Abstract:

A disease on Koelreuteria bipinnata var. integrifoliola was reported in Zhejiang Province in recent years. The disease caused a series symptoms, beginning with a serious bark including phloem crack in stem, later the cracked bark largely shed off and the exposed xylem turned brown. Trees with serous lesions produced less new shoots in spring, wilted and then died in summer. The suspected pathogen was isolated from diseased phloem. After pathogenicity tests in field and re-isolation of the pathogen, the strain KL-1-2 was determined to be responsible for the disease.The fungus colony on PDA was circular or nearly circular in shape with irregular edge and gray, and then turned to black green or black. The fungus had abundant hyphae, villous, septate and irregular branched. Conidia were elliptical (or rounded) and hyaline at the stage of immature. However, conidia became dark brown and septate longitudinally at the stage of mature. Mature conidia size was ranged from (23.2-27.0) μm×(10.8-16.2) μm [average (25.3×13.6) μm]. Its rDNA ITS sequence had 99% similarity with those of Lasiodiplodia theobromae (Patouillard) Griffon=Botryodiplodia theobromae Pat. Morphological characteristics and internal transcribed spacer (ITS) sequences show that the strain KL-1-2 would be Lasiodiplodia theobromae.

Key words: Koelreuteria bipinnata var. integrifoliola, bark cracking, pathogen, Lasiodiplodia theobromae