ARS | Publication request: Biochemical and molecular characterization of insertional mutants of Scleortinia sclerotiorum

Submitted to: Proceedings of the International Sclerotinia Workshop
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 2009
Publication Date: December 15, 2009
Citation: Xiang, M., Wang, X., Chen, W. 2009. Biochemical and molecular characterization of insertional mutants of Scleortinia sclerotiorum. Proceedings of the International Sclerotinia Workshop.

Technical Abstract: Sclerotinia sclerotiorum causes white mold on many agronomic and horticultural crops and causes significant yield losses. Despite numerous studies on pathogenic mechanisms of this devastating pathogen, its pathogenic mechanisms are not completely understood. This study was to characterize insertional mutants that were generated through Agrobacterium-mediated transformation and that have reduced pathogenicity, to elucidate pathogenic mechanisms. Two transformants, M139.2 and M-2.1, with reduced virulence were identified by pathogenicity screening on lentil stems. The transformants were compared with the wild type strain WM-A1 in the following characteristics: growth rate (colony diameter and biomass), mycelium compatibility, and oxalic acid production. Transformant M-2.1 had similar growth rate as the wild type strain in colony diameter, whereas transformant M139.2 was slower in colony expansion on PDA. The M-2.1 showed a highest biomass (dry mycelium weight) in PDB culture and the M139.2 had the lowest biomass. The pH values of the PDB filtrates were 2.4, 2.4 and 2.6 for WM-A1, M139.2 and M-2.1, respectively. Using color change of cultural plate as an indicator of oxalic acid production, M139.2 and the wild type showed the same level of oxalic acid production, and M-2.1 produced less oxalic acid, consistent with the pH values of the filtrates. Inverse PCR and sequence analyses showed that the T-DNA insertion site of M139.2 was in putative nucleoside phosphatase gene and the T-DNA insertion site of M-2.1 was in a putative gene encoding esterase of the alpha-beta hydrolase. Functions of the putative pathogenicity genes are being confirmed employing complementation tests.