Genomic Differences Between Two Fusarium oxysporum Formae Speciales Causing Root Rot in Cucumber

Area of Science:

• Plant Pathology
• Genomics
• Molecular Biology

Background:

• Host specificity in Fusarium oxysporum (Fox) is linked to Secreted in Xylem (SIX) effector proteins.
• These SIX genes are often associated with miniature impala (mimp) elements on accessory chromosomes.
• Mimp-associated effector profiles have been used to characterize Fox formae speciales.

Purpose of the Study:

• To compare the genomes of Fusarium oxysporum f.sp. radicis-lycopersici (Forl) ZUM2407 and Fusarium oxysporum f.sp. radicis-cucumerinum (Forc) V03-2g.
• To investigate the pathogenicity of Forl ZUM2407 and Forc V03-2g in cucumber.
• To assess the applicability of the mimp-based approach for predicting effector profiles in Forl ZUM2407.

Main Methods:

• Pathogenicity assays of Forl ZUM2407 and Forc V03-2g on cucumber plants.
• Comparative genome analysis of Forl ZUM2407 and Forc V03-2g.
• Identification and quantification of SIX genes and mimp elements.
• Analysis of mimp distribution patterns and candidate effector profiles.

Main Results:

• Forl ZUM2407 demonstrated pathogenicity on cucumber, similar to Forc V03-2g.
• The Forl ZUM2407 genome lacked SIX genes, while Forc V03-2g possessed them.
• Forl ZUM2407 had significantly fewer mimp elements (10 copies) compared to Forc V03-2g (36 copies), with a distinct distribution pattern.
• Mimp-based analysis failed to predict Forl ZUM2407's pathogenicity on cucumber.

Conclusions:

• Forl ZUM2407 exhibits pathogenicity in cucumber despite lacking SIX genes and having a different mimp element composition than Forc V03-2g.
• The mimp-based approach may not be universally applicable for predicting effector profiles and pathogenicity in all Fusarium oxysporum formae speciales.
• Forl ZUM2407 likely possesses alternative genome organization and pathogenicity mechanisms not captured by current mimp-associated effector profiling.