RELATIONSHIP BETWEEN MAIZE TOLERANCE TO LOW PHOSPHORUS CONTENT IN THE SOIL AND THE PHOSPHORUS RESPONSIVENESS

Looking for meet the growing worldwide demand for food a significant fraction of crops can be performed on infertile soils. Thus, several programs directed the plant breeding for stress conditions due to low availability of phosphorus (P). In this context, two strategies can be considered: tolerance to low soil P availability, and responsiveness to their availability. So, the aims of this research were to identify the relationship between tolerance to low soil P levels and responsiveness to phosphorus fertilization in tropical maize cultivars. Two experiments were conducted in the Agricultural Sciences Complex of UNITINS (48 degrees 21"47'W, 10 degrees 24"09'S), Palmas, TO, in the 2004/2005 growing season. Thirty six commercial cultivars were evaluated in two contrasting P availability in soil (in each trial). The experimental design was simple lattice (6 x 6), where the plots consisted of two rows of 5.0 m, spaced by 1.0 m, with a density of 50,000 plants ha(-1). The traits evaluated were grain yield and the indexes a) response to the nutrient availability; b) phosphorus use efficiency (considered as tolerance). The most responsive cultivars were NB 7361, 551 BALU, SHS 4070 and SHS 4080. On the other hand, the cultivars XB 7253, AG 7040, CD 308, CD 307 and XB 2271 were more tolerant. In addition, negative significant correlation between tolerance and responsiveness (-0.58**) in tropical maize cultivars was observed.