Entyloma helianthi: identification and characterization of the causal agent of sunflower white leaf smut

ABSTRACTWhite leaf smutis a minor foliar disease of sunflower( Helianthus annuus) in the United States. The disease occurs primarily in greenhouse-grown sunflowersin California and causes leaf spot, defoliation, and a reduction in yield and crop value. Historically, many Entylomaspecimens with similar morphological characters, but infecting diverse plant genera including Helianthus, were called Entylomapolysporum. Recent comparative morphological and molecular work has shown that Entylomaspecies infect hosts within a single genus or species, suggesting that the sunflower Entylomaspecies may not be E. polysporum. In 2015, sunflowerleaf smutmaterial was collected from ornamental sunflowersin a greenhouse in Santa Barbara County, California. Morphologically, this species differed from E. polysporum in having smaller, more regular-shaped teliosporesand prominently developed conidiophores with cylindrical conidia. The rDNA ITS1-5.8S-ITS2 ( internal transcribed spacer[ITS]) region of the sunflowerlea...