Rye (Secale cereale L.) chromosome translocation is reported to enhance yield attributes in common wheat (Triticum aestivum L.). We used 1RS translocations within the spring wheat cultivar “Pavon76” to measure and identify the translocation that is suitable to withstand moisture stress conditions without significant loss in yield potential. Four lines were grown under two water regimes in greenhouse environment in 2011 and 2012. The rye translocation increased root and shoot biomass in some cases, reduced plant height, and delayed maturity in some cases. The 1RS.1BL translocation produced the highest grain yield associated with the lowest root and shoot biomass under both well watered and water stressed conditions. Root and shoot biomass were recorded the highest for 1RS.1AL under well watered condition. However it produced the least biomass for both traits under water stressed conditions. In most cases, lines were not statistically differentiated for seminal root angle, abscisic acid concentration, water use efficiency, and grain yield. Results from our study show that the 1RS.1BL translocation is more suited to produce high grain yield under moisture limiting conditions.
Drought is considered the most widespread limitation to wheat (Triticum aestivum L.) productivity in non-irri- gated production systems [
Villareal et al. [
Studies conducted with specific rye chromosome translocations have shown varying results. Gray bosch et al. [
Cultivar Pavon76, a white spring wheat was developed by International Maize and Wheat Improvement Center (CIMMYT) in 1976 for production under irrigated system. Chromosomal translocations of short arm of rye chromosome 1 (i.e. 1RS) with long arm of chromosome group 1 in Pavon76 were created by Lukaszewski [
Root observation box slightly modified from the one that is described by Bengough et al. [
Five healthy seedlings of each line selected from the root angle study were planted into pots filled with sterilized potting mixture of 1/3 sand, soil and commercial potting mix “Sunshine #1” (sphagnum peat moss, coarse perlite, starter nutrient charge with Gypsum, dolomitic limestone) and grown in the greenhouse at South Dakota State University. Temperature in the greenhouse was maintained at ~25˚C. Each pot contained one seedling. All pots were placed within empty 2L buckets to hold the leached water. Pots were arranged in randomized complete block (RCB) design separated into 2 water treatments; well-watered and water stressed. Starting on the day of transplant, 500 ml (496 g) water was applied to all pots every 3 - 4 days until booting stage or Feekes growth scale 10 as described by Large [
WUE = BiomassT/ΨT − (Ψevap + ΨL) [
Biomass T = total dry biomass (root + shoot) in g,
ΨT − (Ψevap + ΨL) = total water used in kg (i.e. ΨT = total water applied, Ψevap = total water evaporated, ΨL = total water leached)
STI = (Yp)(Ys)/(Ῡp)2 [
Yp = line grain weight (g) in well water environment
Ys = line grain weight (g) in water stress environment
Ῡp = mean grain weight (g) in well water environment over all lines
HI = GW/Abio where,
GW = grain weight
Abio = dry above ground biomass.
Leaf ABA content was measured for all lines tested over both years using Liquid Chromatography-Mass Spectrometry method (LC/MS). Leaf samples (1.5 g) obtained from middle section of fully grown healthy leaves were sent to Proteomics and Mass Spectrometry at Donald Danforth Plant Science Center, St Louis, MO for ABA analysis. In 2011, the ABA assay was conducted in duplicates for each line within each treatment, whereas in 2012 growing season, the assay was run for three leaf samples for each line within each treatment.
All data measured in both trials were subjected to analysis of variance (ANOVA) using PROC GLM in SAS statistical software [
Separate ANOVA was conducted for each experiment carried out in 2011 and 2012. The water regime had highly significant effects on all traits measure in both years except for plant height in 2012 (
Seminal root angle was measure in only 2011 trial. The mean seminal root angles were measure from all seeds that germinated for each line. Only line Pavon76 had all ten seeds germinated and were developed enough to measure the angles. The 1RS.1AL, 1RS.1BL and 1RS.1DL had eight, seven, and six readings taken respectively. The mean seminal root angle ranged from 81.71˚ (1RS.1BL) to 104.4˚ (1RS.1AL) and the lines were not statistically different (LSD0.05) which may be due to variations within lines across replications (
. Analysis of variance showing effect of genotype (line), water treatment (trt) and their interaction for traits measured in 2011 and 2012 greenhouse studies for Pavon76 and its rye translocation lines
Traits | 2011 | 2012 | ||||
---|---|---|---|---|---|---|
Line | Trt | Line × Trt | Line | Trt | Line × Trt | |
Plant Height (cm) | 11.18 | 1025.82*** | 17.28 | 31.18 | 37.25 | 27.26 |
Spike plant−1 | 1.03 | 61.36*** | 0.28 | 0.3 | 216.23*** | 23.36** |
Dry Root (g) | 0.86*** | 1.41*** | 0.35* | 0.22 | 18.98*** | 0.97* |
Dry shoot (g) | 5.82* | 728.04*** | 2.83 | 3.16 | 427.06*** | 7.19 |
Yield (g) | 0.21 | 6.40*** | 0.34 | 1.16 | 21.61*** | 0.54 |
Harvest Index | 55.93 | 313.44*** | 44.78 | 142.4 | 656.42** | 50.03 |
ABA (ng g−1) | 431.44 | 2711.19** | 657.81 | 2943.36 | 6817.54* | 1703.4 |
*, **, *** = Statistical significance level at 0.05, 0.01, and 0.001 probability level.
. Mean and range of seminal root angle measure for Pavon76 and its rye translocation lines
Line | Frequency | Min | Max | Mean |
---|---|---|---|---|
Pavon76 | 10 | 48 | 119 | 91.4 |
1AL | 8 | 59 | 136 | 104.38 |
1BL | 7 | 35 | 140 | 81.71 |
1DL | 6 | 87 | 112 | 96.5 |
LSD0.05 | NS |
LSD0.05 = Differences between the values within the mean column that are narrower than LSD are not statistically different at 0.05 probability level. NS = non-significant at 0.05 probability level.
instances, angles differences among the reading were more than double within the same line. Root architecture is considered as one of the major attributes of drought adaptive crops. We measured angle between the two outermost seminal roots during first pair seminal root phase. Previous studies on seminal root angle reported lower values, which could be due to their measurement of the angle between primary seminal root and one of the first pair of seminal roots and also using entirely different genotypes than the ones used in our study [
Tiller plant−1, spike length, days to heading, and WUE were measured only in the 2011 trial. The measurement of these traits was discontinued in 2012 due to lack of statistical significance among lines for these traits when grown under two water regimes in the study. Average tiller plant−1 ranged from 7.2 (Pavon76 and 1RS.1AL) to 8.75 (1RS.1DL) and 6.6 (1RS.1BL) to 8.25 (1RS.1DL) for well watered and water stressed treatments respectively. The differences between WUE of lines used in this study were very narrow. The difference between the most and the least efficient lines was higher in water stressed treatment (i.e. 0.77 g biomass per kilogram of water). For spike length, the 1RS.1AL produced the longest spikes within well water treatment, whereas Pavon76 had the longest spikes in drought treatment. In both treatments 1RS.1DL produced the shortest spikes, however, the values were not statistically significant (
. Mean and Least Significant Difference (LSD) values of all traits measured in 2011 for Pavon76 and its rye translocation lines grown under well-water and water stress (drought) conditions
2011 | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Trait | Well-Watered | Drought | ||||||||
Pavon76 | 1AL | 1BL | 1DL | LSD0.05 | Pavon76 | 1AL | 1BL | 1DL | LSD0.05 | |
Plant Height (cm) | 51.40 | 47.70 | 52.50 | 48.33 | 3.58 | 40.33 | 40.00 | 38.40 | 38.50 | NS |
Spike plant−1 | 5.00 | 5.20 | 4.20 | 5.67 | NS | 2.00 | 2.40 | 2.00 | 2.50 | 0.57 |
Dry Root (g) | 51.40 | 47.70 | 0.70 | 1.05 | 0.59 | 0.80 | 0.82 | 0.48 | 0.61 | NS |
Dry shoot (g) | 14.59 | 16.09 | 13.50 | 14.20 | NS | 5.69 | 5.70 | 5.26 | 5.04 | NS |
Yield (g) | 1.63 | 2.00 | 2.00 | 1.56 | NS | 1.17 | 0.69 | 1.02 | 0.86 | NS |
Harvest Index | 10.90 | 12.36 | 14.80 | 10.97 | 3.09 | 19.94 | 9.31 | 19.23 | 17.15 | NS |
Tiller plant−1 | 7.20 | 7.20 | 7.80 | 8.75 | NS | 7.00 | 6.75 | 6.60 | 8.25 | NS |
Spike Length (cm) | 9.65 | 10.77 | 9.67 | 9.31 | 0.86 | 9.63 | 8.54 | 9.40 | 8.00 | NS |
Days to Heading | 57.30 | 61.00 | 55.60 | 59.30 | 2.18 | 58.25 | 61.70 | 56.00 | 60.00 | NS |
WUE (g∙kg−1) | 2.53 | 2.75 | 2.42 | 2.78 | NS | 2.28 | 3.05 | 2.55 | 2.86 | NS |
ABA (ng∙g−1) | 26.14 | 39.12 | 30.93 | 36.30 | NS | 62.16 | 36.94 | 96.81 | 53.01 | NS |
LSD0.05 = Differences between the values within a row that are narrower than LSD are not statistically different at 0.05 probability level. NS = non-significant at 0.05 probability level.
significantly different among the lines. Numerically, plant height of 1RS.1BL decreased about 30% when exposed to water stressed condition followed by Pavon76, 1RS.1DL, and 1RS.1AL. The 1RS translocation consistently reduced plant height; however, statistical significance was seen only for well watered treatment in 2011. Height was also affected by water regime in both years. When exposed to water limiting conditions, the most detrimental height effect was seen on 1RS.1AL with more than 7 cm reduction. This finding was consistent with the findings of a study done by Ehdaie et al. [
In 2012, the tested lines did not show significant differences for the measured traits within well water treatment, whereas in drought treatment, lines could be statistically distinguished for only spike per plant and dry root biomass (
. Mean and Least Significant Difference (LSD) values of all traits measured in 2012 for Pavon76 and its rye translocation lines grown under well-water and water stress (drought) conditions
2012 | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
Trait | Well-Watered | Drought | ||||||||
Pavon76 | 1AL | 1BL | 1DL | LSD0.05 | Pavon76 | 1AL | 1BL | 1DL | LSD | |
Plant Height (cm) | 54.80 | 54.42 | 52.36 | 49.84 | NS | 53.14 | 47.74 | 52.82 | 50.00 | NS |
Spike plant−1 | 9.20 | 12.60 | 8.60 | 10.00 | NS | 5.80 | 3.40 | 5.20 | 7.40 | 2.37 |
Dry Root (g) | 2.04 | 2.76 | 1.82 | 1.85 | NS | 0.80 | 0.48 | 0.68 | 1.00 | 0.36 |
Dry shoot (g) | 13.54 | 15.04 | 12.74 | 14.26 | NS | 7.48 | 6.00 | 7.40 | 8.56 | NS |
Grain wt. (g) | 1.66 | 1.40 | 2.42 | 2.32 | NS | 0.32 | 0.44 | 0.92 | 0.24 | NS |
Harvest Index | 12.53 | 9.46 | 19.05 | 16.74 | NS | 3.97 | 5.95 | 12.77 | 2.69 | NS |
ABA (ngg−1) | 42.81 | 49.93 | 58.53 | 64.29 | NS | 67.82 | 94.31 | 50.92 | 141.50 | NS |
LSD0.05 = Differences between the values within a row that are narrower than LSD are not statistically different at 0.05 probability level. NS = non-significant at 0.05 probability level.
One of the major physiological responses of plants when exposed to water deficit environment is the elevation of ABA content. In our study, the lines showed inconsistent levels of ABA in water stress treatment. In 2011, the 1RS.1BL had the highest level of ABA whereas in 2012, the highest level was observed for 1RS.1DL (
The results from this study show that 1RS rye chromosomal translocation to 1BL of wheat is more suited to tolerate moisture stress than the other chromosomal translocations tested. When exposed to water stressed condition, the 1RS.1BL translocation line accumulated more of its photosynthates on grain than other plant parts. The 1RS.1AL consistently produced higher number of spikes and total biomass under the well watered condition in both years, but the spike number (hence the grain weight) significantly decreased under moisture limiting conditions. This suggests that the 1AL translocation is desirable if the goal of a breeding program is to develop lines for environments that are not likely to be exposed to severe moisture deficit. Our greenhouse study attempted to identify suitable rye chromosome (1RS) translocation with the aim of developing lines that are more adaptive to moisture stress conditions. Greenhouse studies do not always simulate the natural growing conditions for plants. Therefore, in order to further consolidate our findings, a field study is essential. In addition, the use of wheat in daily food products may demand the testing of translocation lines for quality attributes within a breeding program. Results from our study show that drought adaptation is a complex trait and may involve several systems within the plant to function as a whole.
Authors wish to acknowledge Center of Excellence on Drought Tolerance Research (CEDTR) at South Dakota State University for providing funding for the study. Likewise we also would like to thank Dr. Adam J. Lukaszewski at University of California, River side for providing plant materials for the study.