Near-isogenic Lines Of Durum Wheat Research Articles

Development of near-isogenic lines of durum wheat (Triticum durum Desf.) for glaucousness inhibitor loci Iw1, Iw3 and Iw4 derived from wild relatives

Development of near-isogenic lines of durum wheat (Triticum durum Desf.) for glaucousness inhibitor loci Iw1, Iw3 and Iw4 derived from wild relatives

Differential accumulation of cadmium in near-isogenic lines of durum wheat: no role for phytochelatins.

Certain cultivars of some crops, including durum wheat (Triticum durum Desf.), have a propensity to accumulate cadmium in the grain. In the 1980s, a Canadian wheat breeding program generated five pairs of near-isogenic lines of durum wheat that vary in cadmium-accumulation. Within each pair, one member accumulates twofold to threefold higher concentrations of cadmium in the shoot and grain. However, the physiological explanation for the high-low phenotype is unknown. We studied correlations between concentrations of cadmium and non-protein thiols, including phytochelatins, in these five pairs of near-isogenic lines to test the hypothesis that differential retention of cadmium-binding complexes in the root would explain the phenotype. The expected high-low pattern of cadmium accumulation was found in three of the pairs. In one pair, cadmium was positively correlated with cysteine and glutathione in the roots and with phytochelatins 2 and 4 in the shoots but in another pair cadmium was strongly negatively correlated with phytochelatins 2 and 4 in the shoots and unrelated to cysteine or glutathione. No correlations between concentrations of cadmium and the non-protein thiols were found in the third pair or in the remaining two pairs. The production of phytochelatins is a well-described response to cadmium but the lack of consistent correlation between cadmium and non-protein thiols in these five near-isogenic lines indicates that complexation with non-protein thiols does not explain differential translocation of cadmium in durum wheat.

Cadmium and zinc partitioning and accumulation during grain filling in two near isogenic lines of durum wheat

Plants can readily accumulate cadmium (Cd), transferring this element to edible leaves, fruits, and seeds. Rice and wheat are among the top crop sources of Cd. Toxic heavy metals like Cd have chemical properties similar to essential micronutrients such as zinc (Zn) and are generally transported in plants by the same transporters as those essential micronutrients. Unfortunately our knowledge of Cd translocation and accumulation in seeds is still unclear. We conducted a partitioning study to assess both the whole plant Cd distribution and accumulation and potential source-sink remobilization during grain filling period in two near-isogenic lines of durum wheat that differ in root to shoot translocation and grain Cd content. We also assessed the role of Zn fertilization in Cd translocation and accumulation in the grains. There was no remobilization of Cd in both lines during grain filling. Although majority of Cd partitioned to the roots in both lines, root to shoot translocation of Cd differed in both lines. In contrast, there were no significant differences in Zn partitioning between the lines and remobilization was observed in different tissues. Although there was some remobilization of Zn, the main source of Cd and Zn is continued uptake and translocation to sources during grain fill.

Accumulation of cadmium in near-isogenic lines of durum wheat (Triticum turgidum L. var durum): the role of transpiration.

Concentrations of cadmium in the grain of durum wheat (Triticum turgidum L. var durum) are often above the internationally acceptable limit of 0.2mgkg(-1). Cultivars that vary in concentrations of cadmium in the grain have been identified but the physiology behind differential accumulation has not been determined. Three pairs of near-isogenic lines (isolines) of durum wheat that vary in aboveground cadmium accumulation (8982-TL 'high' and 'low', W9260-BC 'high' and 'low', and W9261-BG 'high' and 'low') were used to test the hypothesis that the greater amounts of cadmium in shoots of the 'high' isolines are correlated with greater volumes of water transpired. In general, cadmium content was positively correlated with transpiration only in the 'low' isolines. Although shoots of the 'high' isolines of W9260-BC and W9261-BG contained higher concentrations of cadmium than did their corresponding 'low' isolines, they did not transpire larger volumes of water. In addition, isolines of 8982-TL transpired less water than did the other pairs of isolines yet both 'high' and 'low' isolines of 8982-TL contained higher amounts of cadmium than did the other pairs. The difference between 'high' and 'low' isolines appears to be related to the relative contribution of transpiration to cadmium translocation to the shoot. Increased transpiration was associated with increased cadmium content in the 'low' isolines but in the 'high' isolines increased cadmium in the shoot occurred independently of the volume of water transpired.

Characterization of cadmium uptake, translocation and storage in near‐isogenic lines of durum wheat that differ in grain cadmium concentration

Here we examined several physiological properties of two near-isogenic lines of durum wheat (Triticum turgidum var. durum) that differ in grain cadmium accumulation, to identify the function of a gene locus that confers differential grain Cd concentrations. Time- and concentration-dependent uptake and translocation studies using 109Cd were conducted on nutrient solution-grown seedlings. Root extracts were analysed by inductively coupled plasma emission spectrometry, gel filtration and capillary electrophoresis to determine the interaction between Cd and phytochelatins (PCs) in storage of Cd in roots. The two isolines did not differ in time- or concentration-dependent root Cd uptake, but the low grain-Cd-accumulating isoline showed decreased movement of Cd from roots to shoots. All buffer-soluble Cd extracted from roots of both isolines was in the form of a low-molecular-weight PC-containing complex. The data suggest that PC synthesis is not a limiting factor in the differential storage of Cd in roots, and that movement of Cd through the root and into the transpiration stream may be the cause of differential Cd partitioning in the two isolines.

Agronomic Characters of Near-isogenic Lines of Durum Wheat (Triticum durum Desf.)

The present study was conducted in order to analyze the effects of the genes for long glume (P), hairy glume (Hg), black glume (Bg), non-glaucousness (W1I) and purple culm (Pc) on 18 agronomic characters of durum wheat. Six near-isogenic lines (NILs, 10 backcrosses) and their recurrent parent LD222 were used. The experiment was carried out in the experimental field of the Agricultural University of Athens, Greece, over a period of two years. The NILs for P, W1I and Pc differed from LD222 in 14, 7 and 4 traits, respectively. These genes had no effect on plant height but exerted adverse effects on the grain yield traits. The P gene was associated with later heading, increased rachis length and 100-kernel weight, but lower grain yield and yield components. Although the data were not statistically significant, both W1I and Pc genes induced a lower grain yield which was accompanied by a reduction of the 100-kernel weight, kernel weight/spike and number of tillers. On the other hand, the introduction of either the Bg or Hg gene into the LD222 genetic background did not affect appreciably the agronomic traits studied.

Awnedness affects grain yield and kernel weight in near-isogenic lines of durum wheat

The importance of awns in durum wheat (Triticum turgidum L. var. durum) has to be evaluated whenever an increase in grain yield is expected due to a greater photosynthetic capacity of the awned ear. Awned and awnless isolines of durum wheat were compared in a 3-year field trial in Sardinia (Italy). Ear and flag-leaf size, radiation interception, canopy temperature, yield, and yield components were measured.Awns increased the ear surface area from 36 to 59%, depending on their length, which ranged from 5.5 to 13.8 cm. This resulted in an average 4% more radiation intercepted by the awned ears. Canopy temperature was 0.9�C lower, on average, in the awned isolines, and was negatively correlated with kernel weight (r = –0.85**, n = 10), although consistent and marked effects of awns on canopy temperature were only observed in the long-awned lines. Awns positively affected grain yield, with an average increase of 10 and 16%, respectively, in the 2 years in which they affected kernel weight. The irrelevant effect of awns on yield in the year characterised by a severe drought was a consequence of their early desiccation.The effects of awns on grain yield and kernel weight strongly depend on the genetic background, on awn length and functionality, and on the environmental conditions during grain filling.

Analysis of near-isogenic lines of durum wheat (Triticum turgidum L. van durum)

The effects of the genes for long glume (P), hairy glume, non-glaucousness, black glume and purple culm (Pc) on grain and biomass yield in near-isogenic (10 backcrosses) lines of durum wheat cv. LD222 were studied in a field experiment. Long glumes were associated with an increase in rachis length and a decrease in tillering, number of spikes per plant, spikelets per spike, days to heading, over all harvest index and yield. Glaucousness increased grain yield while purple culms reduced grain yield and harvest index. Glume pubescence did not show any significant effect on grain yield and harvest index despite a reduction in the number of tillers per plant. One source of black glumes did not have any significant effect on yield related characteristics while another source had a negative effect on them, indicating that the method employed herein determines the effect of short chromosomal regions rather than those of single genes. Plant height, culm length, 100 kernel weight, and above-ground plant weight were not affected significantly by any of the genes studied.

Yield and carbon isotope discrimination in near-isogenic lines of durum wheat differing in glume length

The objective of this study was to assess the effect of the genes for long glume (P and P2) on carbon-isotope discrimination (Δ) and grain yield (GY) using near-isogenic lines of a durum wheat cultivar, LD222 in Japan and Turkey. The location had major effects on variation of Δ and GY, but the effects of glume length on Δ and GY were little in overall environments. It was suggested that the gene P2 had more adaptive effects than the P gene. The curvilinear relationship between Δ and GY is probably based on the difference between the locations with relatively little genetic variation.

Near-isogenic lines of durum wheat: their development and plant characteristics

The effect of specific plant characteristics on the grain and biomass yield of durum wheat can be accurately determined by using isogenic lines, which, however, were not usually available. This study reported the effects of long glume, glaucousness, glume pubescence, black glume and purple culm on the yield and its associated characteristics in near-isogenic lines of durum wheat cv. LD222, which were developed by continuous backcrossing. The long glume trait which resulted in a large photosynthetic area did not enhance yield. Increased glume size associated with the P gene tended to increase the main culm dominance, characterized such as vigorous main culm and weak tillers, and plant height, but to reduce tillering and spike number. Consequently, grain yield and harvest index declined. Under the adequate water supplying condition of the present study, the glaucous trait was beneficial for grain yield. The trait of glume pubescence did not excert any significant effect on the yield related characteristics in the LD222 background. The traits of black glume and purple culm reduced the number of spikes per unit area and the number of kernels per unit area.