Perithecium Formation and Ascospore Discharge in Fusarium graminearum

Background

The ascomycete fungus Fusarium graminearum is the major causal agent of wheat Fusarium head blight and maize Gibberella stalk rot. This fungus can produce sexual fruiting bodies–perithecia on the surface of colonized host plants, the perithecia overwinters on crop debris and discharge ascospore for next year epidemic (Goswami and Kistler, 2004). Favored by moist and warm conditions, ascospores are forcibly discharged from perithecia and become airborne in air currents as the primary inoculum.

This fungus is homothallic; most strains can produce perithecia on carrot agar easily in vitro (Trail and Common, 2000). The microscopic study and a thorough description of perithecia development have been reported with temporal transcriptomic analysis during sexual development of F. graminearum (Trail and Common, 2000; Hallen et al., 2007). After induction of haploid hyphae at 0 h in vitro, dikaryotic cells formed and perithecium initiated at 24 h, young perithecia with central ascogenous cells and developing walls appeared at 48 h. The central ascospore matured at 144 h (Hallen et al., 2007). Studies have been conducted on factors that affect ascospore discharge and have concluded that relative humidity and temperature significantly affect the discharge process, while the light is not essential but it can help (Trail et al., 2002).

In this protocol, we outline the method of studying perithecium formation and ascospore discharge in F. graminearum, facilitating the identification of genes that have specific roles in sexual development and disease cycle.