Archivio Journal of Plant Pathology

Abstract:

Yunnan pine (Pinus yunnanensis Franch.) is a crucial economic and ecological tree species in Yunnan Province, China. In February 2015, small pieces of stained phloem were collected from the galleries of Tomicus minor infesting P. yunnanensis and transferred to 2% malt extract agar (MEA) at 20°C. The resulting brown to black colonies had light brown and irregular margins. The globose conidia (5.6–) 6x10 (–11) µm in size exhibited non-phialidic conidiogenesis. The morphological characteristics suggested an identification of Ophiostoma tingens (Lagerb. & Melin) Z.W. de Beer & M.J. Wingf., previously described as Ambrosiella tingens (Lagerb. & Melin) L.R. Batra (Batra, 1967). PCRs were conducted using primers NS1/NS4, ITS3/LR3 and BT2E/BT12 for nSSU, nLSU and β-tubulin, respectively (Alamouti et al., 2009). The obtained sequences of strain YMF 1.04939 (1023 bp, 931 bp and 730 bp) were submitted to GenBank with the accession Nos. MF043741, MF043742 and MF043743. BLASTn analysis showed 99% identity with the corresponding sequences of A. tingens isolate CBS 366.53, now O. tingens (EU170277, AF282871 and EU977468). A pathogenicity test was conducted by placing mycelia and sterile agar with 1 cm iron borers in healthy wood of P. yunnanensis; each treatment had ten repeats. After 10 days at 20°C, the staining in the phloem of wood inoculated with O. tingens reached 3.64 cm in average length, while that for control was 2.18 cm. The fungus was re-isolated only from inoculated wood. Although it has been reported in some European countries (Harrington et al., 2010), this represents the first report that O. tingens causes blue-stain in P. yunnanensis in China.