Fusarium Head Blight Inoculum: Species Prevalence and Gibberella zeae Spore Type

Area of Science:

• Plant Pathology
• Agricultural Science
• Mycology

Background:

• Fusarium species, particularly Gibberella zeae, are significant pathogens affecting wheat.
• Understanding the relative abundance and roles of different spore types (ascospores and conidia) is crucial for disease management.

Purpose of the Study:

• To quantify Gibberella zeae ascospores and conidia on wheat spikes.
• To correlate G. zeae inoculum levels with airborne spore counts.
• To assess the efficacy of a bioassay for inoculum detection.

Main Methods:

• Field monitoring of Fusarium species and airborne G. zeae spores over three growing seasons.
• Utilized a 24-h potted-plant bioassay and a spring wheat plot bioassay for spore collection.
• Employed selective media for Fusarium enumeration and microscopic analysis for G. zeae spore typing.
• Used a Burkard cyclonic sampler for airborne spore measurement.

Main Results:

• Fusarium graminearum was the most common Fusarium species on wheat spikes.
• Ascospores of G. zeae were recovered at approximately twice the rate of conidia in both bioassays and air sampling.
• Conidial inoculation resulted in significantly higher colony recovery from wheat spikes compared to ascospore inoculation at equal concentrations.

Conclusions:

• Gibberella zeae is the predominant Fusarium species inoculum in North America.
• Despite the prevalence of ascospores, conidia play a vital role in the primary wheat disease cycle.
• The bioassay technique shows promise for evaluating inoculum levels and spore type contributions.