University of California

Eutypa armeniacae in apricot: Pathogenesis and induction of xylem soft rot


Harley English
J. R. Davis

Authors Affiliations

Harley English was Professor of Plant Pathology, University of California, Davis; J. R. Davis was Professor of Plant Pathology, Idaho Research and Extension Center, Aberdeen, Idaho.

Publication Information

Hilgardia 46(6):193-204. DOI:10.3733/hilg.v46n06p193. July 1978.

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Apricot pruning wounds made at all seasons of the year were susceptible to infection and canker formation resulting from mycelial inoculation with Eutypa armeniacae. Cambial inoculations resulted in comparatively little infection, and inoculations of the inner bark (phloem) were negative. Evidence indicated that the pathogen is inactivated in some infections, and thus sometimes is prevented from forming perennial, girdling cankers. Death of the pathogen did not appear to result from the action of other microorganisms. Invasion of the xylem by E. armeniacae resulted in the formation of gum plugs in some of the tracheary elements, and the development of hyphae in the lumens of vessels, fiber-tracheids, and ray parenchyma cells. The hyphae penetrated cell walls directly or through pits. In advanced stages of infection, the hyphae grew longitudinally within the secondary wall, especially of fiber-tracheids, where, presumably through enzymatic action, they caused the development of soft rot. This soft-rot condition appears to be responsible for the commonly encountered brittle nature of apricot branches killed by this pathogen. The ability of E. armeniacae to cause soft rot was demonstrated histologically, and by its capacity to cause weight loss in inoculated birch wood. The soft-rot phenomenon appears to develop late in the disease syndrone. In vitro studies indicated the ability of the pathogen to produce enzymes that degraded cellulose and xylan. Almond and peach trees were slightly susceptible when wounded tissues were inoculated with mycelia of the fungus.

Literature Cited

Adam D. B. A progress report on a gummosis (dieback) disease in South Australian apricot trees. J. Dep. Agric. S. Aust. 1938. 42:14-29.

Carter M. V. Eutypa armeniacae Hansf. &; Carter sp. nov., an airborne vascular pathogen of Prunus armeniaca L. in southern Australia. Aust. J. Bot. 1957. 5:21-35. DOI: 10.1071/BT9570021 [CrossRef]

Carter M. V. Further studies on Eutypa armeniacae Hansf &; Carter. Aust. J. Agric. Res. 1960. 11:498-504. DOI: 10.1071/AR9600498 [CrossRef]

Carter M. V., Bolay A. Eutypa dieback of apricot is prevalent in Switzerland. Phytopathol. Z. 1972. 75:187-89. DOI: 10.1111/j.1439-0434.1972.tb02613.x [CrossRef]

Carter M. V., Moller W. J. The quantity of inoculum required to infect apricot and other Prunus species with Eutypa armeniacae. Aust. J. Exp. Agric. Anim. Husb. 1971. 11:684-86. DOI: 10.1071/EA9710684 [CrossRef]

Carter M. V., Morvan G. S., Castelain C. An extension of the known distribution of Eutypa armeniacae. Nature (Lond.). 1964. 202:1134-35. DOI: 10.1038/2021134c0 [CrossRef]

Casagrande F., Ouellette G. B. A technique to study the development in wood of soft rot fungi and its application to Ceratocystis ulmi. Can. J. Bot. 1971. 49:155-59. DOI: 10.1139/b71-026 [CrossRef]

Cowling E. B. Comparative biochemistry of the decay of sweetgum sapwood by white-rot and brown-rot fungi. U. S. Dep. Agric. Tech. Bull. 1961. 1258:79

Dingley J. M. Eutypa canker of apricots. Orchardist N.Z. 1960. 33(3):78-79.

Duncan C. G. Wood-attacking capacities and physiology of soft-rot fungi. U. S. For. Serv. For. Proc. Lab. Rep. 1960. 2173:70

English H., Davis J. R. Pathogenic activity of Eutypa armeniacae in apricot. Phytopathology. 1965a. 55:1057 (Abstr.)

English H., Davis J. R. Apricot dieback fungus found on western choke-cherry. Plant Dis. Rep. 1965b. 49:178

English H., O’Reilly H. J., McNelly L. B., DeVay J. E., Rizzi A. D. Cytosporina dieback of apricot. Calif. Agric. 1963. 17(2):2-4.

Eslyn W. E., Kirk T. K., Effland M. J. Changes in the chemical composition of wood caused by six soft-rot fungi. Phytopathology. 1975. 65:473-76. DOI: 10.1094/Phyto-65-473 [CrossRef]

Foster R. C., Marks G. C. Fine structure of the host-parasite relationship of Diplodia pinea on Pinus radiata. Aust. For. 1968. 32:211-25. DOI: 10.1080/00049158.1968.10674126 [CrossRef]

Levy J. The soft rot fungi: the mode of action and significance in the degradation of wood. Adv. Bot. Res. 1965. 2:323-57. DOI: 10.1016/S0065-2296(08)60253-0 [CrossRef]

Liese W. Ultrastructural aspects of woody tissue disintegration. Annu. Rev. Phytopathol. 1970. 8:231-58. DOI: 10.1146/annurev.py.08.090170.001311 [CrossRef]

Matthee F. N., Thomas A. C., Erasmus A. D. Die-back of apricot trees in South Africa caused by Eutypa armeniacae. Phytophylactica. 1974. 6:131-32.

Moller W. J. Apricot disease found on garden shrub. J. Agric. S. Aust. 1964. 67:251

Moller W. J., Kasimatis A. N., Kissler J. J. A dying arm disease of grape in California. Plant Dis. Rep. 1974. 58:869-71.

Nelson N. A photometric adaptation of the Somogyi method for the determination of glucose. J. Biol. Chem. 1944. 153:375-80.

Ramos D. E., Moller W. J., English H. Susceptibility of apricot tree pruning wounds to infection by Eutypa armeniacae. Phytopathology. 1975. 65:1359-64. DOI: 10.1094/Phyto-65-1359 [CrossRef]

Savory J. G. Breakdown of timber by Ascomycetes and Fungi Imperfecti. Ann. Appl. Biol. 1954. 41:336-47. DOI: 10.1111/j.1744-7348.1954.tb01126.x [CrossRef]

Trevelyan W. E., Procter D. P., Harrison J. S. Detection of sugars on paper chromatograms. Nature. 1950. 166:444-45. DOI: 10.1038/166444b0 [CrossRef]

Umezurike G. M. Cellulolytic activities of Botryodiplodia theobromae Pat. Ann. Bot. (Lond.). 1969. 33:451-62.

English H, Davis J. 1978. Eutypa armeniacae in apricot: Pathogenesis and induction of xylem soft rot. Hilgardia 46(6):193-204. DOI:10.3733/hilg.v46n06p193
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