中国腐霉属新记录种——Pythium nunn的形态学鉴定及rDNA-ITS系统发育分析

为了调查北京地区苗圃基地的腐霉属种类,采用花瓣、叶片诱捕法对采集到的土样进行诱导,以分离出腐霉菌。结果表明:有5株形态相似的菌株在形态及培养形状上较为一致,且异于中国已报道的其他腐霉种。运用改进的CTAB法提取菌株的基因组DNA,测定其rDNA-ITS序列,并与模式菌株CBS808.96进行多重序列比对,相似度为99.26%。选取与Pythium nunn同组的所有腐霉种以及其他组别的部分腐霉种,以Phytophthora polymorphica为外类群,采用NJ法构建了系统进化树。根据形态特征及分子序列分析结果,将此5株菌株鉴定为Pythium nunn。Pythium nunn是一种具有生防潜力的卵菌,可以为后续的生物防治研究提供试验基础。     

西葫芦绵腐病、绵疫病、枯萎病、细菌性叶斑病、软腐病、花叶病和根霉腐烂病的识别与防治

介绍了西葫芦绵腐病、绵疫病、枯萎病、细菌性叶斑病、软腐病、花叶病和根霉腐烂病的危害症状、发病特点。提出防治这些病害应加强栽培管理,提高植株抗病能力,采用以铲除菌源和药剂保护为重点的综合防治措施。     

钾施用量对一串红营养生长及钾营养特性的影响

研究适宜一串红生长的钾浓度界限范围,为无土栽培一串红盆花的产业化生产提供科学的施肥依据,通过对一串红不同钾施用量的栽培研究,分析了其外观形态指标、干重、根系生长发育及钾营养特性的变化规律。结果表明,缺钾情况下一串红植株矮小,无法正常生长。供钾浓度在30～400 mg/L之间,株高、冠幅、叶片数的差异不显著,但是30 mg/L的处理不利于植株根系的生长发育,大于300 mg/L抑制了根系的生长发育。供钾浓度从100 mg/L开始,植株出现了钾营养的浪费性吸收。综合考虑施钾对植株各项指标的影响,确定施钾浓度为100 mg/L对一串红的营养生长最适宜。     

油棕猝倒病菌实时荧光PCR检测方法

油棕猝倒病菌(Pythiums plendens)是我国进境植物检疫性有害生物。本试验根据P.splendens rDNA ITS区序列,设计了实时荧光PCR引物pyspF/pyspR及荧光探针pyspT,建立了P.splendens荧光PCR检测方法,检测灵敏度为0.012pg/μL。     

氢氧化钙尿素复合处理芨芨草的效果研究

分别用4％尿素、4％尿素 4％氢氧化钙处理芨芨草，试验结果表明：氢氧化钙尿素复合处理剂可极显著(P＜O．01)提高芨芨草粗蛋白含量，比对照组提高142．61％，增加5．79个百分点。NDF舍量比对照组降低11．51％(P＜0．01)。钙含量比对照组提高1．92倍(P＜0．01)。4％尿素处理芨芨草后．芨芨草DM中CP含量比对照组增加145．81％(P＜0．01)。氢氧化钙尿素复合处理芨芨草后．可分别提高芨芨草DM、OM、NDF有效降解率55．08％、62．04％、28．89oA(P＜0．01)。4％尿素可分别提高芨芨草DM、0M、NDF有效降解率46．61％、50．87％、18．80％(P＜0．01)。     

一串红种子发芽特性研究

研究了温度、光照、水分、覆土厚度对一串红种子发芽的影响。结果表明：在15～25℃范围内，温度越低，种子发芽质量越高，温度高于25℃时，发芽率、发芽势显著下降，到35℃时，处于休眠状态。光照对种子发芽的影响不大。基质含水量的差异对种子发芽影响较大，相对含水量为70％时，种子发芽效果最佳。种子发芽以不覆土或浅覆土为好。     

Sources of resistance to diseases of sugar beet in related Beta germplasm: II. Soil-borne diseases

Between 580 and 700 accessions of related cultivated and wild species of the genus Beta were assessed for resistance to four soil-borne diseases of sugar beet: two seedling damping-off diseases caused by the fungi Aphanomyces cochlioides and Pythium ultimum and two diseases of more mature plants, Rhizoctonia root and crown rot, caused by the fungus R. solani, and Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), a furovirus transmitted by the plasmodiophorid Polymyxa betae. Analysis of resistance data (assessed on an international standardised 1–9 scale of Resistance Scores) indicated that the highest levels of resistance ({RS} 2) to A. cochlioides and P. ultimum were to be found amongst accessions of the more distantly related sections Corollinae (93% of accessions tested) and Procumbentes (10%), respectively; although useful levels could also be found in the more closely related, and sexually compatible, section Beta (1–6%). Resistance to Rhizoctonia was also found in section Beta (5–7%), depending on whether field or glasshouse tests were used, but there was little evidence of generally high levels of resistance to Rhizomania among accessions of this section. None of the accessions of sections Corollinae and Procumbentes exhibited any notable resistance to Rhizoctonia. However, all sections Procumbentes and some sections Corollinae (4%) accessions were highly resistant to Rhizomania. Individuals with high levels of resistance to Rhizomania were identified from within some section Beta and Corollinae accessions, in which there was evidence of segregation.     

Evaluation of soil solar heating for control of damping-off fungi in two forest nurseries in France

Field experiments were carried out at two different forest nurseries during the summer of 1994 to examine the efficacy of soil solarization for the control of damping-off. Both soils hosted Pythium spp., Fusarium spp. and Rhizoctonia solani as damping-off agents. Soil samples from solarized, steamed, fumigated and untreated plots were periodically collected and assayed for soil infectivity. Solarization with a double layer of polyethylene film was as effective as steaming or fumigation in reducing soil infectivity in the uppermost layer. During July the temperature of covered beds rose as high as 50°C at a soil depth of 5cm. The method achieved good control of Pythium spp., the main cause of damping-off at both nurseries, whereas Fusarium spp. were more tolerant. The association of Trichoderma spp. with a reduction of soil infectivity at the last sampling date strongly suggested that biocontrol processes were induced after solarization. Soil solarization provides a suitable method for control of damping-off. Received: 29 October 1996     

Oligotrophic pseudomonads in the rhizosphere: Suppressiveness to Pythium damping-off of cucumber seedlings (Cucumis sativus L.)

Summary Pseudomonads recovered from the cucumber rhizosphere were evaluated for their ability to suppress Pythium ultimum damping-off. Full-strength and 250-fold diluted selective media formulations with King's B medium (KB and KB/250, respectively) as the basal medium were used as the recovery media. Eight per cent of the isolates recovered (11/138) could induce suppression to Pythium damping-off and 45% of these biocontrol agents produced fluorescent pigments. No differences in the ability to induce suppression among the isolates recovered on full-strength and diluted media were detected. The growth rates of the selected isolates indicated that growth in KB broth was faster or equal to that in KB/10. Therefore, no obligate oligotrophs were recovered. Additionally, growth was observed in 15 000-fold diluted KB for 10 of 11 test isolates, which indicated that these isolates were facultative oligotrophs. In general, the faster growing isolates were more likely to induce suppression when used as seed treatments. Finally, the in vitro antifungal properties of test isolates against P. ultimum indicated that 4 of the 11 isolates inhibited P. ultimum.     

可降解络合剂及微生物调控对海州香薷修复污染土壤的效应

盆栽试验研究了海州香薷在Cu、Zn、Pb污染土壤上生长和对Cu、Zn、Pb的富集能力,以及调控剂EDDS、壳聚糖和微生物菌剂对海州香薷重金属吸收的影响。结果表明,Cu223mg/kg,Pb232mg/kg,Zn1068mg/kg的重金属复合污染土壤对海州香薷的生长发育没有明显影响。施用EDDS(3mmol/kg土) 微生物制剂处理组海州香薷叶片中Cu含量高达847mg/kg,Zn含量为745mg/kg;Cu吸收量高达6244μg/株,Zn吸收量为5670μg/株,叶片中Cu、Zn的含量和吸收量均极显著高于对照(p<0.01);3mmol/kg土EDDS处理海州香薷茎中Pb含量显著增加(p<0.05),茎中Pb的吸收量亦显著提高(p<0.05),茎秆中Pb的吸收量为274μg/株。微生物制剂或壳聚糖单独处理对海州香薷生长和金属元素吸收均没有明显的效果。