Distortional Buckling Formulae of Cold-Formed Thin-Walled Rack Members Upright with Rear Flange and Additional Lip Stiffeners

According to the generalised beam theory based on the exist studies, the aim of this paper is to derive the distortional buckling formulae of pined or fixed cold-formed thin-walled rack members upright with rear flanges and additional lip stiffeners. The formulae is adopted to calculate the distortional buckling load and the buckling half-wave length of the member subjected to axial compression or minor and major axis bending. Meanwhile, the results are compared to those of finite strip program CUFSM and other analytical formulae. The derived formulae is proved to be accurate enough. As a result, it may be directly used in practical design as well as further study.     

Conidia of one Fusarium solani isolate from a soybean-production field enable to be virulent to soybean and make soybean seedlings wilted

Fusarium is usually thought to cause soybean root rot,which results in a large quantity of annual yield loss in soybean production,by its secretions including Fusarium toxins and cell wall degrading enzymes,but not by the conidia themselves that do not underlie any virulence so far.Here we report that the conidia of one Fusarium solani isolate are able to be virulent to soybean and make soybean seedlings wilted alone.We isolated them from the wilted plants in a soybean-production field and molecularly identified 17 Fusarium isolates through phylogenetic analysis.Of them,except for one isolate that showed diversity of virulence to different soybeans(virulent to one soybean whereas avirulent to another soybean),the others were all virulent to the two tested soybeans:both conidia cultures and secretions could make soybean seedlings wilted at 5 days post infection,and their virulence had dosage effects that only conidia cultures of at least 5×10~6 conidia mL~(-1) could show virulence to soybean;however,the sole conidia of the F.solani isolate #4 also exhibited virulence to soybean and could make soybean seedlings wilted.Finally,we developed the specific cleaved amplified polymorphic sequences(CAPS)markers to easily differentiate Fusarium isolates.The isolate #4 in this work will likely be used to investigate the new mechanism of virulence of Fusarium to soybean.     

5亿活孢子/克木霉菌水分散粒剂的研制

本文通过木霉菌(Trichodermaspp.)水分散粒剂配方研究,确定配方为:木霉菌活孢子≥5亿润湿分散剂B13%,B21%,C5%,保护剂UV-1 0.3%,崩解剂膨润土5%,粘结剂聚乙二醇2%,载体A1补足100%。质量检测结果表明产品中孢子萌发率75%以上,悬浮率80%以上,润湿时间22 s,崩解时间114 s,产品各项指标符合水分散粒剂的要求。     

苹果轮纹病菌诱导产孢方法

 In order to get a great quantity of spores of Botryosphaeria berengeriana f. sp. piricola, several methods to promote sporulation of the pathogen were compared. The results showed that the wounded young apple fruits within 60-day old was inoculated with mycelia of B. berengeriana f. sp. piricola and induced under the 365 nm-UV-light; when the brown lesion was shown, the young apple began to form pycnidia on the lesion around the inoculation point after 3-5 days irradiation with UV-light and extruded plenty of conidia. This method induced great more conidia than that of irradiating wounded mycelia with UV-light. However, mature apple seldom produced conidia when induced with the same method.     

Within‐ and between‐orchard variability in the sensitivity of Venturia inaequalis to myclobutanil,a DMI fungicide,in the UK

BACKGROUND: Myclobutanil, a demethylation inhibitor (DMI) fungicide, is an important fungicide for controlling apple scab and powdery mildew. Overuse of this fungicide has led to establishment of scab isolates with reduced sensitivity to this fungicide in several countries. Experiments were conducted to determine the sensitivity of the causal agent of apple scab, Venturia inaequalis (Cooke) Winter, to myclobutanil in the UK, in order to assess whether there is a relationship between fungal insensitivity and the number of DMI applications, and establishing whether fungal sensitivity varied greatly within an orchard. RESULTS: Reduced sensitivity of V. inaequalis to myclobutanil was positively related linearly to the number of DMI applications. ED₅₀ values ranged from 0.028 to 1.017 mg L^?1 (average = 0.292) for the baseline population, whereas isolates from two other orchards had much greater ED₅₀ values, ranging from 0.085 to 5.213 mg L^?1 (average = 1.852). There was significant variation in fungal sensitivity to myclobutanil among fungal isolates from different locations within a single orchard. CONCLUSIONS: Spatial spread of insensitive isolates of V. inaequalis to myclobutanil is likely to be limited in distance. Conidia may be an important source of primary inoculum. Myclobutanil should still be effective for most field isolates, but its use should be strategically integrated with other groups of fungicides. Copyright © 2009 Society of Chemical Industry     

糖对稻曲病菌薄壁分生孢子萌发的影响

 以琼脂平板为萌发基质,测定了10种糖化合物(木糖、果糖、山梨糖、核糖、甘露糖、葡萄糖、麦芽糖、半乳糖、乳糖和蔗糖)对稻曲病菌薄壁分生孢子萌发的影响。结果发现,在浓度为1%时,除蔗糖外,其余9种糖对孢子萌发均有不同程度的抑制作用,其中木糖、果糖、山梨糖和核糖的抑制作用强烈;孢子经木糖或果糖处理6h后,并未丧失活力;多种糖混合仍表现为抑制孢子萌发。当各种糖与起刺激作用的马铃薯煮汁分别混合时,表现出明显相反的两种效应,一是马铃薯汁的刺激作用可掩盖甘露糖、葡萄糖、麦芽糖、半乳糖、乳糖和蔗糖的抑制作用;二是木糖、果糖、山梨糖和核糖的抑制作用可掩盖马铃薯汁的刺激作用。表明外源糖化合物及某些生命活性物质可影响薄壁分生孢子萌发。     

Sorghum ergot can develop without local Claviceps africana inoculum from nearby infected plants

Batches of glasshouse-grown flowering sorghum plants were placed in circular plots for 24 h at two field sites in southeast Queensland, Australia on 38 occasions in 2003 and 2004, to trap aerial inoculum of Claviceps africana. Plants were located 20–200 m from the centre of the plots. Batches of sorghum plants with secondary conidia of C. africana on inoculated spikelets were placed at the centre of each plot on some dates as a local point source of inoculum. Plants exposed to field inoculum were returned to a glasshouse, incubated at near-100% relative humidity for 48 h and then at ambient relative humidity for another week before counting infected spikelets to estimate pathogen dispersal. Three times as many spikelets became infected when inoculum was present within 200 m of trap plants, but infected spikelets did not decline with increasing distance from local source within the 200 m. Spikelets also became infected on all 10 dates when plants were exposed without a local source of infected plants, indicating that infection can occur from conidia surviving in the atmosphere. In 2005, when trap plants were placed at 14 locations along a 280 km route, infected spikelets diminished with increasing distance from sorghum paddocks and infection was sporadic for distances over 1 km. Multiple regression analysis showed significant influence of moisture related weather variables on inoculum dispersal. Results suggest that sanitation measures can help reduce ergot severity at the local level, but sustainable management will require better understanding of long-distance dispersal of C. africana inoculum.     

咯菌腈对四种牡丹叶片病原真菌的抑制活性

【目的】探究咯菌腈对牡丹黑斑病菌(Alternaria suffruticosae)、黄斑病菌(Phyllosticta commonsii)、腔孢叶斑病菌(Hainesia lythri)和叶霉病菌(Cladosporium paeoniae)菌丝生长、孢子萌发、芽管伸长及产孢的抑制活性,分析咯菌腈在牡丹病害化学防治上的应用前景。【方法】采用菌丝生长速率法测定咯菌腈对菌丝生长的抑制活性,采用涂布平板法测定咯菌腈对孢子萌发、产孢时间及产孢量、芽管伸长及芽管和孢子形态的影响。【结果】咯菌腈对腔孢叶斑病菌菌丝生长的抑制作用最强,EC_(50)为0.01μg·mL~(-1),其次为黑斑病菌和黄斑病菌,分别为0.07和0.35μg·mL~(-1);咯菌腈对4种病菌的孢子萌发均有较强的抑制作用,对腔孢叶斑病菌的抑制作用最强,其EC_(50)为1.26μg·mL~(-1),对其他3种病菌孢子萌发的EC_(50)在3.27—3.45μg·mL~(-1);0.1μg·mL~(-1)咯菌腈对4种病菌分生孢子芽管伸长的抑制率在40%—70%,表明咯菌腈对4种病菌分生孢子芽管伸长均有明显的抑制作用,浓度越大抑制作用越强,各浓度间差异显著,其中对腔孢叶斑病菌芽管伸长抑制的EC_(50)为0.04μg·mL~(-1),抑制作用最强,对其他3种病菌芽管伸长的EC_(50)在0.08—0.22μg·mL~(-1);咯菌腈对黑斑病菌和黄斑病菌分生孢子和芽管的致畸作用强烈,可导致孢子及芽管膨大、过度分枝,而对叶霉病菌和腔孢叶斑病菌致畸作用较弱,芽管及孢子形态基本正常;咯菌腈可推迟黑斑病菌、黄斑病菌及叶霉病菌的产孢时间,对黑斑病菌产孢量的抑制作用最强,EC_(50)为0.05μg·mL~(-1),对叶霉病菌次之,EC_(50)为0.38μg·mL~(-1),但对腔孢叶斑病菌产孢有促进作用。【结论】咯菌腈对牡丹黑斑病菌及腔孢叶斑病菌的菌丝生长、孢子萌发及芽管伸长均有很强的抑制作用,但对腔孢叶斑产孢具有一定的促进作用;对叶霉病菌和黄斑病菌孢子萌发及芽管伸长、黄斑病菌菌丝生长及叶霉病菌产孢的抑制作用强烈;由于咯菌腈内吸活性较弱,无法抑制已侵入牡丹叶片的病原真菌的生长,故建议作为保护剂在病害发生前施用。     

常用土壤处理除草剂对哈茨木霉的影响

在农业生产中,植物的病原菌、杂草和害虫等有害生物与生防菌处于同一生态环境中,田间喷施化学农药势必会对生防菌的自然控制作用产生不利影响.     

蛹虫草无性型的研究Ⅰ.分生孢子形态观察与发酵液的检测

对蛹虫草的无性型进行培养，观察了分生孢子的形态，并对其深层发酵培养物进行了检测．