First Report of Powdery Mildew Caused by Golovinomyces magnicellulatus var. magnicellulatus on Physalis alkekengi var. franchetii in China
Authors: Liang C. , Xing H. H. , Liu Z. , Cho S. E. , Shin H. D. 
Published: May 2013

Physalis alkekengi var. franchetii (Mast.) Makino, known as Chinese lantern, belonging to Solanaceae, is cultivated for its fruits of medicinal value in East Asia (4). Since July 2010, a powdery mildew has been continuously observed on this plant in Shenyang City in northeastern China. More than 90% of the plants in a garden were affected. Symptoms first appeared as circular to irregular white patches, which progressed to abundant mycelial growth on both sides of leaves and young stems. In the middle of August, chasmothecia were formed abundantly, especially on the lower leaf surface. Voucher specimens were deposited in the herbarium of Qingdao Agricultural University (HMQAU10014, 12047, and 12144). Conidiophores produced 2 to 5 conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of conidiophores were straight and 46 to 65 × 9 to 11 μm. Conidia were ellipsoid to barrel-shaped, 26 to 32 × 13 to 15.5 μm, lacked distinct fibrosin bodies, and produced germ tubes on the subterminal position. Chasmothecia were amphigenous, also cauligenous, 100 to 140 μm across, and contained 10 to 25 asci. Appendages were mycelioid, 0.5 to 4 times as long as the chasmothecial diameter, and 1- to 3-septate. Asci were short-stalked, 45 to 64 × 26 to 34 μm, and contained two ascospores of 18 to 25 × 12.5 to 15 μm. The internal transcribed spacer (ITS) region of rDNA was amplified (3) and sequenced. The resulting 600-bp sequence was deposited in GenBank (Accession No. KC488260). A GenBank BLAST search of complete ITS sequence showed 100% identity with that of Golovinomyces orontii on P. alkekengi var. franchetii (AB077647 ex Japan) and >99% similarity with those of G. magnicellulatus on Phlox paniculata (AB077621 ex Japan, AF011303 ex the United States, and GU945756 and GU945757 ex Korea). G. orontii is currently confined to the Golovinomyces isolates on Cichorioideae (1). On the basis of the morphological characteristics and ITS sequence data, the fungus was identified as G. magnicellulatus var. magnicellulatus (U. Braun) V.P. Heluta (1). It was already noted that Golovinomyces isolates on Physalis and Phlox are phylogenetically close each other (3). A pathogenicity test was conducted by gently pressing a diseased leaf onto leaves of five healthy Chinese lanterns. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 8 days, whereas the control plants remained symptomless. The fungus present on the inoculated plants was morphologically identical to that originally observed on diseased plants, fulfilling Koch's postulates. Powdery mildews of Chinese lantern associated with Golovinomyces species have been known in Korea and Japan (2). A Korean material of Golovinomyces sp. on P. alkekengi var. franchetii was identified as G. magnicellulatus var. magnicellulatus based on morphological characteristics and 100% ITS sequence identity with a Chinese isolate (Shin, unpublished data). To our knowledge, this is the first report of powdery mildew caused by G. magnicellulatus var. magnicellulatus on Chinese lantern in China. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, retrieved March 22, 2013. (3) S. Matsuda and S. Takamatsu. Mol. Phylogen. Evol. 27:314, 2003. (4) Y. Zheng et al. Phytochem. Anal. 23:337, 2012.