Lagena—an overlooked oomycete genus with a wide range of hosts

Abstract

Lagena has so far only been known from the scarcely reported but widespread species Lagena radicicola, which is a parasite of root epidermal cells. While it was mostly reported from a wide range of cereals and other grasses, it has been shown to affect some dicot species under, e.g. tobacco and sugar beet. Due to the wide host spectrum under laboratory conditions, there were no attempts to subdivide the genus into several species, even though some morphological differentiation was reported and the species had been found in several continents. During a survey of diatoms, we came across some parasitoids that would have previously been assumed to be members of the genus Lagenidium. The species exhibited rather narrow host specificity in nature. One species was brought into dual culture with host diatoms of the genus Ulnaria, but could not be transferred to other host genera. Surprisingly, phylogenetic analyses revealed that Lagena radicicola was in a sister clade to that formed by the diatom parasitoids, suggesting a versatile pathogenicity of the genus. Interestingly, several phylogenetic lineages only known from environmental sequencing were clustered with the species found in this study, hinting an undiscovered diversity in the genus Lagena.