Sphaerotheca Pannosa Research Articles

DETECCIÓN DE CENICILLA EN ROSA USANDO PROCESAMIENTO DE IMÁGENES POR COMPUTADORA

Pests and diseases represent a problem in ornamental crops, which at the same time affect the international trade and therefore have to be controlled. The main markets for cut flowers are located in Europe, United States and Japan. Mexico is one of the main suppliers to USA. Roses are currently the most important ornamental crops and also they are very susceptible to diseases, which spread easily. It would be possible to conduct early protection and treatment applications if diseases could be detected on early stage as well as the causal agents. In this research a detection system of powdery mildew(Sphaerotheca pannosa)on rose was developed with Open CV. Open CV is an open source computer vision library, which is written in C and C++ language. The detection was made according to the HSV space color. The source image was converted from the RGB to the HSV space color and the disease and the plant parts were extracted according to the H, S and V information. After that the noise (white objects) was removed. Finally the accuracy of the detection was evaluated. The developed disease detection system is able to detect the powdery mildew disease through the HSV space color with Open CV. Better results were obtained when using close pictures (10 cm). The miss-matched rate caused mostly by halation when using distant pictures could be successfully avoided using active sensing which allows for disease detection even when using distant pictures.

Silicon induced resistance against powdery mildew of roses caused by Podosphaera pannosa

Powdery mildew, caused by Podosphaera pannosa, is a very common disease in greenhouse potted roses, resulting in poor marketing value and hence economic losses. Alternatives to chemical control are necessary, and therefore the ability of silicon (Si) applied to roots to control the disease was investigated, as well as the mechanisms behind the observed disease reductions. Four genotypes of miniature potted roses representing different genetic backgrounds and susceptibility to disease were studied. Plants were watered with a nutrient solution containing either 3·6 mm Si (100 ppm) supplied as K2SiO3 (Si+) or no Si (Si−) before inoculation with P. pannosa. Si application increased leaf Si content two‐ to four‐fold compared to control plants. Confocal microscopy showed that Si deposition was larger in Si+ than in Si− plants and that deposition mainly occurred in the apoplast, particularly in epidermal cell walls. Si application delayed the onset of disease symptoms by 1–2 days and disease severity was reduced by up to 48·9%. The largest reduction was found in the two most resistant genotypes, which also had the highest increase in Si uptake. The Si‐induced disease protection was accompanied by increased formation of papillae and fluorescent epidermal cells (FEC) as well as deposition of callose and H2O2, especially at the sites of penetration and in FEC, which are believed to represent the hypersensitive response. Si treatment reduced powdery mildew development by inducing host defence responses and can therefore be used as an effective eco‐friendly disease control measure.

Evaluating electrolysed oxidising water as a fungicide using two rose varieties (Rosa sp) in greenhouse conditions

The aim of evaluating electrolysed oxidising water (EOW) for controlling botrytis (Botrytis cinerea), powdery mildew (Sphaerotheca pannosa) and downy mildew (Peronospora sparsa) using two greenhouse rose varieties was to verify this new technology’s effectiveness by contrast with traditional chemical handling. Two concentrations of hypochlorous acid in EOW were produced during electrolysis in a P1200 cell and applied at three application volumes using stationary hydraulic pressure equipment. The commercial rose varieties (Rosa sp) used here were the Orlando and Versilia varieties. The EOW used was slightly acidic type C, pH 5.0, having high-oxide-reduction potential (ORP) +850 millivolts (mV). Two types of EOW were evaluated for this study: EOW C-50 (50 ppm HOCl) and EOW C-75 (75 ppm HOCl). The test results showed the feasibility of EOW as a fungicide at the volumes tested here, providing significant control of powdery mildew which has high incidence due to climatic conditions. The best disease control was achieved by applying the highest volume; however, some curled leaflets appeared with this application.

Specific Light-Emitting Diodes Can Suppress Sporulation of Podosphaera pannosa on Greenhouse Roses.

When rose plants bearing colonies of Podosphaera pannosa were placed in a wind tunnel, the number of conidia trapped was directly proportional to intensity of daylight-balanced (white) light from 5 to 150 μmol m-2 s-1. Illumination of samples using blue (420 to 520 nm) light-emitting diodes (LEDs) increased the number of conidia trapped by a factor of approximately 2.7 over white light but germination of conidia under blue light was reduced by approximately 16.5% compared with conidia germination under white light. The number of conidia trapped under far-red (>685 nm) LEDs was approximately 4.7 times higher than in white light, and 13.3 times higher than under red (575 to 675 nm) LEDs, and germination was not induced compared with white light. When mildewed plants were exposed to cycles of 18 h of white light followed by 6 h of blue, red, far-red light, or darkness, light from the red LEDs reduced the number of conidia trapped by approximately 88% compared with darkness or far-red light. Interrupting the above dark period with 1 h of light from red LEDs also reduced the number of conidia trapped, while a 1-h period of light from far-red following the 1 h of light from red LEDs nullified the suppressive effect of red light. Our results indicate that brief exposure to red light during the dark interval may be as effective as continuous illumination in suppressing powdery mildew in greenhouse rose plant (Rosa × hybrida).

SCREENING OF DAMASK ROSE GENOTYPES FOR POWDERY MILDEW RESISTANCE

Podosphaera pannosa is one of the most common diseases that attacks both garden and greenhouse roses worldwide. It is also an important disease of Rosa damascena in Iran. Since Iran appears to be a center of genetic diversity for Damask rose, it is expected that powdery mildew resistance genes would be found. Therefore, a set of Damask roses from diverse regions of Iran (Fars, Isfahan, Kerman and East Azerbaijan provinces) were screened for powdery mildew resistance. The plants were screened for natural infection over two years (2006 and 2007) both in the field and in pots. The diseases index and factor were calculated for each genotype and severity of disease was compared at different scoring times. Screening in the field was not consistent, probably due to non-uniform pathogen distribution, but potted plants that were placed in favorable environmental conditions (half-shade with relatively high humidity) gave consistent ratings over replications. Significant differences in the rate of powdery mildew development were found between genotypes. The East Azerbaijan (colder with higher rainfall and humidity) and Kerman (warmer and dryer region) genotypes were recognized as the most resistant and susceptible genotypes respectively. This is the first report on resistance for powdery mildew in Damask roses. Results are promising for planning the future breeding programs on this valuable species.

Continuous Lighting Reduces Conidial Production and Germinability in the Rose Powdery Mildew Pathosystem.

The effect of day length on production and germinability of conidia and severity of disease caused by Podosphaera pannosa, the causal agent of rose powdery mildew, was studied. Whole potted plants or detached leaves of Rosa interspecific hybrid 'Mistral' were inoculated with P. pannosa and exposed to 0, 12, 18, 20, 22, or 24 h of artificial light per day in growth chambers equipped with mercury lamps. Increasing duration of illumination from 18 to 20 to 24 h per day reduced production of conidia by 22 to 62%. Exposure to 24 h of illumination per day also strongly reduced disease severity compared with 18 h. Our results suggest that increasing day lengths from 18 h per day to 20 to 24 h may suppress the disease significantly and, thereby, reduce the need for fungicide applications against powdery mildew.

Potential use of Olejan 85 Ec for Protecting Some Species of Ornamental Plants Against Diseases

The object of the studies was to assess the effectiveness of the product Olejan 85 EC (85% rapeseed oil) against the disease casual agents of powdery mildew, rust, leaf spot and grey mould. Depending on a casual agent, Olejan 85 EC at the concentration of 1% was used for 2-6 spraying treatments at 7-day intervals. The results of performed experiments revealed that Olejan 85 EC used as a curative spraying treatment on rose and pansy plants significantly reduced the development of powdery mildew. After 4 treatments, it caused a 3.3-fold reduction to complete inhibition of Sphaerotheca pannosa var. rosae development on roses. In the case of pansy plants, it caused a complete inhibition of the development of the fungus S. humuli. The preparation Olejan 85 EC applied curatively against leaf spot, significantly inhibited the development of this disease on rose and pansy. After 6 spray treatments, the product caused at least a 1.9-fold reduction in the development of Diplocarpon rosae on rose. On pansy plants, after 4 applications, it caused a 3.1-to-4-fold reduction in the development of Colletotrichum spp. Olejan 85 EC applied as a curative spraying treatment on chrysanthemum and willow inhibited the development of rust. After 4 applications on chrysanthemum, the product caused at least a 2-fold reduction in the development of Puccinia horiana, with 58% of brown and malformed telia. In the protection of willow, after 2 applications, Olejan 85 EC caused at least a 2.3-fold reduction in the development of Melampsora epitea, and from 32 to 75% of the uredinia turned brown and malformed.

Powdery Mildew Resistance in the Peach Cultivar Pamirskij 5 Is Genetically Linked with the Gr Gene for Leaf Color

Peach powdery mildew (Podosphaera pannosa var. persicae) is a major disease of peach trees [Prunus persica (L.) Batsch]. Various studies on powdery mildew resistance have been conducted in peach. The present study was initiated to determine the inheritance of powdery mildew resistance found in the green leaf peach rootstock ‘Pamirskij 5’. Crosses were carried out between ‘Pamirskij 5’ and the susceptible red leaf peach rootstock ‘Rubira’®. Segregation analysis performed in F1 (1:0), F2 (3:1), and test cross (1:1) progenies indicated single dominant gene control of peach powdery mildew resistance in ‘Pamirskij 5’. Cosegregation analysis provided clear evidence that the loci for powdery mildew resistance and the leaf color trait are very closely linked in ‘Pamirskij 5’. The estimated distance between these loci was 0 ± 3.26 cM for the F2 and 0 ± 0.00 cM for the test cross populations.

Susceptibility of several Japanese plum cultivars to pests and diseases in a newly established organic orchard

The susceptibility of 14 Japanese plum cultivars to an aphid pest and three fungal diseases was analysed during 2007 and 2008 in two experimental orchards, one in organic and the other in conventional management. There was a significantly higher incidence of green peach aphids [ Myzus persicae (Sulzer)] for most of the cultivars in the organically managed treatment. ‘Fortune’, ‘Primetime’, ‘Larry Ann’ and ‘Sapphire’ were the cultivars most affected, and ‘Souvenir’ suffered the lowest attack in both treatments. Shot hole disease ( Wilsonomyces carpophilus) affected both orchards at low levels, and only two cultivars, ‘Santa Rosa’ and ‘Larry Ann’, suffered a moderate attack. Powdery mildew ( Sphaerotheca pannosa) incidence was significantly higher in the conventionally managed orchard and only the ‘Red Beaut’ cultivar was affected. Rust disease ( Tranzschelia spp.) incidence was significantly higher in the organic treatment. The cultivars in which the rust disease appeared earliest and reached the highest levels were ‘Showtime’, ‘Santa Rosa’, ‘Friar’, and ‘Larry Ann’. An intense rust infestation in leaves provoked a premature defoliation in the organic plot, indicating that proper control of this disease is important to maintain tree vigour and yield.

Performance of Garden Roses in North-central Texas under Minimal Input Conditions

One hundred sixteen rose (Rosa spp.) cultivars were evaluated under minimal input conditions in north-central Texas for 3 years. Plant quality data included overall plant performance, number of flowers, percentage of bloom coverage, final vigor, and survival. Disease ratings for black spot (Diplocarpon rosae), petal blight (Alternaria alternata), powdery mildew (Sphaerotheca pannosa), and aphid (Myzus spp.) infestations were previously reported. Of the original 116 cultivars, 25 had 50% or higher mortality during the trial. Own-root cultivars performed significantly better than the grafted cultivars and had significantly better survival (P = 0.001). As a class, the Polyantha cultivars exhibited the best overall performance, mean bloom percentage, final vigor and survival, while cultivars in the Hybrid Tea class had the worst performance in all measures. Foliar nutrient content, bloom number, and mean percentage of bloom were not good predictors of overall performance. Of the diseases monitored, black spot was the most severe and was closely correlated to overall performance and final vigor, but was not the only factor determining overall performance. The top five cultivars in mean overall performance were RADrazz (Knock Out™), Caldwell Pink, Sea Foam, Perle d'Or, and The Fairy, in descending order.

RESISTANCE REACTIONS IN ROSE LEAVES AGAINST POWDERY MILDEW (PODOSPHAERA PANNOSA)

Fungal development of powdery mildew Podosphaera pannosa (Wallr.: Fr.) de Bary (syn. Sphaerotheca pannosa) on rose leaves depends on different resistance mechanisms present in attacked rose genotypes. These mechanisms influence both mycelium formation and sporulation. Two rose species (R. wichuraiana and R. laevigata) and 2 cultivars ('Excelsa' and 'Gomery') were selected to examine microscopically the interaction between fungal development and plant resistance mechanisms. Differences in fungal development and resistance mechanisms were detected in all four rose genotypes. Mycelium formation and sporulation were dependent on the proportion between normal haustoria, abnormal haustoria, papilla formation, physiological responses and intracellular induction of antifungal phenolic compounds (phytoalexins). Two different forms of physiological responses could be observed, with and without cell collapse. Both were induced by H2O2 production of invaded cells, and were very important in limiting the formation of conidiophores. The most important resistance mechanism was, however, the ability to inhibit normal haustorium formation, probably as a constitutive resistance mechanism.

Effect of Biopesticides on Foliar Diseases and Japanese Beetle (Popillia japonica) Adults in Roses (Rosaspp.), Oakleaf Hydrangea (Hydrangea quercifolia), and Crapemyrtle (Lagerstroemia indica)

This study evaluated efficacy of biopesticides for reducing foliar diseases and feeding damage from Japanese beetle adults on hybrid T rose (Rosa spp.), oakleaf hydrangea (Hydrangea quercifolia), and crapemyrtle (Lagerstroemia indica). The materials tested included household soaps with Triclosan active ingredient (Equate® and Ajax®), kaolin clay (Surround®), neem seed oil extract (Triact 70® and Neem Gold®), potassium salt of fatty acids (M-Pede®), horticultural oil (UltraFine® Sunspray oil), and bicarbonate salt (Armicarb®) applied to plants grown under greenhouse, shadehouse, and field conditions. Two fungicides, trifloxystrobin (Strobilurin) and triadimefon (Triazole), and the insecticide carbaryl were included for comparison. All materials tested were effective in controlling black spot (Marssonina rosae, anamorph Diplocarpon rosae) and powdery mildew (Sphaerotheca pannosa) of roses. Kaolin was effective in reducing disease severity of bacterial leaf spot (Xanthomonas campestris) on oakleaf hydrangea and powdery mildew of crapemyrtle. Based on data from repeated trials, the biopesticides were as effective as conventional fungicides in suppressing foliar diseases. Kaolin clay was as effective as carbaryl in controlling Japanese beetle adult feeding damage on oakleaf hydrangea, roses, and crapemyrtle, but other products were not effective. Results from this study indicate kaolin clay may be an alternative product to conventional pesticides in foliar diseases and insect pest management for roses, oakleaf hydrangea, and crapemyrtle.

Characterization of Reactions to Powdery Mildew (Podosphaera pannosa) in Resistant and Susceptible Rose Genotypes

AbstractFungal development of powdery mildew Podosphaera pannosa (Wallr.: Fr.) de Bary on rose leaves depends on constitutive or induced resistance mechanisms present in attacked rose genotypes. The relationship between fungal development and plant resistance was investigated microscopically on young greenhouse leaves of four rose genotypes with different levels of resistance: Rosa wichuraiana, R. laevigata anemoides and R. hybrida cultivars ‘Excelsa’ and ‘Gomery’. Induced plant reactions, hydrogen peroxide production and cross sections through infected leaves were examined. The variation in development of the fungus on these rose genotypes depended on the relative presence of normal haustoria, abnormal haustoria, induced cell reactions, papilla formation or physical barriers. Formation of papillae could arrest up to one third of the successful penetrations. Papillae formation was often succeeded by total cell reaction. Abnormal haustoria were detected as rudimentary haustoria, haustoria with abnormal shape or haustoria without extra haustorial matrix. Post‐haustorial cell reactions, with and without cell collapse, were detected. In non‐collapsed cells, appositions were directed to both cell wall and haustorium. This was followed by accumulation of non‐identified, probably antifungal compounds. Both single and multicell reactions occurred. Hydrogen peroxide was detected during papilla formation and induced cell reactions.

Powdery mildew resistance in roses: QTL mapping in different environments using selective genotyping

Podosphaera pannosa, the causal agent of rose powdery mildew, hampers the production of cut roses throughout the world. A major tool to control this disease is the use of resistant plant material. Single resistance genes, like Rpp1, may be overcome within a few years by high risk pathogens like powdery mildews. Durable resistance could be achieved using quantitative resistances. Here we describe mapping of QTLs for resistance to P. pannosa in six different environments (artificial and natural infections in the greenhouse over 3 years and natural infections in the field over 2 years). AFLPs, RGAs and other marker types were used to construct an integrated linkage map for the diploid population 97/7 containing 233 markers. In a selective genotyping procedure, marker segregation was analysed for 170 of the up to 270 phenotyped individuals. We identified seven linkage groups with an average length of 60 cM, corresponding to seven rose chromosomes in the haploid set. Using an LOD significance threshold of 3.9 we detected a total of 28 QTLs for the nine powdery mildew disease scores under analysis. Using the data from artificial inoculations with powdery mildew race 9, three resistance QTLs explaining about 84% of the variability were mapped. Twelve and 15 QTLs were detected for resistance to naturally occurring infections in the greenhouse and in the field, respectively, over several years.

First report of powdery mildew caused by Podosphaera pannosa on a new host – sour cherry – in Hungary

First report of powdery mildew caused by <i>Podosphaera pannosa</i> on a new host – sour cherry – in Hungary

Situation of peach resistance to diseases in Romania

The resistance of peach cultivars to the most important diseases caused by fungi, bacteria, viruses and mycoplasms was studied in Romania over two working stages in the period between 1985-2005. The major diseases examined were: Cytospora cincta Sacc., Taphrina deformans (Berk) Tul., Moruluua laxa (Aderh. &amp; Ruhl) Honey, Sphaerotheca pannosa var. persicae Woron., Stigmina carpophila (Lev) M.B.Ellis, Pseudomonas syringae pv. syringae, mycoplasm and plum pox potyvirus. Based on the obtained results, the studied cultivars were classified into resistance groups for the different diseases (very resistant, resistant, medium resistant, sensitive and very sensitive).Based on the results of our study, the following gene sources were chosen following the evaluation of the various genetic material in the peach germoplasm fund, in the climatic conditions of Romania: Cytospora cincta: Cullinan, Cardinal, Hamlet, NJF 3, Onakita Gold, Triumf, "Superba de Toamna", Anderson, Weinberger; Stigmina carpophila: Armgold, ARK 109, Stark Early Blaze, Cardinal, Congres; Taphrina deformans: Madeleine Pouyet, Cumberland, Harbelle, Indian Blood, Sulivan, Victoria, Zafrani, Pekin, Naradnji Ranhii; Spaherotheca pannosa var. persicae: Triumf; Congres; Victoria; Armking; Morton; Regina; Nectared 7; ARK 125; ARK 134; Regina.

Assessment of Partial Resistance to Powdery Mildew (Podosphaera pannosa) in a Tetraploid Rose Population Using a Spore-suspension Inoculation Method

Powdery mildew (Podosphaera pannosa) is the most important fungal disease in greenhouse roses and is in practice controlled by fungicides. The creation of novel cultivars with durable resistance to powdery mildew is highly desirable. To understand the inheritance of mildew resistance, a tetraploid rose population with a size of 181 seedlings was obtained by crossing two tetraploid genotypes each having partial resistance. The population and its parents were tested under greenhouse conditions with two well-defined monospore isolates (2 and F1) using artificial inoculation with spore suspensions. Disease score at 11 days post-inoculation, latent period and rate of symptom development were used to describe seedling resistance. The tests for both isolates exhibited a wide and significant variation among genotypes for resistance. The distribution of the genotypic means of the disease scores was continuous and showed a considerable transgression. Statistical analysis, scatter plot of disease scores for the isolates, and correlation analyses indicated that the two isolates differed in pathogenicity. The outcome of the tests showed that the inoculation assay with spore suspensions was a reliable and effective way to screen large numbers of genotypes under greenhouse conditions for genetic and breeding studies. This is the first report on spore-suspension inoculation to be used successfully in rose.

Podosphaera pannosa (syn. Sphaerotheca pannosa) on Rosa and Prunus spp.: Characterization of Pathotypes by Differential Plant Reactions and ITS Sequences

AbstractThe powdery mildew fungus Podosphaera pannosa (Wallr.: Fr.) de Bary (syn. Sphaerotheca pannosa) is a major problem on roses worldwide. Twenty‐six monoconidial isolates of Podosphaera collected on roses and Prunus spp. in Belgium, Germany, France, Denmark, Israel and The Netherlands were characterized on the basis of differential reactions on in vitro rose genotypes and Prunus avium L. and by DNA sequence analysis of the rDNA ITS (internal transcribed spacer) region. Twenty‐four isolates were determined as P. pannosa. Amongst these, different groups could be distinguished. A first group of 18 isolates was highly virulent on rose and avirulent or very weakly virulent on P. avium. A second group of four isolates was highly virulent on both rose and P. avium. Analysis of the ITS sequence could discriminate these two groups of P. pannosa strains by a one base pair difference. Finally, two isolates of powdery mildew collected on Prunus sp. could be classified as P. pannosa based on their ITS sequence, which was identical to the ITS sequence of the isolates only highly virulent on roses. However, these two isolates were not able to infect roses. These results indicate that different strains of P. pannosa exist with varying host specificity. We demonstrated by ITS sequencing and plant reactions that the host range of P. pannosa comprises roses and Prunus spp.

Occurrence of powdery mildew ( Sphaerotheca pannosa) in Japanese plum in Northern Israel and its control

Powdery mildew, caused by the fungus Sphaerotheca pannosa (Wallr.) Lev., is a widespread and destructive disease of nectarine in the northern region of Israel. Powdery mildew has not previously been observed on Japanese plum ( Prunus salicina Lindl.) in this region, and we describe here the first occurrence of powdery mildew on plum trees in the largest growing area in Northern Israel. The first symptoms and signs were observed on 22 April 2000 as single colonies on young plum fruits, and these expanded during the season and covered large parts of the fruit. The disease caused browning and russeting of the fruit surface, and chlorotic spots on mature and coloured fruits until harvest. The disease on leaves was less severe, characterized by chlorotic (bright yellowish) lesions of 5–10 mm diameter on the upper surface and “oil spot” type lesions on the lower surface. Microscopic examinations revealed that the mycelium, conidiophores and conidia were similar to those of S. pannosa that attacks nectarine trees in this region. Cleistothecia were not found during the growing season. Disease rating in two orchards showed that fruits were more infected than leaves. The most severly affected cultivar was ‘Red Beaut’ with 27% and 97%, respectively, of leaves and fruits infected. Field experiments conducted in 2000, 2002 and 2004 showed that foliar applications of DMI (demethylation inhibitor) fungicides reduced disease development, but failed to provide satisfactory control. DMIs were less effective than the strobilurin, kresoxim-methyl and polyoxin B in controlling S. pannosa on fruits and leaves of field-grown Japanese plum trees. However, spraying of sulphur significantly enhanced the inhibitory effect against powdery mildew and provided the highest level of disease control. In the light of experience with S. pannosa in nectarine , it is suggested that intensive use may have led to reduced efficacy of the DMI fungicides in controlling S. pannosa in nectarine and plum orchards. An alternative disease management programme, which integrates early and timely applications of effective fungicides, and tank-mixtures of DMI fungicides with sulphur, may provide an improved level of powdery mildew control and could be valuable to avoid the spread of powdery mildew and to minimize the development of fungicide resistance.

PERFORMANCE OF GARDEN ROSES UNDER MINIMAL INPUT CONDITIONS IN NORTH-CENTRAL TEXAS

To enlarge the palette of environmentally-responsible landscape plants, 117 garden rose cultivars were evaluated under minimal input conditions. Other than mulching and irrigation, no other inputs were provided, including no fertilization and no pesticide applications. Plants were established in completely randomized blocks with four reps in the spring of 1998 with data collection beginning in 2000 and continued through 2002. Data on overall performance (an index comprised of flower number, percent of plant covered with flowers and plant growth) and relative chlorophyll content were collected the first and third week of each month from April through October. Disease ratings or incidence ratings were collected for Diplocarpon rosae Wolf (black spot), Alternaria sp. (petal blight) and Sphaerotheca pannosa (powdery mildew). Statistical analysis was performed on the mean data for all dates. `Knockout' was the top rose for overall quality with little or no disease observed, high foliage quality, and continuous flowers from spring until late in the fall. `Knockout' also ranked among the top rose cultivars in terms of overall nutrient concentrations (N, P, K, and Fe) in new growth tissue. Most of the hybrid tea roses such as `Peace' and `Double Delight' died in at least three blocks due to disease and a lack of vigor.