Variation in Yield, Phosphorus Uptake, and Physiological Efficiency of Wheat Genotypes at Adequate and Stress Phosphorus Levels in Soil

Genetic differences among crop genotypes can be exploited for identification of genotypes more suited to a low-input agricultural system. Twenty wheat (Triticum aestivum L.) genotypes were evaluated for their differential yield response, phosphorus (P) uptake in grain and straw, and P-use efficiency at the zero-P control and 52kgPha-1 rates. Substantial and significant differences were obvious among genotypes for both grain and straw yields at stress (8mgPkg-1 soil, native soil P, no P addition) and adequate (52kgPha-1) P levels. Genotype 5039 produced maximum grain yield at both P levels. Relative reduction in grain yield due to P-deficiency stress [i.e., P stress factor (PSF)] ranged between none and 32.4%, indicating differential P requirement of these genotypes. Pasban 90, Pitic 62, Rohtas 90, Punjab 85, and line 4943 did not respond to P application and exhibited high relative yield compared to those at adequate P level. FSD 83 exhibited the best response to P with maximum value for PSF (32.4%). Genotypes were distributed into nine groups on the basis of relationship between grain yield and total P uptake. Rohtas 90 and lines 4072 and 5039 exhibited high grain yield and medium P uptake (HGY-MP). However, line 5039 with high total index score utilized less P (12.2kgPha-1) than line 4072 and Rohtas 90 (13.5 and 13.6kgPha-1, respectively). Moreover, this genotype also had greater P harvest index (PHI, %) and P physiological efficiency index (PPEI) at stress P level. Pasban 90, Pitic 62, and Pak 81 had the greatest total index score (21), mainly due to high total P uptake, but yielded less grain than lines 5039 and 4072 under low available P conditions. Line 6142 had minimum total index score (15) and also produced minimum grain yield. A wide range of significant differences in PPEI (211 to 365kg grain kg-1 P absorbed at stress and 206 to 325kg grain kg-1 P absorbed by aboveground plant material at adequate P) indicated differential utilization of absorbed P by these genotypes for grain production at both P levels. It is concluded from the results that wheat genotypes differed considerably in terms of their P requirements for growth and response to P application. The findings suggest that PSF, PHI, and PPEI parameters could be useful to determine P-deficiency stress tolerance in wheat.