我国小麦秆锈菌种群动态分析

１９９５～１９９６年间,在我国７省区６２个县点共收集标样２８３份,涉及品种１１７个,分离到菌株４５５份,鉴定出１５个致病类型,其出现类型的发生频率分别是２１Ｃ３ＣＫＲ为１７．５％,２１Ｃ３ＣＦＨ９．６％,２１Ｃ３ＣＫＨ８．８％,２１Ｃ３ＣＦＲ６．０％,２１Ｃ３ＣＴＲ２２．０％,２１Ｃ３ＣＰＲ９．４％,２１Ｃ３ＣＴＨ８．８％,２１Ｃ３ＣＰＨ１１．９％,３４ＭＫＧ１．３％,３４Ｃ２ＭＫＨ０．２％,３４Ｃ２ＭＫＫ０．１％,３４Ｃ２ＭＦＨ３．６％,３４Ｃ２ＭＦＫ０．４％,３４Ｃ１ＭＫＲ和３４Ｃ１ＭＦＲ为０．２％。１９９６年２１Ｃ３ＣＫＲ的出现频率上升为第１位,对Ｓｒ１１有毒力的致病类型出现频率有所下降。     

Pathogenicity and genetic variation of Phytophthora cactorum from silver birch and strawberry

Phytophthora cactorum strains isolated from necrotic stem lesions on Betula pendula seedlings or from Fragaria ananassa plants suffering from crown rot were pathogenic to their host plants. Only isolates from birch caused clear lesions on non-wounded bark of birch. P. cactorum isolates from birch were not detrimental to strawberry. Random Amplified Polymorphic DNA (RAPD) analysis revealed variation within P. cactorum, isolates from silver birch having different banding patterns than those from strawberry. UPGMA analysis clustered isolates from silver birch and strawberry plants into separate groups. The data show that the recent outbreak in Finland of P. cactorum in birch could not be caused by the import of strawberry plants affected by crown rot.     

The effect of fungal infection and nitrogen fertilization on the carbohydrate composition of Rumex obtusifolius leaves

The effect of infection by the rust fungus Uromyces rumicis and fertilization by different concentrations of nitrate or ammonium solutions on the concentrations of alcohol-soluble carbohydrates, fructans and starch in Rumex obtusifolius leaves was investigated. In leaves from healthy plants there was an increase in concentration of alcohol-soluble carbohydrates and fructans as the concentration of nitrate given was decreased, with the exception of nitrogen-stressed plants (those fed less than 10 mM l^-1 nitrate) which had a lower concentration of alcohol-soluble carbohydrates than plants fed 10 mM l^-1 nitrate. There was an increase in fructan and starch concentration in leaves as the concentration of ammonium solution given was decreased. The concentration of alcohol-soluble carbohydrates was reduced in infected leaves and increased in healthy leaves on infected plants, while the fructan concentration increased in infected leaves, compared to healthy leaves. The effects of infection were consistent over the range of nitrogen concentrations used, and thus were additive to the effects of fertilization. These results confirm the known effects of fertilization or fungal infection, singly, and indicate that, when combined, nitrogen deficiency and fungal infection may produce an additive stress on the plant.     

Cloning of <Emphasis Type="Bold">β</Emphasis>-tubulin and succinate dehydrogenase genes from <Emphasis Type="Italic">Uromyces fabae</Emphasis> and establishing selection conditions for their use in transformation

The obligate biotrophic nature of rust fungi calls for an in planta selection scheme as a means of developing a rust transformation technology. We show that the fungicides benomyl (used as its formulated product benlate) and carboxin suppress morphogenesis of the rust fungus Uromyces fabae in vitro and disease in planta, the latter without affecting the health of the host. The limits of their applicability were determined regarding concentration, method of application and optimal time intervals of treatment. Besides procedures for selection, a stable transformation system will also need to include genetic markers allowing to enrich for transformed cells within a large background of untransformed cells. Since the molecular targets of benlate and carboxin had been identified as -tubulin and succinate dehydrogenase, respectively, the corresponding genes (Uf-TBBIand Uf-SUCDHI) were cloned and characterized. Molecular phylogenies demonstrate that both are typical homologs to those of other Basidiomycota. RT-PCR analysis confirmed that both genes are constitutively expressed in all developmental stages of the mitotic uredospore multiplication cycle. Since homologs of Uf-TBB1and Uf-SUCDH1 have been successfully used as selection markers in other fungal systems, they provide valuable tools to develop additional corner stones of a stable transformation system for rust fungi.     

Fungi on roots and stem bases of asparagus in the Netherlands: species and pathogenicity

A survey was made to identify the most important soilborne fungal pathogens of asparagus crops in the Netherlands. Ten plants were selected from each of five fields with a young (1–4 y) first planting, five fields with an old (6–13 y) first planting and five fields with a young replanting. The analysis included fungi present in the stem base and the roots of plants with symptoms of foot and root rot or showing growth decline without specific disease symptoms. Isolates of each species were tested for pathogenicity to asparagus on aseptically grown plantlets on Knop's agar. Symptoms were caused byFusarium oxysporum, F. culmorum, Botrytis cinerea, Penicillium verrucosum var.cyclopium, Cylindrocarpon didymum, Phialophora malorum, Phoma terrestris andAcremonium strictum. F. oxysporum was by far the most common species and was isolated from 80% of the plants. Not all of its isolates were pathogenic to asparagus. Symptoms were caused by 67%, 78% and 93% of the isolates obtained from young first plantings, old first plantings and replantings, respectively.F. culmorum was isolated from 31% of the plants. Two other notorious pathogens of asparagus,F. moniliforme andF. proliferatum, did not occur in our samples.Species causing symptoms in the vitro test that were found on more than 5% of the plants were additionally tested for their pathogenicity in pot experiments.F. oxysporum f.sp.asparagi caused severe foot and root rot, significantly reduced root weights and killed most of the plants.F. culmorum caused lesions on the stem base often resulting in death of the plant.P. terrestris, a fungus only once reported as a pathogen of asparagus, caused an extensive root rot, mainly of secondary roots that became reddish. The fungus was isolated in only a few samples and is not to be regarded as an important pathogen in Dutch asparagus crops.P. malorum caused many small brown lesions on the stem base and incidentally also on the upper part of small main roots. This is the first report of its pathogenicity to asparagus. The fungus is one of the organisms inciting spear rust and it reduced crop quality rather than crop yield.P. verrucosum var.cyclopium andC. didymum did not cause symptoms in pot experiments.Because of its predominance on plants with foot and root rot and its high virulence,F. oxysporum f.sp.asparagi was considered to be the main soilborne pathogen of asparagus in the Netherlands.     

紫花苜蓿根颈生长多样性研究

研究了12个苜蓿材料的根颈直径、入土深度、根颈分枝数、根颈芽4个特征指标,并对不同生育时期的根颈生长进行多样性和相关性分析,结果表明:1)12个苜蓿材料分枝期各多样性指标间都呈正相关关系。根颈入土深度差异性极显著(P0.01),根颈直径、根颈芽数是决定根颈分枝能力的重要因素;2)12个苜蓿材料现蕾期根颈入土深度表现出极显著差异性(P0.01),根颈直径、根颈芽数是决定根颈分枝能力的重要因素;3)12个苜蓿材料开花期根颈直径差异性极显著(P0.01),根颈芽数差异性显著(P0.05);4)不同苜蓿材料间不同生育时期均存在较高的多样性,同一性状的变异系数与多样性指数表现不完全一致,不同生育时期变异系数与多样性指数的变化趋势相同;5)杂20、杂26、杂27、杂97与其他供试苜蓿材料相比,对当地环境适应能力较强,抗性强,具有较高潜在生产潜力。     

番茄颈腐根腐病病原菌及抗病育种研究进展

由尖孢镰刀菌FORL引起的番茄颈腐根腐病是近年来最具破坏性的番茄土传病害之一,该病害严重威胁我国设施番茄的安全生产。综述了番茄颈腐根腐病病原菌生物学特性、发病规律、为害特征及抗病育种等相关研究进展,以期为我国番茄颈腐根腐病的抗病育种提供借鉴。     

小麦多品种混播对条锈病的控制及稳产作用研究（英文）

Wheat stripe rust has become the most dangerous disease which threaten safe yield of wheat in Sichuan Province.It is meaningful to provide technique support for integrated disease control by exploring the effective control measures of wheat stripe rust.Wheat stripe rust dynamic developments of all-planting and mixed-planting have been systematically investigated in this study by taking different mixed-planting combinations among 6 wheat varieties with different resistance levels.The results of this experiment show that the mixed-plantings of 4 and 6 wheat varieties can delay the occurance of wheat stripe rust,slow the speed of disease and decline the damage of disease as well as stabilize yield of wheats.     

小麦秆锈菌单小种与混合小种侵染的流行学研究

以小麦秆锈菌的3个生理小种与感病品种浙麦1号为试材,进行了小麦秆锈菌单小种与混合小种侵染的流行学初步研究,结果表明:小种混合接种较同期的单小种接种的普遍率和严重度高;不同处理的流行曲线为近似的S形,曲线方程为Y=1[1-M×exp(-N×t)],流行曲线下面积为nA=∑i=112(yi+yi-1)(xi-xi-1),且小种混合接种对小麦千粒重的影响最大;小种之间在流行学上存在着互补和拮抗的作用。