Surveys were conducted during the cool‐dry months of June–August 1997 and June–July 1998 for the presence of viruses in irrigated wheat in Central, Copperbelt, Lusaka and Southern Provinces of Zambia in 14 commercial farms and four wheat cultivar plots. Virus symptoms were observed on nine wheat cultivars (Triticum aestivum‘Deka’, ‘Gamtoos’, ‘Lorie II’, ‘MM2’, ‘Nata’, ‘Nkwazi’, ‘P7’, ‘Scan’ and ‘Sceptre’) of South African, Zambian and Zimbabwean origin. Several viruses were identified on the basis of field symptomatology, symptoms developing on mechanically inoculated indicator plant species or cultivars and serology (DAS‐ELISA). The study revealed the occurrence of Brome mosaic virus (BMV), Barley stripe mosaic virus (BSMV), Barley yellow dwarf virus and its strains (BYDV‐PAV and RPV), Soil‐borne wheat mosaic virus (SBWMV), Wheat dwarf virus (WDV), Wheat streak mosaic virus (WSMV) and Wheat spindle streak mosaic virus (WSSMV). DSA‐ELISA tests confirmed these identifications. The prevalence of viruses varied annually and from field to field. BSMV, BYDV‐PAV, SBWMV, WDV, WSMV and WSSMV were found to be the most prevalent viruses. Viruses generally occurred in mixed infections of 3–6 viruses and the most common virus complex consisted of 4 viruses (50%), viz. BYDV, SBWMV, WDV and WSSMV. Five‐ and six‐virus complexes were relatively less common (20% each) whereas 3‐virus complex was noticed in only 10% cases. SBWMV and WSSMV have been found to be new to Africa and Zambia and are reportedly vectored by a fungal protist –Polymyxa graminis. BYDV strains MAV and SGV were also tested but gave negative results against their antisera.

Germ tubes of Uromyces fabae differentiated into appressoria wh ich were deliminated either by one or two septa. These appressoria developed rapidlyon artificial membranes as well as on leaf surfaces.Fluorescein-conjugated wheat germ aggJutinin (WGA) bound strongly tO the germ tube walls of U. fabae and its binding ability did not differ significantly in 3, 5 and 7 hold germ tubes. The binding of WGA was less on the appressorium. Measurement of fluorescence with a lnicroscope photometer revealed two times more binding sites on germ tube walls than on appressoria. No binding of WGA was noticed on substomatal vesicles and infection hyphae. The binding of WGA was completely inhibited by preincubation with hydrolysate of chitin. Biflding patterns of other Jectins were quite different. Canavalia ensiformis lectin did not bind tO any structure, the Jectins of Griffonia simplicifolia and Lotus tetragonolobus bound weakly to all structures, the lectins of Phaseolus vulgaris and Arachis hypogaea bound only tO substomatal vesicles and infection hyphae, and the Ricinus communis lectin bound only tO the infection hyphae. Based on these observations it appears that infection structure surface of U. fabae, besides having chitin as a component, also contain some other carbohydrates such as galactOse and fucose.

Teleutospores of Puccinia horiana P. Henn. germinate soon after their formation. Promycelia germinating on microscope slides have a tendency to grow in length and become narrow in outline; when germinating in situ, developing promycelia are short and stout, and show a lobed apical cell. The promyceliurn is usually three-celled, but at times it is one-or two-celled.Two basidiospores are usually produced by each promycelium (observed range one to three). Basidiospores are uni-or binucleate at first, but later become multinucleate. They germinate rapidly on microscope slides and on host leaves, when sufficiently wet. Three different patterns of basidiospore germination were observed.

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