NEW DISEASE REPORTS
Blackwell Publishing Ltd
Plant Pathology (2006) 55, 578
Doi: 10.1111/j.1365-3059.2006.01427.x
Brown spot of tangerine hybrid cultivars Minneola, Page and Fortune caused by Alternaria alternata in Iran M. Golmohammadia*, M. Andrewb, T. L. Peeverb, N. A. Peresc and L. W. Timmerd a
Department of Plant Pathology, Iran Citrus Research Institute, PO Box 335, Ramsar-Mazandaran, Iran; bDepartment of Plant Pathology, Washington State University, Pullman, WA 99164-6430; cUniversity of Florida, GCREC, 14625 CR672, Wimauma, FL 33598; and dUniversity of Florida, CREC, 700 Experiment Station Road, Lake Alfred, FL 33850, USA
A new disease of the tangerine hybrid cultivars Minneola (Citrus tangerina cv. Dancy × C. paradisi cv. Duncan); Page (Minneola × C. clementina); and Fortune (C. tangerina × C. clementina) was observed in the Mazandaran Province of Iran in summer 2002. Brown, necrotic lesions surrounded by yellow halos, characteristic of alternaria brown spot of citrus, were found on young leaves and fruit. Affected young fruit and leaves abscised prematurely and mature fruit was unmarketable due to light brown, circular, depressed lesions on its surface. A fungus was isolated from the infected leaves, fruit and twigs and was identified as Alternaria alternata based on the morphological characteristics of the conidia. Pathogenicity tests were conducted by inoculating 10 detached, immature leaves of the varieties Minneola and Page with droplets of conidial suspensions (105 conidia mL−1) and incubating them in a moist chamber at 25°C. Necrotic spots with characteristic yellow halos developed on the leaves after 3 days. Reisolation of the same fungus from diseased tissue of both inoculated cultivars fulfilled Koch’s postulates. DNA was extracted from five isolates and a partial endopolygalacturonase gene was PCR-amplified and sequenced for each (Peever et al., 2002,
2004). Sequences of all five isolates were identical, and in blast searches of the NCBI database the closest matches were A. alternata accessions AY295023·1 (isolate EGS 44-160); AY295021·1 (isolate BC2-RLR-1s); and AY295022·1 (isolate EGS44-159) with 99·8, 99·8 and 99·6% sequence similarity, respectively. Phylogenetic analyses revealed that isolates from all three hosts clustered in clade 3, together with brown spot isolates from Israel, Turkey, South Africa and Australia (Peever et al., 2002). These results, in conjunction with the morphological characterization and pathogenicity tests, confirm the identity of the fungus as A. alternata. This is the first report of alternaria brown spot of citrus in Iran. References Peever TL, Ibañez A, Akimitsu K, Timmer LW, 2002. Worldwide phylogeography of the citrus brown spot pathogen, Alternaria alternata. Phytopathology 92, 794–802. Peever TL, Su G, Carpenter-Boggs L, Timmer LW, 2004. Molecular systematics of citrus-associated Alternaria species. Mycologia 96, 119–34.
*E-mail:
[email protected]. Accepted 15 November 2005 at www.bspp.org.uk/ndr where figures relating to this paper can be viewed.
Plant Pathology (2006) 55, 578
Doi: 10.1111/j.1365-3059.2006.01372.x
First report of Alternaria mali causing necrotic leaf spot of apples in Turkey Blackwell Publishing Ltd
H. Ozgonen* and G. Karaca Suleyman Demirel University, Faculty of Agriculture, Plant Protection Department, 32260 Isparta, Turkey During surveys performed in apple orchards in Isparta Province, small, circular, brown-bordered, purplish-brown spots were seen on apple leaves. The enlarging spots coalesced and became darker on some apple cultivars. One fungus was repeatedly isolated from leaf samples obtained from six different locations in the province. It formed dark olive, circular, velvety colonies on potato dextrose agar. Mycelia were septate, pale brown and had an average diameter of 4·2 µm. Conidia, with an average size of 20·6 × 9·25 µm, had both transverse and longitudinal septa and a short false beak, and were formed in long chains. The pathogen was identified as Alternaria mali (Sawamura, 1990; Bulajic et al., 1996). Pathogenicity of A. mali isolates was tested by inoculation with a conidial suspension (106 conidia mL−1) on detached, wounded apple leaves and on apple seedlings in orchards. Symptoms were observed on detached leaves 3 days after incubation in a humidity chamber at 25°C, and were similar to those developing on leaves of inoculated seedlings. Reisolations yielded the same fungus. In addition, isolates were grown on Czapek-Dox medium for 6 days at same temperature, without shaking. At the end of this period,
culture filtrate was obtained and applied to the underside of wounded leaves as described by Johnson et al. (2000). Necrotic spots were observed on the leaves 24 h after inoculation. These results supported the contention that A. mali causes disease by producing a toxin. This is the first report of alternaria necrotic leaf spot of apples caused by A. mali in Turkey. References Bulajic A, Fladjic N, Babovic M, Sutton TB, 1996. First report of Alternaria mali on apples in Yugoslavia. Plant Disease 80, 709. Johnson RD, Johnson L, Kohmoto K, Otani H, Lane CR, Kodama M, 2000. A polymerase chain reaction-based method to specifically detect Alternaria alternata apple pathotype (A. mali), the causal agent of Alternaria blotch of apple. Phytopathology 90, 973–6. Sawamura K, 1990. Alternaria blotch. In: Jones AL, Aldwinckle HS, eds. Compendium of Apple and Pear Diseases. St Paul, MN, USA: APS Press, 24 –5.
*E-mail:
[email protected]. Accepted 5 October 2005 at www.bspp.org.uk/ndr where figures relating to this paper can be viewed.
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