scholarly journals Absence of Oospores of Downy Mildew of Grape Caused by Plasmopara viticola as the Source of Primary Inoculum in Most Western Australian Vineyards

Plant Disease ◽  
2005 ◽  
Vol 89 (7) ◽  
pp. 777-777 ◽  
Author(s):  
B. X. Killigrew ◽  
K. Sivasithamparam ◽  
E. S. Scott
Keyword(s):  
Downy Mildew ◽  
Secondary Infection ◽  
Plasmopara Viticola ◽  
The State ◽  
Annual Rainfall ◽  
Infected Leaf ◽  
Wine Grape ◽  
Primary Inoculum ◽  
The North ◽  
Plant Pathol

Grapevine downy mildew, caused by the obligate, oomycete pathogen, Plasmopara viticola, was first recorded in Western Australia (W.A.) in 1998 (2) and has subsequently been observed in most viticultural regions of the state. Heterothallism in P. viticola was established by Wong et al. (3), whereby more than one mating type of the pathogen is required for sexual reproduction to occur. Oospores are considered to be the source of primary inoculum for this disease with further, secondary infection being advanced by asexual inoculum. However, recent research in European vineyards suggests that the majority of infection throughout the growing season arises via sexually derived (oosporic) inoculum (1). Since downy mildew is relatively new to W.A., few surveys have been conducted to study populations of the pathogen within the state. It is also noteworthy that the incidence of oospores in Australian vineyards has not been reported. The objective of this research was to assess the occurrence and type of inoculum of P. viticola in W.A. vineyards. A total of 1,266 P. viticola-infected leaf discs (LD) from eight wine-grape (775 LD), five table-grape (450 LD), and seven unknown (41 LD) cultivars grown in 16 vineyards in 10 geographically separate regions of W.A. were collected in the growing seasons of 2001-2003. These regions range from Chittering in the north to Albany in the south and received 700 to 1,200 mm annual rainfall, mostly in winter. Each LD was cleared in 1 M KOH at 60°C for 12 to 24 h and then was assessed for the presence of oospores with light microscopy. Leaves showing “mosaic”-type lesions (older infection) late in the season were collected where possible to ensure colony maturity and an increased likelihood of oospore formation. All LD from all regions were negative for the presence of oospores except for samples from a single vineyard (approximately 1,200 mm annual rainfall), where all 140 LD from six wine-grape cultivars contained oospores. The discovery that oospores were present in only one of 16 sampled vineyards provides a rare opportunity to study gene flow in field populations of the pathogen with time and to determine sources of primary inoculum where overwintering of P. viticola may not involve oospores. References: (1) S. McKirdy et al. Plant Dis. 83:301, 1999. (2) A. Rumbou et al. Eur. J. Plant Pathol. 110:379, 2004. (3) F. P. Wong et al. Plant Pathol. 50:427, 2001.

scholarly journals Effect of Detergent on the Quantification of Grapevine Downy Mildew Sporangia from Leaf Discs

HortScience ◽  
2015 ◽  
Vol 50 (5) ◽  
pp. 656-660 ◽  
Author(s):  
Atsushi Kono ◽  
Akihiko Sato ◽  
Bruce Reisch ◽  
Lance Cadle-Davidson
Keyword(s):  
Downy Mildew ◽  
Leaf Disc ◽  
Plasmopara Viticola ◽  
Inhibitory Effect ◽  
Tween 20 ◽  
Infected Leaf ◽  
Grapevine Downy Mildew ◽  
Visual Rating ◽  
Leaf Discs ◽  
Highly Correlated

Grapevine downy mildew (DM), caused by the oomycete Plasmopara viticola (Berk. & Curt.) Berlese & de Toni, is a major disease, especially in humid viticultural areas. Development of resistant cultivars is an important objective for grapevine breeding. To establish a reliable and inexpensive quantitative method to aid in breeding for DM resistance, we improved the method for counting the number of sporangia on leaf discs, and developed a method for counting the number of sporangia in solution. To prevent the loss of DM sporangia from adhesion onto plastic ware, we found as little as 0.01% Tween 20 was effective. On the other hand, this detergent was shown to have a severe inhibitory effect upon DM infection of leaves. We developed a sporangia counting method using dried droplets of DM suspensions, and the method was highly correlated with counting by hemacytometer (R2 > 0.96). The nonparametric Spearman’s rank correlations between visual rating and the number of the sporangia were as high as ρ = 0.82 to 0.91, suggesting that evaluation by the visual rating could provide a good estimate of the sporangia numbers on leaf discs. We established a high-throughput and inexpensive method with acceptable accuracy for DM resistance evaluation based on a leaf disc assay, and our results suggested that visual ratings of infected leaf discs provide a good estimate of sporangia numbers.

scholarly journals Susceptibility of Cold-Climate Wine Grape Cultivars to Downy Mildew, Powdery Mildew, and Black Rot

Plant Disease ◽  
2017 ◽  
Vol 101 (7) ◽  
pp. 1077-1085 ◽  
Author(s):  
David S. Jones ◽  
Patricia S. McManus
Keyword(s):  
Powdery Mildew ◽  
Downy Mildew ◽  
Management Strategies ◽  
Plasmopara Viticola ◽  
Cold Climate ◽  
Black Rot ◽  
Wine Grape ◽  
Plant Host ◽  
Northern United States ◽  
Grape Cultivars

Lack of knowledge regarding the susceptibility of cold-climate hybrid wine grape cultivars may be leading to the overuse of fungicides and underutilization of plant host resistance to combat disease in the northern United States. To provide new insights on diseases of cold-climate cultivars and to update management recommendations, disease was evaluated in three vineyards containing eight cultivars that were not sprayed with fungicides in 2015 and 2016. Disease severity or incidence of downy mildew (Plasmopara viticola), powdery mildew (Erysiphe necator), and black rot (Guignardia bidwellii) were measured from bud break until 2 weeks after harvest. Cold-climate cultivars ranged widely in susceptibility to different diseases and, although several cultivars were relatively resistant to two diseases, no cultivar was highly resistant to all three diseases. Additionally, a difference between foliar and fruit susceptibility for all three diseases was noted in several cultivars. These data provide a foundation for developing low-spray and certified organic disease management strategies for cold-climate wine grape cultivars based on susceptibility to disease.

scholarly journals Climatic risk of grape downy mildew (Plasmopara viticola) for the State of São Paulo, Brazil

2008 ◽  
Vol 65 (spe) ◽  
pp. 60-64 ◽  
Author(s):  
Emília Hamada ◽  
Raquel Ghini ◽  
Paulo Rossi ◽  
Mário José Pedro Júnior ◽  
Jeferson Lobato Fernandes
Keyword(s):  
Relative Humidity ◽  
Downy Mildew ◽  
Plasmopara Viticola ◽  
Sao Paulo ◽  
The State ◽  
Geographical Information ◽  
Weather Data ◽  
Climatic Data ◽  
São Paulo ◽  
Grape Downy Mildew

Viticulture in Brazil has been growing in importance in recent years. In the State of São Paulo, a significant percentage of the production is basically destined to in natura consumption and, more recently, much effort has been made by institutions to revitalize the viticulture in the State. Among fungal diseases, the downy mildew (Plasmopara viticola) is one of the main diseases affecting this crop in Brazil, with extreme damage effects on its production. The objective of this study was to estimate the incidence of the downy mildew on grape under the climatic conditions of the State of São Paulo, based on a mathematical model and using Geographical Information System - GIS tools. The study considered the months from September to April, a period in which the downy mildew can affect grapevines under development. Mean temperature and relative humidity were the basic weather data entered in the GIS database. Leaf wetness duration was estimated from relative humidity measurements. Climatic data entered in the GIS were used to calculate and produce maps depicting the severity of the grape downy mildew, through the application of a disease model. Three cities were evaluated (Jales, Jundiaí, and São Miguel Arcanjo), since they represent the main vineyard centers in the State. The adopted methodology permitted quantifying the severity of the grape downy mildew not only in spatial terms, identifying the variability among the different regions of the State, but also in temporal terms, along the months, making an adequate distinction of the studied cities.

Optically-assessed preformed flavonoids and susceptibility of grapevine to Plasmopara viticola under different light regimes

2008 ◽  
Vol 35 (1) ◽  
pp. 77 ◽  
Author(s):  
Giovanni Agati ◽  
Zoran G. Cerovic ◽  
Anna Dalla Marta ◽  
Valentina Di Stefano ◽  
Patrizia Pinelli ◽  
...  
Keyword(s):  
Downy Mildew ◽  
Large Scale ◽  
Plasmopara Viticola ◽  
Vitis Vinifera L ◽  
Infected Leaf ◽  
Light Regimes ◽  
Polyphenolic Content ◽  
Non Destructive ◽  
Large Scale Screening

The role of flavonoids in the response of plants to Plasmopara viticola, the phytopathogen agent of downy mildew, was studied in the Vitis vinifera L. cultivar Sangiovese. Grapevines in the vineyard were exposed to two light regimes, 100% and 35% of full sunlight in order to induce differences in total leaf polyphenolic content. Epidermal leaf phenolic compounds were assessed optically, using the Dualex chlorophyll fluorescence-based portable leaf-clip. Dualex data were calibrated by means of HPLC analysis of extracts from the same measured leaves. Good correlations were obtained with total flavonoid contents, which consist mainly of quercetin 3-O-glucuronide. From the Dualex non-destructive measurements, we showed that full-sun exposed leaves contained 75% more flavonoids than shaded leaves. Inoculation of leaves with P. viticola sporangia resulted in a significantly lower infected leaf area in sun-lit leaves compared with shaded ones, as seen from subsequent analysis of the downy mildew severity. These results indicated an inverse relationship between preformed flavonoids and the susceptibility of grapevines to downy mildew. The rapid optical method for the non-destructive assessment of flavonoids presented here could be useful for large scale screening and predicting V. vinifera susceptibility to P. viticola.

Plasmopara viticola. [Descriptions of Fungi and Bacteria].

1989 ◽  
Author(s):  
G. Hall
Keyword(s):  
Geographical Distribution ◽  
Secondary Infection ◽  
Plasmopara Viticola ◽  
Early Summer ◽  
Plant Diseases ◽  
Infected Leaf ◽  
Active Growth ◽  
Grape Vine ◽  
Distribution Maps ◽  
Leaf Tissues

Abstract A description is provided for Plasmopara viticola. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: Ampelopsis brevipedunculata, A. hederacea, A. heterophylla, A. veitchii, Ampelocissus acetosa, A. latifolia, A. salmonea, Cissus caesia, C. gracilis, C. hypoglauca, C. polyantha, Cordifolia sempervirens, Cinerea sp., Parthenocissus quinquefolia, P. tricuspidata, Solonis robusta, Vitis aestivalis, V. amurensis, V. arizonica, V. berlandieri, V. californica, V. cinerea, V. coignetiae, V. cordifolia, V. girdiana, V. labrusca, V. lanata, V. monticola, V. pagnuccii, V. riparia, V. romaneti, V. rupestris, V. silvestris, V. treleasei, V. vinifera. DISEASE: Grape vine downy mildew; the fungus is an obligately biotrophic plant pathogen. All tissues bearing stomata are infected, becoming discolored, malformed and necrotic. Lesions on affected organs develop a white felt of sporangiophores. Leaves are most susceptible to attack during active growth in early summer, and when very mature in the autumn. Sporangiophores may appear directly on healthy green leaf tissues with no overlying lesion, or as a dense felt under yellow oily lesions on the upper surface (if humidity is high, 5-15 days after infection), or may be absent, leaves presenting only a mosaic of small, angular yellow or dark-red blemishes, limited by the secondary veins (mainly on old leaves in the autumn). During early growth, whole branches are attacked, but later only the extremities of branches are invaded. Infected shoots turn brown, curl up or become hooked at their tips. Nodes are more susceptible to attack than internodes. Tendrils, petioles, inflorescences and bunches also develop similar brown spots and lesions. Bunches are susceptible until the grapes are 5-6 mm diam., after which infection is rare (grey rot followed later by brown rot). Subsequent browning and desiccation of the bunch is caused by penetration of the bunch stalk by mycelium from earlier infections elsewhere. GEOGRAPHICAL DISTRIBUTION: See CMI Distribution Maps of Plant Diseases 221. TRANSMISSION: Oospores present in infected leaf tissues from the previous season's crop germinate in the spring, when air temperatures exceed 12°C and at least 10 mm rain falls in 24 hours, releasing zoospores into water or onto very moist soil from sporangia (64, 2458). Zoospores are projected onto vine leaves near the soil by rain splash, germinate to give hyphae and penetrate tissues via their stomata. Sporangia are liberated in moist air only, are disseminated by air currents, and remain viable for five days in dry air, producing secondary infection sites. Production of sporangia occurs at a relative humidity of 95-100%, and an air temperature of 13-27°C (optimum 18-22°C). Mycelium may overwinter between the bud scales and in diseased leaves, but it has not been established whether this contributes substantially to re-infection of healthy leaf tissues the following spring. There is no evidence for systemic transmission.

First assessment of Goidanich Index and aerobiological data forPlasmopara viticolainfection risk management in north-west Spain

2019 ◽  
Vol 157 (2) ◽  
pp. 129-139 ◽  
Author(s):  
M. Fernández-González ◽  
A. Piña-Rey ◽  
E. González-Fernández ◽  
M. J. Aira ◽  
F. J. Rodríguez-Rajo
Keyword(s):  
Downy Mildew ◽  
Secondary Infection ◽  
Plasmopara Viticola ◽  
Biological Sensors ◽  
Vegetative Period ◽  
Phenological Data ◽  
North West ◽  
Vegetative Cycle ◽  
Infection Cycles ◽  
Western Spain

AbstractThe climate of north-western Spain, with high temperatures and relative humidity during the grapevine vegetative cycle, can especially favour the development of fungal diseases in vineyards. One of the most important diseases is downy mildew, caused by the fungusPlasmopara viticola. The aim of the current study is to propose a system containing phenological data, biological sensors of pathogen indicator and the agrometeorological Goidanich Index in order to optimize the application of downy mildew fungicide treatments. The study was conducted in a vineyard of the ‘Ribeiro’ Designation of Origin region from 2005 to 2016 during theVitisvegetative period. Aerobiological sampling was performed using a LANZONI VPPS-2000 volumetric trap. The highest number of infection cycles was recorded during the 2009 harvest, with a total of 16 cycles. Years with fewer infection cycles were 2008, 2011 and 2012 (13 cycles). Primary infections were produced during the third fortnight of April and a high amount of secondary infection cycles were detected by the Goidanich algorithm during the fruit development and berry ripening stages. The best estimators of theP. viticolaspore concentrations were the fungus spore levels during the previous day, the average temperature 5 days before and rainfall 2 days before. The regression equation obtained accounted for the 95.9% of the spore concentration variation. The combination of the Goidanich index and biological sensors provides a valuable tool to establish an accurate, modern, integrated downy mildew pest-management strategy.

scholarly journals Analysis of Climatic Risk Favorability of Grapevine Fungal Disease Occurrence for Santa Teresa, Espírito Santo State, Brazil

2019 ◽  
Vol 11 (14) ◽  
pp. 121
Author(s):  
Lucas Alves Rodrigues ◽  
Evandro Chaves de Oliveira ◽  
Maria Emília Borges Alves ◽  
Ramon Amaro de Sales ◽  
Jadier de Oliveira Cunha Junior ◽  
...  
Keyword(s):  
High Risk ◽  
Downy Mildew ◽  
Meteorological Data ◽  
Weather Conditions ◽  
Plasmopara Viticola ◽  
The State ◽  
Fungal Diseases ◽  
Soil Conditions ◽  
Climatic Risk ◽  
Disease Occurrence

The State of Espírito Santo, Brazil, has micro-regions with different climatic and soil conditions, which promote grapevine cultivation vine in several municipalities. However, the grape production process is strongly threatened by foliar fungal diseases, and its control increases the cost of production significantly. In turn, the use of models of prediction of disease occurrence allows the identification of regions with climatic risk potential for grapevine. Hence, the objective of this work was to analyze the agro-climatic favorability of climatic risk for occurrence of fungal diseases of downy mildew (Plasmopara viticola) and Botrytis cinerea on the grapevine for the municipality of Santa Teresa, in the state of Espírito Santo. Predictive models of favorability of downy mildew and B. cinerea were used. The number of sprayings was determined by the calendar system and by the rainfall system, according to the length of the cycle. Therefore, a series of meteorological data from 2007 to 2016 was used. The results showed that the frequency of days with low risk of mildew was 2%, medium risk 5%, high risk 93%. For B. cinerea, these values were 32%, 68%, and 0%, with low, medium and high risk, respectively. The number of required sprayings, according to the weather conditions, was lower than the number of sprayings recommended by the calendar system. The relationship between the risk of occurrence of the evaluated diseases showed a higher agro-meteorological favorability of occurrence of mildew in relation to B. cinerea.

Ras al Khaimah: further archaeological discoveries

Antiquity ◽  
1976 ◽  
Vol 50 (200) ◽  
pp. 216-222
Author(s):  
Beatrice De Cardi
Keyword(s):  
United Arab Emirates ◽  
The State ◽  
Focused Attention ◽  
North East ◽  
The North ◽  
History Of ◽  
The City

Ras a1 Khaimah is the most northerly of the seven states comprising the United Arab Emirates and its Ruler, H. H. Sheikh Saqr bin Mohammad al-Qasimi, is keenly interested in the history of the state and its people. Survey carried out there jointly with Dr D. B. Doe in 1968 had focused attention on the site of JuIfar which lies just north of the present town of Ras a1 Khaimah (de Cardi, 1971, 230-2). Julfar was in existence in Abbasid times and its importance as an entrep6t during the sixteenth and seventeenth centuries-the Portuguese Period-is reflected by the quantity and variety of imported wares to be found among the ruins of the city. Most of the sites discovered during the survey dated from that period but a group of cairns near Ghalilah and some long gabled graves in the Shimal area to the north-east of the date-groves behind Ras a1 Khaimah (map, FIG. I) clearly represented a more distant past.

A Synopsis of Dicliptera (Acanthaceae) in Brazil, with the Description of Two New Species

2020 ◽  
Vol 45 (2) ◽  
pp. 340-348
Author(s):  
James Lucas da Costa-Lima ◽  
Earl Celestino de Oliveira Chagas
Keyword(s):  
New Species ◽  
South America ◽  
The State ◽  
Northeastern Brazil ◽  
Mato Grosso ◽  
The North ◽  
New Synonyms ◽  
Two New Species ◽  
Mato Grosso Do Sul ◽  
A New Species

Abstract—A synopsis of Dicliptera (Acanthaceae) for Brazil is presented. Six species are recognized: Dicliptera ciliaris, D. sexangularis, and D. squarrosa, widely distributed in South America; D. purpurascens, which ranges from the North Region of Brazil (in the state of Acre) to eastern Bolivia; D. gracilirama, a new species from the Atlantic Forest of northeastern Brazil; and D. granchaquenha, a new species recorded in dry and semideciduous forests in Bolivia and western Brazil, in the state of Mato Grosso do Sul. Furthermore, we propose new synonyms and designate lectotypes for eleven names. An identification key to the six accepted Dicliptera species in Brazil is provided.

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