In vitro growth of gelatin suspensions of uredospores of Puccinia graminis f. sp. tritici

Abstract

A comparison was made of the growth of the Australian isolate of Puccinia graminis Pers. f. sp. tritici Eriks. & E. Henn. race ANZ 126-6,7 on 1.5% Difco Bacto-Agar using water and 15% gelatin as suspension media for seeding uredospores on the media. A range of media was tested, the basic constituents being 3% glucose, Czapek's minerals, peptone, and 1% bovine serum albumin. Spores embedded in gelatin gave much better growth than those applied to the agar surface in water suspension in all media. Sodium citrate (0.2%) inhibited growth; pectin (0.2%) did also, but partial recovery occurred later. Best growth was on the basic medium seeded with uredospores in gelatin. The mycelium was white and fluffy in appearance at first, but collapsed later as a dense brown stroma developed beneath it. Diffusion of brown pigment into the agar medium took place with the gelatin, but not the water series. Sporulation was observed after 60 days in a few colonies and was located in the brown stroma. Spores were non-pigmented, oval in shape, and similar in size to typical uredospores. It is suggested that the physical environment around the spores affects growth.