Work has progressed on our mineral stress studies using the maize composite, "Supermix." We presented data in the last newsletter indicating that aluminum response is primarily determined by a multi-allelic series at a single locus. Among our present objectives is to study the interaction between high aluminum, low calcium and low phosphorus stress response. This should help us better understand the mechanism of aluminum response.
Selections were made last Spring for aluminum, calcium and phosphorus response on 2-week old maize seedlings grown in different nutrient stress solutions. Selection was on the basis of primary root growth for aluminum response and visual deficiency symptoms for calcium and phosphorus response. The most stress-resistant and stress-susceptible seedlings were transplanted to the field and selfed. Eight to fourteen full-sib families were thus obtained for each group. Response of the full-sib family selections compared to response of full-sib randomly chosen controls estimates the selection effect.
Selection for calcium efficiency and inefficiency was not markedly successful. Aluminum and phosphorus selection was quite effective, as demonstrated in the tables below. The data compare seedlings grown for two weeks in stress and non-stress solutions.
Mineral analysis of both selections is still being completed. We will also be running the aluminum selections under phosphorus and calcium stress, and the phosphorus selections under aluminum and calcium stress.
Finally, other groups selected for differences in root size will be tested under all three stresses to see if root size affects stress response.
E. William Stockmeyer and Herbert L. Everett
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