Mildew Research Articles

Some Genetic, Biochemical and Morphological Analysis of Selected Powdery Mildew Strains at the Beginning of Sporulation on Barley

The present work analyzes some characteristics of four powdery mildew pathotypes, RU-3, Sk-5/11, Sk-12/1 and A-4/0, selected from the wild strains of BGH from Central European regions. Our results showed that the studied BGH strains differ in the virulence and avirulence genes in their genomes, in prolongation of their asexual phase of the growth and also in morphological and biochemical characteristics. Protein analysis confirmed the genetic differences between the studied powdery mildew pathotypes. Abundant acid glucanases in all studied BHG pathotypes were found between molecular weights Mr ? 25-35 kDa and 11-22kDa. Races RU-3 and A-4/0 also contained low molecular weight glucanases with Mr ? 9-14kDa. Immunological analyses showed higher specificity of pathogen chitinases to plant antibody compared to barley cultivars carrying different dominant/semidominant resistance genes. Rabbit antibody prepared against the plant interacellular acid chitinase Chi 14.4 (PR-4) gave the positive signal for two powdery mildew races, Sk-5/11 and A-4/0. These pathotypes were more aggressive compared to races Sk-12/1 and RU-3. Their genomes contained more virulence genes and asexual phase of the growth was shorter. Ultrastructural analyses of BGH body in the sensitive barley cultivar cells, showed presence of virus like particles, which probably play role by the synthesis of some PR-proteins with hydrolytic function. Genetic and biochemical analyses indicate that some powdery mildew pathotypes contain genes in their genome which are orthological to those in their hosts, which makes them suitable subjects for the future as a source of new resistance genes for plant breeding.

The variability of juvenile period, fruits size and response to diseases attack on F1 interspecific apple hybrids and the efficiency of selection.

Interspecific hybridizations represent one of the apple breeding methods by which a wide variability can be achieved, useful for creating new cultivars. The study of 2190 interspecific hybrids, obtained from 25 combinations among crab apple species (Malus coronaria, M. floribunda, M. niedzwetzkyana, M. zumi, M. prunifolia) and different apple cultivars, points out a large variability of the F1 seedlings for several traits, with significant importance in apple breeding programs. The first year of fructification, as mean per hybrid combination, varied from 6 (M. zumi x 'Jonathan') to 9.3 years; the average hybrid's age for fructification was 7.4 years. The size of fruits among families varied from 1.5 ('Starkrimson' x M. prunifolia) to 4.0 ('Reinette Baumann' x M. zumi), the mean being settled at 2.8 (therefore below mark 3, meaning 'small fruits'). The lowest infection rate both for apple scab and powdery mildew attack was noticed at hybrids from M. coronaria x 'Reinette Baumann'. On the whole, the hybrids with genitors of 'species x cultivars' type have had an early fruiting and a better resistance to scab and powdery mildew, compared to the ones from 'cultivars x species' combinations. The large variability of the studied traits gave the possibility to identify offsprings with desirable characteristics on nine hybrid combinations. Among these, 53 elite plants were selected, with a strength of selection of 2.42%, therefore a relative low value, correlated with the peculiarities of the interspecific population and the selection criteria for dessert apple.

PCR-RFLP is a useful tool to distinguish two powdery mildew pathogens of flowering dogwood (Cornus florida)

PCR-RFLP is a useful tool to distinguish two powdery mildew pathogens of flowering dogwood (Cornus florida) Ainong Shi1,3, Stella Kantartzi2, Margaret Mmbaga3, and Pengyin Chen4 1 Syngenta Seeds, 2369 – 330th St. Slater, IA 50224, USA; Otis L. Floyd Nursery Research Center, Tennessee State University, McMinnville, TN 37110, USA; Department of Plant, Soil and Agricultural Systems, Southern Illinois University Carbondale, Carbondale, IL 62901, USA; Department of Crop, Soil, and Environmental Sciences, University of Arkansas, Fayetteville, AR 72701, USA. * Corresponding author. Email: ainong.shi@syngenta.com or ainong_shi@hotmail.com. ABSTRACT

Proteome Changes in Wheat Varieties Brock and Jing 411 after Inoculating <I>Blumenia graminis</I>

The protein of resistant wheat(Triticum aestivum L.) variety Brock and susceptible variety Jing 411 was extracted from leaves and separated using two-dimensional polyacrylamid gel electrophoresis(2-DE) at 12 h,3 d,and 5 d after inoculating prevalent race No.15 of B.graminis f.sp.tritici.In Brock,compared with control with no pathogen inoculation,at least six protein spots of 43 kD/pI 6.7,43 kD/pI 6.9,43 kD/pI 7.2,28 kD/pI 5.8,26 kD/pI 5.5 and 26 kD/pI 6.5 obviously increased in content at 12 h time point;and five protein spots of 48 kD/pI 5.6,43 kD/pI 6.9,43 kD/pI 7.2,28 kD/pI 5.8 and 26 kD/pI 5.5 increased in content at 3 d time point.At 5d after inoculation,12 novel proteins were induced,viz.16 kD/pI 7.6,42 kD/pI 6.5,40 kD/pI 4.8,40 kD/pI 4.6,31 kD/pI 5.7,16 kD/pI 4.6,20 kD/pI 8.3,50 kD/pI 6.7,48 kD/pI 6.6,28 kD/pI 5.7,23 kD/pI 4.8 and 25 kD/pI 4.7;simultaneously,two protein spots that were observed earlier disappeared.In Jing 411,three protein spots of 21 kD/pI 6.4,18 kD/pI 5.4,and 14 kD/pI 7.0 increased in content at 12 h after inoculation.At the 3 d time point,two protein spots of 80 kD/pI 5.4 and 14 kD/pI 7.0 increased in content,however,one protein spot(16 kD/pI 5.4) showed decrease in protein abundance.At the 5 d time point,three protein spots of 50 kD/pI 7.3,40 kD/pI 7.3,and 24 kD/pI 7.2 and two protein spots of 40 kD/pI 4.8 and 14 kD/pI 7.2 showed increase and decrease in protein abundance,respectively,but there were no novel protein spots induced.Among the 12 novel protein spots induced in Brock,six spots were identified using MALDI-TOF-MS and NCBI database searching,which were F-box and leucine-rich repeat protein,heavy metal transport/detoxification protein,endo-beta-1,3-glucanase(two isozymes) ,beta-1,3-glucanase precursor and zinc finger protein.These proteins are involved in a wide range of physiological processes,such as cell cycle control,development,phytohormone response,and resistance to fungal disease.Thus,the proteome changes in Brock and Jing 411 leaves are probably associated with the resistance and susceptibility to powder mildew,respectively.

Uso da biomassa cítrica no controle de doenças da soja

Actually soybean is the main product of Brazilian agricultural sector. This crop requires a high technology input to yield increases. Diseases are one of the problems that could impair the yields. The control of diseases, in the most cases, increases costs of production and moreover has a negative impact in the environment. For this reason, the induction of resistance is appointed as a alternative control method. This method is established by the activation in the host plant, of latent defense mechanisms. Thus, aims this work were verify the effect of citric biomass at concentrations of 0.75; 1.5 and 3.0 mL L-1 , for the control of mildew (Peronospora manshurica), powdery mildew (Microsphaera diffusa), rust (Phakopsora pachyrhizi) and late season diseases (Cercospora kikuchii and Septoria glycines), as well as to verify the effects on production components and productivity of soybean. Plants without treatment and treated with Piraclostrobin + Epoxiconazol (0.5 L ha-1 ) were used as control. Results show that citric biomass at 3 mL L-1 reduced the mildew severity in 62% and powdery mildew severity in 35%, however did not reduce severity for rust and late season diseases. Yields did not differ between the plants treated with different citric biomass concentrations as compared with control plants without treatment and were 20% lower as compared to fungicide treated plants. This could be a result of increases of metabolic costs, resulted by the induction of resistance mechanisms. Results suggesting that, the citric biomass could contribute to control of soybean diseases, as well supply sequential studies.

Interaction between Acremonium byssoides and Plasmopara viticola in Vitis vinifera

Summary. The endophytic fungus Acremonium byssoides was isolated from the leaves of grapevine cv. Regina Bianca to determine whether it could act as an antagonistic endophyte of the downy mildew agent Plasmopara viticola. The occurrence of this fungus was ascertained in 34 grapevines (cultivars Regina Bianca, Catarratto and Insolia) representing all the grapevine plants in an experimental vineyard located in Sicily and which had never been treated with any fungicides. The isolation frequency of the endophytic Acremonium strains was assessed in several plant organs by means of monthly samplings over a 2-year period. The endophyte was found in all the grapevines, with higher frequencies in the cv. Regina Bianca in the buds, and in the cooler months of the year. All the strains collected from the leaves, and most of the strains from the buds of cv. Insolia were identifi ed as A. byssoides by conventional means. The presence and spatial distribution of A. byssoides was determined in asymptomatic or P. viticola-infected leaves of the grapevine cv. Insolia using an optimised staining technique and differential interferential contrast light microscopy, as well as laser scanning microscopy. A. byssoides was a natural colonizer of grapevines and actively parasitized P. viticola. Culture fi ltrates and the crude extract of A. byssoides obtained from a cv. Insolia foliar strain, completely inhibited P. viticola sporangia.

ALFALFA CROP -DISEASES AND CONTROL TECHNIQUES

Alfalfa crop is considered queen of forage plants, but if we want to get a good production we need to respect all the techniques. Also we need to know all diseases, pets and prevention techniques. The attack of pathogens can reduce the production with over 40%. The most important diseases which produce damage on alfafa crop are: Alfalfa mosaic virus or Lucerne mosaic virus, Downy mildew of Lucerne - Peronospora aestivalis, Alfafa powdery mildews - Erysiphe communis Grew. E. medicaginis Dietr., Alfalfa leaf spot Pseudopeziza medicaginis Sacc., Alfalfa yellow leaf spot- Pseudopeziza josenii Nannf., f.c. Sporonema phacidioides Desm., Alfalfa rust-Uromyces striatus Schroter, Alfalfa phomosis - Phoma melaena Mont. et Dur. To gain high productions on alfalfa cultures are recommended the following measures: introducing rotation of culture with annual plants especially cereals, choosing optimal seeding densities; to use healthy certified seed callousness sorts; destroying of spontaneous leguminous; monitories and to fight against of vector insects; to harvest (mowing) and destruction of ill plants diminishes otherwise the attack expand.

BIODIVERSITY AMONG INDIAN JUJUBE (ZIZIPHUS MAURITIANA LAMK.) GENOTYPES FOR POWDERY MILDEW AND OTHER TRAITS

Indian ber (Ziziphus mauritiana Lamk.) is one of the most ancient fruits indigenous to India. It grows throughout the tropical, sub-tropical and arid regions. There is little information available on the genetic diversity of this important underutilized fruit crop. The reduction of genetic variability makes the crop vulnerable to diseases and other adverse factors. Morphological variation among thirty five important ber genotypes collected from different parts of India were studied at CCS Haryana Agricultural University, Hisar, India, during 2005-2006. Ten morphological traits viz., powdery mildew, leaf length, leaf breath, leaf area, fruit weight, fruit length, fruit breath, stone weight, stone length, stone breath were recorded and data analyzed by using Mahalanobis's D2 Statistic using Tocher's method. All the genotypes were classified into VII distinct clusters. Cluster I was the largest with nine genotypes followed by cluster IV (six genotypes). Clusters VI and VII were the most divergent with an inter cluster distance of 5.162. This suggests that the parents for hybridization could be selected especially for powdery mildew resistance (Sanori No. 5, Noki and Mirchia) and smaller stone size (Illaichi and Kishmish) from these diverse clusters, in order to develop useful disease resistant and smaller stone size breeding material for Indian jujube.

Comparison of grape seedlings population against downy mildew by using different provocation methods.

This research was conducted to compare a laboratory technique leaf disk with hotbed and field evaluations in the screening of large populations of grape seedlings ( Vitis spp.), towards downy mildew ( Plasmopara viticola Berk. et Curt.) resistance. Seedlings produced by crossing two hybrid families, in ( Vitis amurensis Rupr. x Vitis vinifera L.) x (Franco-American hybrid x Vitis vinifera L.) and the antipodal crossing of the Franco-American hybrid x Vitis vinifera L. x (Franco-American hybrid x Vitis vinifera BC) combinations. The 'Bianca', 'Merzling', 'Kunleany', 'Hibernal' and 'Hibia' cultivars were used. These varieties were rated for sporulation on five levels, from 0 to 80 percent. Sporulation ratings were assessed at the first and second rating. Significant differences were signalled between field evaluations and the leaf disk technique. Furthermore, a highly significant correlation was found between the leaf disk technique and hotbed evaluation. The leaf disk procedure appeared to be a good predictor of field resistance and is more practical than the hotbed provocation method for the screening of large populations.

Risk of powdery mildew (Erysiphe necator) outbreaks on grapevines in relation to cluster development

Recently, severe and very destructive outbreaks of powdery mildew (Erysiphe necator) have occurred on grapevines (Vitis vinifera) in central and northern Chile. Powdery mildew epidemics may develop from inoculum surviving as mycelia on buds infected the previous season and/or as cleistothecia surviving on leaves and bark. Cluster susceptibility changes throughout the growing season, with young berries being highly susceptible and mature berries being relatively resistant. The risk of infection can be predicted based on the maximum air temperature. Aiming to improve the effi cacy of powdery mildew control, this research was performed to study the risk of powdery mildew outbreaks in relation to grapevine cluster development. Our results demonstrated that fungicide spray application (kresoxim-methyl, 65-70 mg·L -1 or myclobutanil, 24 mg·L -1 ) at full fl owering (stage 23) provided the best control of cluster powdery mildew on grapevine cvs. ‘Criolla’, ‘Pedro Jimenez’ and ‘Semillon’. In contrast, disease incidence and severity invariably increased on clusters sprayed at other grapevine stages. This wasrelated to the presence of highly favorable temperature conditions prevailing during fl owering with moderate to high infection risk indexes. In conclusion, grapevine stages occurring between the beginning of fl owering and the appearance of small berries (stages 19 through 29) were the most critical stages for powdery mildew development. Therefore, fungicide treatments applied during fl owering appeared to be essential to control of grapevine powdery mildew. En los ultimos anos, el oidio ( Erysiphe necator ) de la vid ( Vitis vinifera ) ha tenido especial importancia economica en la zona central y norte de Chile. Epidemias se desarrollan a partir del micelio latente que sobrevive en yemas infectadas la temporada precedente y/o a partir de cleistotecios desarrollados en hojas u otros organos infectados de la vid. La susceptibilidad de los racimos varia a traves de la temporada, siendo muy susceptibles las bayas jovenes y resistentes en la medida que maduran. El riesgo de infeccion se puede pronosticar en funcion de la temperatura maxima del aire. Con el proposito de mejorar la eficacia del control del oidio, se realizo este trabajo con el objetivo de estudiar el riesgo de infeccion en funcion del desarrollo del racimo. Los resultados obtenidos demostraron que las aplicaciones fungicidas (kresoxim-metil, 65-70 mg·L -1 or miclobutanil, 24 mg·L -1 ) aplicadas a inicios de plena floracion (estadio 23) proporciono el mejor control del oidio en los racimos de vides cvs. ‘Criolla’, ‘Pedro Jimenez’ y ‘Semillon’. Por el contrario, la incidencia y severidad invariablemente aumento en racimos tratados en otros estadios. Esto se relaciono con la existencia de temperaturas del aire muy favorables al desarrollo de oidio,.las que predominaron durante la floracion, determinando indices de riesgo de infeccion moderados a altos. En conclusion, los estadios del desarrollo comprendidos entre inicios de la fl oracion y bayas pequenas (estadios 19 a 29) fue el periodo mas critico para el desarrollo del oidio. Por lo tanto, tratamientos fungicidas aplicados durante la floracion son indispensables para controlar esta enfermedad.

RECHEARCH REGARDIN OF PATOGENS AGENTS FROM FOREST CULTURES IN THE 2006 YEAR

SUMMARY The present state of our country’s forests is chara cterized by decline, pressure and stress factors, w hich greatly influence their integrity and continuity. Therefore it is imperative that the sylviculturists take immediate drastic action for the ecological reconstruction an d restoration of the forests. In this context, it is necessary, among other conservation measures, to afforest and refore st entire areas, both in normal and extreme resorts . To achieve this, it is required that the forestatio n material be produced in the appropriate quantity, quality and variety for the process. This objective can be achieved only when applying modern methods and a modern technology for the prevention and control of the pathogenic agents to be found in solarium and nurseries. Research has been carried out aiming at determining the diseases and their causes in nurseries and plantations as well as establishing the control met hods and techniques. Thus we tried to: identify the pathogenic agents that frequently lead to loses in nurseries a nd solarium; know the main pathogenic agents from the point of view of biology, etiology and of modern control tec hnologies; establish efficacy for a large spectrum of fungicides and of the applicable doses and concentrations, res pectively; establish the optimal phenological stage s of treatment application. As a result of the research and experiments carried out over the last year we conclude the following: a).The most dangerous pathogenic agents remain Laphodermium pinastri and Septoria parasitica for resinous plants, Dothiochiza populea and Cytospora chysosperma for Euro American poplars. b).The pathogens responsable of the plantlets “damp ing-off”, which is: Fusarium spp., Rhizoctonia solani, Pythium ultimum, Alternaria spp.,etc. The most varied mycoflora was observed in soil nutrition, and resinous seed. c).There is a large spectrum of new fungicides whic h can efficiently control mildew in the case of oak plants or other diseases present in nurseries, plan tations or regenerations and forest solaria. d).The fungicides Systhane, Karathne and Alert performed very well in experiments proving a n efficacy of up to 90% in the control of oak-plant mildew produced by the pathogen Microspaera abbreviata (f.c. Oidiu alphitoides). e).We registered the fungicides Systhane and Folpan and the Inter-ministry Commission for the control of mildew and soil pathogens. f).The fungicides Alert and Karathne with very good results are to be tested for another year for clarifications regarding the most efficient concent ration. g).The fungicides Previcur performs very well in co ntrolling the pathogens in solaria therefore the experimental biological sheet was made with respect to its registration. h).What is extremely important for the prevention o f pathogen agent infections is the moment of the treatment application and this timing varies with t he climatic factors, consequently prevention treat ments are recommended i).The obtained results can be applied in all the a rea and ranger districts whose activity is the prod uction of forest saplings, in solaria or/and nurseries; these are to apply the products and technologies present ed in this study.

EFFICACY OF SOME FUNGICIDES IN COMBATING MILDEW PRODUCED BY THE PHYTO PATHOGEN MICROSPHAERA ABBREVIATA IN NATURAL REGENERATIONS OF OAKS

In the natural regeneration of oak trees, on the background of intense accumulation on the level of the crowns of the seeding plants, strong attacks of phyto pathogens are registered that cause the so called mildews and the most important of them is Microsphaera abbreviata. The effects of mildews are manifested by diminutions of growing and biomass accumulations, with direct repercussions on the further quality of the attacked exemplars. As the age of the attacked exemplars is younger, as the intensity and degrees of attack are stronger. In this phase, the only measure of quick intervention, with direct effects is the chemo therapy. It is important to use only biodegradable substances, with no remanence on soil level. There are a lot of substances that may be used in fighting against mildew. This work proposes to verify the efficiency of some new fungicides (Systhane, Karathane, Trifmine and Alert), compared to the standard product Bumper 250 EC ) and of course with samples, untreated. The concentrations and doses for applying were differently fixed for each substance depending on the technical instruction for the use of products.

PROTECTION COMPLEXES’ INFLUENCE UPON ONION YIELD UNDER WESTERN FIELD CONDITIONS

The information concerning yield losses represent the best synthesis of the effects exerted by pathogen agents and pests upon onion crop. These information originate in the observations performed during 2003-2005 in the untreated control variant, compared to the variants in which we have applied protection complexes and also in the comparisons between the variants with the experience mean ( M ) and with the protection complexes mean (M cp). Yield differences compared to the control variant (Mt) are between 8.93-17.83 t/ha. The yield achieved in all seven variants is statistically assured, and the significances of yield differences are very significantly positive. Analyzing the significance if yield differences, by reporting it to the experience mean (M ), we may notice an evident differentiation per variants of the significance degree, namely a very significantly positive significance is available in only three variants (V5, V6 and V3). In V1 the significance is just positive, while in the variants V2 and V4 there is no significance, and in variants V7 and V8 it is very significantly negative. When the reference of yield differences was made only to the yield average achieved under the influence exerted by the protection complexes, excluding the yield achieved in V8 – untreated control variant, the situation changed dramatically, namely the yield has statistical cover only in two variants, difference significance being very significantly positive in V5 (Ridomil Gold MZ 68 0,25 % + Victenon 50 WP 0,075%) and distinctly significantly positive in V6 (Ridomil Gold Plus 42,5 WP 0,3% + Mospilan 20 SP 0,025%). There is no significance in the variants V3, V2 and V1, and in the variants V7 and V4 yield difference significance is very significantly negative, respectively distinctly significantly negative. As a general conclusion, we may say that the protection complexes from V5 (Ridomil Gold MZ 68 0,25 % + Victenon 50 WP 0,075%) and V6 (Ridomil Gold Plus 42,5 WP 0,3% + Mospilan 20 SP 0,025%) had the best effects in fighting against the two diseases (onion downy mildew - Peronospora destructor (Berk.) Casp and bulb rot - Botrytis allii Munn.) and the pest (onion fly – Delia antiqua Meig.), fact also proved by the level of yields achieved, by their statistical cover and the highest assessment degree of yield difference significance. The weakest effect in fighting against the two diseases and the pest belonged to the protection complex from V7 (Dithane M45 0,2% + Fastac 10EC 0,02%), because the significance of yield differences compared to M and M cp is very significantly negative.

Erysiphe azaleae (Erysiphales) - a new species of powdery mildew for Slovakia and further records from the Czech Republic.

Sweet, Slovakia: Podunajska nižina Basin,Tesarske Mlyňany, Arboretum, 7. X. 2005, leg. K. Bacigalova, SAV; Podunajska nižinaBasin, Bratislava, Botanical Garden, 11. X. 2005, 28. X. 2005, leg. K. Bacigalova, SAV;Podunajska nižina Basin, Bratislava-Prievoz, Parkova street, 30. X. 2005, leg.A. Petrik, SAV; Czech Republic: Praha, Botanical Garden of Charles University,20. IX. 2005, leg. J. Markova, PRC; western Bohemia: Klenci pod Cerchovem, Dily,18. IX. 2005, leg. D. Kozakova, PRC.On

THE EVOLUTION OF THE QUALITY OF GRAPES AND WINES IN THE MURFATLAR CONDITIONS, YEARS 2004-2005

The Murfatlar vineyard biotope, by climatic, pedologic and relief factors had a strong influence on the physiological and biochemical vine process in all period of viticulture year. The climatic factors are those that have many variations who influenced in direct way harvest quality and quantity in each year. The research was made at Murfatlar in the 2004-2005 years. In this period were effectuated observations and determinations in entire vegetative period at the own clones and varieties: Pinot gris 13 Mf, Chardonnay 25 Mf, Columna and Mamaia. The climatic conditions of the mentioned period has a different evolution in comparison with multiyear mean, affecting the growing and maturation processes and the evolutions of the main diseases and pests. Analyzing the temperature factor it is observed an increasing of the yearly summation in all three years in comparison with the multiyear value – over 12,3 0C face with 11,0 0C. The pluviometric regimes show that these years had higher sums of the precipitation – over 550 mm given the normal with 419,8 mm but with precipitations repartitions, generally, outside of the vegetative period. Exception were registered in the August 2004 with 144,0 mm and July and September 2005 with 207,2 mm respectively 142,8 mm precipitations who generated an increasing of the main diseases attack.The downy mildew was manifested late in plantations, after 13.07. The powdery mildew was presented in each plantation with various intensities in concordance with number of treatments and type of fungicides applied. The gray dote was observed mainly on the Pinot gris grapes. The grapes mouth developed all three generations with attack frequency between 12 – 15 %.

Observations on the behaviour of different populations of Plasmopara viticola resistant to Qol fungicides in Italian vineyards

Grapevine downy mildew, caused by Plasmopara viticola, is probably the most damaging fungal disease of grapevine world-wide. Among the fungicides recently developed for downy mildew control is the QoI class of fungicides, which inhibits mitochondrial respiration. Since 1999, selected P. viticola populations in northern Italy have been monitored for resistance to QoI fungicides. Detached leaf discs and whole potted plants were used under controlled conditions to test the sampled populations. QoI-resistant populations of P. viticola were found in all the vineyards sampled in 2001 and 2002 in Trentino Alto Adige and Friuli Venezia Giulia, where failure in QoI control was reported. Many of the populations had minimum inhibition concentration (MIC) values 3– 30 times higher than those of sensitive reference populations. Populations of P. viticola sampled from vineyards in Piedmont, where no QoI fungicides had previously been used, showed MIC values equal to, or lower than those of the reference populations. Most of the P. viticola populations collected in Trentino Alto Adige in 2001 showed high virulence in leaf disc test and were not controlled by QoI fungicides, applied both at field and double field rates in the whole plant test. Most of these populations retained their virulence in the subsequent leaf disc test in water.

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.

Side effects of some fungicides on the population of Typhlodromus exhilaratus Ragusa and Phytoseius finitimus Ribaga sensu Denmark (1966) (Parasitiformes, Phytoseiidae) on grapevines in Tuscany

Results of two years of field trials carried out in 2000 and 2001 are reported in this paper. The field research was conducted in Tuscany in two different vineyards with protocols planned to control the activity against powdery mildew and downy mildew and to discover the impact of different fungicides on Phytoseiids present on vine trees at the two sites. The results confirm Sulphur and Copper-Oxychloride as the most selective fungicides but with unsatisfactory control of both diseases in seasons with high disease pressure. The field trials basically involved powdery mildicide products, whereas against downy mildew, Copper-Oxychloride was tank mix applied for all treatments. The program of applications which included the alternation of Sulphur and Quinoxyfen gave the best results against powdery mildew with a moderate impact on phytoseiids. Typhlodromus exhilaratus Ragusa and Phytoseius finitimus Ribaga sensu Denmark (1966) were the phytoseiids detected. Both predatory mites showed a strong resistance to the various strategies used.

Controlling Efficacy of Strobilurin Derivatives against Wheat Powdery Mildew and Eyespot

数種のストロビルリン系化合物およびDMI剤を用い室内における殺菌活性と圃場における防除効果の関係について, コムギうどんこ病およびコムギ眼紋病を対象として比較検討した. 圃場におけるコムギうどんこ病に対する防除効果は, 室内試験における殺菌活性と一致せず, 浸透移行性が高く, ベーパーによる活性が認められたクレソキシムメチル, トリアジメホンおよび (E)-2-[2-(3-トリフルオロメチル-5-クロロピリジン-2-イルオキシメチル) フェニル]-2-メトキシイミノ-N-メチルアセトアミドの3剤が高い防除効果を示し, 浸透移行またはベーパーにより新たに展開する葉を保護することが重要な要素と考えられた. 一方, 眼紋病に対しては高い菌糸伸長阻害活性を示し, 浸透移行性の低かった (E)-2-[2-(2, 5-ジメチルフェノキシメチル) フェニル]-2-メトキシイミノ-N-メチルアセトアミド (SSF-129) およびプロクロラズが, 圃場においても高い防除効果を示し, 菌糸伸長阻害活性が高くかつ付着した化合物が長期に散布部位に残ることが重要な要素と考えられた.

RESISTANCE TO POWDERY MILDEW IN BARLEY LANDRACES FROM MOROCCO

A total of 44 accessions of barley landraces from Morocco were screened for resistance to powdery mildew. Nineteen of the tested landraces showed resistance reactions and 45 lines were selected. Sixteen of these lines were tested at the seedling stage with 17, and another 29 lines with 23 differential isolates of powdery mildew respectively. Six lines (170-1-3, 172-3-2, 173-1- 2, 181-3-5, 201-3-2, 201-3-3) were identified that have resistance to all the prevalent European powdery mildew virulence genes. It was postulated that 3 different resistance alleles (Mlat, Mla6, and Mla14) are present in the tested lines either alone or in combination. Among the tested lines 8 (18.0%) had one specific gene for resistance and 37 (82.0%) had a combination of different genes for resistance. Among specific resistance alleles the most common was Mlat whose presence was postulated in 20 (44.4%) of the tested lines. The distribution of reaction type indicated that about 79.0% of all reaction types observed were classified as powdery mildew resistance (scores 0, 1 and 2). The majority (65.0%) of resistance reaction types observed in the tested lines was intermediate reaction type 2. The use of new effective sources of resistance from Moroccan barley landraces for diversification of resistance genes for powdery mildew in barley cultivars is discussed.