Understanding the Interactions between Biomass, Grain Production and Grain Protein Content in High and Low Protein Wheat Genotypes under Controlled Environments

Abstract

Grain protein content (GPC) is a key quality attribute and an important marketing trait in wheat. In the current cropping systems worldwide, GPC is mostly determined by nitrogen (N) fertilizer application. The objectives of this study were to understand the differences in N response between high and low GPC wheat genotypes, and to assess the value of biomass growth analysis to assess the differences in N response. Six wheat genotypes from a range of high to low GPC were grown in low, medium and high N, under glasshouse conditions. This experiment was designed around non-destructive estimation of biomass using a high throughput image-based phenotyping system. Results showed that Spitfire and Mace had higher grain N% than Gazelle and QAL2000, and appeared to demand more N to grow their biomass. Moreover, at low N, Spitfire grew faster and achieved the maximum absolute growth rate earlier than high N-treated plants. High grain N% genotypes seem able to manage grain N reserves by compromising biomass production at low N. This study also indicated the importance of biomass growth analysis to show the differences in the N responsiveness of high and low GPC wheat.

Strengths and Weaknesses of National Variety Trial Data for Multi-Environment Analysis: A Case Study on Grain Yield and Protein Content

“…The NVT data show that a 1 t/ha increase in yield leads to an average GPC loss of 0.45% and 1.63% in ET0 and ET4, respectively. Previous studies on wheat also found a stronger negative relationship between yield and GPC under low N compared to high N supply [20,33,51]. The strong GPC-yield trade off under low N conditions can be due to a higher priority for the plants to maintain grain number and weight than for grain protein accumulation.…”

“…In order to assess the reliability of the ET effects on yield and GPC, six varieties were examined and compared to the full dataset (Figures 4 and 5). The same varieties were used previously to examine their responses to N application in a controlled environment where plant growth rates were assessed [33]. In the previous study, it was found that the severity of stress, in that case the stress was induced through N starvation, intensified the negative relationship between yield and GPC.…”

“…The strong GPC-yield trade off under low N conditions can be due to a higher priority for the plants to maintain grain number and weight than for grain protein accumulation. A study on wheat [33] showed that under low N, high GPC varieties bred for low yielding environments sacrificed biomass and, consequently, yield in order to reserve N for grain protein. Conversely, low GPC varieties selected for high yielding regions used the available N primarily for biomass and yield regardless of grain N concentration.…”

“…Achieving significant genetic gain for both yield and protein is difficult, given the large environmental and relatively small genetic component. Controlled environment studies have been helpful in understanding the impact of stress on the yield/protein relationship [11,20,33] but these results require validation through actual field trials. Here we have explored the option of exploiting the extensive field trial data used to evaluate germplasm across a large number of environments.…”

“…Our previous study in a controlled environment indicated a stronger inverse relationship between grain yield and GPC under low nitrogen (N) treatment in selected wheat varieties [33]. Since N deficiency can be associated with water availability [34,35], it is worthwhile to search the effect of ETs on the grain yield-GPC relationship.…”