GENETIC-VARIATION AMONG MAIZE GENOTYPES FOR PHOSPHORUS-UPTAKE AND PHOSPHORUS-USE EFFICIENCY IN NUTRIENT SOLUTION

Parental genotypes and their derived hybrids of maize (Zea mays L.) we re studied in nutrient solution for phosphorus (P)-uptake and P-use ef ficiency under greenhouse conditions. In the first trial, three hybrid s were evaluated: HS 1227, HS 7777 (simple-crosses), and HD 7974 (HS 1 227 x HS 7777). In the second trial, four inbred lines [L4 and L40 (P- inefficient), L29 and L42 (P-efficient)], three Fl hybrids [(L29xL42), (L40xL4), (L4xL29)], and a commercial hybrid (AG 401), were tested. P lants were grown with 0.360 mmol P in 2.7 liter pots, up to 29 days (1 st experiment) and 21 days of age (2nd experiment). Thereafter, plants were transferred to a P-free nutrient solutions for 24 hours, before three P levels were added(0.180, 0.360, and 0.720 mmol P). Phosphorus uptake rates (depletion) were determined under controlled conditions d uring 5.25 hours (1st experiment) and 3.5 hours (2nd experiment). Plan ts were also evaluated for shoot and root dry matter, root length, P c ontent, P distribution, and P-use efficiency. Most the favorable chara cteristics for P uptake and use efficiency identified in some of the p arental genotypes, in both experiments, were also found in the derived hybrids, indicating that the P-efficiency characters studied might be heritable and under genetic control.