Ascosphaera aggregata contamination on alfalfa leafcutting bees in a loose cell incubation system

The alfalfa leafcutting bee, a solitary bee used to pollinate alfalfa seed crops, is seriously affected by chalkbrood, a larval disease caused by the fungus Ascosphaera aggregata. One attempt to control the disease includes removing nests from the nesting boards (the “loose cell” system). We report here that adults emerging from the loose cells are heavily contaminated with A. aggregata spores. The contamination levels are not as high as previously reported for bees emerging directly from the boards, but they are still a likely focus for disease spread and may need to be targeted in chalkbrood control strategies.     

温度、相对湿度和pH对蜜蜂球囊菌孢子萌发的影响

研究了温度、相对湿度和pH对蜜蜂球囊菌(Ascosphaeraapis)孢子萌发3个阶段(活化、膨大、产生萌发管)的影响．结果表明,孢子活化和膨大在15～40和(25～40)±0．5℃范围内受温度的影响不明显(P＞0．05);萌发管仅发生在25～37±0．5℃,最适温度位于(31～35)±0．5℃．相对湿度越大,越有利于孢子萌发,而相对湿度低于80％对孢子萌发极为不利．孢子萌发的3个阶段在pH为5～7．8时几乎不受pH变化的影响,而在pH值较低影响很大．可见,A．apis是一种高度专一的蜜蜂幼虫病原体．     

Effect of short‐duration high temperatures on weed seed germination

Thermal soil disinfestation techniques are effective reducers of weed seedbank and weed emergence. Two experiments (Expt 1 and Expt 2) were conducted to test the effect of brief exposure to varying temperatures on the seed germination of Amaranthus retroflexus, Echinochloa crus‐galli, Galinsoga quadriradiata, Portulaca oleracea, Setaria viridis and Solanum nigrum. To this end, species seeds were moistened with loamy‐sand soil and placed into test tubes. The tubes were heated rapidly and then cooled by dipping them into a hot water bath until target temperatures were achieved. Expt 1 temperatures ranged between 55°C and 85°C at 5°C intervals and Expt 2 ranged between 48°C and 86°C at 2°C intervals. Thereafter, the tubes were dipped into a cooling (1°C) water bath. Exposure to target temperatures ranged between 2 s and 5 s. Soil temperatures were monitored using embedded thermocouples. A log‐logistic dose–response model described the effect of heating on seed germinability; temperatures required for 99% reductions were calculated. On the basis of the predictive model equation used, weed species' germination sensitivity to high temperature exposure can be ranked as follows: E. crus‐galli (79.6°C), S. viridis (75.8°C), S. nigrum (74.6°C), P. oleracea (72.2°C), A. retroflexus (70.9°C) and G. quadriradiata (68.1°C). The interval between no effects to complete seed devitalisation occurred at temperatures varying from 6.5°C to 15.7°C. Seed size and weight varied directly with heat tolerance. Study results not only inform the timing and optimal adjustment for effective thermal soil treatment, but also demonstrate a relatively simple and generalizable methodology for use in other studies.     

光照和温度对尖叶拟船叶藓孢子萌发及原丝体发育的影响

用组织培养法和光学显微镜技术初步研究了光照和温度对尖叶拟船叶藓孢子萌发及原丝体发育的影响。结果表明：（1）光照是影响孢子萌发的主要环境因子,20℃环境下,24h光照4d的孢子萌发率达83.3％;温度下黑暗培养的孢子30d也不能萌发,转光照后4d的萌发率可达84.6％;（2）温度是影响原丝体发育的主要环境因子,连续光照下,20℃的原丝体生长最快、分枝最多、分化最早,第31天可长达651.64μm;25℃次之,只有379.12μm;而自然光照下5-10℃环境下的孢子萌发率（18d为70.2％）和原丝体生长速度（127.44μm）均最慢;（3）原丝体发育到一定阶段,断裂为单个细胞,单个细胞再萌芽出新原丝体。     

In vitro evaluation of the effects of some plant essential oils on Ascosphaera apis,the causative agent of Chalkbrood disease

Ascosphaera apis is one of the major fungal pathogens of honey bee broods and the causative agent of Chalkbrood disease. The factors responsible for the pathogenesis of Chalkbrood disease are still not fully understood, and the increasing resistance of A. apis to commonly used antifungal agents necessitates a search for new agents to control this disease. The in vitro antifungal activities of 27 plant essential oils against two isolates of A. apis (Aksu-4 and Aksu-9) were evaluated. Out of the 27 plant essential oils tested, 21 were found to be effective in killing both isolates of A. apis. Based on their minimum fungicidal concentration (MFC) values, the effective oils were grouped into three categories: highly effective, moderately effective and minimally effective. Mountain pepper oil, Kala Bhangra oil, spearmint oil, babuna oil, betel leaf oil, carrot seed oil, cumin seed oil and clove bud oil were highly effective, with MBC values between 50.0 μg/mL and 600.0 μg/mL. Mountain pepper was the most effective essential oil, with an MBC value of 50.0 μg/mL. Citral and caryophyllene containing oils were the most effective with MIC 50 ppm. The essential oils tested exhibited significant antimicrobial activities against both strains of A. apis, and they may contain compounds that could play an important role in the treatment or prevention of Chalkbrood disease of honeybee.     

The effect of high temperatures on seed germination of one native and two introduced conifers in Patagonia

We examined the effect of thermal shock on the germination of seeds of three conifers, two introduced (Pseudotsuga menziesii and Pinus ponderosa), and one native to Patagonia (Araucaria araucana). Previous research has suggested increased susceptibility to invasions in burnt areas, and therefore, the effect of simulated fire (heat) on seed germination in these native and introduced species was compared. Seeds were heated to two different heat intensities (50°C and 100°C) for 1 or 5 min, which is within the temperature range reached in the upper soil layers during forest fires. Germination tests were then carried out in a growth chamber. The heat treatments had a negative effect on the germination of P. menziesii at temperatures of 100°C, and a negative effect on the germination of P. ponderosa at the temperature of 100°C and the exposure of 5 min. The heat treatments had no affect at all on A. araucana. The species with larger seeds (A. araucana) had higher survival rates after the thermal shocks. Also intraspecific differences in seed sizes possibly point at larger seeds surviving thermal shocks better than smaller seeds. In addition, thermal shock caused a delay in the onset of germination in the two introduced species, while it did not change the time for germination in A. araucana.     

The effect of thiram concentration on the spore germination of isolates of Cochliobolus carbonum

Inhibition of spore germination of selected isolates ofCochliobolus carbonum was studied with increasing concentrations of thiram. Isolate differences were detected for the TMTD polymodal curve. This difference was shown to be heritable and independent of tolerance to thiram as indicated by vegetative growth. The polymodal TMTD curve of spore germination inhibition inC. carbonum may result from two (or more) thiram sensitive loci each genetically conditioned independently.A joint contribution of the Department of Plant Pathology and the Pesticides Research Laboratory. The Pennsylvania State University, University Park 16802.     

Effects of itraconazole on the sporocysts wall of the entomopathogenic fungi Ascosphaera apis as revealed by the scanning electron microscope

The young sporocysts had a wrinkled sporocyst wall, numerous papillae on the wall surface and the wall was granular and porous. In the itraconazole-treated culture, the walls of the young sporocysts were also wrinkled, but the characteristic papillae were replaced by larger lumps which were densely packed and coated the entire surface of the sporocyst wall. The mature sporocysts walls were smooth and possessed numerous papillae. In the itraconazole-treated culture, the walls of mature sporocysts walls were also smooth but possessed densely packed larger lumps instead of papillae. At higher magnification, each of the lumps were found to consist of numerous globules. No pores were observed as they were in the normal sporocyst wall.     

蕨类植物孢子萌发影响因素的研究进展

蕨类植物经孢子萌发 ,产生配子体和形成孢子体 ,从而完成其世代交替的生活史 ;其中孢子萌发在整个生活周期中起着关键性的作用。简要介绍了近年来关于孢子萌发的研究进展。     

Effect of high temperatures on seed germination of two woody Leguminosae

Cytisus scoparius and Genista florida regenerate after fire by stump-sprouting but also by seed. Seeds of these species were heated to a range of temperatures similar to those registered on the surface soil during natural fires (from 50 to 150 °C) and a range of exposure times (from 1 to 15 min). No germination was observed at high temperatures, 130 °C, when the exposure time was 5 min or more. However, moderate heat treatments (at 70 and 100 °C) significantly increased the rate of germination relative to controls. Cytisus scoparius is more favoured by fire action than Genista florida, with germination rates slightly greater following 100 °C for 5 min and 130 °C for 1 min than after mechanical scarification.     

The time dependence of bacterial spore germination.

The absorbance of a suspension of germinating bacterial spores describes a sigmoidal time dependence. This behavior is accurately described by a model which considers that the spore must pass through an intermediate state before reaching its final, germinated state. By attributing to each of these three states a characteristic turbidity coefficient, it is possible to write an expression for the absorbance of the suspension at any time after initiation of germination. The transition between neighboring states is characterized by a probability coefficient which is a function of the experimental variables, but which is independent of time. It is thus possible to separate the underlying time dependence of germination itself, characterized by the changes of state, from the observed manifestation of this phenomenon.