Occurrence and molecular characterization of Actinidia virus C (AcVC), a novel vitivirus infecting kiwifruit (Actinidia spp.) in China

Kiwifruit (Actinidia spp.) is an economically important fruit crop in the world. China is the largest producer of kiwifruit in terms of both acreage and yield. In this study, a novel virus, tentatively named Actinidia virus C (AcVC), was discovered in Actinidia deliciosa ‘Xuxiang’ grown in commercial kiwifruit fields in the Shaanxi province, a major kiwifruit-growing region in China. Sequencing of the complete genome showed that AcVC has 7,668 nucleotides (not including the poly-(A) sequence). Complete genome comparison and phylogenetic analysis showed that AcVC is most closely related to AcVA and then to AcVB. AcVC shares 69.2% nucleotide identity with AcVA (GenBank accession number JN427014 ). Based on these data, Actinidia virus C is assigned as a new tentative member of the genus Vitivirus in the family Betaflexiviridae. AcVC was found to infect A. deliciosa and A. chinesis, the two major cultivated kiwifruits. Infection frequency of AcVC varied with the kiwifruit-growing regions and cultivars in the Shaanxi province of China.     

Methionine deficiency and its hydroxy analogue influence chicken intestinal 3-dimensional organoid development

Methionine and its hydroxy analogue(MHA)have been shown to benefit mouse intestinal regeneration.The intestinal organoid is a good model that directly reflects the impact of certain nutrients or chemicals on intestinal development.Here,we aimed to establish a chicken intestinal organoid culture method first and then use the model to explore the influence of methionine deficiency and MHA on intestinal organoid development.The results showed that 125-mm cell strainer exhibited the highest efficiency for chicken embryo crypt harvesting.We found that transforming growth factor-b inhibitor(A8301)supplementation promoted enterocyte differentiation at the expense of the proliferation of intestinal stem cells(ISC).The mitogen-activated protein kinase p38 inhibitor(SB202190)promoted intestinal organoid formation and enterocyte differentiation but suppressed the differentiation of enteroendocrine cells,goblet cells and Paneth cells.However,the suppression of enteroendocrine cell and Paneth cell differentiation by SB202190 was alleviated at the presence of A8301.The glycogen synthase kinase 3 inhibitor(CHIR99021),valproic acid(VPA)alone and their combination promoted chicken intestinal organoid formation and enterocyte differentiation at the expense of the expression of Paneth cells and goblet cells.Chicken serum significantly improved organoid formation,especially in the presence of A8301,SB202190,CHIR99021,and VPA,but inhibited the differentiation of Paneth cells and enteroendocrine cells.Chicken serum at a concentration of 0.25%meets the requirement of chicken intestinal organoid development,and the beneficial effect of chicken serum on chicken intestinal organoid culture could not be replaced by fetal bovine serum and insulin-like growth factor-1.Moreover,commercial mouse organoid culture medium supplemented with A8301,SB202190,CHIR99021,VPA,and chicken serum promotes chicken organoid budding.Based on the chicken intestinal organoid model,we found that methionine deficiency mimicked by cycloleucine suppressed organoid formation and organoid size,and this effect was reinforced with increased cycloleucine concentrations.Methionine hydroxy analogue promoted regeneration of ISC but decreased cell differentiation compared with the results obtained with L-methionine.In conclusion,our results provide a potentially excellent guideline for chicken intestinal organoid culture and insights into methionine function in crypt development.     

参与式林业——参与式发展在森林管理中的实践

介绍了参与式林业的基本内容和执行参与式林业项目的基本过程.参与式林业的关键是实现群众参与,需要分析森林与社区和群众生产及生活的联系,重视社区和群众在森林管理中的作用.我国参与式林业的实践历史悠久而富有成效,我国林业的可持续发展不能离开乡村群众的参与.为了实现森林的可持续经营,需要把森林的社区管理和森林的国家管理有机结合起来.合适的参与式途径、合理的利益分配机制和正确的林地林木权属关系是引导当地群众参与林业活动的基本要素.     

江苏盐城黑嘴鸥繁殖期不同阶段行为时间分配及活动规律

1999— 2 0 0 2年夏季对江苏盐城黑嘴鸥繁殖期不同阶段行为时间分配及活动规律进行了定量研究。结果表明 :繁殖前期黑嘴鸥各种行为具有较强的规律性 ,其出现频率依次为 :取食 39 36 % ,休整 37 95 % ,运动 9 4 8% ,警戒 8 30 % ,饮水 5 0 3% ;繁殖后期黑嘴鸥成鸟的各种行为不具明显的规律性 ,其出现的频率依次为取食 4 2 5 3% ,休整 1 4 2 1 % ,运动 1 7 6 5 % ,警戒 1 4 5 2 % ,饮水 1 0 93%。繁殖后期运动和警戒行为所花费的时间比繁殖前期显著增加 (P <0 0 0 1 ) ,休整行为显著减少 (P <0 0 0 1 ) ,导致这种差异性主要是取食地点的变化和后期的育雏行为。黑嘴鸥雌雄抱孵时间比为 1 2 4∶1。抱孵时间随孵化天数的增加而相应延长 ,一次抱孵时间最长可达到 2 0 1min。     

华北落叶松人工林的生物量估算参数

分析华北落叶松人工林4个典型区域(关帝山、五台山中山区、五台山盆地区和塞罕坝)的生物量估算参数(生物量转扩因子、生物量扩展因子和根茎比)及其区域分异。结果表明:关帝山林区和五台山林区(中山区和盆地区)的生物量转扩因子平均值间无显著差异(P>0.05)且都大于塞罕坝林区(P<0.05);关帝山林区、五台山盆地区和塞罕坝林区的生物量扩展因子平均值间无显著差异(P>0.05)且都小于五台山中山区(P<0.05);生物量转扩因子和生物量扩展因子随林龄、平均胸径和蓄积量的增加而减小并趋于稳定;4个区域的根茎比平均值间无显著差异(P>0.05);根茎比随林龄和平均胸径的增加而增加(P<0.01),但与林分密度和蓄积量无显著相关性(P>0.05)。由于不同区域的生物量转扩因子和生物量扩展因子平均值间存在显著差异,故而建议按区域选择它们的值,并尽可能利用它们与林分测量指标的函数关系来确定。     

平茬对银杏叶产量质量影响的研究

叶用银杏的栽培管理是银杏GAP生产建设的重要组成部分。平茬修剪是叶用银杏栽培管理中的重要环节,直接影响到叶子的产量与质量。该文通过3年的试验研究发现:平茬较不平茬者好;生产中以栽植密度45000株/hm2、高度40cm的银杏为宜;采叶期在7月下旬至8月下旬。此技术可在黄淮海及其相似地区银杏药用采叶园中推广应用。     

抚育间伐对人工林凋落物分解的影响

抚育间伐是提高林分生产力的有效措施之一, 以往研究主要集中在间伐对凋落物分解速率、养分归还量以及对土壤肥力影响等直接效果方面, 而对间伐引起这些变化的原因涉及较少。文中主要综述了抚育间伐后凋落物性质、林下植被、林内小气候和土壤性质等的变化情况, 以及这些变化对凋落物分解的影响作用。     

南方亚高山区日本落叶松自由授粉子代优良单株选育研究

建始县长岭岗林场29 a生日本落叶松自由授粉家系子代测定林为研究对象,通过对生长性状进行遗传变异分析,结果表明:不同家系之间树高和材积存在极显著差异,不同家系之间的胸径存在显著差异,各生长性状的家系遗传力大于单株遗传力,表型变异(CVP)均明显高于遗传变异(CVG),日本落叶松家系间和家系内个体间存在较大的差异;利用最佳线性预测(BLP)方法采用家系与家系内个体联合估算育种值,按入选率为10%,选择出40个优良单株,为该地区营建高世代种子园及品种遗传改良与推广提供优质材料和科学依据。