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Article

Degenerated Virulence and Irregular Development of Fusarium oxysporum f. sp. niveum Induced by Successive Subculture

1
Department of Plant Pathology, National Chung Hsing University, Taichung City 402204, Taiwan
2
Innovation and Development Center of Sustainable Agriculture (IDCSA), National Chung Hsing University, Taichung City 402204, Taiwan
3
Department of Plant Medicine, National Pingtung University of Science and Technology, Pingtung 912301, Taiwan
4
Plant Medicine Teaching Hospital, General Research Service Center, National Pingtung University of Science and Technology, Pingtung 912301, Taiwan
5
Chiayi Experiment Branch, Taiwan Agricultural Research Institute, Chiayi 611002, Taiwan
*
Author to whom correspondence should be addressed.
J. Fungi 2020, 6(4), 382; https://doi.org/10.3390/jof6040382
Received: 30 September 2020 / Revised: 27 November 2020 / Accepted: 12 December 2020 / Published: 21 December 2020
(This article belongs to the Special Issue Plant Fungal Pathogenesis)
Successive cultivation of fungi on artificial media has been reported to cause the sectorization, which leads to degeneration of developmental phenotype, and virulence. Fusarium oxysporum f. sp. niveum (Fon), the causal agent of watermelon Fusarium wilt, forms degenerated sectors after successive cultivation. In the present research, we demonstrated that subculture with aged mycelia increased the incidence of degenerations. To further investigate the differences between the Fon wild type (sporodochial type, ST) and variants (MT: mycelial type and PT: pionnotal type), developmental phenotypes and pathogenicity to watermelon were examined. Results in variants (PT2, PT3, PT11, and MT6) were different from ST with mycelia growth, conidia production and chlamydospore formation. Virulence of degenerated variants on susceptible watermelon Grand Baby (GB) cultivar was determined after inoculation with Fon variants and Fon ST. In root dipping methods, Fon variants showed no significant differences in disease progress compared with ST. Fon variants showed a significant decrease in disease progression compared with ST through infested soil inoculation. The contrasting results of two inoculation methods suggest that the degenerative changes due to repeated successive cultivation may lead to the loss of pathogen virulence-related factors of the early stage of Fon infection process. Therefore, cell wall-degrading enzymes (CWDEs; cellulase, pectinase, and xylanase) activities of different variants were analyzed. All Fon degenerated variants demonstrated significant decreases of CWDEs activities compared with ST. Additionally, transcript levels of 9 virulence-related genes (fmk1, fgb1, pacC, xlnR, pl1, rho1, gas1, wc1, and fow1) were assessed in normal state. The degenerated variants demonstrated a significantly low level of tested virulence-related gene transcripts except for fmk1, xlnR, and fow1. In summary, the degeneration of Fon is triggered with successive subculture through aged mycelia. The degeneration showed significant impacts on virulence to watermelon, which was correlated with the reduction of CWDEs activities and declining expression of a set of virulence-related genes. View Full-Text
Keywords: Fusarium oxysporum f. sp. niveum; degenerated variants; pathogenicity; virulent factors; watermelon Fusarium wilt; cell wall-degrading enzymes Fusarium oxysporum f. sp. niveum; degenerated variants; pathogenicity; virulent factors; watermelon Fusarium wilt; cell wall-degrading enzymes
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MDPI and ACS Style

Chang, T.-H.; Lin, Y.-H.; Wan, Y.-L.; Chen, K.-S.; Huang, J.-W.; Chang, P.-F.L. Degenerated Virulence and Irregular Development of Fusarium oxysporum f. sp. niveum Induced by Successive Subculture. J. Fungi 2020, 6, 382. https://doi.org/10.3390/jof6040382

AMA Style

Chang T-H, Lin Y-H, Wan Y-L, Chen K-S, Huang J-W, Chang P-FL. Degenerated Virulence and Irregular Development of Fusarium oxysporum f. sp. niveum Induced by Successive Subculture. Journal of Fungi. 2020; 6(4):382. https://doi.org/10.3390/jof6040382

Chicago/Turabian Style

Chang, Tao-Ho, Ying-Hong Lin, Yu-Ling Wan, Kan-Shu Chen, Jenn-Wen Huang, and Pi-Fang Linda Chang. 2020. "Degenerated Virulence and Irregular Development of Fusarium oxysporum f. sp. niveum Induced by Successive Subculture" Journal of Fungi 6, no. 4: 382. https://doi.org/10.3390/jof6040382

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