<Emphasis Type="Italic">Spongospora subterranea</Emphasis> soil contamination and its relationship to severity of powdery scab on potatoes

We investigated soil contamination by Spongospora subterranea f. sp. subterranea (Sss) and disease severity of powdery scab in 29 potato fields in Hokkaido, Japan, using a hydroponic culture method with tomato seedlings as bait plants. The quantity of Sss infection on the roots of bait plants was evaluated using the polymerase chain reaction (PCR) and expressed in terms of the infection potential in the soil. The infection potential was positively correlated with the disease severity of harvested tubers, whereas the spore ball density determined using PCR had an indistinct relationship with disease severity. The infection potential can be useful in evaluating soil contamination and in applying countermeasures against powdery scab.     

Heterogeneity of the aerial concentration and deposition of ascospores of <Emphasis Type="Italic">Venturia inaequalis</Emphasis> within a tree canopy during the rain

Scab is an important disease of apple and its control depends almost exclusively on frequent use of fungicides. Primary scab infection in the spring assumes several steps: ascospore maturation, liberation of ascospores that become airborne, deposition on susceptible tissues, and infection. However, the spatial heterogeneity of ascospores within the tree canopy is unknown. Aerial concentration of ascospore (ACA), ascospore concentration in rain water (ACR) and ascospore deposition (AD) were therefore measured at six heights (20–257 cm from the ground) with rotating-arm air samplers, funnels, and greased glass slides, respectively, during five rain events in 2001 and in 2002. In addition, ACR and AD were measured at eight locations within tree canopy at 196 cm height. Apple scab was assessed at the end of the primary infection period in each sampling location within the apple tree. A similar experimental design was used in 2003 to study the spatial heterogeneity of both AD and primary scab lesions. ACA and AD decreased with increasing height, while ACR increased with increasing height. Based on both variance to mean ratio and the power law relationship in both years, the ACR was heterogeneous, while AD was heterogeneous only during the peaks of ascospore release. The ACR was significantly higher at the centre of the trees and the AD was significantly higher at the centre and at the western edge of the trees. Only the cumulative AD was significantly correlated with apple scab lesions at the same location (r = 0.83). In 2003, a similar pattern of spatial heterogeneity within the tree canopy was observed for AD and primary scab lesion counts and there was a linear relationship (R ² = 0.84) between these two variables. It was concluded that ACR and AD within the tree canopy are not randomly distributed at least during peaks of ascospore release and that AD is a good estimate of primary scab lesion development. This spatial heterogeneity should be considered when estimating ascospore deposition using mathematical models or when quantifying ascosporic inoculum using spore samplers.     

A dynamic model forecasting infection of pear leaves by conidia of <Emphasis Type="Italic">Venturia nashicola</Emphasis> and its evaluation in unsprayed orchards

A dynamic model, called VenInf, was developed to forecast infection of pear leaves by conidia of Venturia nashicola. By simulating conidial infection processes following a rain event, the model estimates % conidia that successfully infected leaves at the end of an infection period. The model is mainly derived from logistic models developed from recent laboratory and glasshouse experimental results on infection of pear seedlings to estimate the rates of infection and mortality. It simulates the conidial infection process at 5 min intervals using temperature, relative humidity (RH), surface wetness and rainfall as input. The model was evaluated against pear scab in four unsprayed orchards in China over a 4-year period. In all orchards, all significant disease increases were associated with infection periods predicted by the model. In one orchard, in 2004 the incidence of leaf infection remained very low (<3%) during the entire season despite the model forecasting several severe infection periods. Results of orchard evaluation suggest that the model is able to identify all important potential infection periods. Thus, further field studies should be carried out to determine whether and how the model can be used in practice to assist farmers in making decisions on fungicide applications.     

Li~+、肌醇与Ca~(2+)对苹果、梨、山楂花粉萌发和花粉管生长的影响

观测了苹果（金冠）、梨（鸭梨）、山植（面值）的花粉萌发和花粉管生长情况,结果表明,Li2SO4的浓度越高、处理时间越早,花粉萌发和花粉管生长的抑制程度越大,Ca2+和肌醇可不同程度地逆转上述效应。因此认为,细胞内一定量的肌醇和Ca2+是果树花粉萌发和花粉管生长所必需的,并对维持正常的肌醇磷脂代谢是至关重要的。     

湿段天气在小麦赤霉病定量预报中的应用

通过本县小麦感病期内逐日气象观测资料统计分析,发现在该期内各日２：００、８：００、２０：００的空气相对湿度达８５％,１４：００达８２％,且在此湿度标准上持续３０ｈ以上,平均气温达１２℃的湿段天气累计持续时间长,小麦赤霉病发生重。依据湿段天气段在小麦感病的穗期开展赤霉病的短期定量预测,１０年次的回报病穗率误差为２个百分点左右,７年次的预报病穗率误差为０．２９￣５．２个百分点。     

CaM在梨花芽分化过程中的含量变化

以梨为试材，对成花过程中的短枝芽和叶所含钙调素（ＣａＭ）的含量进行了测定。（１）短枝芽的ＣａＭ含量在整个成花前后都明显高于新梢芽的含量，特别是在成花的发端期突然成倍增加，形成高峰；（２）短果枝叶的ＣａＭ与新梢叶有着相近的变化趋势，但在成花前后，短果枝叶的ＣａＭ含量明显高于新梢叶；（３）ＣａＡｃ处理可以使短枝芽所含ＣａＭ的峰值提前出现，ＴＦＰ处理可明显降低ＣａＭ含量和延迟其峰值到来。还就ＣａＭ在成花过程中的作用及与Ｃａ２＋的关系等问题进行了讨论。     

几种药剂对石榴疮痂病的防治

在山东枣庄石榴疮痂病Dothiorella sp．是石榴枝干、果实上一种新发生的严重病害，用不同药剂、不同施药方法和施药时间对其进行了防治。结果表明，35％百菌敌5倍液于春季(4月上旬)轻刮涂刷枝干上的病斑，效果最好；防治果斑试验，以50％多菌灵WP500倍液效果最好，防治时间为6月上旬、中旬、7月上旬3次。     

石榴溃疡病害病原学研究

对石榴溃疡病害3菌株所引起的病害症状、病原菌的形态学特征、培养学特性、生理学特性及分子遗传多样性等方面进行比较研究.结果表明:石榴疮痂病与石榴果实上增生型症状的病原菌具有更近的亲缘关系,应为同一病原菌引起,推测该病原菌首先侵染石榴侵染枝干,然后侵染石榴的花萼和果实;而石榴干腐病病原菌主要侵染枝干,是否侵染果实及引起症状特征需要继续进行研究和鉴定.     

苹果黑星病的研究进展

苹果黑星病是苹果重要的病害之一,发病严重时可导致苹果严重减产和品质下降。该病害在世界许多国家都有发生,各国对苹果黑星病的分布、流行规律、病原菌致病性、生物学特性、寄主的抗病性及抗病基因、防治方法和病害监测等方面进行了广泛深入的研究。我国对苹果黑星病的研究起步较晚,尚待深入。本文综合近年来的文献资料,从苹果黑星病病原菌、致病机制和抗病机制、防治、抗药性、检测及预测预报等方面进行阐述,以期为该病害的绿色防控提供科学依据。     

安徽省中南部小麦赤霉病气象等级预报方法研究

针对安徽省农业气象业务服务中小麦赤霉病气象等级预报模型精度不高问题,基于安徽省中南部滁州、庐江、池州和宣城4个代表站历年小麦赤霉病病穗率、发育期及对应气象资料,采用线性相关、回归分析等方法,建立基于雨日和雨量的综合降水指数气象等级预报模型,并对模型进行拟合检验和预测检验。结果表明滁州地区小麦赤霉病发生关键为始穗前5d至始穗后25d、庐江为始穗前8d至始穗后20d、池州为始穗前7d至始穗后24d、宣城为始穗前4d至始穗后24d。对建立的区域小麦赤霉病气象等级预报模型进行拟合检验和预测检验发现:滁州地区预测模型的拟合准确率和预测准确率分别为86.8%和92.0%,庐江分别为87.6%和70.0%,池州分别为85.6%和88.0%,宣城分别为88.3%和84.0%。因此,本研究建立的区域小麦赤霉病气象等级预报模型可用于安徽省中南部农业气象业务服务。