Two new species of Pustula (Albuginales, Oomycota) from northern Iran

The order Albuginales contains the causal agents of white blister rust disease and currently comprises the three genera Albugo, Pustula, and Wilsoniana. Following surveys conducted during the growing seasons of 2018-2019, samples of white blister rust pathogens of the genus Pustula were taken from three asteraceous hosts including Senecio vernalis, S. vulgaris, and Xeranthemum inapertum in the northern Iranian provinces Golestan and Guilan. Based on morphological and molecular analyses, two new species, Pustula senecionis sp. nov. on Senecio spp. and Pustula thinesii sp. nov. on Xeranthemum inapertum, are introduced and illustrated. The latter species can be distinguished from P. spinulosa by its smaller oospores, and primary and secondary sporangia, and from P. centaurii by its smaller oospores and secondary sporangia.