Diseases and Disorders Associated with Environmental Stress in Sustainable Olive Orchards in Australia

Diseases and Disorders Associated with Environmental Stress in Sustainable Olive Orchards in Australia

V. Sergeeva and R. Spooner-Hart | View Article The main aim of our research is to contribute to the knowledge on diseases and disorders of olives in Australia. Based on our diagnostic and field research work we report several new records of fruit rots and of fungi associated with foliage, trunk and root diseases. As well as being affected by a range of pathogenic diseases, olives are also subject to non-pathogenic disorders, such as damage by heat and sun, wind, fire and other weather conditions, water-logging and irregular watering or nutrient imbalances, all of which interfere with the normal physiological processes in trees. As a result, reduced crop set and fruit size as well as a range of other symptoms such as frost, chilling, hail injuries, and sunburn can be directly caused by environmental conditions. Moisture, temperature, sunlight, nutrition and soil characteristics can all affect plant growth. If one of these factors is out of balance it may lead to environmental stress which may, in turn, result in a greater tendency to become...
Colletotrichum clavatum sp. nov. identified as the causal agent of olive anthracnose in Italy

Colletotrichum clavatum sp. nov. identified as the causal agent of olive anthracnose in Italy

Roberto Faedda, Giovanni Enrico Agosteo, Leonardo Schena, Saveria Mosca, Salvatore Frisullo. Gaetano Magnano Di San Lio and Santa Olga Cacciola | View Article Molecular analyses of a large population of isolates, previously identified as group B or genetic group A4 of the Colletotrichum acutatum species complex, mainly of Italian origin from olive, but also from other hosts collected since 1992, confi rmed a well-resolved phylogenetic lineage with distinctive phenotypic characters which can be recognized as a separate species. Based on RAPD genomic fi ngerprinting, ITS and β-tubulin DNA sequences, this species was clearly distinct from C. acutatum sensu stricto, C. fi oriniae and C. simmondsii as well as from the genetic groups A1, A6, A7 and A8, all previously referred to as C. acutatum sensu lato. Group A4 is widespread in Europe, being responsible for olive anthracnose epidemics in some Mediterranean countries, including Greece, Italy, Montenegro, Portugal and Spain; moreover, it causes anthracnose diseases on a wide range of other hosts including about 20 different genera of woody and herbaceous plants, ornamentals and fruit trees. This new anamorphic taxon is described as Colletotrichum clavatum sp....
Colonization of Olive Inflorescences by Verticillium dahliae

Colonization of Olive Inflorescences by Verticillium dahliae

Carlos Trapero, Luis F. Roca, Esteban Alca´ntara and Francisco J. Lo´ pez-Escudero | View Article Verticillium wilt of olive, caused by Verticillium dahliae Kleb., is the most severe disease affecting this crop in most olive growing countries. In this study, the presence of viable structures of V. dahliae in dried inflorescences from wilted olive shoots was investigated. The pathogen was found inside peduncles and flowers, by assessing the number of typical star-shaped microsclerotial colonies formed onto the modified sodium polypectate agar medium. Microsclerotia of V. dahliae were observed inside the peduncles under the stereoscopic microscope. The presence of microsclerotia in these easily decomposable olive tissues shows that infected inflorescences can act as a source of inoculum for Verticillium wilt...
A stem canker disease of olive (Olea europaea) in New Zealand

A stem canker disease of olive (Olea europaea) in New Zealand

R. K. Taylor, C.N. Hale, W. F. T. Hartill | View Article A disease complex, with symptoms that include stem cankers and tip die-back, is reported in New Zealand olives (Olea europaea L.). Bacteria from stem cankers of olive were consistently isolated as pale lemon-yellow colonies on King’s medium B. On the basis of microbiological, molecular, and pathogenicity tests the bacterium isolated was identified as Xanthomonas sp. The bacterial isolates allowed verification of Koch’s postulates on young olive trees. As a result of our findings we suggest that the stem canker on olive is caused by Xanthomonas sp. In addition a fungus identified as Fusicoccum luteum was consistently isolated from stem cankers and tip die-back. In inoculated plants F. luteum occasionally formed cankerous symptoms though not as aggressively as Xanthomonas sp. At this stage it is not clear what role F. luteum has in primary...