scholarly journals The development and characteristics of periderm and rhytidome in Eucalyptus marginata

2009 ◽  
Vol 57 (3) ◽  
pp. 221 ◽  
Author(s):  
E. O'Gara ◽  
K. Howard ◽  
I. J. Colquhoun ◽  
B. Dell ◽  
J. McComb ◽  
...  
Keyword(s):  
Phytophthora Cinnamomi ◽  
Single Type ◽  
Secondary Phloem ◽  
Phloem Tissue ◽  
Axillary Shoots ◽  
Eucalyptus Marginata ◽  
Thin Walled ◽  
Periderm Formation ◽  
Shoot Emergence ◽  
Internal Production

To understand the pathway used by Phytophthora cinnamomi Rands to penetrate the bark of jarrah, the present study describes unwounded periderm and rhytidome development. Periderm formation is described from its initiation in 4-week-old seedlings to the formation of rhytidome in saplings. Periderm in young seedlings consists of a single type of phellem, namely thin-walled suberised cells. In older seedlings where multiple layers of periderm have formed, layers of thick-walled lignified phellem cells in compacted bands alternate with thin-walled suberised cells. Rhytidome formation in older lignotuberous seedlings and in sapling jarrah occurs through the isolation of secondary phloem by periderm. The rhytidome consists of expanded and partially disintegrated secondary phloem tissue sandwiched between layers of phellem cells. Localised periderm formation beneath stomata results in the formation of lenticels, which are ephemeral features. Superficial periderms occur at sites of leaf and shoot abscission, and of lateral shoot emergence. Concealed axillary shoots lack cuticle on emergence. As the trees age, the internal production of lignified and suberised periderm and rhytidome results in an impenetrable barrier to invasion by P. cinnamomi. However, external sites including lenticels and leaf and shoot abscission and emergence areas, all provide points of ingress in unwounded stems.

Development of Lesions Caused by Phytophthora cinnamomi in the Secondary Phloem of Eucalyptus marginata

1983 ◽  
Vol 31 (2) ◽  
pp. 197 ◽  
Author(s):  
JT Tippett ◽  
SR Shea ◽  
TC Hill ◽  
BL Shearer
Keyword(s):  
Phytophthora Cinnamomi ◽  
Wall Material ◽  
Secondary Phloem ◽  
Phloem Tissue ◽  
Lesion Development ◽  
Eucalyptus Marginata ◽  
Parenchyma Cells ◽  
Lesion Extension ◽  
Sieve Tubes ◽  
Intermittent Activity

Phytophthora cinnamomi Rands invaded the secondary phloem of inoculated roots and stems of Eucalyptus marginata Donn. ex Sm. For 12 months after inoculation, lesion development was followed in coppice stems. As lesions extended, the phloem or inner bark became discoloured due to the accumulation and oxidation of polyphenols. Starch also was deposited in the necrotic phloem. The primary wall material of sieve tubes and associated parenchyma was hydrolysed but fibres were unaffected. Fungal spread was most rapid in the outer phloem tissue where cells were loosely packed and characterized by many expanded parenchyma cells. Fungal invasion of the inner phloem resulted in cambial kill. Roots were not girdled by the fungus in the first 12 months after inoculation, as they resisted tangential spread of the fungus more effectively than coppice stems. Lesions were contained once necrophylactic (wound) periderms formed in the bark. Although the necrophylactic periderm restricted fungal activity during winter and spring, the fungus did 'break-out' in summer and invade new areas of phloem in 50% of the inoculated roots and stems. Summer lesion extension was usually associated with kino production: a series of kino veins reflected the intermittent activity of the fungus. Once the characteristics of typical lesions were recognized, interpretation of root lesions resulting from natural infections was possible.

Comparative Behaviour of Phytophthora Species in the Secondary Phloem of Stems and Excised Roots of Banksia grandis and Eucalyptus marginata

1987 ◽  
Vol 35 (1) ◽  
pp. 103 ◽  
Author(s):  
BL Shearer ◽  
BJ Michaelsen ◽  
HJ Warren
Keyword(s):  
Response Curve ◽  
Growth Response ◽  
Phytophthora Cinnamomi ◽  
Similar Rate ◽  
Phytophthora Species ◽  
Phytophthora Cactorum ◽  
Secondary Phloem ◽  
Eucalyptus Marginata ◽  
Temperature Growth ◽  
Rates Of Growth

We inoculated excised roots under controlled laboratory conditions and inoculated stems in the field to compare the behaviour of Phytophthora cactorum, P. cambivora, P. cinnamomi A2, P. citricola, P. cryptogea A1 and A2, P. megasperma var. sojae and P. nicotianae var. parasitica in the secondary phloem of Banksia grandis and Eucalyptus marginata. Most of the Phytophthora species grew in excised roots of E. marginata at a similar rate. Of the Phytophthora species with similar rates of growth in E. marginata roots, P. cinnamomi was the only species that consistently grew faster in excised roots of B. grandis than in roots of E. marginata. The growth of the Phytophthora species in excised roots under controlled conditions was significantly correlated with growth in intact stems in the field. Over a range of temperatures between 10 and 25°C, the slope of the temperature-growth response curve for P. cinnamomi in excised roots of B. grandis was greater than that for P. citricola. At temperatures between 27 and 31°C, growth rates of P. cinnarnomi in excised roots of B. grandis were 1 cm or more per day compared with 0.3 cm per day for P. citricola. Differences in growth rate in the roots of the widespread understorey species B. grandis can be important to the epidemiology of a Phytophthora species in the E. marginata forest. Phytophthora cinnamomi with fast rates of growth in roots of B. grandis is more likely to have inoculum in the vicinity of major roots of E. marginata than are Phytophthora species with slow rates of growth.

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.

Site and Seasonal Effects on Susceptibility of Eucalyptus marginata to Phytophthora cinnamomi

1989 ◽  
Vol 37 (6) ◽  
pp. 481 ◽  
Author(s):  
JT Tippett ◽  
JF Mcgrath ◽  
TC Hill
Keyword(s):  
Phytophthora Cinnamomi ◽  
Water Status ◽  
Fungal Growth ◽  
Soil Nutrient ◽  
Nutrient Status ◽  
Seasonal Effects ◽  
Soluble Carbohydrate ◽  
Eucalyptus Marginata ◽  
Relative Water ◽  
Stem Lesions

Susceptibility of Eucalyptus marginata stems and roots to invasion by Phytophthora cinnamomi was compared at four sites in the northern jarrah forest and reasons for differences in tree susceptibility were sought. The sites were located in both the low (750 mm year -I ) and high (1 100 mm year -1) rainfall zones and differed in understorey composition and soil nutrient status. Stems were inoculated at monthly intervals between October 1983 and April 1984. Measurement of stem lesions induced by inoculation showed that rate of fungal growth in trees at all sites generally increased during the October-December (1983) period. During February and March (1984) there was a large difference in the susceptibility of stems and roots in low-rainfall zone sites compared with those in high-rainfall zone sites. Roots inoculated during February at three of the four sites showed the same relative susceptibilities as stems inoculated one week later. Mean relative water contents (RWC) of the phloem (inner bark) were used to compare the water status of the saplings at the four sites and the observed inhibition of the fungus in the sapling stems and roots at the driest sites, coincided with the months when phloem RWC values were at their lowest. Phloem was also sampled from pole-sized trees at the four sites and seasonal changes in RWC values, soluble carbohydrate concentrations and phenols were monitored for 12 months. Soluble carbohydrate concentrations in the phloem of some of the saplings inoculated at each site were also determined. Concentrations of carbohydrates and phenols did change seasonally and differed between sites but no evidence was found to suggest that they had a direct effect on fungal growth.

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