Chapman SC

Dreccer MF

Shorter R

van Herwaarden A

English

Sydney eScholarship

 1Spring wheat lines contrasting in stem water soluble carbohydrate concentration: growth, nitrogen absorption and partitioning  Dreccer MF1, van Herwaarden A2, Chapman SC2 and Shorter R2 1 CSIRO Plant Industry, Cooper Laboratory, PO Box 863, University of Queensland, Warrego Highway, Gatton, QLD 4343 Australia, 2CSIRO Plant Industry, 306 Carmody Rd, St Lucia, QLD 4067, Australia  ABSTRACT  We studied a small set of recombinant inbred lines contrasting in stem water soluble carbohydrates (WSC) concentration across a range of environments ranging from moderate water stress to fully irrigated. The aim was to check for consistency in genotypic rankings and potential trade-offs between WSC storage, grain number and yield. The pattern of WSC concentration was modulated by water availability, with rainfed trials reaching maximum levels before anthesis. Early sown irrigated trials seemed the best option to discriminate lines for WSC concentration for selection purposes since genotypic differences were already detectable at anthesis and observed until late grain filling.   High WSC lines achieved similar or greater yields than their low WSC counterparts; their relative advantage was larger in irrigated compared to rainfed trials. High WSC lines had a lower grain number per unit area linked to a lower number of spikes and stems per unit area, fewer but heavier spikes and lower grain number per unit spike weight. The observed changes in plant type behind the high WSC phenotype were accompanied by higher potential and attainable individual grain weight.   INTRODUCTION  In wheat, water soluble carbohydrates (WSC) stored in the stems have been acknowledged as contributing to maintenance of grain filling rate when photosynthesis declines due to various stresses, e.g. drought (Palta et al., 1994), heat stress (Blum et al., 1994) and possibly disease (Blum, 1998). Genetic variation exists for WSC accumulation in the stems at anthesis and it has been suggested that breeding for high WSC should be possible due to its high heritability (Ruuska et al, 2006).   In the context of selection, it is important to determine if there would be any negative consequences to yield or its components if stem WSC concentration was positively selected for. In this study we investigated potential trade-offs between WSC storage, grain number and yield. We monitored biomass, N and WSC concentration (WSCc, mg WSC g-1 dry weight) and amount (WSCa, g m-2) in a small set of recombinant inbred lines (RILs) contrasting in stem WSC level, across a broad range of environments ranging from moderate water stress to fully irrigated.   MATERIAL AND METHODS  The RILs were part of the Seri/Babax population described by Olivares-Villegas et al. (2007) and had shown transgressive segregation for stem WSCc at anthesis (SB003 and SB010: low WSCc, SB062 and SB169: high WSCc) but otherwise similar anthesis date and height. Genetic map and QTL information (McIntyre et al., 2006) was used to select the two lines of each group such that they were as genetically diverse as possible.   In 2006, six field trials were conducted at the CSIRO experimental station in Gatton (Queensland, 27.55ºS lat, 152.33ºE long) at several planting dates and combinations of irrigation and nitrogen supply (Table 1). Individual seed weights were used to target 150 plants m-2 for each genotype. Bordered biomass cuts were made during the crop cycle, depending on the trial, at the start of stem elongation, booting, anthesis or 100°Cd after anthesis, early grain filling, mid-late grain filling (ca. 450°Cd after anthesis) and maturity. Plants were dissected in organs, green leaf area measured, and harvest index calculated on a dry weight basis at maturity. At heading, individual spikes from main stems or first cohort tillers were tagged. These were used to collect data on the number of fertile florets, grain set and grain growth rate. Light interception was calculated from radiation measurements with a ceptometer. In the rainout-shelter experiments soil water was measured with a neutron moisture meter. The levels of total water soluble were determined as in van Herwaarden et al. (1998). Nitrogen was determined by combustion analysis.   The potential maximum contribution of WSC to grain was calculated as the maximum stem WSCa minus WSCa at maturity. Remobilisation efficiency was calculated as ‘1 – WSCaMaturity / WSCaMaximum’. An estimate of structural biomass in the stems at anthesis was calculated as the anthesis stem biomass minus the protein and the WSCa.    2 Table 1.Trials, treatments and experimental design Trials Sowing date Watering regime Treatments Design ROS-1SD 6th June, 2006 Initial soil water; rain-out shelterGenotypes: SB003 (low WSC) and SB062 (high WSC)RBD, 4 reps.  ROS-2SD 17th July, 2006 Initial soil water;  rain-out shelter Genotypes: SB003 and SB062  RBD, 4 reps. IRR-1SD 6th June, 2006 Fully irrigated Genotypes: SB003 and SB062  RBD, 3 reps. IRR-2SD 17th July, 2006 Fully irrigated Genotypes: SB003 and SB062  RBD, 3 reps. NRFED 14th June, 2006 Rain fed Genotypes: SB003, SB10, SB062, SB169 Nitrogen: 176 (high) and 90 (low) kg ha-1 RBD, 3 reps. NIRR 23rd May,2006 Rain plus tactical irrigations Genotypes: SB003, SB010, SB062, SB169 Nitrogen: 262 (high) and 158 (low) kg ha-1RBD, 4 reps.  Figure 1. Grain number per m-2 vs. WSC concentration in stems plus sheaths around anthesis (a) and WSC concentration in stems plus sheaths around anthesis vs. stem number m-2 at the same time. In (b) arrows point from SB062 to SB003, dashed arrow indicates NIRR and full arrow is for IRR-2SD.                 Figure 2. Potential contribution of WSC per grain to average individual grain weight (a) grouped regression n=22, R2=76.4, P<0.001; grain number per spike weight vs individual spike dry weight (a).                   RESULTS AND DISCUSSION The WSCc in stems around anthesis was lower in SB003 and SB010 than in SB062 and SB169, consistent with previous observations. The pattern of WSC deposition was modulated by water availability. Rainfed crops reached the peak of WSCc before anthesis, when some internodes were still elongating, as observed by Goggin and Setter (2004). In irrigated crops, the stem WSCc peak was generally reached during grain filling, up to 400 °Cd (Tb=0°C) after anthesis. Early sown irrigated field experiments can be used to extend the window of sampling opportunities to establish genotypic rankings for WSCc for up to ca. 20 days after anthesis in our environments.  2505000100001500020000250000 50 100 150 200SB010SB062SB169SB003Y=12020-8217/(1-0.023x)R2=56.2, P<0.001, n=24Stem WSC around anthesis (mg g-1)aGrain number (# m-2)Grain number (# m-2)Stem number around anthesis (m-2)Stem WSC around anthesis  (mg g-1 ) by = -0.30x + 280.29R2 = 0.32, P<0.003, n=24050100150200250200 300 400 500 600 700SB003SB010SB062SB169Stem WSC around anthesis  (mg g-1 )Grain number (# m-2)Grain number (# m-2)Stem WSC around anthesis  (mg g-1 )Stem WSC around anthesis  (mg g-1 )y = -175.5x + 177.5R2 =0.68, P<0.001, n=240204060801001201401600.20 0.40 0.60 0.80Individual spike weight (g spike -1 )SB062SB169SB003SB010-1)Grains per indivspike dry wt (g-1))Grain number per spike dry weight (# g-1 )Grain number per spike dry weight (# g-bIndividual grain weight (mg)Individual grain weight (mg)2025303540455055600 2 4 6 8 10Potential WSC contribution (mg grain -1)Individual grain weight (mg)SB062SB169SB003SB010Low WSCHigh WSCbAverage grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)aAverage grain weight (mg)-1)Grains per indivspike dry wt (g-1))Grain number per spike dry weight (# g-1 )Grain number per spike dry weight (# g- -1 )Grains per indivspike dry wt (g-1))Grain number per spike dry weight (# g-1 )Grain number per spike dry weight (# g-Individual grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Average grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Average grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Average grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Individual grain weight (mg)Average grain weight (mg) 3The classification of genotypes according to WSCc had significant effects for the majority of yield related attributes. Yields spanned from ca. 4.6 to 8.5 t ha-1, with high WSC lines yielding similarly or up to 18% more than low WSC lines. This trend was not based on differences in total biomass production but in harvest index. Consistently across trials, high WSC lines had 8 to 22% lower grain number per unit area and 17 to 51% higher average individual grain weight compared to low WSC lines. The lower number of grains per unit area in high WSC lines was a result of the lower number of spikes per unit area, which was not compensated by their slightly higher number of grains per individual spike as calculated at maturity.   Features of stem WSC deposition that could have compromised grain number determination are, its timing with respect to the spike growth period and the accumulation of WSC in the peduncle. We found no evidence of a trade off between WSC accumulation (g m-2) and attainable or potential yield, despite the negative association between the grain number per m-2 and stem WSCc at anthesis (Figure 1a). Each spike in high WSC lines was not necessarily C or N limited because (a) high WSC lines also had a lower number of stems per m-2 (Figure 1b) and (b) on a per stem basis, high WSC lines had both higher WSCa, heavier spikes with higher N amount and concentration, and more fertile florets and grains per spike (data not shown). The lower tiller number range observed in the high WSC lines could be interpreted as a conservative strategy that maximises the amount of resources per stem and results in a cascade of effects, such as higher WSC per stem (Figure 1b) and more grains per spike. The degree of variation in stem WSCc observed at a particular stem number per m-2 at anthesis was expected, not only because of the range of environments involved but also because by anthesis, remobilisation was already underway in rainfed trials (examples of irrigated trials illustrated with arrows in Figure 1b). While differences in tillering may not be the only mechanism involved (Xue et al., 2008), its stability makes it a candidate to help explain the observed high heritability of stem WSCc (Ruuska et al., 2006). A similar phenotype, high stem WSCc-few stems has been reported to perform well under drought (Dreccer et al., 2008) or maintains high grain filling rates (Triboi and Ollier, 1991).  The potential contribution of WSC to grain yield was greater in high WSC lines and in early sown irrigated trials (data not shown); high WSC lines had both higher WSCa and remobilisation efficiency. The observed changes in plant type behind the high WSC phenotype were accompanied by higher potential and attainable individual grain weight. Individual grain weight, from the average pool or at particular positions within central spikelets (data not shown), was greater in high WSC lines (Figure 2a). Interestingly, low WSC lines attained a lower final grain weight compared to high WSC ones at greater levels (>5 mg grain-1) of potential WSC contribution per grain (Figure 2b). This supports the hypothesis that high WSC lines may have a higher potential grain weight per se, hence able to translate WSC into higher grain weight. High WSC lines had a lower grain number per unit spike weight at anthesis (Figure 2b). Whether this could account for structural differences in the spike, such as larger vascular bundles, allowing larger or faster delivery of sugars to the grains is worth testing. Trials are being conducted to determine if the WSCc varies genetically with planting density.   REFERENCES  Blum A, Sinmena B, Mayer J, Golan G, Shpiler L (1994). Stem reserve mobilisation supports wheat-grain filling under heat stress. Australian Journal of Plant Physiology 21, 771-781. Blum A (1998) Improving wheat grain filling under stress by stem reserve mobilisation. Euphytica 100, 77-83. Dreccer MF, Chapman SC, Ogbonnaya FC, Borgognone MG, Trethowan RM (2008) Crop and environmental attributes underpinning genotype by environment interaction in synthetic bread wheats evaluated in Mexico and Australia. Australian Journal of Agricultural Research 59, 447-460. Goggin DE, Setter TL (2004) Fructosyltrasnferase activity and fructan accumulation during development in wheat exposed to terminal drought. Functional Plant Biology 31, 11-21. McIntyre CL, Chapman SC, Mathews KL, van Herwaarden A, Reynolds M, Shorter R (2006) Identification of germplasm and genomic regions for traits relevant to wheat production in drought environments. 2006 Proc 13th Australasian Plant Breeding Conference. Christchurch NZ. 18-21 April, 2006 CD. Olivares-Villegas JJ, Reynolds MP, McDonald GK (2007) Drought-adaptive attributes in the Seri/Babax hexaploid wheat population. Functional Plant Biology 34, 189-203. Palta JA, Kobata T, Turner NC (1994) Carbon and nitrogen in wheat as influenced by postanthesis water deficits. Crop Science 34, 118-124.  Ruuska SA, Rebetzke GJ, van Herwaarden AF, Richards RA, Fettell NA, Tabe L, Jenkins CLD (2006) Genotypic variation in water-soluble carbohydrate accumulation in wheat. Functional Plant Biology 33, 799-809. Triboi E, Ollier JL (1991) evolution et role des reserves glucidiques et azotes des tiges chez 21 genotype de ble. Agronomie 11, 239-246. van Herwaarden AF, Richards RA, Farquhar GD, Angus JF (1998) ‘Haying-off’, the negative grain yield response to nitrogen fertiliser. I Biomass, grain yield and water use. Australian Journal of Agricultural Research 49, 1067-1081. Xue GP, McIntyre CL, Jenkins CLD, Glassop D, van Herwaarden AF, Shorter R (2008) Molecular Dissection of Variation in Carbohydrate Metabolism Related to Water-Soluble Carbohydrate Accumulation in Stems of Wheat. Plant Physiology 146, 441–454.  

Spring wheat lines contrasting in water soluble carbohydrate concentration: growth; notrogen absorption and partitioning

https://ses.library.usyd.edu.au/bitstream/2123/3378/1/P176.pdf

Spring wheat lines contrasting in water soluble carbohydrate concentration: growth; notrogen absorption and partitioning

Abstract

Similar works

Full text

Available Versions

Sydney eScholarship