Homothallism in Sclerotinia minor

Area of Science:

• Mycology
• Plant Pathology
• Genetics

Background:

• Sclerotinia species are significant fungal pathogens.
• Previous research suggested S. minor and S. sclerotiorum were homothallic based on self-fertility.
• Sclerotinia trifoliorum was known to be bipolar heterothallic with dimorphic ascospores.

Purpose of the Study:

• To clarify the reproductive mechanisms of Sclerotinia minor and Sclerotinia sclerotiorum.
• To investigate the mating system and ascospore characteristics in these Sclerotinia species.

Main Methods:

• Culturing of ascospores from Sclerotinia isolates.
• Induction of apothecia formation from single ascospores.
• Observation and characterization of ascospore morphology (monomorphic vs. dimorphic).

Main Results:

• Isolates of S. minor and S. sclerotiorum demonstrated self-fertility of all eight ascospores within an ascus.
• Apothecia were successfully raised from all eight ascospores of tetrads from multiple S. minor isolates and one S. sclerotiorum isolate.
• Ascospores were predominantly monomorphic, with rare instances of dimorphism observed, similar to S. trifoliorum.

Conclusions:

• Sclerotinia minor and Sclerotinia sclerotiorum are confirmed as homothallic ascomycetes.
• Inbreeding appears to be the predominant breeding mechanism for S. minor.
• While predominantly monomorphic, rare ascospore dimorphism exists in S. minor and S. sclerotiorum, warranting further investigation.