Abstract
Pycnidiospores of Phyllosticta citricarpa from pure cultures, symptomatic citrus black spot Valencia orange fruit and peelings were evaluated for their potential to infect and colonise citrus black spot-free Eureka lemon leaf litter in a controlled environment and in the field in different production regions of South Africa. Leaf litter, consisting of freshly detached green and old brown leaves that were exposed to viable pycnidiospores under controlled conditions or in the field underneath citrus trees, were not infected and colonised by P. citricarpa. Ascospores, conforming to Guignardia citricarpa, the pathogen, or G. mangiferae, a cosmopolitan endophyte, were collected with a Kotzé Inoculum Monitor from leaves placed in the field only at Tzaneen and Burgersfort. Distinguishing between these two species on ascospore morphology alone is not possible. A diagnostic polymerase chain reaction conducted on representative leaf material from all the treatments revealed the presence of only G. mangiferae on 12.5% of the treatments. This study demonstrated the failure of P. citricarpa pycnidiospores to infect citrus leaf litter under controlled and field conditions. Symptomatic citrus black spot fruit or peel lying on the ground underneath citrus trees, therefore, cannot lead to infection and colonisation of freshly detached leaves or natural leaf litter or represent a source of inoculum in citrus orchards for these leaves.
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Agostini JP, Peres NA, Mackenzie SJ, Adaskaveg JE, Timmer LW (2006) Effect of fungicides and storage conditions on postharvest development of citrus black spot and survival of Guignardia citricarpa in fruit tissues. Plant Disease 90, 1419–1424.
Baayen RP, Bonants PJM, Verkley G, Carroll GC, Van der Aa HA et al. (2002) Nonpathogenic isolates of the citrus blackspot fungus, Guignardia citricarpa, identified as a cosmopolitan endophyte of woody plants, G. mangiferae (Phyllosticta capitalensis). Phytopathology 92, 464–477.
Brodrick HT (1969) Physiological studies with Guignardia citricarpa Kiely. DSc thesis, University of Pretoria, South Africa.
Calavan EC (1960) Black spot of citrus. Californian Citrograph 46, 22–24.
Cobb NA (1897) Letters on the diseases of plants: Black spot of the orange. Agricultural Gazette New South Wales 8, 229–231.
De Goes A, Baldassari RB, Feichtenberger E, Aguilar-Vildoso CI, Sposito MB (2000) Cracked spot, a new symptom of citrus black spot. In ‘Abstracts of the 9th congress of the international society of citriculture’. p. 145. (University of Florida: Orlando, FL)
Doidge EM (1929) Some diseases of citrus prevalent in South Africa. South African Journal of Science 26, 320–325.
European Union (1998) Commission decision of 8 January 1998 recognizing certain third countries and certain areas of third countries as being free of Xanthomonas campestris (all strains pathogenic to Citrus), Cerospora angolensis Carv. et Mendes and Guignardia citricarpa Kiely (all strains pathogenic to Citrus). Official Journal of European Communities 15, 41–42.
Kiely KB (1950) Control and epiphytology of black spot of citrus on the central coast of New South Wales. New South Wales Department of Agriculture, Science Bulletin 71.
Kiely TB (1948) Preliminary studies of Guignardia citricarpa, n. sp.: The ascigerous stage of Phoma citricarpa McAlp. and its relation to black spot of citrus. Proceedings of the Linnean Society of New South Wales 73, 249–291.
Korf HJG (1998) Survival of Phyllosticta citricarpa, anamorph of the citrus black spot pathogen. MSc dissertation, University of Pretoria, South Africa.
Kotzé JM (1963) Studies on the black spot disease of citrus caused by Guignardia citricarpa Kiely, with particular reference to its epiphytology and control at Letaba. DSc thesis, University of Pretoria, South Africa.
Kotzé JM (1981) Epidemiology and control of citrus black spot in South Africa. Plant Disease 65, 945–950.
Kotzé JM (1996) History and epidemiology of citrus black spot in South Africa. Proceedings of the International Society of Citriculture 2, 1296–1299.
Mabiletsa P (2003) Republic of South Africa, Citrus Annual 2003. Global Agriculture Information Network Report SF3037, 1–11.
McOnie KC (1963) Kan bespuitings vir swartvlek ook melanose beheer? The South African Citrus Journal 357, 27–28.
McOnie KC (1964a) Orchard development and discharge of ascospores of Guignardia citricarpa and the onset of infection in relation to the control of citrus black spot. Phytopathology 54, 1448–1453.
McOnie KC (1964b) Source of inoculum of Guignardia citricarpa, the citrus black spot pathogen. Phytopathology 54, 64–67.
McOnie KC (1964c) The latent occurrence in citrus and other hosts of a Guignardia easily confused with G. citricarpa, the citrus black spot pathogen. Phytopathology 54, 40–43.
McOnie KC (1965) Source of infection for black spot of citrus. The South African Citrus Journal 378, 5.
McOnie KC (1967) Germination and infection of citrus by ascospores of Guignardia citricarpa in relation to control of black spot. Phytopathology 57, 743–746.
Meyer L, Slippers B, Korsten L, Kotzé JM, Wingfield MJ (2001) Two distinct Guignardia species associated with citrus in South Africa. South African Journal of Science 97, 191–194.
Meyer L, Sanders GM, Jacobs R, Korsten L (2006) A one-day sensitive method to detect and distinguish between the citrus black spot pathogen Guignardia citricarpa and the endophyte Guignardia mangiferae. Plant Disease 90, 97–101.
Paul I, Van Jaarsveld AS, Korsten L, Hattingh V (2005) The potential global geographical distribution of citrus black spot caused by Guignardia citricarpa (Kiely): likelihood of disease establishment in the European Union. Crop Protection 24, 297–308. doi: 10.1016/j.cropro. 2004.08.003
Sutton BC, Waterson JM (1966) ‘Guignaridia citricarpa. Description of pathogenic fungi and bacteria. No 85.’ (CAB International: Wallingford, UK)
Truter M, Kotzé JM, Janse van Rensburg TN, Korsten L (2004a) A sampler to determine available Guignardia citricarpa inoculum on citrus leaf litter. Biosystems Engineering 89, 515–519. doi: 10.1016/ j.biosystemseng.2004.08.018
Truter M, Labuschagne PM, Korsten L (2004b) Inoculation of citrus leaves at different leaf ages with Guignardia citricarpa. In ‘3rd citrus research symposium’. p. 37. (Citrus Research International: Modimolle, South Africa)
Wager VA (1949) The occurrence of the black-spot fungus in the citrus areas of South Africa. Farming in South Africa 24, 367–369.
Wager VA (1952) The black spot disease of citrus in South Africa. Science Bulletin of the Department of Agriculture of the Union of South Africa 303, 1–52.
Whiteside JO (1965) Black spot disease in Rhodesia. Rhodesia Agricultural Journal 64, 87–91.
Whiteside JO (1967) Sources of inoculum of the black spot fungus, Guignardia citricarpa, in infected Rhodesian citrus orchards. Rhodesia, Zambia and Malawi Journal of Agricultural Research 5, 171–177.
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Truter, M., Labuschagne, P.M., Kotzé, J.M. et al. Failure of Phyllosticta citricarpa pycnidiospores to infect Eureka lemon leaf litter. Australasian Plant Pathology 36, 87–93 (2007). https://doi.org/10.1071/AP06087
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DOI: https://doi.org/10.1071/AP06087