Rice false smut pathogen, Ustilaginoidea virens, invades through small gap at the apex of a rice spikelet before heading

Abstract

Ustilaginoidea virens, the false smut pathogen of rice, produces false smut balls on spikelets after heading. To clarify how the fungus invades spikelets during the booting stage, we developed a fungal strain that expresses a green fluorescent protein gene and injected conidia from this strain into rice sheaths. Observations at 48 h post-inoculation showed many conidia were present on spikelet surfaces, and the conidia had germinated and the hyphae have gradually grown by 120 h post-inoculation. By 144 h, hyphae had invaded spikelets through their apices, via the small gap between the lemma and palea and had already reached all floral organs.