Elicitors of resistance: durability and specificity
1991
Newton, A.C. | Reglinski, T. | Lyon, G.D. (Scottish Crop Research Inst., Invergowrie, Dundee (United Kingdom))
Resistance elicitors derived from yeast cell walls and other biotic sources effectively protect detached leaves of barley from infection with powdery mildew (Erysiphe graminis f.sp. hordei) in proportion to their ability to elicit phytoalexin accumulation in soybeans. On detached leaves over 95 percent reduction in infection could be achieved. In the field elicitors were applied with a water but otherwise without formulation optimization, and were shown to be effective in controlling mildew on spring barley. Disease control, yield and thousand grain weight effects were cultivar specific. In the highly susceptible cv Golden Promise and the defeated resistance cv Triumph all treatments reduced mildew infection. Treatments were most effective on cv Triumph where one yeast extract reduced infection by over 50 percent, and several treatments either equalled or exceeded respective fungicide values for yield and thousand grain weight. Resistance elicitors work by "warming-up" or "priming" the resistance mechanisms so that they respond faster when the pathogen is recognised. Measurements of papilla formation following infection after elicitor treatment showed that the mode of action may be to accelerate their formation in a similar way to Mlo resistance. If the effect is upon the resistance mechanism regulatory genes (suppressor genes) and not upon the recognition genes themselves it will probably be durable. Cultivar resistance expression differences may be attributable to resistance mechanism or regulatory gene differences, but yield response differences may be due to secondary effects on host metabolism affecting disease tolerance
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