Effect of Mineral Nutrition on Take-all of Wheat

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Abstract
Take-all of wheat caused by Gaeumannomyces graminis var. tritici developed on significantly fewer roots, and plants had a lower disease severity index when P, K and Mg were made available to the wheat roots in a silica sand rooting medium at twice, compared with 1/2, the concentration in normal Hoagland''s solution. Ca and S had no significant effect on take-all either at half or twice the concentration in normal Hoagland''s solution. The increased P, K and Mg also resulted in the greatest increase in root development compared with Ca and S, which had the least effect on numbers of roots. Increasing N (as nitrate) from half to twice Hoagland''s resulted in significantly more roots per plant, but disease severity on a given plant did not change significantly. Zn and Cu treatments each resulted in more roots and less take-all plant when supplied either to roots or leaves compared with treatments where those nutrients were withheld completely. Mn, and possibly Fe, also had suppressive effects on take-all as the supply was increased when applied in the rooting medium but not when applied by foliage sprays. In the field, the addition of Zn and Zn plus Peach resulted in less take-all in wheat plots under irrigation at Lind, Washington [USA]; and Zn, Cu and a mixture of Zn, Cu, Mn and Fe each reduced take-all of nonirrigated (rainfed) wheat in plots at Puyallup. The reduction of disease in the field was significant (P = 0.05) only at low and moderate levels of disease intensity. Certain macronutrients and micronutrients have the potential for limiting take-all, either by lessening susceptibility of the host tissues to the pathogen, promoting the formation of new roots, or by both mechanisms.