宁夏温室瓜菜白粉病菌鉴定及病害流行预测模型构建

为明确宁夏回族自治区温室瓜菜白粉病菌的分类地位,对采自该地区温室的南瓜、黄瓜和甜瓜上的白粉病菌基于ITS序列分析进行分子鉴定;利用孢子捕捉器对温室中甜瓜白粉病菌的孢子量进行监测,分析环境因子、孢子量和病情指数之间的关系,并采用逐步回归分析法构建温室甜瓜白粉病的流行预测模型。结果表明,基于ITS序列的分子鉴定结果,3种瓜菜白粉病的病原菌均为单囊壳白粉菌Podosphaera xanthii。发病期间,每日温室中甜瓜白粉病菌的孢子量在12:00—16:00时段最多,占24 h内总孢子量的34%~81%,20:00—08:00时段最少;白粉病菌孢子的释放与光照强度有关,相关系数为0.602。第t天的病情指数与标准累积温度、标准累积湿度、t-4 d前08:00—12:00时段的累积孢子量、第t-4天16:00—20:00时段的孢子量均具有显著的相关性,相关系数分别为0.935、0.938、0.956和0.921。以标准累积湿度和第t-4天16:00—20:00时段的孢子量为预测变量构建了温室甜瓜白粉病流行预测模型,决定系数为0.962,表明该模型具有较好的实际应用价值。     

Trichomes: interaction sites of tomato leaves with biotrophic powdery mildew pathogens

The present study aimed to explore the possibility of using the type I trichomes of tomato (Solanum lycopersicum) to monitor the infection processes of powdery mildews by microscopy. Individual trichome cells of two tomato genotypes were inoculated with pathogenic and non-pathogenic powdery mildew species, Pseudoidium neolycopersici, Erysiphe trifoliorum and Podosphaera xanthii. On the trichome cells of the tomato cultivar Moneymaker, hyphae of the pathogenic Pseudoidium neolycopersici (isolates KTP-03 and KTP-04) grew vigorously; whereas hyphal growth of the non-pathogenic Erysiphe trifoliorum and Podosphaera xanthii ceased after appressorium formation, which was associated with papilla formation and hypersensitive cell death, respectively. Similar infection processes of the tested powdery mildews were seen in Moneymaker epidermal cells. Therefore, tomato trichomes are suitable for analysing, at individual cell level, the infection processes of different pathotypes of powdery mildews and for observing the cytological responses of plants by non-pathogenic powdery mildews. On the other hand, it was observed that both isolates KTP-03 and KTP-04 failed to produce conidiophores on the hyphae elongating on Moneymaker trichomes. Similarly, no conidiophores were produced on the hyphae elongating on trichomes of Solanum peruvianum LA2172, which is resistant to KTP-03 and susceptible to KTP-04. Interestingly, delayed cell death occurred in LA2172 epidermal cells, which were attacked by KTP-03 hyphae elongating from trichomes and conidiophores were formed on new hyphae growing from the leaf epidermal cells. Thus, leaf trichomes and epidermal cells of the wild tomato species LA2172 reacted differently to the avirulent isolate KTP-03.     

白粉寄生孢寄生黄瓜白粉菌的特性研究

采用白粉寄生孢（Ampelomyces quisqualis Ces.AQ）接种离体条件下赛璐酚上黄瓜白粉菌［Sphaerotheca fuliginea (Schlecht)Poll.］和活体条件下黄瓜白粉菌后,通过棉兰染色和显微观察分析,初步明确了白粉寄生孢的侵染寄生过程。白粉寄生孢分生孢子产生芽管可入侵黄瓜白粉菌的分生孢子、菌丝、分生孢子梗;有时黄瓜白粉菌串生的分生孢子、分生孢子梗可被2~3条白粉寄生孢的菌丝寄生,随着寄生过程的进一步发展,黄瓜白粉菌的分生孢子梗基部膨大成无色的椭圆形或球形,其上逐渐产生由黄色至褐色的白粉寄生孢的分生孢子器,器内含有大量的分生孢子。     

Resistance levels of cucumber to <Emphasis Type="Italic">Podosphaera xanthii</Emphasis> in a growth chamber are related to haustorial formation and hyphal branching frequency

To clarify relationships between powdery mildew resistance of cucumber and hyphal developmental state of the pathogen, haustorial formation and the hyphal branching frequency were compared among cucumber varieties that differ in resistance levels to powdery mildew pathogen Podosphaera xanthii. Cotyledons of four cultivars were inoculated with P. xanthii. By 2 days after inoculation, secondary haustoria had developed from the first hyphal cell that formed beside the conidium in susceptible cultivars. The fungus on susceptible cultivars also tended to have hyphal branches just after the hyphal cell producing haustoria.     

Colonization of rose by Sphaerotheca pannosa (Wallr.) Lév. var. rosae Wor.

Colonization of rose by powdery mildew (Sphaerotheca pannosa) is described in terms of mycelium growth, conidiophore production and sporulation in time. The data used are gathered during different years, put together and treated by means of graphic models. Colonies could be separated into fast and slow growing colonies. Colonies initiated on leaves of increasing age showed a decreasing growth rate. Production of conidiophores and conidia started on the same day, and the relative activity of conidiophore production reached its maximum 6 days after the end of the latency period, followed 1 day later by the maximum activity of conidium production. Both conidiophore and conidium production continued for a long time at a low level. The effect of leaf age on conidiophore production found expression in differences in production rate during the first days of colony development and in final production levels. Observations on naturally infected leaves in an outdoor experiment showed a rapid decrease of sporulation on leaves of 10 days and older. Highest percentages of sporulating leaf area were observed on leaves between 7 and 10 days old.     

苦瓜白粉病病原菌和生理小种的鉴定及苦瓜对白粉病的抗性遗传分析

为明确海南省苦瓜白粉病的病原菌、生理小种及苦瓜对白粉病的抗性遗传规律,结合形态学鉴定和分子鉴定解析白粉病菌及生理小种种类,通过显微镜观察白粉病菌侵染过程,并应用主基因+多基因混合遗传模型分析法探讨苦瓜对白粉病的主要抗性遗传规律。结果表明:采集自海南省6个市(县)的苦瓜白粉病病原菌均为单囊壳白粉菌Sphaerotheca fuliginea,属生理小种2F,该菌在侵染苦瓜叶片时有4个关键时期:接种后4 h为分生孢子萌发高峰期,8 h为附着孢形成高峰期,16～24 h为次生菌丝形成高峰期,5 d为分生孢子梗形成高峰期。将其接种于苦瓜抗、感品系,对白粉病的抗性符合2对加性-显性-上位性主基因+加性-显性多基因模型,主基因和多基因共同控制苦瓜对白粉病的抗性,其中以主基因遗传为主,且会受到环境变异的影响。根据苦瓜抗性遗传规律,F2代主基因遗传率最高,受环境影响最小,在苦瓜的白粉病抗性育种中,以早期世代F2代作为有效选择世代。研究表明白粉病菌侵染叶片的前2 d是白粉病防治的最佳时期,所以在白粉病易发的物候期,可将防治时间提前1～2 d。     

Monitoring physiological races of<Emphasis Type="Italic">Podosphaera xanthii</Emphasis> (syn.<Emphasis Type="Italic">Sphaerotheca fuliginea</Emphasis>), the causal agent of powdery mildew in cucurbits: Factors affecting race identification and the importance for research and commerce

Identification of the physiological races ofPodosphaera xanthii (syn.Sphaerotheca fuliginea), the causal agent of powdery mildew in cucurbits, is based upon the differing responses of various melon cultigens to the pathogen. Eight races of the pathogen have been identified to date in the USA, Africa, Europe and around the Mediterranean Sea, and four new races were reported from greenhouse melons in the major growing area of Japan. Plant responses to powdery mildew may be affected by environmental factors such as light intensity, temperature and humidity, as well as by age and nutritional status of the plants. The same factors affect the accuracy and reliability of race identification. In an attempt to overcome those obstacles, the genetic diversity ofP. xanthii was studied using molecular markers. Unfortunately, no correlation was found between DNA polymorphism and the race of the pathogen as identified by biological tests. The usefulness of race identification as a guide for the grower in selecting appropriate cultivars is limited because changes or shifts in the pathogen population are common. Such changes may be found among growing seasons, geographic regions and hosts, and also within a single greenhouse during a single season. On the other hand, race identification is important for basic research and is especially important for the commercial seed industry, which requires accuracy in declaring the type and level of resistance to powdery mildew in its products. http://www.phytoparasitica.org posting March 2, 2004. Contribution from the Agricultural Research Organization. No. 501/04.     

小豆白粉病菌的鉴定与小豆品种抗白粉病评价

为明确小豆白粉病病原菌的种类以及小豆种质资源对白粉病的抗性,采用形态学和系统发育学方法对近年来在北京市发生的小豆白粉病病原菌种类进行鉴定,并采用室内苗期人工接种法评价小豆常见栽培品种（系）对白粉病的抗性。结果表明,从北京市采集的感白粉病小豆病样中培养获得病原菌BJ1,该菌能在小豆叶片和茎上产生明显的白色粉斑,分生孢子梗直立,不分枝,分生孢子单细胞,成链状着生于分生孢子梗上,呈椭圆形或卵圆形。通过rDNA-ITS序列系统发育分析,小豆白粉病菌BJ1被鉴定为白粉菌目白粉菌科的苍耳叉丝单囊壳Podosphaera xanthii。室内苗期人工接种条件下,19个供试小豆品种（系）接种小豆白粉病菌BJ1后均可发病,其中9个审定品种均表现为中度感病或高度感病,10个优良品系发病略轻。     

Biological control mechanisms of D-pinitol against powdery mildew in cucumber

D-pinitol is an effective agent for controlling powdery mildew (Podosphaera xanthii) in cucumber. In this study, we determined the mechanisms of D-pinitol in controlling powdery mildew in cucumber plants. We compared P. xanthii development on cucumber leaf surface treated with D-pinitol or water (2 mg ml⁻¹) at different time points after inoculation. The germinating conidia, hyphae, and conidiophores of the pathogen were severely damaged by D-pinitol at any time of application tested. The highest level of suppression of fungal development was obtained at 3 days after inoculation. The contents of chlorophyll, total phenolics, flavonoid, and gallic acid and its derivatives (GAD); the activities of phenylalanine ammonialyase (PAL), polyphenoloxidase (PPO), peroxidase (POX), and superoxide dismutase (SOD); and the expression of the genes encoding for PR-1, peroxidase (POX), lipoxygenase (LOX1), chitinase (Chit1) were higher in the cucumber leaves treated with D-pinitol and inoculated than in the leaves either treated with D-pinitol or inoculated with the pathogen. These results suggest that D-pinitol triggers several plant defense responses in cucumber leading to pathogen suppression and resistance to powdery mildew.     

Effect of potassium silicate on epidemic components of powdery mildew on melon

The effects of silicon (Si) supplied in the form of potassium silicate (PS) were evaluated on epidemic components of powdery mildew of melon under greenhouse conditions. The PS was applied to the roots or to leaves. In the first experiment, epidemic components were evaluated after inoculation with Podosphaera xanthii. In the second experiment, the disease progress rate was evaluated on plants subjected to natural infection. The area under the disease progress curve was reduced by 65% and 73% in the foliar and root treatments, respectively, compared to control plants, as a consequence of reductions in infection efficiency, colony expansion rate, colony area, conidial production and disease progress rate. However, root application of PS was more effective than foliar application in reducing most of the epidemic components, except for infection efficiency. This can be explained by the high Si concentration in leaf tissues with root application, in contrast to the foliar treatment where Si was only deposited on the external leaf surfaces. The effects of PS reported in this study demonstrated that powdery mildew of melon can be controlled, and that the best results can be achieved when PS is supplied to the roots.     

Characteristics and host range of tomato powdery mildew

The anamorphic state of a powdery mildew, which first appeared on tomato in the UK in 1987, currently listed as Erysiphe orontii (anamorph Oidium violae ), was examined microscopically on both tomato and alternative hosts. Host range studies were also carried out. In 1993–95, species and cultivars of plants from 26 of the 30 families listed as hosts of E. orontii were inoculated with tomato powdery mildew in the glasshouse and assessed for susceptibility on a 0–3 scale based on degree of sporulation and growth. Thirteen families contained species or varieties that were susceptible and a total of 80 varieties, including many economically important Cucurbitaceae and Solanaceae, supported sporulation to some extent (susceptibility score 1–3). Necrosis was not a constant feature of plants exhibiting resistance, as it could accompany sporulation on some susceptible varieties. Microscopic measurements showed that conidial size, conidiophore length, conidiophore foot-cell length and width, and the number of cells distal to the foot-cell were remarkably constant between samples of powdery mildew taken from tomato each year and from the various alternative hosts. Based on the production of conidia singly, the presence of nipple-shaped to moderately lobed appressoria, and occurrence of straight conidiophores, it is concluded that this fungus on tomato should more correctly be named Oidium lycopersicum until the sexual stage is discovered. The highly polyphagous nature of this powdery mildew would suggest that it represents a potential risk to UK agriculture and horticulture, but the failure to recover any powdery mildew from 120 samples of potato, including varieties Cara and Maris Piper, on which the tomato powdery mildew could sporulate in the glasshouse, suggests that environmental factors may play a key role in preventing establishment of this powdery mildew on alternative hosts on a commercial scale in the field.     

Microcyclic conidiogenesis in powdery mildews and its association with intracellular parasitism by <Emphasis Type="Italic">Ampelomyces</Emphasis>

Microcyclic conidiogenesis (MC), a process defined as the production of conidia on a spore without any, or only a minimal, involvement of hyphal growth, has recently been reported in a little known powdery mildew species, Oidium longipes. To investigate whether this was an isolated case or it is a more general phenomenon in powdery mildew fungi, germinating conidia of eight species of the Erysiphales were examined using light microscopy. The following species were included in this work: Erysiphe necator on grapevine, Blumeria graminis f. sp. hordei on barley, Podosphaera xanthii on cucumber, Erysiphe sp. on Ligustrum vulgare, O. longipes on Petunia x grandiflora, O. neolycopersici on tomato, Golovinomyces cichoracearum on Rudbeckia laciniata and Sawadaea sp. on Acer negundo. In all these species, up to 4% of the germinated conidia exhibited MC. Moreover, when colonies of E. necator and O. neolycopersici, on detached grapevine and tomato leaves, respectively, were treated with a conidial suspension of Ampelomyces, the intracellular pycnidia of these mycoparasites appeared in microcyclic conidiophores. This represents a yet undescribed method of accelerating asexual reproduction in this mycoparasite. In the life cycle of powdery mildews, the importance of MC is still not clear but it should be taken into consideration when conidial germination is studied on the host surface for purposes such as epidemiology or species identification.     

Changes in abundance and infectivity of powdery mildew conidia from cucumber plants treated systemically with lithium chloride

Systemic treatment of cucumber plants with lithium chloride reduced the numbers of conidia produced by colonies of powdery mildew, Sphaerotheca fuliginea , growing on leaves, and lowered the infectivity of conidia produced from those leaves when they were applied to leaves of untreated plants. Production of conidiophores was lower in both lithium-treated and calcium-deprived plants, and lithium slightly decreased the calcium content of leaves. When the lithium-containing growth medium was supplemented with phosphate, conidiophore production was still markedly reduced, although leaves had normal levels of calcium. Fungal development was not correlated with either the calcium or phosphorus content of leaves. It is concluded that, although severe calcium deficiency can inhibit fungal development, the inhibitory effects of lithium are not mediated through alterations in calcium or phosphorus uptake by host tissues.     

Virulence variation of cucurbit powdery mildews in the Czech Republic – population approach

Kosman diversity models were applied to analyses of virulence (disease reaction patterns) variation of 115 isolates of two cucurbit powdery mildew (CPM) species, Golovinomyces orontii (Go) and Podosphaera xanthii (Px), collected in the Czech Republic from 2010 through 2012. Diversity within and distances between Go and Px populations and each other in a spatio-temporal context and with regard to original host plant species were analyzed based on virulence patterns of individual isolates on a set of 21 melon (Cucumis melo L.) race differential genotypes. Significant differentiation among the Go and Px pathogen populations was revealed, and the results clearly demonstrate and confirm that the set of differential C. melo genotypes is well composed because of high differentiation capacity. Differentiation of pathogens among years was significant for both species. No significant difference between Go isolates from different host plant species was established due to high variability among Go isolates, but there was significant host-specific differentiation among Px isolates. Differentiation of pathogens among regions was not detected. These results revealed high virulence variation in isolates of Go and Px, and their spatio-temporal fluctuations. High diversity in virulence of Go isolates supports the treatment of Go as a complex of different (sub)species with distinct virulence factors. Similar relationships of selected Go isolates in a UPGMA dendrogram in a previously reported multigene phylogenetic tree support the logic and suitability of the Kosman assignment based approach to population studies of organisms with asexual or mixed modes of reproduction. The approach applied in this study provides a complex view of virulence structures of powdery mildew populations, and when combined with race determination and denomination on melon, it may serve as a base to understandvirulence variation of these CPM species from a spatio-temporal viewpoint.     

Effect of culture filtrates of seventeen fungicolous fungi on sporulation of cucumber powdery mildew

Culture filtrates of 17 different fungal species thriving upon other fungi were tested for their ability to reduce sporulation of cucumber powdery mildew,Sphaerotheca fuliginea.All culture filtrates reduced the number of healthy conidiophores. However, the differences in activity between the various treatments were not as conspicuous as after application of spore suspensions. The best results were obtained with culture filtrates ofCalcarisporium arbuscula. These reduced the number of healthy conidiophores to ca. 2% of the unsprayed control plants.     

An apparatus for collecting total conidia of Blumeria graminis f.sp. hordei from leaf colonies using electrostatic attraction

Conidia from living conidiophores of barley powdery mildew ( Blumeria graminis f.sp. hordei ) on host leaves were collected consecutively using an electrostatic spore collector. The collector consisted of an electrical conductor plate linked to an electrostatic voltage generator and insulator plates placed abreast on a timed conveyer. The conductor plate was negatively charged by the potential supplied from the voltage generator. The negatively charged conductor plate caused dielectric polarization of the insulator plate, and the surface charge on the insulator plate attracted mature conidia abstricted from conidiophores on colonies growing on leaves placed 2 cm from the insulator plate. The surface charge on the insulator plate was proportional to the voltage applied to the conductor plate. Under optimized conditions, abstricted conidia were attracted to the electrostatically activated insulator plates without any detriment to their survival. During a colony's life span of c . 460 h, conidia were released throughout the day and c . 12 × 10⁴ conidia were collected during the lifetime of the colony. This is the first report on the direct quantification of progeny conidia produced by powdery mildew infecting host leaves.     

Components of spore production in apple powdery mildew (Podosphaera leucotricha)

The morphology of powdery mildew ( Podosphaera leucotricha) colonies of known age was studied on six apple cultivars inoculated in a glasshouse. Colonies were observed first on the older leaves. Mean disease incidence ranged from about 20% for cv. Laxton's Superb to about 45% for cv. Crispin. Conidiophore density (number of conidiophores/mm² colony) was higher on younger than on older leaves, higher on the upper than on the lower leaf surface, and decreased with the age of the colony. The number of hyphal interceptions on a line transect was higher on the upper surface but the ratio of conidiophore density to hyphal interceptions was greater on the lower surface and did not differ with colony age or cultivar. The number of conidia/conidiophore was higher on the younger leaves and on the upper surfaces and was at a maximum 7-12 days after the first sign of the colony. The number of conidia/mm² colony was higher on lower surfaces, especially of the younger leaves. There was generally an associated variation between cultivars in components of spore production.     

Evaluation of biological control agents for managing cucurbit powdery mildew on greenhouse-grown melon

An evaluation was made of the ability of two mycoparasite-based products AQ10® ( Ampelomyces quisqualis ) and Mycotal® ( Lecanicillium lecanii ), as well as three strains of Bacillus subtilis , to manage powdery mildew disease, caused by Podosphaera fusca on melon seedlings maintained under different regimes of relative humidity and on plants grown under greenhouse conditions in Spain. In every case fungal and bacterial biocontrol agents (BCAs) performed better under conditions of high relative humidity (90–95% RH). In greenhouse experiments, the effectiveness of the mycoparasites to manage powdery mildew was absolutely dependent on mineral oil. The strains of B. subtilis provided disease control similar to that achieved with the mycoparasites or the fungicide azoxystrobin. Microscopic analysis showed the ability of these bacterial strains to efficiently colonize leaf surfaces and revealed the occurrence of antagonistic interactions between biological agents and P. fusca structures. These results confirmed the usefulness of these BCAs for managing powdery mildew on greenhouse-grown cucurbits either as single products or as a component of integrated control programmes.     

Comparative effects of temperature and humidity on the activity of three potential antagonists of rose powdery mildew

Three reported antagonists of cucumber powdery mildew,Stephanoascus flocculosus, Stephanoascus rugulosus, andTilletiopsis washingtonensis, were tested and compared under different environmental conditions for their potential for controlling rose powdery mildew, caused bySphaerotheca pannosa var.rosae. Under controlled conditions in vitro, all three fungi induced a rapid collapse of conidia, conidiophores and hyphae ofS. pannosa var.rosae on detached leaflets of miniature roses within 48 h following their application, as observed under a SEM. Both temperature and relative humidity (r.h.) affected the activity of the antagonists differently. The colonization of powdery mildew was maximal at 26 °C, especially forSt. rugulosus andT. washingtonensis. Maximal colonization was achieved at the highest r.h. tested (90%) for all three antagonists but onlySt. flocculosus maintained a colonization of 80% or better under lower r.h. These observations stress the importance of considering environmental conditions when assessing the activity of antagonistic microorganisms.     

Morphological and molecular characterization for a Japanese isolate of tomato powdery mildew Oidium neolycopersici and its host range

 A single conidium of tomato powdery mildew was isolated from heavily infected leaves of tomato (cv. Moneymaker) grown in the greenhouse of Kinki University, Nara Prefecture, Japan. It was successively multiplied so the morphological and taxonomic characteristics of the pathogen and its host range under high humidity conditions could be analyzed. The isolate KTP-01 of the tomato powdery mildew optimally developed infection structures at 25°C under continuous illumination of 3500 lx. More than 90% of the conidia germinated and developed moderately lobed appressoria. After forming haustoria, the pathogen elongated secondary hyphae from both appressoria and conidia. The hyphae attached to leaf surfaces by several pairs of appressoria and produced conidiophores with noncatenated conidia. In addition to its morphological similarity to Oidium neolycopersici, the phylogenetic analysis (based on the sequence of internal transcribed spacer regions of rDNA) revealed that KTP-01 could be classified into the same cluster group as O. neolycopersici. In host range studies, KTP-01 produced abundant conidia on the foliage of all tomato cultivars tested and tobacco (Nicotiana tabacum), and it developed faint colonies accompanied by necrosis on leaves of potato (Solanum tuberosum), red pepper (Capsicum annuum), petunia (Petunia × hybrida), and eggplant (S. melongena). The pathogen did not infect other plant species including Cucurubitaceae plants, which have been reported to be susceptible to some foreign isolates. Thus, the present isolate of the tomato powdery mildew was assigned as O. neolycopersici, a pathotype different from foreign isolates of the pathogen. Received: December 5, 2002 / Accepted: December 26, 2002 Acknowledgments This work was supported in part by a Grant-in-Aid (12660050) from the Ministry of Education, Culture, Sports, Science, and Technology of Japan. We express our deepest thanks to professor Dr. Y. Sato, Toyama Prefectural University, for his kind and valuable suggestion on taxonomic analysis of the powdery mildew pathogen described in the present study.