First Report of Bismarck Palm Anthracnose Caused by <i>Colletotrichum siamense</i> in China

Abstract

Bismarck palm (<i>Bismarckia nobilis</i> Hildebr. & H. Wendl.) is one of the most sought after palms. A severe disease of Bismarck palm was discovered in Wenchang, Hainan Province, China, in July 2010. The main symptoms were russet to gray-white lesions at the tip of leaflets, and the irregular-shaped lesions surrounded by reddish to brown halos. The lesions gradually extended to base of the compound leaf, and entire infected leaves dried up at the advanced stage. A fungus was consistently obtained on the potato dextrose agar medium and the colonies were grayish white, cottony aerial mycelia, with peach to orange conidial masses. The conidia were hyaline, one-celled, and cylindrical with obtuse to slightly rounded ends. A multi-locus approach was utilized to identify the casual pathogen. Molecular phylogenetic trees were constructed using six combined loci, and strain BWZ2 clustered with the ex-type strains of <I>C</I>. <i>siamense</i> (CBS 112983) in the maximum likelihood phylogenetic tree. The pathogenicity test indicated that typical gray-white lesions surrounded by brown halos were observed on all the inoculated leaflets at 7 days post inoculation. On the basis of the biological characteristics, pathogenicity, and analyses of the concatenated sequences of the <I>ACT</I>, <I>CHS1</I>, <I>GAPDH</I>, <I>HIS</I>, ITS, and <I>TUB2</I> genes, the causal agent was identified as <i>Colletotrichum siamense</i> Prihastuti, L. Cai & K. D. Hyde. This is the first report of Bismarck palm anthracnose caused by <I>C</I>. <i>siamense</i>.