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.

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.

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.

Resistance of Eucalyptus Spp. To Invasion by Phytophthora cinnamomi

1985 ◽  
Vol 33 (4) ◽  
pp. 409 ◽  
Author(s):  
JT Tippett ◽  
TC Hill ◽  
BL Shearer
Keyword(s):  
Phytophthora Cinnamomi ◽  
Field Studies ◽  
Laboratory Method ◽  
Lesion Development ◽  
Eucalyptus Marginata ◽  
Mine Site ◽  
Inoculation Methods ◽  
Close Proximity ◽  
Moderately Resistant

The resistance of 21 Eucalyptus spp. to Phytophthora cinnamomi Rands was assessed using wound inoculation methods. Aggressive lesions were observed in Eucalyptus marginata Uarrah) only. Lesion development was initially compared in E. marginata and E. calophylla (moderately resistant). Further comparisons were made of lesions in roots and stems of E. marginata, E. calophylla, E. patens and E. Wandoo growing in close proximity, in forest south-east of Perth. E. wandoo was the most resistant; the fungus failed to establish. As stems proved convenient for inoculation, summer stem inoculation trials were made to rate the resistance of 21 Eucalyptus spp. grown on a rehabilitated mine site. Lesions formed in the species of the Monocalyptus and Corymbia subgeneric groups but did not develop in species of the subgenus Symphyomyrtus. An alternative laboratory method of rating susceptibility of roots to invasion was also tested. Excised roots of three eucalypts, Banksia grandis and Xanthorrhoea preissii were inoculated and incubated at 25°C. Length of the root invaded was recorded; results were not well correlated with those from field studies.

Pathological anatomy of the bacterial phloem canker disease of Juglans regia

1970 ◽  
Vol 48 (6) ◽  
pp. 1055-1060 ◽  
Author(s):  
Norman W. Schaad ◽  
E. E. Wilson
Keyword(s):  
Juglans Regia ◽  
Leaf Tissue ◽  
Sieve Tube ◽  
Secondary Phloem ◽  
Subsequent Formation ◽  
Canker Disease ◽  
Secondary Stage ◽  
Parenchyma Cells ◽  
Sieve Tubes ◽  
Two Stages

Erwinia rubrifaciens Wilson, Zeitoun, and Fredrickson invades sieve tubes and parenchyma cells of the nonfunctional secondary phloem of Persian walnut, Juglans regia L. Because the sieve plate pores are great enough in diameter to allow passage of the bacteria, the nonfunctional phloem system provides an avenue along which the bacteria moves long distances up and down the bark. Functional phloem, on the other hand, does not exhibit symptoms of the disease nor is it found to contain the bacteria. Although the bacteria invade the ray parenchyma and move radially through these elements to the outer xylem, bacteria are not found to enter the xylem vessels. In culture, E. rubrifaciens produces long flexuous flagella. When taken from inoculated leaf tissue, however, it does not possess flagella. Hence, transport of bacteria from one sieve tube to another appears to be by apoplastic movement. Internal symptoms develop in two stages: a primary stage due to invasion of degenerate sieve tubes, and a secondary stage due to invasion of parenchyma cells and subsequent formation of wound callus. Pressure from wound callus induces vertical cracks in the bark. A slimy substance containing the bacteria exudes through the cracks to the bark surface, thereby allowing dispersion of the bacteria.

Control of experimental Phytophthora cinnamomi stem infections of Rhododendron, Leucadendron and Eucalyptus by dimethomorph, fosetyl-Al and metalaxyl

1990 ◽  
Vol 30 (1) ◽  
pp. 139 ◽  
Author(s):  
GC Marks ◽  
IW Smith
Keyword(s):  
Phytophthora Cinnamomi ◽  
Lesion Development ◽  
Potassium Dihydrogen ◽  
Foliar Sprays ◽  
Soil Drench ◽  
Test Conditions ◽  
Lesion Extension

The efficacy of dimethomorph, (E,Z)-4-[3- (4-chloropheny1)-3-(3,4-dimethoxypheny1)-1 -acryloyl] morpholine, in controlling Phytoplzthora cinnanionii stem infections of Rhododendron, Leucadendron and Eucalyptus was compared with that of fosetyl-Al, metalaxyl and phosphonate (potassium dihydrogen phosphonate) in a phytotron and greenhouse. The plants were inoculated on the stem and the effect of the fungicides applied either as foliar sprays or root drenches on lesion development was measured. The results showed that dimethomorph inhibited lesion extension when applied as a soil drench at rates of 0.6 and 1.2 mg a.i./mL. When used as a soil drench dimethomorph was about as effective as fosetyl-A1 and somewhat less effective than metalaxyl. When applied as foliar sprays, dimethomorph was ineffective and phosphonate was markedly superior to fosetyl-Al. Single applications of the fungicides tested were not able to kill P. cinnanzonzi in established infections within the duration of the experiment and under the test conditions which strongly favoured the fungus. Dimethomorph was slightly phytotoxic to Eucalyptus sieberi at dosages of 1.2 mg a.i./mL.

Adaptive and diagnostic significance of the bark of Stryphnodendron polyphyllum (Leguminosae) from the Cerrado

2017 ◽  
Vol 65 (2) ◽  
pp. 157 ◽  
Author(s):  
Paula C. B. Vergílio ◽  
Carmen R. Marcati
Keyword(s):  
Sensu Stricto ◽  
Plant Tissues ◽  
Gallery Forest ◽  
Ecological Studies ◽  
Secondary Phloem ◽  
Diagnostic Significance ◽  
Trade Off ◽  
Parenchyma Cells ◽  
Sieve Tubes ◽  
Diagnostic Traits

Bark comprises structurally and functionally complex plant tissues, providing a rich source of traits for taxonomic, phylogenetic, evolutionary and ecological studies. We compared bark traits of Stryphnodendron polyphyllum Mart. (Leguminosae) specimens growing in two Cerrado habitats (cerrado sensu stricto and gallery forest, being fire-prone and non-fire-prone habitats respectively), to determine which bark traits could be considered diagnostic and adaptively informative. We analysed the anatomy and thickness of the periderm, cortex, primary and secondary phloem, and also the bark histochemistry. Stryphnodendron polyphyllum is distinctive from other Stryphnodendron species reported in the literature, by the presence of a rhytidome, stratified lenticels and the non-collapsed parenchyma cells in the non-conducting phloem, which are, therefore, diagnostic traits for this species. Bark of S. polyphyllum showed a trade-off in resource allocation between the periderm and secondary phloem, whereas the thicker rhytidome seemed to be associated with fire protection in specimens from the fire-prone habitat, the wider sieve tubes in the thicker conducting secondary phloem indicated efficiency of photosynthate transport in the specimens from non-fire-prone habitat.

scholarly journals Influence of Low Oxygen Levels in Aeroponics Chambers on Eucalypt Roots Infected with Phytophthora cinnamomi

Plant Disease ◽  
1998 ◽  
Vol 82 (4) ◽  
pp. 368-373 ◽  
Author(s):  
Treena Burgess ◽  
Jen McComb ◽  
Giles Hardy ◽  
Ian Colquhoun
Keyword(s):  
Root Growth ◽  
Nutrient Solution ◽  
Phytophthora Cinnamomi ◽  
Disease Development ◽  
Optimal Conditions ◽  
Low Oxygen ◽  
Lesion Development ◽  
Eucalyptus Marginata ◽  
Root Extension ◽  
Fine Spray

Aeroponics root chambers were designed to evaluate the influence of low oxygen on disease development in clones of Eucalyptus marginata susceptible or resistant to infection by Phytophthora cinnamomi. Actively growing 7-month-old clones of E. marginata were transferred into the aeroponics chambers, into which a nutrient solution was delivered in a fine spray, providing optimal conditions for root growth. Prior to inoculation by zoospores of P. cinnamomi under normal oxygen, the roots were exposed to four treatments: (i) normal oxygen, approximately 8 mg of O2 liter-1; (ii) 6 days of hypoxia, 2 mg of O2 liter-1; (iii) anoxic acclimatization 2 days at 2 mg of O2 liter-1, 2 days at 1 mg of O2 liter-1, 2 days at 0.5 mg of O2 liter-1, 2 days at 2 mg of O2 liter-1, and 6 h at <0.05 mg of O2 liter-1; and (iv) 6 h of anoxia, <0.05 mg of O2 liter-1. Root extension during hypoxia was greatly reduced. Lesion development was least for roots exposed to hypoxia and greatest for roots exposed to anoxia for 6 h, suggesting increased resistance of E. marginata to P. cinnamomi following hypoxia.

Structure and seasonal development of secondary phloem of Juglans regia

1970 ◽  
Vol 48 (6) ◽  
pp. 1049-1053 ◽  
Author(s):  
Norman W. Schaad ◽  
E. E. Wilson
Keyword(s):  
Juglans Regia ◽  
Growth Increment ◽  
Seasonal Development ◽  
Secondary Phloem ◽  
Early Season ◽  
Central California ◽  
Late Season ◽  
Growth Increments ◽  
Parenchyma Cells ◽  
Sieve Tubes

In Persian walnut (Juglans regia L.), as in other deciduous dicotyledonous trees, a small (0.5 mm) amount of secondary phloem is functional for only one season and a large amount is nonfunctional. In 1968 in Central California the cycle of phloem development began in late February and ended sometime before mid-October. The phloem annual ring was composed of distinctive tangential bands, allowing easy distinction of seasonal growth increments. Each growth increment could be divided into early- and late-season tissue. Early-season phloem, composed principally of large sieve tubes, was separated from late-season phloem by a band of fibers. The late-season phloem was composed of a mixture of narrow sieve tubes, parenchyma cells, and, occasionally, an incomplete tangential band of fibers. The annual rings were not crushed except for the early-season phloem, which was somewhat compressed by growth of the woody cylinder. The bark of walnut becomes thicker with age because of this and the enlargement of parenchyma cells.

Elemental Analysis of Phloem Tissue in Lemna Minor Root Tips

1980 ◽  
Vol 38 ◽  
pp. 798-799
Author(s):  
Patrick Echlin ◽  
Thomas Hayes ◽  
Clifford Lai ◽  
Greg Hook
Keyword(s):  
Vascular Tissue ◽  
Lemna Minor ◽  
Atomic Weight ◽  
Companion Cell ◽  
Root Tips ◽  
Phloem Tissue ◽  
Cell Stage ◽  
Phloem Parenchyma ◽  
Parenchyma Cells ◽  
Xylem Element

Studies (1—4) have shown that it is possible to distinguish different stages of phloem tissue differentiation in the developing roots of Lemna minor by examination in the transmission, scanning, and optical microscopes. A disorganized meristem, immediately behind the root-cap, gives rise to the vascular tissue, which consists of single central xylem element surrounded by a ring of phloem parenchyma cells. This ring of cells is first seen at the 4-5 cell stage, but increases to as many as 11 cells by repeated radial anticlinal divisions. At some point, usually at or shortly after the 8 cell stage, two phloem parenchyma cells located opposite each other on the ring of cells, undergo an unsynchronized, periclinal division to give rise to the sieve element and companion cell. Because of the limited number of cells involved, this developmental sequence offers a relatively simple system in which some of the factors underlying cell division and differentiation may be investigated, including the distribution of diffusible low atomic weight elements within individual cells of the phloem tissue.

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.

Sign in / Sign up

Export Citation Format

Share Document