EFFECTIVENESS OF METHODS FOR ESTIMATING D ROUGHT TOLERANCE OF MAIZE (ZEA-MAYS L) GENOTYPES

Hungary is increasingly suffering from drought. A screening method for identifying more water stress tolerant maize hybrids would be an inex pensive and quick solution to eliminate yield decreases and fluctuatio ns. For this reason a two-season field experiment with two water suppl ies and 6 maize hybrids was carried out at Keszthely, Hungary. The tes t methods were: a, water uptake estimated weekly by soil moisture decr eases; b, proline accumulation as one of the responsible biochemical c ompounds for water retention ability; c. infrathermometrical plant str ess measurements for temporary soil-plant water status; d, grain yield evaluation under non stress and stress conditions. Methods were evalu ated by their selectivity and reproducibility. Each method has been pr oved to be selective, but their trends showed substantial differences. This fact raised the demand of complex evaluation. For instance, afte r silking infra stress indices and grain yields showed a good correlat ion. But yield is not the most proper basis for a comparison as yieldi ng ability is coupled with lower drought tolerance. Tendencies are als o influenced by genetically determined sink-source relationship Defoli ation as a method for expressing drought tolerance was rejected becaus e sink-source relationship disturbed the tendencies. Since the entire probleme of drought tolerance depends on reactions to different water supplies, the better understanding of water transport and use of maize is necessary. For this purpose an in situ sap sampling method has bee n developed, which is described in detailes.