A GREENHOUSE SCREENING TECHNIQUE FOR ACID SOIL TOLERANCE IN MAIZE

Evaluating maize (Zea mays L.) in the field for tolerance to soil acid ity is expensive and provides variable results. To identify alternativ e screening techniques for maize, the present study adapted a pot bioa ssay already used for other crops. Two experiments were conducted. One included a set of diallel crosses from eight parents and the other a set of 10 open-pollinated cultivars. These materials were evaluated un der field conditions, in nutrient solution, and in pots containing 2 k g of soil. The best results were obtained after growing plants for 14 d in pots containing soils having intermediate stress (45-65% Al satur ation). Fresh root weight, total length (or lateral root length), and visual scoring provided the best separation between tolerant and susce ptible genotypes, lacked a significant genotype x soil interaction, an d were efficient, simple, and rapid measurements. Significant phenotyp ic correlations (approximate to 0.55) were observed between these vari ables and yield in the held. While efficiently distinguishing tolerant from susceptible genotypes, the pot bioassay could not clearly detect differences in levels of tolerance. This technique should be useful m ainly in the early stages of maize breeding. Results suggest that maiz e possesses several mechanisms for tolerance to soil acidity.