Abstract: Curvularia leaf spot, caused mainly by Curvularia lunata, is a widespread plant disease in China.  In the recent years, directional host selection by the pathogen, which likely results in the virulence differentiation in pathogens, is widely reported.  Among the hallmarks potentially associated to pathogen variation in virulence, superoxide dismutase gene Sod has been found to be closely related to the enhancement of virulence.  In the present study, the full-length of Sod was obtained via Blastn alignment against GenBank and the whole genome of C. lunata.  In order to understand the role of Sod in the virulence variation in C. lunata, targeted gene disruption was performed to construct Sod mutants.  The cell wall degrading enzyme (CWDE) activities and toxin production of ΔSod were not distinctly different from wild-type strain CX-3 and its complon.  However, at an early stage of infection, ΔSod virulence appeared to be lower than CX-3 and the complon, while at a later stage, its virulence gradually returned to the level of CX-3 and the complon.  Furthermore, the melanin production of ΔSod was significantly reduced compared to CX-3 and the complon, suggesting that Sod gene influences the virulence by regulating melanin production at an early stage of infection but is not essential for pathogenicity.  However, the disruption of Sod did not significantly affect the transcriptional expression of the melanin biosynthesis-associated genes, brn1 and scd.  Therefore, we infer that Sod in C. lunata are involved, to some extent, with the virulence in maize leaf, but still needs further studies to have a clear understanding of its mechanism.

Key words:  Curvularia lunata, Sod, gene function, infection