Surface Root System of Eucalyptus marginata Sm.: Anatomy of Non-Mycorrhizal Roots.

1981 ◽  
Vol 29 (5) ◽  
pp. 565 ◽  
Author(s):  
B Dell ◽  
IM Wallace
Keyword(s):  
Root System ◽  
Phytophthora Cinnamomi ◽  
Epidermal Cells ◽  
Outer Cortex ◽  
Eucalyptus Marginata ◽  
Mycorrhizal Roots

The anatomy of surface feeder roots of Eucalyptus marginata was investigated. Two types of long roots were recognized: (a) those with thick-walled epidermal cells, and (b) those with a lignified outer cortex. The hypodermis of short roots was often suberized and the inner layers of the cortex had lignified secondary walls. The occurrence of lignified and suberized layers is discussed in relation to possible infection by Phytophthora cinnamomi.

Structure of the Surface Root System of Eucalyptus Marginata Sm. And Its Infection by Phytophthora Cinnamomi Rands

1981 ◽  
Vol 29 (1) ◽  
pp. 49 ◽  
Author(s):  
SR Shea ◽  
B Dell
Keyword(s):  
Root System ◽  
Phytophthora Cinnamomi ◽  
Lateral Roots ◽  
High Density ◽  
Summer Drought ◽  
Eucalyptus Marginata ◽  
Mycorrhizal Roots ◽  
Small N ◽  
A Site

The structure of the surface root system of jarrah (Eucalyptus marginata) trees was examined on a number of freely drained upland sites with different fire and management histories. The roots typically occurred in patches but in some stands formed extensive sheets. On excavation; this surface root system was composed of pads ranging in size from 10 cm to 1-3 m in diameter and c. 5 cm thick. The pads consist of short roots 1-3 mm long (which commonly form dense clusters around lateritic pebbles) which arise from small (n - 1)*th order laterals 0.5-1.5 cm long connected to (n - 2)*th order laterals 2-5 cm long and up to 0.7 mm in diameter. Mycorrhizal roots were common throughout the surface root pads. During the summer drought many of the short lateral roots die but the main framework of the roots of the surface pads is perennial. Following rains or irrigation, new, short lateral roots form rapidly from the framework of roots in the surface pads. Phytophthora cinnamomi was consistently recovered from short lateral roots and from the perennial roots (n - 1, n - 2) which form the framework of the root pads at a site in diseased forest where a high density of P. cinnamomi had been induced in the soil by irrigation. We hypothesize that the destruction of some of the perennial components of the root pads could explain why P. cinnamonzi can cause the decline and death of jarrah in an environment only marginally favourable for the fungus.

Periodicity of Fine Root Growth in Jarrah (Eucalyptus marginata Donn Ex Sm.)

1983 ◽  
Vol 31 (3) ◽  
pp. 247 ◽  
Author(s):  
B Dell ◽  
IM Wallace
Keyword(s):  
Root Growth ◽  
Fine Root ◽  
Phytophthora Cinnamomi ◽  
Late Summer ◽  
Late Winter ◽  
Summer Drought ◽  
Root Pathogen ◽  
Eucalyptus Marginata ◽  
Fine Root Growth ◽  
Mycorrhizal Roots

The timing of new surface root growth in jarrah (Eucalyptus marginata) was followed for a 15-month period in the field. The periodicity of new root growth was similar for long roots, non-mycorrhizal and mycorrhizal root clusters. Root growth was initiated during two peak periods in spring (September-October) and following autumn rain (May-June). Little new root activity was recorded in late winter (August) or during summer drought. Rapid root growth occurred within 2 days of a storm (47 mm rain) in February. In addition, short roots formed after very light showers of rain (<5 mm) in late summer. Much of the framework for fine feeder roots was built up after autumn rain. In contrast to new long root growth which was equally spread between spring and late autumn, the majority of new mycorrhizal roots were produced from May to July. Root growth ceased when warm surface soils dried out and commenced when the soils were moist after rain. Much of the new root growth in jarrah occurred when the root pathogen Phytophthora cinnamomi was active in the soil.

The Microflora of Unsuberized Roots of Eucalyptus calophylla R.Br. And Eucalyptus marginata Donn ex Sm. Seedlings Grown in Soil Suppressive and Conducive to Phytophthora cinnamomi Rands. II. Mycorrhizal Roots and Associated Microflora

1979 ◽  
Vol 27 (3) ◽  
pp. 255 ◽  
Author(s):  
N Malajczuk
Keyword(s):  
Electron Microscope ◽  
Mycorrhizal Fungi ◽  
Electron Microscope Study ◽  
Phytophthora Cinnamomi ◽  
Differential Susceptibility ◽  
Eucalyptus Marginata ◽  
Different Types ◽  
Mycorrhizal Roots ◽  
Conducive Soil ◽  
Stimulation Of

Mycorrhizal root development was more frequent in Eucalyptus calophylla than in Eucalyptus marginata in field and pot samples of soil conductive to Phytophthora cinnamomi. Morphologically different types of mycorrhizas were also observed in the two species, which suggested preferential stimulation of mycorrhizal fungi, and this was supported by cross-inoculation experiments with fungal symbionts isolated from mycorrhizal roots and from basidiomycete sporophores. Isolation of bacteria from mycorrhizal roots, and low power electron microscope study of these roots, indicated a significant mycorrhizosphere effect. Populations of bacteria varied quantitatively and qualitatively for different mycorrhizal roots. In suppressive soil few mycorrhizal roots were formed in either species. It is suggested that the different types of mycorrhizal roots and their associated bacterial microflora may contribute to differential susceptibility of the two species to infection by P. cinnamomi in conducive soil.

Infection by Phytophthora cinnamomi Rands of Roots of Eucalyptus calophylla R.Br. and Eucalyptus marginata Donn. ex Sm

1977 ◽  
Vol 25 (5) ◽  
pp. 483 ◽  
Author(s):  
N Malajczuk ◽  
AJ Mccomb ◽  
CA Parker
Keyword(s):  
Phytophthora Cinnamomi ◽  
Light And Electron Microscopy ◽  
Inhibitory Effect ◽  
Lateritic Soil ◽  
Root Damage ◽  
Mature Trees ◽  
Cortical Cells ◽  
Eucalyptus Marginata ◽  
Seedling Roots ◽  
Loam Soil

On lateritic podzolic soils in Western Australia Eucalyptus calophylla is resistant to Phytophthora cinnamomi whereas Eucalyptus marginata is susceptible and eventually killed by the pathogen. On loam soils both eucalypts are resistant. Possible mechanisms for resistance of E. calophylla in lateritic soil and the inhibitory action of loam soils were investigated. Aseptically raised eucalypt seedlings succumbed to infection in liquid culture tubes. The mechanism of infection was compared by light and electron microscopy which showed similar fungal invasion and penetration into roots of both eucalypt species. Vegetative hyphae initially penetrated intercellularly and proliferated rapidly within cortical and stelar tissue. Intracellular invasion of these tissues occurred 48hr after initial infection through dissolution of the host cell wall. Chlamydospores were formed within a number of cortical cells. Unsuberized roots of mature trees produced aseptically showed reactions to invasion similar to those of the eucalypt seedling roots. Suberized roots were not invaded. The addition of small quantities of lateritic soil to sterile sand so as to introduce soil micro-organisms without altering the chemical and physical status of the sand, and subsequent inoculation of the sand with P.cinnamomi, resulted in a reduction of root damage on both eucalypts when compared with seedlings raised in sterile sand. Roots of E.calophylla were less severely damaged than those of E.marginata. The addition of small quantities of loam soil significantly reduced root damage in seedlings of both species. These results parallel both pot experiments and field observations, and suggest that microorganisms of the rhizosphere may be an important factor in the resistance of E.calophylla to infection, and in the inhibitory effect of loam soil on P.cinnamomi.

scholarly journals Re-evaluation of Phytophthora Species Isolated During 30 Years of Vegetation Health Surveys in Western Australia Using Molecular Techniques

Plant Disease ◽  
2009 ◽  
Vol 93 (3) ◽  
pp. 215-223 ◽  
Author(s):  
Treena I. Burgess ◽  
Janet L. Webster ◽  
Juanita A. Ciampini ◽  
Diane White ◽  
Giles E. StJ. Hardy ◽  
...  
Keyword(s):  
New Taxa ◽  
Western Australia ◽  
Dna Sequences ◽  
Phytophthora Cinnamomi ◽  
Sequence Data ◽  
Phytophthora Species ◽  
Molecular Techniques ◽  
Similar Species ◽  
Eucalyptus Marginata ◽  
Similar Morphology

For 30 years, large-scale aerial photography has been used to map the extent of Phytophthora dieback disease in native forests in the southwest of Western Australia, with validation of the observations involving routine testing of soil and root samples for the presence of Phytophthora cinnamomi. In addition to P. cinnamomi, six morpho-species have been identified using this technique: P. citricola, P. megasperma, P. cryptogea, P. drechsleri, P. nicotianae, and P. boehmeriae. In recent years, many new Phytophthora species have been described worldwide, often with similar morphology to existing species; thus, as many of the isolates collected in Western Australia have been difficult to identify based on morphology, molecular identification of the morpho-species is required. Based on amplification of the internal transcribed spacer (ITS) region of the rDNA gene, sequence data of more than 230 isolates were compared with those of existing species and undescribed taxa. P. inundata, P. asparagi, P. taxon PgChlamydo, P. taxon personii, and P. taxon niederhauserii were identified based on sequence data. Phylogenetic analysis revealed that nine potentially new and undescribed taxa can be distinguished. Several of the new taxa are morphologically indistinguishable from species such as P. citricola, P. drechsleri, and P. megasperma. In some cases, the new taxa are closely related to species with similar morphology (e.g., P.sp.4 and P. citricola). However, the DNA sequences of other new taxa such as P.sp.3 and P.sp.9 show that they are not closely related to morphologically similar species P. drechsleri and P. megasperma, respectively. Most of the new taxa have been associated with dying Banksia spp., while P.sp.2 and P.sp.4 have also been isolated from dying Eucalyptus marginata (jarrah). Some taxa (P.sp.3, 6, and 7) appear to have limited distribution, while others like P.sp.4 are widespread.

Pathogenic Variability in Australian Isolates of Phytophthora cinnamomi

1993 ◽  
Vol 41 (6) ◽  
pp. 721 ◽  
Author(s):  
MJ Dudzinski ◽  
KM Old ◽  
RJ Gibbs
Keyword(s):  
Phytophthora Cinnamomi ◽  
Growth Period ◽  
Species Variation ◽  
Eucalyptus Marginata ◽  
Disease Symptoms ◽  
Horticultural Crops ◽  
Damage Reduction ◽  
Single Clone ◽  
Pathogenic Variability ◽  
Stable Characteristic

Forty-two isolates of Phytophthora cinnamomi were obtained from native vegetation and horticultural crops within Australia. They represented a broad spectrum of geographical and host origins, both mating types, and all identified Australian isozyme genotypes. All isolates were tested for their pathogenicity to a single clone of Eucalyptus marginata by inoculation of soil in which plants were growing. Differences in pathogenicity were expressed as extent of root damage, reduction of plant growth, period to first visible disease symptoms and time to plant death. Significant variation between isolates was detected. Pathogenicity was unrelated to mating type and isozyme properties. A subset of these 42 isolates encompassing a range of virulence gave generally consistent rankings for pathogenicity variates when re-inoculated twice into plants derived from the original clone. This suggests that pathogenicity is a relatively stable characteristic. Detection of differences in susceptibility to P. cinnamomi between three selected E. marginata. clones was influenced by the pathogenicity of isolates. Only the more pathogenic isolates were useful in this regard. Seedling stems of five eucalypt species were inoculated with virulent and less virulent isolates of P. cinnamomi. This method detected variation in both pathogenicity in the fungus and susceptibility in the host species. Variation in pathogenicity within Australian populations of P. cinnamomi should be taken into account by the choice of isolates of proven virulence when selecting for resistance in trees and other woody hosts.

Distribution of Phytophthora cinnamomi in the northern jarrah (Eucalyptus marginata) forest of Western Australia in relation to dieback age and topography

2002 ◽  
Vol 50 (1) ◽  
pp. 107 ◽  
Author(s):  
K. L. McDougall ◽  
G. E. St J. Hardy ◽  
R. J. Hobbs
Keyword(s):  
Spatial Distribution ◽  
Western Australia ◽  
Aerial Photography ◽  
Phytophthora Cinnamomi ◽  
Ex Situ ◽  
Patchy Distribution ◽  
Jarrah Forest ◽  
Eucalyptus Marginata ◽  
Almost All

The spatial distribution of Phytophthora cinnamomi Rands at seven dieback sites in the jarrah (Eucalyptus marginata Donn. ex Smith) forest of Western Australia was determined by the following two baiting techniques: in situ baiting with live Banksia grandis Willd. seedlings and ex situ baiting of sampled soil and root material. Four areas within each site were sampled, reflecting dieback age and position in the landscape. Approximate dieback ages of 50, 20 and 5 years were determined by aerial photography. The 50-year-old age class was divided into wet valley floor and dry gravelly slope. Phytophthora cinnamomi was recovered most frequently from the 5-year-old (dieback fronts) and wet 50-year-old areas by both baiting techniques. It was recovered from more than twice as many areas and about five times as many samples when in situ B. grandis baits were used compared with ex situ soil and root baiting. Almost all recoveries from in situ baits were made between October and December. From both methods, it appears that P. cinnamomi has a patchy distribution within dieback sites in the northern jarrah forest. It is easily detected only on dieback fronts and wet valley floors. On dry gravelly sites affected 20 years or more ago, P. cinnamomi is rare and may even be absent at some sites. This makes confident detection of the pathogen difficult. In situ baiting at least allows a temporal component to the sampling and will be a useful method of detection in areas where P. cinnamomi is rare or transient.

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