ALUMINUM TOLERANCE OF SEGREGATING WHEAT POPULATIONS IN ACIDIC SOIL AND NUTRIENT SOLUTIONS

Increased demand for wheat (Triticum aestivum L.) cultivars tolerant to acid-soil stress has accelerated genetic research on aluminum (Al) tolerance in soil and solution media. Our objective was to characterize the genetic segregation of tolerant and susceptible plants from two populations in an Al-toxic Porters soil (coarse-loamy, mixed, mesic Umbric Dystrochrepts), and in nutrient solutions with 0.09, 0.18, 0.36, 0.72, and 0.90 mM Al. Rapid bioassays were applied to determine seedling responses of two Al-tolerant (Cardinal and Becker) and two susceptible cultivars (GK Zombor and GK Kincso) and their F2 progenies. In the Al-toxic soil, Becker/Kincso F2 and Cardinal/Zombor F2 exhibited contrasting segregation patterns but with similar heritability values (0.60 and 0.57, respectively). Higher values of root length in soil were dominant in Cardinal/Zombor F2 (degree of dominance, d = 0.98), but dominance was absent (d = 0.07) for Becker/Kincso F2. The results of the soil and nutrient-solution experiments were not entirely consistent; gene expression appeared to be influenced by the concentration of Al in the nutrient solution. The frequency of susceptible F2 plants increased proportionately to the increase in Al concentration for both populations. This unexpected pattern provides further evidence that segregation wheat populations cannot always be explained by single-gene inheritance.