First report of Leptosphaeria sclerotioides on Brassica napus in Northwestern China

In 2020, diseased seedlings of winter oilseed rape (Brassica napus) with cankered taproots as well as abundant sclerotium-like structures in the soil surrounding the roots were found in Longxi County of Gansu province of northwestern China. A fungus with production of pycnidia was isolated from the diseased roots, and it was identified based on morphological characteristics, molecular phylogeny (ITS, LSU) and PCR detection with the specific primers. The fungus was identified as Leptosphaeria sclerotioides Gruyter, Aveskamp & Verkley [anamorph: Phoma sclerotioides (Preuss) ex Sacc.]. Re-inoculation of isolates of P9 and P10 of L. sclerotioides on winter oilseed rape (B. napus cultivar ‘Zhongshuang No. 9’) in Wuhan caused formation of abundant sclerotium-like structures in soil surrounding the roots, but failed to produce root cankers as those observed in Gansu possibly due to lack of long peroid of low-temperature conditioning in Wuhan. In spite of this, plant height, pod number and seed yield of oilseed rape were significantly reduced in the treatment with L. sclerotioides P9 and P10, compared to the control treatment. To the best of our knowledge, this is the first report of L. sclerotioides on B. napus in China and the finding broadened our understanding about the natural distribution of this psychrophilic fungus.