Phytoplasma associated with a witches’ broom disease of Gleditsia sinensis (Fabaceae) newly reported in China

Abstract

Gleditsia sinensis (Chinese honeylocust) is widely distributed in China due to its important use in traditional Chinese medicine. In August of 2008, G. sinensis trees in Shanxi Province, exhibited symptoms of witches’ broom, stunting, smaller leaves, and yellowing gradually becoming browning: a phytoplasma infection was suspected. Total DNA was extracted from 0·5 g of phloem tissue from leaf midribs and stems of eight plants with, and eight plants without symptoms (Angelini et al., 2001). DNA was analyzed for phytoplasma by a nested PCR assay using phytoplasma universal 16S rDNA primers R16mF1/R16mR1 and R16F2n/R16R2 (Gundersen & Lee, 1996). PCR products of 1·4 and 1·2 kb, respectively, were produced from all plants with symptoms, but not from symptomless plants. Restriction fragment length polymorphism (RFLP) analyses of R16F2n/R16R2 amplicons with AluI, HhaI, TaqI, EcoRI, HaeIII, RsaI and HpaII endonucleases, indicated that all plants with symptoms contained a phytoplasma strain of group 16SrV (‘Candidatus Phytoplasma ulmi’), subgroup B (16SrV-B). The G. sinensis phytoplasma 16S rDNA sequence (GenBank Accession No. FJ457095) scored the highest identity (99%) with those of group 16SrV, thereby confirming strain identity based on RFLP. Phytoplasmas of 16SrV have previously reported on jujube (Zhu et al., 1997) and paper mulberry (Liu et al., 2004) causing witches’ broom in China. This is the first report of a ‘Candidatus Phytoplasma ulmi’-related strain affecting G. sinensis in China.