First Report of Stachybotrys chartarum Causing Leaf Blight of Tillandsia tenuifolia in China

Tillandsia tenuifolia L. is an air plant that is native to Bolivia, Brazil, and Venezuela. It was introduced to China in 2006. In September 2008, a leaf blight of T. tenuifolia 'Bronze Tip' was observed in a greenhouse in Jurong, Jiangsu. Severe infection led to death of foliage, shoot rot, and eventual mortality of whole plants. The pathogen was isolated from the diseased leaves on potato dextrose agar and subsequently further cultured on a slide culture for 7 days. Anamorphic structures were examined under a compound microscope. Diseased plant parts were covered with abundant conidia, phialides, conidiophores, and mycelia of the pathogen. Conidiophores were simple or branched, zero to two septate, hyaline, smooth at base, brown, smooth to rough at upper portion, and 47.9 ± 7.6 × 4 ± 0.4 μm (n = 30). Phialides were one-celled, obovate, hyaline to pale brown, 8.8 ± 0.9 × 5.3 ± 0.3 μm (n = 20), and in whorls. Conidia were one-celled, ellipsoid to subglobose, dark brown to black, rough to ridged, 10.4 ± 1.4 × 6.2 ± 0.9 μm (n = 30), and in slimy masses. Using morphological characters, the pathogen was identified as Stachybotrys chartarum (Ehrenb.) S. Hughes (1). The living culture was deposited in the China General Microbiological Culture Collection Center (CGMCC 3.13634). S. chartarum, a saprophyte with a worldwide distribution, grows on various substrates such as soil, paper, dry walls, and wood. (2). It was also isolated from moldy sorghum seed and soybean root lesions (3,4). Pathogenicity on T. tenuifolia was confirmed by Koch's postulates in the laboratory. Ninety-six leaves on four plants were pricked with a sterilized needle and inoculated with a suspension of 6.35 × 10⁶ conidia ml^-1. Forty-seven leaves on two plants were pricked and sprayed with sterile water as controls. All the plants were kept in a growth chamber with a 12-h photoperiod, 28 ± 1°C, and relative humidity of 70 ± 3%. Initial lesions, which were water soaked, slightly sunken, and pinhead size, appeared on the inoculated plants in 7 days and expanded to 1.5 to 2.0 mm in 21 days. Necrotic spots subsequently coalesced and caused the death of the leaves. Infected shoots were rotten and shed leaves from the basal area. The plants died within 45 days. Symptoms were similar to those observed in the greenhouse. S. chartarum was reisolated from infected leaves. Control plants remained healthy. To confirm the identity of our isolate, DNA sequence was obtained from the internal transcribed spacer (ITS) region and deposited in GenBank (GU945205). The ITS sequence was 100% identical to S. chartarum strains whose DNA sequences were deposited in GenBank. To our knowledge, this is the first report of S. chartarum causing leaf blight on T. tenuifolia. The popularity of T. tenuifolia continues to grow in China. The disease should be monitored to determine its risk and economic significance in China and other regions. References: (1) S. C. Jong and E. E. Davis. Mycotaxon 3:409, 1976. (2) P. M. Kirk. Mycopathologia 115:149, 1991. (3) S. Li et al. Mycopathologia 154:41, 2002. (4) J. Y. Liang and J. K. Bai. J. Shenyang Agric. Univ. 19:27, 1988.