CRYPTOCOCCUS ADELIENSIS A YEAST SPECIES INCITING STEM CANKER ON STONE FRUIT TREES

B. Borhani, H. Rahimian, V. Babaeizad, E. Zohour

Abstract


Yeast isolates were consistently recovered from symptomatic branches of stone fruit trees showing twig and stem cankers indistinguishable from those caused by bacterial agents, especially Pseudomonas syringae pv. syringae, which have been prevalent throughout Khorasan province (northern Iran). Dark brown to black sunken lesions develop on twigs and branches, turning to typical stem cankers upon expansion. Yeast-like round, white to light cream-coloured, mucoid colonies were the predominant or the sole colony type recovered on sucrose nutrient agar from cankers. Yeast cells were circular and ca. 6.5 μm in diameter. The internal transcribed spacer (ITS) region of the rDNA and the D1/D2 domain of the large subunit (LSU) rDNA were amplified by PCR using primer pairs ITS4/ITS5 and NL1/NL4, (Kurtzman and Robnett, 1998; White et al., 1990), respectively. PCR products were sequenced, their sequences were aligned and compared with those deposited in GenBank. Sequences of the ITS (accession No. KC479045) and D1/D2 (accession No. KC196119) of a representative isolate showed 99-100% identity with those of Cryptococcus adeliensis isolates. The fatty acid composition of a representative isolate and of the type strain of C. adeliensis (CBS 8351) was determined by gas chromatography. Both isolates shared identical fatty acids profiles, with oleic acid (C18:1) and linoleic acid (C18:2) being the major fatty acids. Canker symptoms were reproduced on peach (Prunus persica) and nectarine (P. persica var. nucipersica) budlings inoculated with yeast suspensions (5×107 cells/ml). The same yeast was reisolated from cankers. Stem canker caused by C. adeliensis represents a hitherto undescribed disease of fruit trees. This yeast species has previously been isolated from decaying algae and from a human patient suffering from meningitis (Scorzetti et al., 2000; Rimek et al., 2004).

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DOI: http://dx.doi.org/10.4454/JPP.V95I3.031

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