Showing papers on "Plant disease resistance published in 1969"

Leaf rust resistance of some European varieties of wheat

Abstract: Twenty-one European wheat varieties from the World Wheat Assortment in Prague-Ruzynĕ (Czechoslovakia) that were resistant to leaf rust were tested with Canadian leaf rust races 1, 5, 9, 11, 15, 30, 58, and 126. The patterns of rust reaction and genetic studies on representative varieties suggest that the varieties Belocerkovskaja 198, Bezostaja 1, Mironovskaja 264, Mironovskaja 808, Osetinskaja 3, Rannaja 12, Skorospelka 3b, Fertodi 293, and Sladkovicovo K 1004 have gene Lr3, the variety Halle 9H39 has gene Lr1, the varieties Erythrospermum 142, 953, and 974 I.Z.R. have genes Lr1 and Lr3, and the variety Etoile de Choisy gene Lr16. The other varieties tested (Flevina, Sambo, Stabil, Uhcetice 22/IV, and 22/V) have reactions that are different from any of those of the single gene lines tested. The varieties Weique and Salzmunder Bartweizen were resistant to all races tested.

Physiology of disease resistance in sugarcane with particular reference to red rot

Abstract: Resistance to fungal and bacterial diseases of sugarcane is a hypersensitive reaction (HR). Meristematic tissues do not respond with HR; therefore, though present in differentiated cells, HR is not useful against root rot which destroys the root tips. Resistance against this disease is an exclusion phenomenon depending on the actinomycete and fungal flora of the rhizosphere. HR in red rot is related to the speed of activation of polyphenol oxidase (PPO) and this in turn is affected by temperature. On juvenile leaves, following germination of spores of an avirulent strain of the red rot pathogen, diffusates contain a factor (a phytoalexin) inhibitory to the germination of other spores. Dormant infections in bud scales and leaf-scar tissue is associated with partial resistance. Accumulation of phenolic aglycones in sublethal concentrations in host cells in response to infection induces formation of dormant structures of the pathogen. Higher temperatures (Ca 32° C.) favour development of avirulent types, whereas at lower temperatures virulent types persistin vivo. Rapid degeneration of the pathogen and greater host resistance at higher temperatures explain the infrequency of red rot in tropical areas; the reverse favours the frequent epiphytotics in sub-tropical areas.