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The Mode of Sclerospora sorghi Infection of Sorghum Bicolor Leaves. B. L. Jones, Assistant Professor, Texas A&M University Agricultural Research and Extension Center, Weslaco, Texas 78596; Phytopathology 61:406-408. Accepted for publication 25 November 1970. DOI: 10.1094/Phyto-61-406.

The mechanism by which Sclerospora sorghi penetrates grain sorghum leaves was determined using conidia as inoculum. Germ tubes grew at random on the surface of the leaves and irregular swellings developed in germ tubes at epidermal cell junctions, but no penetration was observed. When a germ tube reached a stoma, elongation ceased and an appressorium formed over the stomatal opening. Once inside, the penetrating structure enlarged to form an oval-shaped substomatal vesicle. This vesicle then gave rise to one or more infection hyphae. Conidia formed during the night, germinated soon after discharge, and penetration was complete by 7:00 am. Haustoria were observed in host cells 3 hours later. This indicates that S. sorghi can enter its host and establish infection in 3 to 4 hours.