Spring barley grown in field conditions
The field-grown spring barley grain yields (Table ) showed that in 2007 the average yield was higher in the high-N field, while in 2008 the average yield was higher in the low-N trial. The overall grain yield trends were very similar to the plant-height trends (Fig. S1 in Supplementary data
, available online) in that the low-N treatment in 2007 had the overall lowest grain yields for all genotypes.
Table 2. Grain yield, total plant N, N uptake efficiency (NUpE), N utilization efficiency (NUtE) and NUE for ten spring-barley genotypes grown in field conditions during the 2007 and 2008 growing seasons at either low (115 Kg N ha−1 in 2007; 119 kg N ha (more ...)
Spring barley grown in potted growth chamber
The four genotypes showed some effects from being grown in N-limiting conditions (Fig. ). Genotype (P ≈ 0·000) and N concentration (P ≤ 0·05) were significant factors contributing to shoot dry weight at anthesis, with genotype as most significant. All the genoptype pairings were significantly different in shoot weight (P ≤ 0·01) except for Vivar versus CDC-Copeland. Barley grown at 25 and 75 % N were significantly different (P ≤ 0·045) in shoot dry weight, with the higher N supply allowing for higher shoot dry weight.
Fig. 1. Morphological characteristics of four spring-barley genotypes grown in Sunshine mix #4 in a growth chamber, at four different N concentrations (25, 50, 75 and 100 % N). In (A) and (B), measurements were taken at anthesis, when 50 % of the plants for each (more ...)
The flag leaf width measurements at anthesis showed that genotype (P ≈ 0·000) and N concentration (P ≤ 0·01) were both significant factors contributing to this characteristic. All genotype pairings were significantly different (P ≤ 0·048) except for Morex versus Kasota. Barley grown at 25 versus 75 % N (P ≤ 0·027) and 25 versus 100 % N (P ≤ 0·001) were significantly different in flag leaf width. The plants supplied with higher N supply grew wider flag leaves, except for Morex which showed a slightly lower flag leaf width at 100 % N than at 75 % N, although not significantly so.
Genotype and N concentration were both equally significant factors (P ≈ 0·000 each) contributing to the shoot dry weight of the potted barley at maturity. All the genotypes versus CDC-Copeland were significantly different in shoot dry weight (P ≤ 0·001), while no other pairings showed any significant differences. Barley grown at 25 and 50 % N versus 100 % N (both at P ≈ 0·000) were significantly different in shoot dry weight. Like the shoot dry weight at anthesis, the higher N supply allowed for a larger shoot dry weight at maturity too. By maturity though, Morex, Vivar and Kasota were all very similar in shoot dry weight to each other.
Genotype (P ≈ 0·00) and N concentration (P ≤ 0·09) were both significant factors contributing to grain yield of the potted growth chamber-grown barley. As well, the different genotypes responded to differing N concentrations significantly for grain yield (P ≈ 0·00). All genotype pairings were significantly different (P ≤ 0·16) except for Morex versus Vivar. Barley grown at 50 % N versus 100 % N was significantly different in grain yield (P ≤ 0·05). Morex and Vivar both showed higher grain yields with higher N supply; however, Kasota and CDC-Copeland both had lower grain yields at 100 % N supply as compared with the other three, lower N supplies.
Spring barley grown in hydroponic growth chamber
Figure shows the shoot, root and total dry weight of four genotypes at varying N treatments at 42 DAG, just prior to anthesis.
Fig. 2. Morphological characteristics of four spring-barley genotypes grown in a hydroponic growth chamber, at four different N concentrations (0·5, 2, 4 and 8 mm nitrate): (A) shoot dry weight; (B) root dry weight; (C) total dry weight. Measurements (more ...)
Genotype was not a significant factor, while N concentration was a significant factor (P ≈ 0·000) contributing to shoot dry weight of the hydroponic barley. The shoot dry weight of barley grown at 0·5 mm N was significantly different from the rest of the dry weights (P ≈ 0·000), being much lower in weight for all genotypes than the barley grown at the higher N supply.
Genotype (P ≤ 0·048) and N concentration (P ≈ 0·000) were both significant factors contributing to root dry weight of hydroponic barley. Also, different genotypes respond to differing N concentrations significantly (P ≤ 0·004) for root dry weight. Kasota and CDC-Copeland were significantly different from each other (P ≤ 0·046), while all other pairings were not. Barley grown at 0·5 mm N was significantly different for root dry weight from the other three higher N supplies (P ≤ 0·002) while the root dry weights of barley grown at 2 mm N was also significantly different from the other root dry weights of barley grown at any other N supply (P ≤ 0·004). All genotypes showed suppressed root dry weights at the lowest N supply, and for the highest N supply, except for Kasota which had the largest root dry weight at 8 mm N. Although the root dry weights were very low for the 0·5 mm N supply, they were also much longer than the roots of the plants grown at the higher N levels (data not shown).
For the total dry weights of the hydroponically grown barley, genotype was not significant while N concentration was a significant factor (P ≈ 0·000). Barley grown at 0·5 mm N was significantly lower in total dry weight than the barley grown at 2, 4 or 8 mm N (P ≈ 0·000). There was no significant difference in total dry weight of the plants grown at the higher N supply.
Amino acid concentrations were measured in the shoots of Vivar and Kasota grown in field trials in 2008 at both low and high available N (Table ). Six amino acids – asparagine (asn), histidine (his), arginine (arg), methionine (met), tryptophan (trp) and proline (pro) –increased significantly (P ≤ 0·09) in Kasota when grown on high N compared with low N. There were no significantly different amino acid concentration changes in Vivar grown on high to low N. Four amino acids – glutamate (glu), glycine (gly), threonine (thr) and pro –were measured at significantly (P ≤ 0·09) higher levels in Kasota grown at high N versus Vivar at high N. Six amino acids – glu, asn, glutamine (gln), thr, alanine (ala) and leu (leu) – were found to increase significantly in Kasota again, versus Vivar, when both genotypes were grown at low N.
Amino acid concentrations (μmol g−1 f. wt) in shoots of Vivar and Kasota grown in the field with either low (119 kg N ha−1) or high (198 kg N ha−1) N fertilizer in 2008
PCA of these data retained 92·3 % of the variation in PC1 and 4·8 % in PC2, accounting for 97·1 % of the variation (Fig. A). The amino acid data grouped between genotypes when grown at high N only. One group comprised Kasota shoots grown at high N while the other group was Vivar at both N treatments and Kasota at low N. These first two principal components were significant (P < 0·0) using the permutation test 500 times. The loading plot for Fig. A (data not shown) showed that the gln concentration was much higher in the high N-grown Kasota than the rest of the analysed tissue. Pro, asn and thr concentrations were also elevated in Kasota shoots at high N, but to a lesser degree than gln.
Fig. 3. Principal component analysis (PCA) of amino acid metabolite levels from (A) the shoots of Vivar and Kasota genotypes grown in field conditions at low and high supplied N in the Canadian 2008 growing season (V-Lo, V-Hi, K-Lo and K-Hi) and (B) the roots (more ...)
Amino acid concentrations were measured in the roots and shoots of Vivar and Kasota grown in hydroponic growth-chamber conditions at 0·5, 4 and 8 mm nitrate (Table ). Significant differences (P ≤ 0·05) in amino acid concentrations were determined for a variety of comparisons. Four amino acids – his, phenylalanine (phe), isoleucine (ile) and lysine (lys) – were all significantly reduced in concentration in the shoots of Kasota grown at 4 mm N versus 0·5 mm N, whereas in the roots, aspartate was the only amino acid significantly changed in Kasota grown at 0·5 versus 4 mm N, being found in increased concentration at the higher N supply. There was no significant change in amino acid concentrations in the shoots of Kasota grown at either 4 or 8 mm N, while, in the roots, thr and tyrosine (tyr) both significantly increased in Kasota grown at 8 mm N versus 4 mm N. Glu significantly increased in the shoots of Vivar grown at 4 mm N versus 0·5 mm N, while, in the roots, glu and ala both significantly increased in Vivar grown at 4 mm N versus the lower N supply. When Vivar and Kasota, both grown at 0·5 mm N, were compared there was an increase in phe in the shoots in Kasota, but no significant change in the root amino acid concentrations. When the amino acid concentrations are compared between 0·5 mm N-grown Kasota roots and shoots, six were significantly different – asp, glu, serine (ser), thr, ala and phe –all with higher concentrations in the shoot. There were no significant differences between 4 mm N-grown Kasota roots and shoots. When Kasota was grown on 8 mm N there were again six amino acids with significantly different concentrations – glu, gly, ala, tyr, trp, and leu – but this time gly, ala, trp and leu were higher in concentration in the roots than the shoots. Comparison of the roots and shoots of 0·5 mm N-grown Vivar showed five significantly different concentrations of amino acids – glu, thr, ala, trp, and leu – with the last two higher in the roots than the shoots. At 4 mm N, Vivar had significantly different concentrations of glu, gln and lys in the roots and the shoots, with gln and lys higher in the roots than the shoots. At 8 mm N, asp, tyr, ile and leu were found in significantly different concentrations between the Vivar roots and shoots, asp being higher in the shoots and the rest higher in the roots.
Amino acid concentrations (μmol g−1 f. wt) in shoot and root of Vivar and Kasota grown hydroponically with either 0·5, 4 or 8 mm nitrate as the nitrogen source
PCA of these data retained 77·5 % of the variation in PC 1 and 12·4 % in PC 2, accounting for 89·9 % of the variation (Fig. B). The amino acid data grouped mainly between tissue type and moderately by N treatment, but not according to genotype. One of the two main groups comprised shoots from both genotypes while the other group was roots from both genotypes. For the secondary groups, one was of both genotypes and tissue types grown with 0·5 mm nitrate, while the other was both genotypes and tissue types grown at 4 and 8 mm nitrate. These first two principal components were significant (P < 0·0) using the permutation test 500 times. The loading plot for Fig. B (data not shown) showed that the gln concentration was much higher in the roots, while glu and ala concentrations were much higher in the shoots. Asn and ser were also elevated mainly in shoots, while thre was elevated in either shoots or roots, independent of either N treatment or genotype.
The NUpE, NUtE and NUE were calculated for the ten barley genotypes grown in field conditions at low and high N for 2007 and 2008 (Table ). NUE was calculated for the four barley genotypes grown in potted growth-chamber conditions (Table ). NUpE was calculated for the four barley genotypes grown hydroponically in growth-chamber conditions (Table ).
Grain yield and NUE of four spring-barley genotypes potted in the growth chamber at 100, 75, 50 and 25 % N
Total Kjeldahl N (TKN) from above-ground biomass sampled at just prior to anthesis and N uptake efficiency (NUpE) of four spring-barley genotypes grown hydroponically at 0·5, 2, 4 and 8 mm N
In the low-N field conditions for both 2007 and 2008, the above-average NUE genotypes were also all above average in NUtE, but not NUpE, with the exception of Excel in 2007 and Sundre in 2008 (Table ). This was not the case for the genotypes grown on high N – in this treatment some of the above-average NUE genotypes were also either above average for NUtE or NUpE, but not all. It was rare to find an above-average NUE genotype that was also above average for both NUpE and NUtE. Vivar grown with high N was the only genotype above average for all three N efficiency components for 2007 and 2008. In 2008, Sundre and Xena grown on high N, also showed above-average NUE, NUpE and NUtE values. For the rest of the above-average NUE genotypes, they were either also above average for NUpE or above average for NUtE (Table ).
In general there were three genotypes, Vivar, Excel and Ponoka that were consistently above average for NUE at both N treatments over both growing seasons. There were no consistently below average genotypes for both N treatments in both years; however, Bentley was below average for NUE for both years at low-N conditions while Seebe was below average for both years at high N conditions.
The NUE genotypes in this study were not grouped according to spike head or malt/feed types.
The NUE of four genotypes grown in potted growth-chamber conditions were calculated (Table ). CDC-Copeland, a two-row malt variety, had poor grain yields when grown at high N, resulting in poor NUE, although at the two lower N treatments the grain yield was improved. Conversely, Morex, a six-row feed variety, increased grain yield with increased available N. The top two NUE genotypes were Morex and Vivar, at all four N treatments, while Kasota and CDC-Copeland trailed behind in NUE, both faring the poorest at 100 % N.
The NUpE was calculated for the four genoptypes grown hydroponically at the four different N concentrations supplied (Table ). All genotypes showed a decrease in NUpE as the N supply increased. The genotypes were also fairly consistent with each other as to the level of NUpE at each N supply, except for Vivar which showed a much higher NUpE at 0·5 mm N than the other three genotypes.