The Genetic Control of Grain Protein Content under Variable Nitrogen Supply in an Australian Wheat Mapping Population

<div><p>Genetic variation has been observed in both protein concentration in wheat grain and total protein content (protein yield). Here we describe the genetic analysis of variation for grain protein in response to nitrogen (N) supply and locate significant genomic regions controlling grain protein components in a spring wheat population. In total, six N use efficiency (NUE) field trials were carried out for the target traits in a sub-population of doubled haploid lines derived from a cross between two Australian varieties, RAC875 and Kukri, in Southern and Western Australia from 2011 to 2013. Twenty-four putative Quantitative Trait Loci (QTL) for protein-related traits were identified at high and low N supply and ten QTL were identified for the response to N for the traits studied. These loci accounted for a significant proportion of the overall effect of N supply. Several of the regions were co-localised with grain yield QTL and are promising targets for further investigation and selection in breeding programs.</p></div

The Genetic Control of Grain Protein Content under Variable Nitrogen Supply in an Australian Wheat Mapping Population - Fig 1

<p>Grain protein concentration (GPC, %) (A) and Protein yield (PY, kg ha-1) (B) of RAC875 and Kukri in nitrogen (N) use efficiency field trials across Australian sites. The vertical error bars represent the standard errors of the predicted means after spatial analysis.</p

Phenotypic performance of RAC875 × Kukri population for protein-related traits across southern Australian trial sites in three seasons (2011–2013).

<p>Phenotypic performance of RAC875 × Kukri population for protein-related traits across southern Australian trial sites in three seasons (2011–2013).</p

The location, climate and basic soil characteristics, growing conditions and average grain yield (GY, kg ha^-1) of five southern Australian trial sites used for nitrogen use efficiency field trials in this study.

<p>The location, climate and basic soil characteristics, growing conditions and average grain yield (GY, kg ha^-1) of five southern Australian trial sites used for nitrogen use efficiency field trials in this study.</p

Comparison of the loci identified in this study with previous reports of loci associated with grain protein or nitrogen content.

<p>The loci identified in this study are shown on the right of each stylized chromosome while those found in previous studies are labelled as GNC (Grain nitrogen/protein content) on the left. The positions are only approximate since a direct alignment of the loci is not possible since the markers and maps are very different and the studies vary greatly in their level of genetic resolution. The superscript numbers before each GCN loci refer to the reference.</p

Phenotypic correlation coefficients of grain yield (GY, kg ha^-1) and grain protein concentration (GPC, %) for all genotypes, parental lines and doubled haploid lines, in nitrogen use efficiency field trials in southern Australia, 2011–2012.

<p>Correlation coefficients of GY and GPC in the trials are in bold.</p

Additional file 4: Figure S3. of Genetic association of stomatal traits and yield in wheat grown in low rainfall environments

Morphological features of a single stomata. Arrows indicate aperture length (APL) and width (APW) and guard cell length (GCL) and width (GCW). Aperture area (APA) and guard cell area (GCL) were calculated by multiplying the length and width of the rectangle. (DOCX 261 kb

Additional file 1: Figure S1. of Genetic association of stomatal traits and yield in wheat grown in low rainfall environments

Frequency distribution of phenotypes for stomatal size related traits and yield in the RAC875/Kukri DH lines based on means obtained over each experiment. a) Lameroo, b) Roseworthy, c) Well watered conditions in the glasshouse, d) Drought conditions in the glasshouse. Arrows indicate phenotypic values of RAC875 (R) and Kukri (K). (PPTX 264 kb

Genomic regions underlying the single effect of nitrogen (N) on grain yield-BLUPs, adjoining markers (closest in bold), peak position (cM), logarithm of odds (LOD), <i>R</i>^<i>2</i> (%) and additive effect in trials at various Australian sites.

<p>Genomic regions underlying the single effect of nitrogen (N) on grain yield-BLUPs, adjoining markers (closest in bold), peak position (cM), logarithm of odds (LOD), <i>R</i>^<i>2</i> (%) and additive effect in trials at various Australian sites.</p

Distribution of doubled haploid lines for grain yield at high rate of nitrogen (N) fertilisation at six trial sites in South Australia and Western Australia.

<p>For each site, grain yields of RAC875 and Kukri are shown by the positions of the letters R and K, respectively.</p