DIFFERENTIAL GROWTH RESPONSE, PHOSPHORUS ABSORPTION, TRANSPORT AND UTILIZATION BY WHEAT GENOTYPES UNDER PHOSPHORUS DEFICIENCY Soil and Environmental Sciences Division, Nuclear Institute of Agriculture, Tandojam, Pakistan

Abstract

Genotypic differences in phosphorus (P) acquisition and/or utilization can be exploited to enhance the efficiency of P fertilizers and crop productivity on P-deficient soils. Wheat genotypes were evaluated for relative growth rate, P absorption, transport and utilization in a hydroponic study at deficient P (10 µM) and adequate P (200 µM) levels. Phosphorus deficiency drastically reduced dry matter production, P accumulation in root and shoot, relative growth rate (RGR) of shoot, P absorption rate (PAR), and P transport rate of wheat genotypes. However, root- shoot ratio, RGR of root, and P utilization rate (PUR) of shoot and root increased significantly (P ? 0.001) in response to P deficiency. The genotypes SDW-4, SWD-6, YCBW-10 were found superior regarding dry biomass production and relative growth rate of shoot at low P, and therefore can be considered as P-efficient. Strong positive correlation of shoot dry matter with PUR of shoot (r = 0.80, P ? 0.001), while a non-significant relationship with PAR (r = 0.12, P ? 0.05) showed that P utilization was the dominant mechanism for high P efficiency in most of genotypes under P deficiency. The P-efficiency of SDW-6 and YCBW-10 at low P level could be explained by their higher PAR and PUR. However, P utilization appeared to be the main strategy for high P efficiency in SDW-4. The results suggested that wide variations exist among wheat genotypes for mechanisms responsible for P efficiency under low P supply which can be exploited in breeding ventures.