Phosphorus affects high-molecular-weight glutenin subunits and glutenin macropolymer size distribution in wheat grains

Two winter wheat (Triticum aestivum L.) cultivars, Jimai20 and Shannong12, differing in phosphorus (P) utilization efficiency, were selected to study the effect of P application rate on changes in glutenin macropolymer (GMP) size distribution and the content of high-molecular-weight glutenin subunits (HMW-GS) in wheat grain. Four P levels (0, 40, 100 and 160 kg/ha) were applied under N1 (112.5 kg/ha) and N2 (225 kg/ha) conditions in the field, in 2008/09 and 2009/10. The results showed that increased P levels favoured HMW-GS synthesis under N1 conditions, but had a less pronounced effect under N2. When compared with the control, the volume proportions of <10 mu m GMP particles in grains of both cultivars were significantly decreased, and those of >100 mu m were increased in response to P application. The volume proportions of 10-100 mu m GMP particles in the cultivars Jimai20 and Shannong12 were respectively lower and higher in response to P application than with no P fertilizer. At maturity, for both cultivars, total HMW-GS content was negatively correlated with GMP particle volume of <10 mu m, but positively correlated with that of >100 mu m. These observations suggest that both P and N affect protein synthesis in wheat grains and there exists a relationship between HMW-GS content and the synthesis of large GMP particles (>100 mu m). The NxP interaction was the most important factor to regulate the HMW-GS and GMP contents.