estimation of the incidence of yellowing symptoms suggested a very high incidence of CABYV in the fields. Twelve CABYV isolates were characterized by sequencing two regions of the viral genome, open reading frame (ORF) 3 and ORFs 4/5. Overall, Egyptian isolates were very similar among them, and had higher similarity values with a French than with a Chinese isolate. The average nucleotide diversity for ORF 3 was significantly higher than for the other two regions, indicating that variability is not evenly distributed along the viral genome. The ratios between nucleotide diversity values in non-synonymous (d _N ) and synonymous (d _S) positions (d _N /d _S) for each ORF showed that the three ORFs are evolving under different pressures, although predominantly under purifying selection. Phylogenetic analyses revealed that these Egyptian isolates, with only one exception, shared the same clade with a French isolate. Moreover, these analyses suggested that Egyptian isolates belong to the Mediterranean group described previously.     

Screening for resistance to Diaporthe toxica in lupins by estimation of phomopsins and glucoseamine in individual plants

Immunological and biochemical assays were developed for screening for resistance to Diaporthe toxica in individual plants of narrow-leafed lupins ( Lupinus angustifolius ). The former was an enzyme-linked immunosorbent assay (ELISA) for measuring phomopsin mycotoxins and the latter gave an estimation of glucoseamine in infected stem pieces. Stems of L. angustifolius seedlings were inoculated with conidia from D. toxica cultures and, as expected with this latent disease, remained symptomless for 21 days after inoculation. At this time, phomopsins were measured in excised stems that had been incubated for 6 or 8 days to allow mycelial growth from latent infection structures, thereby increasing the phomopsins to detectable levels in individual plants. The estimation of glucoseamine was carried out on the same stems that had been assayed for phomopsins. The method was based on the alkaline deacetylation of chitin to chitosan, the glucoseamine residues of which are de-aminated with nitrous acid, yielding an aldehyde which is determined colorimetrically. At six days after excision, both tests clearly distinguished the very resistant, resistant, intermediate and susceptible lines and they may be useful in large-scale resistance screening in lupin breeding programmes. The ELISA of phomopsins is easier to use and would be particularly useful in the elimination of susceptible plants and those plants expressing intermediate levels of resistance during early generations of the breeding programme.     

Studies of the mechanism of action of asulam in plants. Part I: Antagonistic interaction of asulam and 4-aminobenzoic acid

Studies have been carried out on the herbicidal action of asulam [methyl (4-aminophenylsulphonyl)carbamate] and sulphanilamide, alone or in association either with 4-aminobenzoic acid (4ABA) or 4, 6-diamino-1-(3, 4-dichlorophenyl)-1, 2-dihydro-2, 2-dimethyl-1,3,5-triazine (DCDT). The soaking of wheat seeds (Triticum estivum L.) for 12 h at 30°C in asulam and DCDT in a 10:1 ratio doubled the inhibition of root growth produced by soaking in asulam alone; the addition of 4ABA partially reversed the activity of asulam. Foliar applications of a mixture of asulam + DCDT (1.1 + 0.55 kg ha^?1) markedly increased the activity of asulam in susceptible wheat, wild oat (Avena fatua L.), tolerant flax (Linum usitatissimum L.), and in Stellaria media L. The activity of asulam at 1.1 kg ha^?1 was reversed by 4ABA at 2.2 kg ha^?1 by about 50% in wheat and wild oat, 82% in flax and 100% in S. media. The results indicate that asulam and sulphanilamide act by similar mechanisms in apparently inhibiting the biosynthesis of folic acid.     

Molecular characterization of the phytoplasmas associated with toon trees and periwinkle in India

In November 2008 in Himachal Pradesh and Chandigarh regions in India, toon trees and periwinkles were observed to have formed short internodes, small leaves and witches’-broom symptoms, typical of phytoplasma infection. The symptomatic toon and periwinkle samples were tested with universal PCR tests, and the 16S rRNA, rplB-rpsC, secA and secY genes were sequenced. The causal agents belonged to subgroup 16SrI-B of ‘Candidatus Phytoplasma asteris’, based on 16S rDNA, ribosomal protein gene, secA and secY phylogenetic analysis.     

Mechanism of hydantoin ring opening in iprodione in aqueous media

The hydrolysis kinetics of iprodione in alkaline solutions of pH 8.3 to 12 at 25°C have been determined by ultraviolet spectrophotometry. Under these conditions, iprodione leads quantitatively and irreversibly to N-(3,5-dichloroanilinocarbonyl)-N-(isopropylaminocarbonyl)glycine. The reaction is not subject to a general basic catalysis and the rate law takes the form K_obs = K_OH- [OH^?1]. The activation entropy of -77 J mol^?1deg^?1, the value of the kinetic solvent isotope effect k_OH?/k_OD? of 0.79 and the value of 0.60 for the Hammett parameter σ, obtained for the hydrolysis of a series of 3-aryl-N-isopropyl-2,4-dioxoimidazolidine-1-carboxamides are all in agreement with the rate-determining attack by the hydroxyl ion on the carbonyl in the 4-position of the hydantoin ring of the fungicide.