Inhibition of Phytophthora Cinnamomi Lesion Development in Eucalyptus Sieberi Through Moisture Stress.

1985 ◽  
Vol 14 (3) ◽  
pp. 55 ◽  
Author(s):  
IW Smith ◽  
GC Marks
Keyword(s):  
Phytophthora Cinnamomi ◽  
Moisture Stress ◽  
Lesion Development

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.

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.

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 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.

Quantifying the value proposition for white clover persistence on a New Zealand summer-dry hill-country farm

2020 ◽  
Vol 82 ◽  
pp. 199-209
Author(s):  
Mike B. Dodd ◽  
Katherine N. Tozer ◽  
Iris Vogeler ◽  
Rose Greenfield ◽  
David R. Stevens ◽  
...  
Keyword(s):  
White Clover ◽  
Net Present Value ◽  
Moisture Stress ◽  
Simulation Modelling ◽  
Low Fertility ◽  
System Modelling ◽  
Value Proposition ◽  
Hill Country ◽  
The North ◽  
Farm System

The improvement in forage quality and quantity of summer-dry hill country pasture resulting from the introduction of clover is well recognised. However, ensuring the persistence of the commonly availablecultivars is challenging, in the face of seasonal moisture stress, intensive grazing, competition from established well-adapted pasture species, low soil fertility and low soil pH – conditions typical of the East Coast of the North Island. Here we quantify the value proposition associated with the introduction of white clover into a case study on a Gisborne sheep and beef farm, using a six-step process. A topographically explicit approach is taken, using an understanding of the underlying spatial variability, based on a combination of soil and pasture measurements, APSIM simulation modelling of pasture growth and farm system modelling of enterprise performance. We show that from a baseline of a typical low-fertility, diverse species hill country pasture, white clover introduction can increase spring and summer forage consumption by 17%, enabling inclusion of an additional 6-month bull finishing enterprise generating a 32% greater carcass weight production and leading to a 49% improvement in farm system EBIT. This represents a positive net present value of over $360,000 for the original investment in white clover establishment into existing pastures.

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.

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