Assessment of Partial Resistance to Powdery Mildew (Podosphaera pannosa) in a Tetraploid Rose Population Using a Spore-suspension Inoculation Method

Powdery mildew (Podosphaera pannosa) is the most important fungal disease in greenhouse roses and is in practice controlled by fungicides. The creation of novel cultivars with durable resistance to powdery mildew is highly desirable. To understand the inheritance of mildew resistance, a tetraploid rose population with a size of 181 seedlings was obtained by crossing two tetraploid genotypes each having partial resistance. The population and its parents were tested under greenhouse conditions with two well-defined monospore isolates (2 and F1) using artificial inoculation with spore suspensions. Disease score at 11 days post-inoculation, latent period and rate of symptom development were used to describe seedling resistance. The tests for both isolates exhibited a wide and significant variation among genotypes for resistance. The distribution of the genotypic means of the disease scores was continuous and showed a considerable transgression. Statistical analysis, scatter plot of disease scores for the isolates, and correlation analyses indicated that the two isolates differed in pathogenicity. The outcome of the tests showed that the inoculation assay with spore suspensions was a reliable and effective way to screen large numbers of genotypes under greenhouse conditions for genetic and breeding studies. This is the first report on spore-suspension inoculation to be used successfully in rose.     

An Aqueous Extract of the Dry Mycelium of Penicillium chrysogenum Induces Resistance in Several Crops under Controlled and Field Conditions

We have examined the effect of Pen, an aqueous extract of the dry mycelium of Penicillium chrysogenum, on plant–pathogen interactions. Pen controlled a broad range of pathogens on several crop plants under greenhouse and field conditions. Pen protected grapevine from downy and powdery mildew (caused by Plasmopara viticola and Uncinula necator), tomato from early blight (caused by Phytophthora infestans), onion from downy mildew (Peronospora destructor) and apple trees from apple scab (caused by Venturia inaequalis) to a similar extent as fungicides such as copper and sulphur or well-known inducers such as benzothiadiazole or β-aminobutyric acid. Pen had no major direct fungicidal effect and is thus supposed to protect plants by activating their defense mechanisms. The raw material for extraction of Pen was available in constant quality, a prerequisite for commercial application. Under certain conditions, Pen caused phytotoxic side effects. The symptoms mostly consisted of small necrotic spots or, more rarely, of larger necrotic areas. The development of the symptoms was dependent on several parameters, including concentration of Pen, the number of applications, the persistence on the plant tissue, the plant species and variety and environmental conditions. In grapevine, a partially purified fraction of Pen was much less toxic than the crude Pen extract, but protected the plants to a similar extent against P. viticola. Our data show that Pen has interesting and unique properties as a plant protection agent, but more research is needed to further reduce its phytotoxic side effects.     

Lipid metabolism in tomato and bean as a sensitive monitor for biocontrol of wilt diseases

The lipids metabolism of tomato and bean plants during biological control of wilt pathogens (Fusarium oxysporum f.sp.lycopersici andF. oxysporum f.sp.phaseoli, respectively) byBacillus subtilis was investigated. The interaction of wilt pathogens with both tomato and bean caused an imbalance and drastic reduction in total lipids, triacylglycerol, sterol and all phospholipd fractions except phosphatidic acid. The application of a formulated biocontrol agent,B. subtilis, eliminated the detrimental effect of both wilt pathogens and consequently prevented catabolism of lipid fractions in both tomato and bean. Moreover, the changes in the lipid fractions as a sensitive monitor for biocontrol of wilt diseases suggest a positive correlation between the application ofB. subtilis and improvement in the host metabolism towards anabolism. http://www.phytoparasitica.org posting Sept. 20, 2006.     

Note: First record in crete ofHercinothrips femoralis in greenhouse banana plantations

In 2004 the banded greenhouse thrips,Hercinothrips femoralis (Reuter) (Thysanoptera: Thripidae), was recorded for the first time in greenhouse-grown organic banana in the area of Sitia (northeastern Crete). Banana fruits were severely damaged by the thrips infestation and a typical smoky-red discoloration of the fruit was observed. Pest control was poor using either high-pressure washing with potassium fatty acids, or commercially available thrips predatorsNeoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae) andOrius laevigatus (Fieber) (Hemiptera: Anthocoridae). During 2005H. femoralis was also found causing severe damage in conventional banana plantations in Arvi, the main banana-growing area of Crete. http://www.phytoparasitica.org posting Sept. 17, 2006.     

转基因番茄F2代的贮藏特性研究

以F1′、F2、F3、NR四个转基因番茄基因型为实验材料,研究了转反义乙烯基因F2代番茄果实的贮藏特性,据此对转基因番茄各基因型的贮藏特性作综合分析评价。结果表明,F3基因型果实的失重率、腐烂率最低,果柄拉力最大,外观形态最好,贮藏特性最好;其次是F1′和NR基因型;而F2基因型最差。     

协同增效型拮抗细菌组合CL-7和CL-8的稳定性及其对加工番茄的促生防病效果

将加工番茄根际土壤中筛选到的单一拮抗细菌进行复配，筛选获得两个具有促生拈抗作用的细菌组合CL-7和CL-8。经过20代转管连续培养检测细菌组合的稳定性，结果表明，这两个拮抗细菌组合从13代之后，其pH值基本稳定，组合内菌落种类及数目也基本稳定；且12代后抑菌活性基本保持不变。和单一拮抗菌株相比，CL-7和CL-8均能显著增加对番茄立枯病菌、辣椒疫霉病菌和枯萎病菌的抑菌效果。发芽和苗期灌根试验结果表明，拮抗细菌组合CL-7和CL-8可显著促进加工番茄幼芽及苗期的生长，苗期鲜重分别增加了147．620k和176．190k，干重分别增加了143．75％和143．75％。在温室和田间条件下，细菌组合CL-7和CL-8对加工番茄立枯病的防治效果都很显著，分别可达25．1％、40．1％和52．2％、55．5％。     

番茄资源对叶霉病的抗性鉴定和SSR标记遗传变异分析

 对62份番茄种质资源进行了抗番茄叶霉病鉴定, 共筛选出抗病材料17份, 其中对全部生理小种(1.2.3、1.2、2.3、1.2.3.4、1.2.4)均表现抗病或免疫的材料9份;抗3个生理小种的材料4份;抗2个生理小种的材料2份;抗4个生理小种的材料2份。并应用SSR标记技术对62份种质资源进行了遗传多样性分析, 50对SSR引物中筛选出11对多态性明显、条带清晰、反应稳定的引物, 共扩增出94条谱带, 平均每个引物扩增出8.55条带, 多态性条带比例达63.94%, 遗传相似系数在0~1之间, 表现出丰富的遗传多态性, 可将番茄野生种和栽培种分开, 反映了种间的遗传差异。     

加工番茄种子发芽及苗期耐冷性差异研究

通过低温下种子发芽鉴定和苗期低温处理后生理生化指标的测定等方法,研究了9个加工番茄品种种子萌发期和幼苗期的耐冷反应。结果表明,供试材料对低温反应存在差异;种子萌发期耐冷性鉴定温度为15、20℃;低温下植株电解质渗透率、叶片细胞内可溶性糖含量均有上升;根据各品种种子发芽率、幼苗冷害指数、植株电解质渗透率、叶片可溶性糖含量综合评定,UC-82、里格尔、石番18号、红霸这4个品种抗冷性较好。     

Pathogenicity assays restrict the species Xanthomonas campestris into three pathovars and reveal nine races within X. campestris pv. campestris

The species Xanthomonas campestris (Vauterin) groups bacteria associated with cruciferous plants. In order to clarify and refine the pathovar and race structures within X . campestris , 47 representative strains of six pathovars were characterized for their pathogenicity on a large host range of Brassicaceae, including all original hosts. Three diseases were observed on tested plants: (i) black rot disease on cruciferous plants; it was proposed that all strains causing black rot on at least one cruciferous plant be grouped in the single pathovar X . c . pv. campestris ; (ii) leaf spot disease caused by X . c . pv. raphani on hosts belonging to the Brassicaceae and Solanaceae; the sequenced strain 756C identified as X . c . pv. armoraciae was included in this pathovar and the existence of another leaf spot disease caused by X . c . pv. armoraciae was not supported; and (iii) bacterial blight of garden stocks caused by X . c . pv. incanae . No plants susceptible to X . c . pv. barbareae were found. Strains that did not induce any symptom on cruciferous plants tested, including their original hosts, were removed from the pathovar scheme and were named X . campestris only. Three new races were described in addition to the six races previously described within X . c . pv. campestris . The sequenced strains ATCC 33913 (CFBP 5241) and Xcc 8004 (CFBP 6650) belonged to race 3 and to race 9 (one of the new races described), respectively.     

尖角突脐孢菌在温室环境下侵染稗草的致病体系研究

稗属（Echinochloa）杂草是全世界水稻等作物生产中的一类恶性杂草。人工除稗安全但费时费力，化学除稗高效但伴随农产品安全和环境相融友好方面的潜在风险。因此，寻求安全高效的除稗活性成分和施药技术成为国际上除稗剂发展的重要方向之一。在研究和开发生物除稗剂的技术体系中，满足高通量筛选安全、高效的除稗生防因子的温室检测体系是极为重要的支持平台，同样，生物除稗剂的田间科学施药技术亦应依据生防因子在稗草上致病和致害所需的最佳条件来制定。基于此，亟需探明生防因子侵染稗草致病的相关条件并建立快速有效的生防因子除稗效果温室检测体系和田间施药技术。本文系统研究了影响尖角突脐孢菌侵染稗草的相关因子，建立了稳定的温室环境下尖角突脐孢菌侵染稗草的致病体系。