Xylona heveaebelongs to the recently described class Xylonomycetes (Ascomycota). This novel clade was described based on strains isolated mainly as sapwood endophytes ofHevea brasiliensis(rubber tree). Six loci were used to place this new lineage within the Leotiomyceta; however, its evolutionary relationships with the other classes still remain unresolved. We only know the morphology of its anamorphic state (A). Conidiomata are pycnidial, astromatic and composed of thin-walled cells forming tissue textura angularis. Conidial masses (B) are liberated through the apical rupture of the pycnidia (ostiole absent). Conidiophores are absent. Conidiogenous cells are enteroblastic, phialidic, discrete, hyaline and presented one collarette (C). Conidia are apically rounded with two lateral obtuse projections appearing heart-shaped (narrower and truncated at base), hyaline when young, turning dark brick when mature, aseptate, thick-walled, smooth and guttulated (D). After ca. 3 weeks, both types of agar acquired a vinaceous diffusing pigment, especially at the margins of the growing colony.
We believe thatXylonamay represent a true endophytic lineage since no close relatives have been found as saprotrophs or plant pathogens, not even from environmental surveys. In marked contrast to many foliar endophytes, the strains we isolated failed to degrade cellulose and ligninin vitro, suggesting that this species might use different pathways to obtain nutrients from their hosts. (MycoCosm-JGI 2015)
