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Title: First report of sunflower white mold caused by Sclerotinia minor Jagger in Inner Mongolia region, China

item LI, M - Inner Mongolian Agriculture University
item ZHANG, Y - Inner Mongolian Agriculture University
item WANG, K - Inner Mongolian Agriculture University
item HOU, Y - Inner Mongolian Agriculture University
item ZHOU, H - Inner Mongolian Agriculture University
item JIN, L - Inner Mongolian Agriculture University
item Chen, Weidong
item ZHAO, J - Inner Mongolian Agriculture University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2015
Publication Date: 1/12/2016
Citation: Li, M., Zhang, Y.Y., Wang, K., Hou, Y.G., Zhou, H.Y., Jin, L., Chen, W., Zhao, J. 2016. First report of sunflower white mold caused by Sclerotinia minor Jagger in Inner Mongolia region, China. Plant Disease. 100:211.

Interpretive Summary: Sclerotinia white mold is a devastating, wide spread disease of many economically important crops. Most of the diseases are recognized as caused by Sclerotinia sclerotiorum. The other two species of Sclerotinia, S. minor and S. trifoliorum, have narrower host ranges with limited distribution, but their host range and distribution could be under reported, because of the perception of the prevalence of S. sclerotiorum. Identifying the exact pathogen species is important for devising management strategies because the different species have different life cycles and different alternative host plants. Here we report for the first time of Sclerotinia white mold of sunflower caused by S. minor in China. Documenting S. minor as a pathogen of sunflower will facilitating future diagnostics of sunflower diseass in China and elsewhere, and will be useful in implementing management strategies.

Technical Abstract: During the 2014 growing season, sunflower plants with symptoms of basal stem rot and whole plant wilt were observed in sunflower fields in Inner Mongolia, China. The average disease incidence was between 10-15%. Tiny (0.30 to 2.68 mm) black sclerotia were usually observed on the stem of infected plants. Although sunflower white mold caused by S. sclerotiorum has been observed in this region before, the sclerotia formed on the diseased plants were too small for the pathogen to be S. sclerotiorum. From a total of 171 samples, seven were chosen randomly for identification. Upon isolation, the emerging mycelia were hyphal-tipped three times and subcultured on PDA. The sclerotial morphology resembled those of Sclerotinia minor Jagger. To confirm the species molecularly, total genomic DNA was isolated from mycelia. The internal transcribed spacer of nuclear rDNA was amplified. The ITS sequences of all 7 isolates were the same and 99% identical to an S. minor sequence deposited in the GenBank database (KF859929.1). One ITS sequence from this study was deposited in GenBank and assigned accession number KP340982. Pathogenicity was tested with both stem and petiole inoculation. Water-soaked lesions were observed at the inoculation sites 2 days post inoculation (dpi). The lesion expanded along the stem, and white mycelium and also black tiny sclerotia were observed at the infected sites 5 dpi; the whole plants showed withered and lodged symptom 7 dpi. No symptom was observed on the control plants. The fungus was consistently re-isolated from the inoculated stem and tiny sclerotia formed on PDA plate were consistent with S. minor. Although S. minor causing sunflower white mold has been reported in Australia, Bulgaria, Canada, Chile, Kenya, New Zealand, Spain and USA (Farr et al. 2014), to the best of our knowledge, this is the first report of S. minor caused sunflower white mold in China.