Synopsis Varieties of wheat and of barley differed widely in their tolerance to acid soils containing high levels of KCl‐extractable Al. With few exceptions, varieties developed in the eastern United States were more tolerant than those developed in the Plains and Western States. Wheat varieties from Brazil were exceptionally tolerant. The results indicate that certain varieties have been selected for properties that are closely associated with their abilities to tolerate Al in acid soils.

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Kernel density, a component of test weight, is not associated with variety when considering Eastern soft wheats Triticum aestivum L. em Thell. (aestivum group), but seems to be related to environment. Air spaces within the grain appear to be a major factor in determining kernel density.Packing efficiency (the percent of bulk volume occupied by grain), the second component of test weight, is associated with variety. Grain shape and surface characteristics such as humping, dorsal or lateral depressions, and wrinkling, cause variations in void space ratio; hence they directly affect random packing efficiency.These conclusions were based on results with normal, well‐filled grain; any appreciable shriveling of grain confounds varietal and environmental effects.

‘Khapli’ emmer is resistant to those cultures of Erysiphe graminis f. sp. tritici with which it has been inoculated. ‘Yuma’ durum, which had Khapli as one parent, is resistant to the same E. graminis tritici cultures. Both Khapli and Yuma are tetraploids.A dominant gene for resistance to the powdery mildew fungus, herein designated as Pm4, has been transferred from Khapli into the genetic background of the hexaploid wheat variety Chancellor. The new line of Chancellor (Khapli ✕ Chancellor8) is homozygous for resistance and appears identical to Chancellor in morphological characters.A dominant gene for resistance to E. graminis tritici has been transferred from Yuma into Chancellor. Present evidence indicates that this gene is identical with that in Chancellor from Khapli.The gene from Khapli (Pm4) has been shown to be at a locus different from Pm1, Pm2, and Pm3.