Fungus Phytophthora Cinnamomi Research Articles

Monoclonal antibodies to isolate-, species-, and genus-specific components on the surface of zoospores and cysts of the fungus Phytophthora cinnamomi

Monoclonal antibodies have been raised to components on the surface of glutaraldehyde-fixed zoospores and cysts of an isolate of the pathogenic fungus Phytophthora cinnamomi. Hybridoma supernatants were screened using an immunofluorescence assay, and of 35 cell lines producing antibodies that reacted with the P. cinnamomi cells, 10 have been selected and their specificities examined in detail. The monoclonal antibodies were found to possess a valuable spectrum of taxonomic specificities, and have revealed, for the first time, the presence of isolate-specific antigens on the surface of P. cinnamomi cells. The monoclonal antibodies were tested against six isolates of P. cinnamomi, six species of Phytophthora, and three species of Pythium. In addition to the isolate-specific monoclonal antibodies, species-specific and genus-specific markers which are unambiguous in tests conducted so far have been obtained. The monoclonal antibodies have also revealed the presence of spatially restricted antigens on the surface of the zoospores. Some of these segregated antigens are species-specific and others are more general, occurring in all Phytophthora and Pythium species examined. All of the monoclonal antibodies promise to be of great assistance in investigations of the biology and taxonomy of P. cinnamomi. The methods described should be readily applicable to studies of other fungal pathogens.

Early regrowth in rehabilitated bauxite minesites as breeding habitat for birds in the jarrah forest of south-western Australia

Summary A survey was undertaken lo assess 5 to 10-year-old rehabilitated bauxite minesite vegetation as suitable habitat for birds while breeding during spring in the jarrah (Eucalyptus marginata) and marri (E. calophylla) forest at Jarrahdale. Western Australia. The minesites had been rehabilitated and revegetated with local shrub species and a mix of local and eastern eucalypts resistant to the root rot fungus Phytophthora cinnamomi. Twenty-one species of birds used the former minesites for foraging or hunting while breeding; twelve of these were found nesting or rearing fledglings in the revegetation. Among the breeders were four understorey dwelling species which were otherwise uncommon in surrounding upland forest or (in two cases) confined in stream zone undergrowth. Total densities of all pairs or groups breeding in minesites were similar to those in nearby forest. Breeding territories often spanned areas of both minesite and forest around the edge of pits. Eleven other species were found breeding ...

The detection of monoclonal antibodies specific for surface components on zoospores and cysts of Phytophthora cinnamomi

Immunofluorescent and enzyme-linked immunosorbent screening methods have been used to detect monoclonal antibodies (MAbs) raised to surface components of zoospores and cysts of the fungus Phytophthora cinnamomi. The efficacy of the techniques was tested with a view to meeting the following criteria: (1) a capacity to detect spatially, developmentally, and taxonomically restricted antigens; and (2) a capacity to handle the testing of large numbers of supernatants during hybridoma screening. Both types of assay detected cell lines producing antibodies to P. cinnamomi cells, but one immunofluorescent method utilizing multiwell microscope slides proved to be superior to the other techniques. We were thus able to detect MAbs which (a) bound only to zoospores or to cysts of P. cinnamomi but not to both, and (b) bound only to restricted parts of the zoospore surface.

Studies on the cell surface of zoospores and cysts of the fungus Phytophthora cinnamomi: nature of the surface saccharides as determined by quantitative lectin binding studies.

The nature of the surface saccharides of zoospores, "partially encysted zoospores" and cysts of the root-rotting fungus Phytophthora cinnamomi, has been examined by quantitative lectin binding studies. Zoospores bound concanavalin A (Con A), but did not bind any of a variety of other lectins tested. In contrast, both cysts and "partially encysted zoospores" bound soybean agglutinin (SBA) as well as Con A. This indicates that accessible alpha-D-glucosyl/alpha-D-mannosyl-containing glycoconjugates predominate at the zoospore surface, whereas both alpha-D-glucosyl/alpha-D-mannosyl and galactosyl and/or N-acetyl-D-galactosaminosyl residues are accessible at the surface of cysts and "partially encysted zoospores." Neither Ulex europeus lectin nor wheat germ agglutinin (WGA) bound to any of the three cell preparations, indicating the absence of accessible alpha-L-fucosyl and N-acetyl-D-glucosaminosyl residues.

Studies on the cell surface of zoospores and cysts of the fungus Phytophthora cinnamomi: The influence of fixation on patterns of lectin binding.

The study of the surface properties of zoospores and cysts of the fungus Phytophthora cinnamomi required a fixation regime that would preserve the cells adequately and not interfere with binding and detection of probes on the cell surface. When they were fixed in 4% formaldehyde (F), specific binding of concanavalin A-fluorescein isothiocyanate and rhodamine-labeled soybean agglutinin was obtained. However, electron microscopy showed that preservation was so poor that intracellular binding sites had become exposed. By contrast glutaraldehyde (G), even at concentrations as low as 0.05%, gave good preservation of the zoospores but induced high levels of nonspecific fluorescence, making its use impractical for studies using fluorescent probes. Addition of 1-4% F to 0.05-0.8% G reduced the level of G-induced fluorescence while not diminishing the quality of ultrastructural preservation. This effect was evaluated quantitatively and an optimum fixation regime for the fungal cells, namely, 0.2% G and 2-4% F in 50 mM PIPES buffer, was determined. This combined fixative facilities correlated fluorescence and ultrastructural labeling with lectins and immunocytochemical probes.

Rate of Growth of Banksia grandis Willd. (Proteaceae) in Western Australian Forest

Banksia grandis is a major understorey component of the jarrah forest and is a refuge of the soil fungus Phytophthora cinnamomi which kills many native plant species and threatens timber production. This paper presents data on the rate of growth of the lignotuber, shoot and stem of B. grandis. Length of the seedling lignotuber increased 0.23 cm year-1 over 3 years, that of saplings and trees increased 0.44 cm yea-1. The period for a seedling to attain 1.3 m height was calculated as c. 15 years. Short-term diameter increment of trees averaged 0.19-0.27 cm year-1, indicating that diameter at breast height of 20 cm should be attained in c. 80-100 years; this estimate is also supported by direct and indirect long- term data. Watering, shading and spraying with insecticide had no significant influence on height growth of saplings. Four years after fire, sapling coppice from large lignotubers nearly attained the height of the plant before the fire. Trees, but not saplings, grew faster after logging of forest. The significance of these growth rates is discussed in relation to two methods (mechanical removal, moderate-intensity fire) proposed to reduce the abundance of B. grandis in the jarrah forest.

The Effect of Cations on Zoospores of the Fungus Phytophthora cinnamomi

Swimming zoospores of the fungus Phytophthora cinnamomi exposed to a range of ions were much more sensitive to cations than anions. One cation, Ca2+, induced zoospores to encyst and subsequently germinate, but most cations induced encystment only and were toxic at higher concentrations. In general, the sensitivity of zoospores to a cation increased with its charge density. At 0·3 μm, La3+ reduced the viability of a zoospore population to 50%, while Fe3+ (20 μm) and Mn2+ (50 μm) induced encystment with only a slight decrease in viability. The other divalent and monovalent cations tested (Mg2+, Ca2+, Ba2+, Li+, Na+, K+, Cs+, NH4 +) were effective in inducing encystment or reducing viability at higher concentrations. Each ion showed a distinctive concentration–response curve. Only F−and CH3COO−among the anions tested (Cl−, NO3 −, F−, H2PO4 2-, SO4 2−, CH3COO−) had any effect on zoospores, and at 20 mm (pH 6·0) they reduced viability. The cysts (cystospores) of the fungus were generally less sensitive to cations than were swimming zoospores, and only Cs+and K+(50 mm) reduced viability to the same extent in each population. Both zoospores and cysts of this fungus had a broad tolerance to pH and temperature, but cysts were more resistant to low temperatures than were motile zoospores.

Volatile Components From the Roots of Acacia pulchella R.br. And Their Effect on Phytophthora cinnamomi Rands

A steam-volatile extractive of the roots of Acacia pulchella has been shown to inhibit the growth of the pathogenic fungus Phytophthora cinnamomi. The extractive restricted mycelial growth, suppressed sporangial production and germination and reduced zoospore germination of the fungus when grown axenically. Examination by gas chromatography of the headspace vapours of whole roots indicated the presence of 270 organic components. Of these, 78 components were identified and an additional 56 tentatively identified by combined gas chromatography and mass spectrometry. The major volatile compounds identified were 2- and 3-methylbutanol, hexanol, pentanal, 2- and 3-methylbutanal, 4- methylacetophenone and carbon disulfide. The antifungal activity of the root volatiles and the resistance of A . Pulchella to invasion by P. cinnamomi are discussed.

Saponins of Acacia pulchella

Acid hydrolysis of the saponins isolated from the roots of Acacia pulchella R. Br, gave two triterpene aglycones of known structure and a mixture of monosaccharides. The triterpenes have been identifiedas oleanolic acid (1) and echinocystic acid (3). The monosaccharide mixture contained glucose, galactose, arabinose, xylose and rhamnose. Preliminary results of the effects of the saponin fraction upon the pathogenic fungus Phytophthora cinnamomi Rands. are reported.

Recovery of Phytophthora cinnamomi from native vegetation in a remote area of new South Wales

Soil samples were taken in native forest areas of south-eastern New South Wales, and were examined for the presence of the root-rot fungus Phytophthora cinnamomi by the lupin-baiting technique. The fungus was recovered from areas with a history of disturbance by agriculture and forestry, and also from remote, undisturbed areas. In the disturbed areas the fungus was more readily recovered from diseased than non-diseased sites, and it seems likely that it is totally or partially responsible for disease induction. The results of this survey suggest that P. cinnamomi is indigenous to the region studied, and that it has been a significant factor in the development of the present distribution of certain native plants.

Oospore Production in Phytophthora Cinnamomi in the Presence of Trichoderma Koningii

The soil-borne fungus Phytophthora cinnamomi Rands is a particularly impor-tant pathogen in Australia because of its consistent association with root-rot disease of a wide variety of exotic and native plant species. It was thought originally to have been introduced from south-east Asia (Crandall and Gravatt 1967), but evidence recently obtained (Pratt, Heather, and Shepherd, unpublished data), suggests that it may be indigenous to eastern Australia and may have been partly instrumental in determining the distribution of certain susceptible species, particularly Eucalyptu8 spp.

Transcontinental Occurrence of Al and A2 Strains of Phytophthora Cinnamomi in Australia

The fungus Phytophthora cinnamomi Rands is regarded as heterothallic with compatible mating strains designated Al and A2 (Gallegly 1970). Although the fungus has a world-wide distribution the Al strain has been reported only from North America and Hawaii (Galindo and Zentmyer 1964; Haasis, Nelson, and Marx 1964).

Root rot of passionfruit vine(Passiflora edulis Sims.)in the Auckland area

Abstract In the Auckland district of New Zealand wilt and collapse of passion-fruit vines (Passiflora edulis Sims.) have been shown to be caused by the root fungus Phytophthora cinnamomi Rands. The fungus root pathogen Thielaviopsis basicola (Berk.&Br.) Ferraris was isolated from root lesions of unthrifty, slow–growing plants. The occurrences of both fungi on passionfruit vines are new host records for New Zealand. Crown canker, common in most passionfruit-growing areas in New Zealand, caused by a wound invasion by the secondary pathogen Fusarium sam-bucinum Fckl. is not associated with these fungi. The passionfruit vine vascular wilt fungus F. oxysporum Schl. f. sp. passiflorae Purss apud Gordon common in Australia has not been found in New Zealand.

Biosynthesis of β-1,3- and β-1,6-linked glucan by [formula omitted][formula omitted] hyphal walls

Three lines of evidence were obtained to show that uridine diphosphoglucose (UDPG) is the natural precursor for the synthesis of β-1,3- and β-1,6-linked glucan(s) of the hyphal walls of the plant pathogenic fungus Phytophthora cinnamomi : 1) isolation of UDPG from the mycelium; 2) demonstration of UDPG pyrophosphorylase in a soluble fraction of the cytoplasm; 3) enzymic polymerization of glucose from UDP[ 14C]G into alkali-insoluble glucan by a washed hyphal wall preparation. Most of the glucan synthesizing enzyme(s) was found in the hyphal walls. Seemingly the fungal cell wall has the capability to polymerize one of its components autonomously.