Presence Of Phytophthora Research Articles

Movement of Phytophthora spp. in Maryland's Nursery Trade.

Phytophthora spp. cause major losses in the nursery industry worldwide. However, a clear demonstration of the route of movement has not been previously shown. A survey of 10 Maryland nurseries was conducted over a 3-year period to investigate the presence of Phytophthora spp. on newly arrived plants, mainly from West Coast suppliers. Local nursery plants, irrigation water, and potting media were also sampled for Phytophthora spp. Isolates were identified using a combination of morphological characteristics and DNA sequencing. Species identified included Phytophthora cactorum, P. cambivora, P. cinnamomi, P. citrophthora, P. drechsleri, P. elongata, P. gonapodyides, P. hydropathica, P. irrigata, P. lacustris, P. multivora, P. nicotianae, P. pini, P. plurivora, and P. syringae. P. taxon pgchlamydo was also isolated from irrigation water. Eight of the abovementioned Phytophthora spp. were isolated in association with incoming material, indicating that the movement of these pathogens continues to occur. Asymptomatic plant material was the main route of introduction of Phytophthora spp. to Maryland nurseries. Results also indicated that several Phytophthora spp. could be found in Maryland nurseries in association with infested potting media of asymptomatic plants. Although P. ramorum was not detected, our surveys underscore the significance of nursery practices that allow introductions of these significant plant pathogens to new geographic locations.

Extracts of the endemic resurrection plant Haberlea rhodopensis stimulate in vitro growth of various Phytophthora spp. pathogens

The Phytophthora pathogens are among the most important pests in the modern agriculture and forestry. This makes them a subject of intensive studies, including laboratory experiments with in vitro culture on various plant-derived media. Here we show that leaf extracts from the resurrection endemic plant Haberlea rhodopensis stimulates significantly the in vitro growth of various isolates from several Phytophthora species. The extracts stimulate the formation of oospores in some heterothallic species. In this respect, the idea to propose Haberlea extracts as a potential ingredient of culture media for Phytophthora spp. maintenance under controlled conditions or as a component of detection systems for Phytophthora presence in nature seems quite attractive and promising.

English

We have been planting blight resistant American chestnut seedlings on reclaimed coal mined areas in Southeastern Ohio, which was once within the natural range of the American chestnut. Towards the goal of restoring the American chestnut, we are testing suitable sites that can aid survival, growth and establishment of planted seedlings pre-inoculated with ectomycorrhizal fungi. Prior to the arrival of the chestnut blight fungus, pathogens of the genus Phytophthora were introduced in the USA that were responsible for the ink disease or root-rot resulting in wide-spread death of chestnut trees in southern states. Although these pathogens were not observed elsewhere, recent reports indicate their presence in some northern states, including Ohio. We have been testing each location targeted for chestnut plantings for the presence of Phytophthora, specifically P. cinnamomi. The work reported here shows results obtained from seven different sites in southeastern Ohio where reclamation was done 3-20 years ago. Soil was collected at a depth of 4-5 at several locations within each site. A positive control containing ~4 cfu/10 g soil was used in the analysis. We used two different techniques for identifying the pathogen: 1. Direct isolation of the pathogen from the soil using selective media; 2. Using chestnut leaves as a baiting technique followed by selection on plates. In both cases, final identification was done by DNA isolation and sequencing using Phytophthora-specific primers. Our results showed that, at least in the locations we tested, P. cinnamomi was not detected. Because most of these lands were only recently reclaimed, it is possible that the pathogen may not have established there yet. However, samples from locations that were reclaimed more than 2 decades ago also showed absence of this fungus. Results suggest that this pathogen is either not as wide-spread in Ohio as in southern states or mined sites are not favorable for its existence and spread.

First records of Phytophthora spp. based on DNA analysis in Lithuania

The assessment of alien invasive species of Phytophthora genus causing serious forest tree species diseases was carried out in Lithuania. The presence of Phytophthora DNA was recorded for the first time using real-time PCR analysis on 23 DNA samples. The sampling included wood from diseased trees, leaves from shrubs, leaves baited in water, and soil samples taken around diseased plants. Extracted DNA from soil and plant tissues was tested for the presence of Phytophthora. All analysed samples were positively recognized by Phytophthora-specific probe during real-time PCR which proved the presence of pathogens in environmental samples.

Thuja occidentalis: a new host for Phytophthora lateralis

In February and March 2011, Scottish Government Plant Health Inspectors submitted three potted Thuja occidentalis cv. 'Emeraude' plants to SASA requesting a test for the presence of Phytophthora. They were collected in a nursery in central…

Phytophthora plurivora T. Jung & T. I. Burgess and other Phytophthora species causing important diseases of ericaceous plants in the Czech Republic

Ornamental nurseries, garden centres, public gardens and urban greenery in the Czech Republic were surveyed in 2006–2009 for the presence of Phytophthora spp. and the diseases they cause on ericaceous plants. Diseased plants such as Rhododendron spp., Pieris floribunda, Vaccinium sp., and Azalea sp. showed various symptoms including leaf spot, shoot blight, twig lesions or stem, root and collar rot. Nearly 140 Phytophthora isolates were collected from symptomatic plants in different areas of the country. Of the Phytophthora spp. on ericaceous plants or in their surroundings, P. plurivora appeared to be the most common species. Herein, we focus on the most frequently occurring species, P. plurivora, and describe its morpho-physiological and pathogenicity features and confirm its identity based on ITS sequences of rDNA. In addition, we give a list of other Phytophthora spp. including P. cactorum, P. cambivora, P. cinnamomi, P. citrophthora, P. megasperma, P. multivora, P. ramorum, and P. gonapodyides that we identified on the basis of their cultural and morphological characteristics and DNA sequences. We also discuss their importance in cultivated and natural ecosystems.

First Report of Bud Rot Caused by Phytophthora palmivora on African Oil Palm in Colombia.

A bud rot disease, referred to as "pudricion del cogollo" or PC (for its name in Spanish), is a major disease of oil palm in four production areas of Colombia. Even though the disease has been studied for more than 40 years in Central and South America, the causal agent remained unknown (1). Infection first develops in the palm heart (cogollo) above the meristematic zone. Initial external symptoms appear as necrotic lesions on the sides of the spear leaf (youngest, unexpanded leaf) and the sizes of the lesions remain static as tissues emerge, expand, and mature. Under favorable environmental conditions (temperature around 26°C and relative humidity above 80%), further rotting of the heart eventually destroys the bud. A baiting technique with papaya and cocoa fruits was successfully used to trap the causal agent from symptomatic spear leaf tissue collected from the provinces of Nariño and Santander (2), where the disease is severe. Small, triangular-shaped pieces were removed from healthy fruits that had been surface sterilized, and a corresponding piece of diseased oil palm tissue was inserted into the hole and sealed with the removed fruit tissue. The whole fruit was wrapped with plastic and incubated at 25°C. Once the fruit traps showed initial necrotic symptoms, fruit tissue from the advancing point of the lesions was plated on Phytophthora-selective media. Four isolates of Phytophtora palmivora, all A2 mating type, were obtained during this study and each presented similar white and depressed mycelium when grown on oatmeal agar (OMA) medium. Papillated, ellipsoidal sporangia with short pedicels had an average size of 37.1 (breadth) × 52.8 μm (length). Chlamydospores averaged 35.1 μm in diameter and were similar to those observed in diseased palm tissue. DNA from the Phytophthora isolates was used as a template for PCR using ITS1/ITS4 primers. BLASTn analysis of the ITS sequences (GenBank Accession No. GQ398157) showed 99.9% homology with P. palmivora. The sequences of the four isolates were identical. For pathogenicity testing, cultures were grown on OMA. Two milliliters of distilled water containing 40,000 sporangia were injected into the base of the spear leaf of 105 nursery palms; the same number of palms was injected with 2 ml of distillated water as controls. Initial PC symptoms were observed 3 to 4 days after inoculation on 85% of inoculated palms and 15% of these palms developed typical bud rot symptoms under favorable conditions. No symptoms were observed on the controls. The presence of Phytophthora was confirmed by light microscopy and P. palmivora was reisolated from symptomatic palms with the fruit-baiting technique. The presence of Phytophthora in the four Colombian growing areas was also confirmed using Agdia (Elkhart, IN) immunostrips followed by DNA extraction from the Immunostrip wick and ITS sequencing to confirm the species. To our knowledge, this is the first report of P. palmivora causing PC on oil palm in Colombia.

Involvement of Phytophthora species in white oak (Quercus alba) decline in southern Ohio

SummaryThis study was initiated to investigate the possible role of Phytophthora species in white oak decline (Quercus alba) in southern Ohio at Scioto Trail State Forest. Surveys demonstrated the presence of four species of Phytophthora including one novel species. By far, the most common species was P. cinnamomi; P. citricola and P. cambivora were isolated infrequently. In few instances, P. cinnamomi was isolated from fine roots and necroses on larger roots. No special pattern of incidence was found, but P. cinnamomi was more commonly isolated from greater Integrated Moisture Index values suggesting moist lower bottomlands favour this Phytophthora species. When tree crown condition was examined relative to the presence of Phytophthora, no significant association was found. However, roots of declining P. cinnamomi‐infested trees had 2.5 times less fine roots than non‐infested and healthy trees, which was significantly different. The population densities of P. cinnamomi from declining trees were significantly greater than from healthy trees, suggesting increased pathogen activity that has the potential to cause dieback and decline and possibly the cause of a reduced fine root amount found on declining trees.

English

Plant pathogens of the genus Phytophthora may pose a threat to trees on reclaimed mine lands. The presence of these pathogens in forest soils of Appalachia has been documented, but their presence and relative distribution in mine spoils is unknown. Soil samples from mine spoils at the Bent Mountain, KY reforestation site were tested for presence of Phytophthora spp., and, specifically, P. cinnamomi, using a soil-baiting method. Loose-graded mine spoils (brown sandstone, gray sandstone, mixed spoil, and shale) dumped in 2005 and 2007 at the Bent Mountain reforestation site were tested monthly from May to October 2007 for Phytophthora at the surface (top 0-10 cm) using a soil baiting method. Soils collected from two non-mined control sites within Robinson Forest and Berea Forest were also tested using the same method. Colonies obtained from the baiting method were isolated in PARP-H V8 Phytophthora- selective medium and incubated at 25°C. Colonies with Phytophthora-characteristic morphology were tested by PCR. PCR results, confirmed by DNA sequencing, indicate that P. cinnamomi was successfully isolated using the baiting method from forest soils. No Phytophthora spp. were detected by the baiting method from mine spoils. Future work will involve testing water that has infiltrated through mine spoils for presence of Phytophthora spp. Water collected from lysimeters will be filtered to capture mycelial fragments or reproductive structures of Phytophthora species through exclusion on the filter membrane and the membrane will be subjected to DNA extraction and PCR. The presence of Phytophthora spp. in spoils and water in comparison to media physiochemical characteristics, aqueous geochemistry of infiltrated waters, and tree growth with regards to reforestation efforts on different tailing media will be evaluated.

Root Colonizing and Biocontrol Competency of Serratia plymuthica A21-4 against Phytophthora Blight of Pepper

The biocontrol agent Serratia plymuthica A21-4 readily colonized on the root of pepper plant and the bacterium moves to newly emerging roots continuously. The colonization of A21-4 on the pepper root was influenced by the presence ofPhytophthora capsici in the soil. When P. capsici was introduced in advance, the population density of A21-4 on the root of pepper plant was sustained more than cfu/g root until 3 weeks after transplanting. On the other hand, in the absence of P. capsici, the population density of A21-4 was reduced continuously and less than cfu/g root at 21 days after transplanting. S. plymuthica A21-4 inhibited successfully the P. capsici population in pepper root and rhizosphere soil. In the rhizosphere soil, the population density of P. capsici was not increased more than original inoculum density when A21-4 was treated, but it increased rapidly in non-treated control. Similarly, the population density of P. capsici sharply increased in the non-treated control, however the population of P. capsici in A21-4 treated plant was not increased in pepper roots. The incidence of Phytophthora blight on pepper treated with A21-4 was 12.6%, while that of non-treated pepper was 74.5% in GSNU experimental farm experiment. And in farmer`s vinyl house experiment, the incidence of the disease treated with the fungicide was 27.3%, but treatment of A21-4 resulted in only 4.7% of the disease incidence, showing above 80% disease control efficacy.

Influence of the stabilisation of organic materials on their biopesticide effect in soils

Some organic materials have shown a suppressive effect on several diseases induced by soilborne plant pathogens. We have carried out a laboratory experiment (microcosm) to ascertain the influence of the stabilisation process of sewage sludge on it biopesticide effect when Pythium ultimum or Phytophthora sp. were introduced to soil as pathogens for pea or pepper. When P. ultimum was introduced there was a 63.8% reduction in the weight of the stems grown in the control, 47.6% in the presence of sewage sludge, but only 24.7% with compost. The same biopesticide effect was evident from the weight of the roots. The biopesticide effect was also strong when compost was used as organic amendment in the presence of Phytophthora, as could be seen from stem and shoot weight and length. The data showed that the degree of stabilisation of the organic material (compost) had a positive influence on it biopesticide effect. The changes undergone by a soil after the addition of organic materials helped to explain the biopesticide effect of the amendment. The organic treatments reduced P. ultimum and Phytophthora sp. populations.

Phytophthora species in oak ecosystems in Turkey and their association with declining oak trees

From 1999 to 2001, a survey on the occurrence of Phytophthora spp. in the rhizosphere soil of healthy and declining oak trees was conducted in 51 oak stands in Turkey. Seven Phytophthora spp. were recovered from six out of the nine oak species sampled: P. cinnamomi, P. citricola, P. cryptogea, P. gonapodyides, P. quercina, Phytophthora sp. 1 and Phytophthora sp. 2. The most frequently isolated species, P. quercina, was very common on slopes susceptible to drought. It occurred in four different climatic zones and on six Quercus spp., suggesting that it is native to oaks. The second most common species, P. citricola, was separated into three subgroups: type C was recovered only in Anatolia, whereas A and B occurred only in the European part of Turkey. Phytophthora cinnamomi was recovered at one site only, and may not be involved in oak decline in Turkey. The other four species were recovered sporadically. On affected sites there was a significant association between deteriorating crown status and the presence of Phytophthora spp., particularly P. quercina. The occurrence of Phytophthora species was significantly influenced by soil pH. Stem inoculation tests on oak seedlings revealed that Q. petraea was the most susceptible species.

Phytophthora Species Associated with Cranberry Root Rot and Surface Irrigation Water in New Jersey.

A lupine baiting technique was used to detect the presence of Phytophthora spp. in several streams, irrigation reservoirs, and drainage canals used in cranberry cultivation. P. cinnamomi was found to be widely distributed throughout the study area in the southern New Jersey Pinelands, and was present both upstream and downstream of agricultural activities. A second species, identified as P. megasperma, was more restricted in its distribution and was never isolated from a water system that did not also contain P. cinnamomi. In a survey of commercial cranberry production, 80% of the acreage represented (approximately 37% of total New Jersey production area) was exposed to one or both Phytophthora spp. through application of infested water from irrigation reservoirs. Based on the widespread distribution of P. cinnamomi, it is likely that this pathogen was introduced many years prior to its discovery on cranberry in the 1980s, which corresponded to the adoption of overhead irrigation in the crop. There were slight differences between the two species in seasonal occurrence. The highest levels of P. cinnamomi were found during the summer months (July to August) whereas P. megasperma was highest during the spring (April to May) and fall (September to October) months.

Phytophthora species in oak forests of north-east France

Phytophthora species were surveyed from the end of 1997 through July 1998 in oak forests in NE France. Healthy (Amance) or declining (Illwald) forests were compared. The Phytophthora population in both was diverse and locally abundant. At least eight species were present at Amance and six at Illwald. At Amance Phytophthora species had a localized distribution in water and low-lying soils. At Illwald distribution was more uniform apparently due to flooding events. Most often recovered were P. citri- cola, P. gonapodyides and P. quercina. P. gonapodyides was ubiquitous in water and colonized leaf debris. P. quercina was widely distributed in soil but not abundant, and was found in sites that did not otherwise appear to favor Phytophthora. No correlation was detected between presence of Phytophthora in soil and health of trees. Unusual combinations of environmental factors may be

Using a Phytophthora- specific Immunoassay Kit to Diagnose Raspberry Phytophthora Root Rot

A commercially available serological assay kit (flow-through enzyme-linked immunosorbent assay, Phytophthora F kit) was compared to a culture-plate method for detecting Phytophthora spp. in apparently diseased (phytophthora root rot) and apparently healthy red raspberry (Rubus idaeus subsp. strigosus Michx.) plants. During 4 years of testing, 46 tests were conducted on apparently diseased roots. All diseased plants gave a strong positive reaction, a result indicating that Phytophthora spp. were present. Of the 46 plants that tested positive, Phytophthora spp. were recovered from all but one using a selective medium for Phytophthora and the culture-plate method. When the same test was conducted on 27 apparently healthy plants, all had a negative reaction for the presence of Phytophthora except one sample, which had a slight positive reaction. No Phytophthora spp. were isolated from any apparently healthy plants. Our results indicate that the serological test kit enables rapid, dependable, on-site diagnosis of raspberry phytophthora root rot.

TRANSMISSION OF PHYTOPHTHORA PARASITICA IN AN EBB AND FLOW SUBIRRIGATION SYSTEM

The root rot fungus Phytophthora parasitica is known to be very destructive to annual vinca (Catharanthus roseus). Phytophthora produces motile zoospores which swim freely in water, posing a special threat to crops grown using a recirculating water supply. Vinca were transplanted into 7 cm square pots containing a sphagnum peat:perlite medium. The medium was inoculated with the pathogen and plants were then placed in one row on each ebb and flow bench. Untreated vinca were placed in six additional rows on the benches. Separate benches were used to space plants at a distance of either 1 cm or 4 cm between pots. Plants were harvested biweekly over a six week period and tested for presence of Phytophthora. Cumulative results of root sampling revealed pathogen movement to 60% of untreated plants spaced at 1 cm, and to 30% of those spaced at 4 cm. Severe root injury (injury to root system ≥ 25%) was exhibited in 36% of the closer spaced plants, compared to 13% of those spaced at 4 cm. Phytophthora zoospores were detected in one tank which was used to irrigate plants spaced at 1 cm. Closer plant spacing enhanced the pathogen's ability to infect healthy plants.

Species, mating types and pathogenicity of Phytophthora distributed in citrus orchards in Taiwan

From July 1976 to May 1980 soils and diseased tissues of citrus were collected from 229 citrus orchards in all 15 counties on the island of Taiwan, and assayed for the presence of Phytophthora by baiting with discs of citrus leaves and plating on selective medium. Phytophthora species were isolated from 108 citrus orchards in 14 of 15 counties. Both A 1 and A 2 mating types of P. parasitica and P. palmivora were isolated only from central and southern counties most of which are in the tropical region. P. citricola and A 1 but not A 2 mating type of P. citrophthora and P. cinnamomi were isolated mainly from the subtropical region of the central and northern counties. All of them were pathogenic to sweet orange. P. heveae, P. insolita and an undescribed species of Phytophthora infrequently isolated from soils were non-pathogenic to sweet orange.

Baiting, pathogenicity, and distribution ofPhytophthora megaspermavar.sojaein New Zealand asparagus soils

Abstract Ten-day-old asparagus seedlings floated over flooded soil were used as a bait to isolate and identify Phytophthora megasperma var. sojae. The seedlings were injured before use by removing the seed remnants and pinching the radicle and plumule with forceps. P. megasperma var, sojae was baited from asparagus soils throughout the main production areas of New Zealand. From 22 asparagus fields, several isolates were more virulent than one from an area where there was low plant survival. There was no relationship between soil types, drainage, or plant survival and presence of Phytophthora in the fields surveyed. The possible use of this technique for estimating the soil inoculum concentration for quantitative assessment of the importance of Phytophthora is discussed.

Effect of mycorrhizal status of avocado seedlings on root rot caused byPhytophthora cinnamomi

The mycorrhizal fungusGlomus fasciculatus stimulated growth of avocado seedlings in the presence or absence ofPhytophthora cinnamomi. It appeared thatG. fasciculatus had no effect upon infection byP. cinnamomi or subsequent disease development.