Ultrastructural studies on antagonist Phoma pomorum and Hemileia holarrhenae-the rust pathogens of bitter oleander

Rust of Bitter Oleander (Holarrhena antidysenterica) caused by Hemileia holarrhenae cause huge loss as well as reduction of its medicinal value. Present investigation deals with a fungal bioagent, Phoma pomorum parasitizing the rust pathogen H. holarrhenae. SEM studies revealed that uredial sori of H. holarrhenae were completely overgrown by mycelia of the Phoma pomorum. The hyphae of P. pomorum penetrated through surfaces of the rust pathogen uredosorus. The uredospores of rust were often seen penetrated and lysed by P. pomorum. Moreover, the uredospores of rust had shown flaccidity and were collapsed and divested of spikes on the spore wall surface. Our results form the maiden report of hyperparasitism of P. pomorum on H. holarrhenae in bitter oleander. These results need further re-confirmation and further screening to establish the potential antagonistic effects of P. pomorum on rust diseases induced by Hemileia spp in bitter oleander and other hosts.