Mechanisms of aluminum tolerance in Triticum aestivum (wheat). V. Nitrogen nutrition, plant-induced pH, and tolerance to aluminum; correlation without causality?

1988 ◽  
Vol 66 (4) ◽  
pp. 694-699 ◽  
Author(s):  
Gregory J. Taylor

An aluminum-tolerant cultivar ('Atlas-66') and an aluminum-sensitive cultivar ('Scout-66') of Triticum aestivum L. were grown in solution culture under conditions of varying [Formula: see text] and [Formula: see text] supply with or without 75 μM aluminum. Plants grown with a low [Formula: see text] ratio in solution maintained a higher solution pH than plants grown with a high [Formula: see text] ratio. Although root growth of 'Scout-66' was greater under high [Formula: see text], high solution pH conditions, the relative tolerance of the cultivars to Al was unaffected by the [Formula: see text] ratio and by solution pH. The superior Al tolerance of 'Atlas-66' could not be explained solely by its ability to maintain a high solution pH in mixed nitrogen solutions.

1985 ◽  
Vol 63 (12) ◽  
pp. 2181-2186 ◽  
Author(s):  
Gregory J. Taylor ◽  
Charles D. Foy

Five cultivars of Triticum aestivum L. (wheat) were grown for 21 days in solution cultures with aluminum (+Al) (74 μM) and without Al (−Al) at an initial pH of 4.5. Patterns of nitrogen depletion and pH change were biphasic. Ammonium [Formula: see text] was rapidly depleted and solution pH declined during phase I. Depletion of nitrate [Formula: see text] was most rapid and solution pH increased after [Formula: see text] was exhausted from solutions (phase II). Cultivar tolerance to Al was negatively correlated with the rate of pH decline induced by cultivars, and the rate of pH decline was positively correlated with the rate at which cultivars depleted [Formula: see text] from +Al and −Al nutrient solutions. Cultivar tolerance to Al was also negatively correlated with the rate of [Formula: see text] depletion from +Al and −Al solutions. Cultivar tolerance to Al was positively correlated with the rate of [Formula: see text] depletion during phase II but only when plants were grown with Al. These results support the hypothesis that differential Al tolerance among cultivars of T. aestivum is caused by differences in the rate of [Formula: see text], and possibly [Formula: see text], uptake. Such diffferences in N preference may have caused differences in pH and Al solubility in the nutrient solutions.


1995 ◽  
Vol 22 (4) ◽  
pp. 531 ◽  
Author(s):  
PR Ryan ◽  
E Delhaize ◽  
PJ Randall

Aluminium (Al) can stimulate the efflux of malate and other organic acids from root apices of wheat (Triticum aestivum L.) seedlings. This response has been implicated in a mechanism of Al tolerance since the amount of malate released from an Al-tolerant genotype was 5-10-fold greater than the amount released from a near-isogenic, but Al sensitive, genotype. In the present study, 36 wheat cultivars were screened for Al tolerance and for the amount of malate released from their root apices with a standard A1 treatment. Excised root apices (3.0 mm) were used to measure malate efflux, and the relative tolerance to Al was determined from root growth measurements in 3 and 10μM AlCl3 with 200 μM CaCl2, pH 4.3. There was a significant correlation between relative tolerance of the genotypes to Al and the amount of malate released from their root apices. Growth measurements were also used to investigate the amelioration of Al toxicity by exogenous malate. In the presence of 3 μM Al alone, relative root growth of an Al-sensitive genotype was reduced to 13% of the control. Addition of 10 μM malate to the solution increased relative root growth to 50%, and 20 �M malate completely alleviated the Al-induced inhibition of root growth. The results support the hypothesis that the Al-stimulated efflux of malate from root apices is involved in a general mechanism for Al tolerance in wheat.


1989 ◽  
Vol 67 (5) ◽  
pp. 1305-1308 ◽  
Author(s):  
Sheila M. Macfie ◽  
Gregory J. Taylor ◽  
Keith G. Briggs ◽  
John Hoddinott

Thirty cultivars of Triticum aestivum differed in tolerance of manganese (Mn) as determined by relative root growth in solution culture. Based upon a root weight index (RWI = root weight in the presence of 500 μM Mn divided by control root weight), Mn tolerance ranged from 0.08 to 0.88. All Canadian Western Red Spring (CWRS) cultivars tested were Mn sensitive. Cultivars bred for high yield were more Mn tolerant, especially 'Norquay' (RWI = 0.88) which was the only cultivar with a RWI > 0.70. The cultivars 'Norquay' and 'Columbus' were selected as standards for Mn tolerance and Mn sensitivity, respectively. 'Norquay' showed maximum root growth at 100 μM Mn, a concentration which was toxic to 'Columbus', and differential tolerance was maintained up to 1000 μM Mn in solution. Differences between 'Norquay' and 'Columbus', grown in excess Mn, were also observed in the accumulation of biomass with time. In contrast with previous studies, Mn tolerance was positively correlated with Al tolerance (R2 = 32.7, p = 0.001) in the cultivars tested.


Genome ◽  
1995 ◽  
Vol 38 (6) ◽  
pp. 1213-1220 ◽  
Author(s):  
Daryl J. Somers ◽  
J. Perry Gustafson

This study examined the changes in gene expression induced by aluminum (Al) stress in wheat root tips. Seedlings of Triticum aestivum L. cvs. Katepwa (Al sensitive), Maringa (Al tolerant), and Alikat (Al tolerant near isoline; 'Katepwa'*3/'Maringa') and a F2 population derived from 'Katepwa' × 'Alikat', were grown for 3 days in either 0 or 1 μg∙mL−1 Al. Polypeptides were labeled with 35S-methionine prior to separation by gel electrophoresis. There were a few polypeptides from whole cell lysates that showed enhanced expression in all of the genotypes in 1 μg∙mL−1 Al, however, the whole cell lysate and microsomal polypeptide profiles also revealed numerous unique changes in gene expression in Al-sensitive 'Katepwa' at 1 μg∙mL−1 Al; the latter cosegregated with only the Al-sensitive F2 bulks. The microsomal polypeptide profiles of the Al-tolerant lines 'Maringa' and 'Alikat' changed marginally in the presence of Al and these changes were also reflected in the Al-tolerant F2 bulks. The data showed that there were many changes in gene expression which cosegregated with Al sensitivity and suggest that Al tolerance in wheat may rely on constitutively expressed polypeptides.Key words: wheat, aluminum, protein synthesis, segregation.


Genome ◽  
1992 ◽  
Vol 35 (4) ◽  
pp. 689-693 ◽  
Author(s):  
William A. Berzonsky

Toxicity to aluminum (Al) limits wheat (Triticum aestivum L. em. Thell.) yields. 'Atlas 66', a soft red winter wheat classified as tolerant (root growth ≥ 0.5 cm after Al stress) to 0.44 mM Al, was hybridized with tetraploid (4x) and hexaploid (6x) 'Canthatch', a hard red spring wheat classified as sensitive (root growth < 0.5 cm after Al stress) to 0.44 mM Al. Progenies produced from these hybridizations were tested for tolerance to 0.44 mM Al in solution to ascertain the number of genes and the genomes of 'Atlas 66', which determine tolerance to aluminum. Tests of 'Atlas 66', 6x-'Canthatch', and the F1's resulting from hybridizations between the parents indicated that dominant, nuclear genes carried by 'Atlas 66' determine tolerance to 0.44 mM Al. Segregation ratios for the F2 significantly differed from ratios expected for a dominant, duplicate genetic mechanism. F1 backcross segregation ratios did not significantly differ from ratios expected for dominant, duplicate nuclear genes for tolerance to aluminum. The expression of genes for tolerance to 0.44 mM Al for 'Atlas 66' appears to be more complex than is predicted by the existence of two dominant genes. A crossing scheme, which involved hybridizing 4x-'Canthatch' with 'Atlas 66', was executed to produce 42-chromosome plants having recombinant A- and B-genome chromosomes and D-genome chromosomes derived exclusively from 'Atlas 66'. Eleven F6 and F7 lines, developed from these plants, were selfed and plants in the F6 generation were backcrossed to 'Atlas 66' and 6x-'Canthatch'. The F6 and F7 lines were subjected to 0.44 mM Al in solution as were the backcrosses. While none of the lines had more than 50% of their seedlings classified as sensitive to Al in the F6 generation, four lines exhibited such a response in the F7 generation. In general, backcrossing the F6 lines to 6x-'Canthatch' increased sensitivity to Al, while backcrossing to 'Atlas 66' increased tolerance. Results suggest that genes for tolerance to Al in 'Atlas 66' wheat are not all located on D-genome chromosomes.Key words: aluminum tolerance, genomic inheritance, Triticum.


1997 ◽  
Vol 45 (4) ◽  
pp. 285-292 ◽  
Author(s):  
Kay M. Cocker ◽  
Martin J. Hodson ◽  
David E. Evans ◽  
Allan G. Sangster

Seedlings ofTriticum aestivumL. (cv. Celtic) were suspended in plastic tubs containing 500 μmol L−1Ca(NO3)2and 31 μmol L−1KC1 as background solution. A1C13(0 and 100 μmol L−1) and Na2SiO3.5H2O (0 and 2000 μmol; L−1) were added to this basal nutrient medium, and solution pH was set at 4.2 or 4.6. Tubs were aerated and supplied with a continuous flow of pH-adjusted test solution. Plants were grown for 4 d in a growth cabinet at 25 °C with a 16 h photoperiod. At pH 4.2 and 4.6 root length of the seedlings was inhibited at 100 μmol L−1Al. An amelioration of Al-induced toxicity symptoms was observed in the 100 μmol L−1A1/2000 μmol L−1Si treatment at pH 4.6, but not at pH 4.2. Both the shoot (S) and root (R) dry weight of seedlings treated with 100 μmol L−1Al were reduced when compared with controls. Treatment with Al increased S:R ratios, and this effect was ameliorated by Si, but only at pH 4.6.Al content of roots treated with 100 μmol L−1Al or 100 μmol L−1Al/2000 μmol L−1Si increased significantly when compared with controls. More Al accumulated in the roots of seedlings of the 100 μmol L−1Al/2000 μmol L−1Si treatment than in the 100 μmol L−1treatment. Al treatment reduced root and shoot K concentrations under both pH regimes, and Si did not ameliorate this effect. Al treatment had little effect on seedling Ca levels.Three treatments were selected for a microanalytical investigation of the basal third of the root, and the zone 3.5 mm behind the root tip: 2800 μmol L−1Si; 75 μmol Al; and a combination of the two. When plants were grown in 2800 μmol L−1Si the major silica deposition sites in the roots were the endodermal walls. In the 75 μmol L−1Al treatment, Al was mainly located in the epidermal and hypodermal walls. Al treatment caused a leakage of phosphorus into these cell walls. When both 2800 μmol L−1and 75 μmol L−1Al were present in the nutrient solution, only Si was deposited in the endodermal walls, while both elements were present in the epidermal walls. Leakage of phosphorus appeared to be prevented in the presence of Si.


Author(s):  
Z. M. Kuramshina ◽  
R. M. Khairullin ◽  
Yu. V. Smirnova

In this study, we tested the effect of two strains of bacteria B. subtilis 26D and 11ВМ on three varieties of wheat Triticum aestivum L.: Omskaya 35, Kazakhstanskaya 10 (spring), Volzhskaya qualitative (winter).The peculiarity of the plants response to endophytic inoculation depended on the strain of the microorganism, the concentration of cells in the preparation, and the variety of wheat during the experiment in Petri dishes. Both strains showed a strong growth-stimulating effect when seed was inoculated with suspensions of bacteria with a concentration of 106 cells/ml. There was no effect when seed cells were inoculated with bacteria at a concentration of 109 cells / ml. Plants varieties Omskaya 35 were most responsive to inoculation with endophytes. The variety was well responsive to the inoculation of bacteria cells at different concentrations. The variety Volzhskaya quality had the least growth stimulation. Plants of this variety responded well when grown in soil, unlike experiments in Petri dishes. The variety Kazakhstanskaya 10 was less responsive when growing plants in Petri dishes. There was no difference between the size of the shoots of inoculated and non-inoculated plants of the variety Kazakh 10, only stimulation of root growth was observed. It was concluded that there is a pronounced responsiveness of wheat varieties to the effect of endophytic strains of bacteria B. subtilis 26D the basis of biofungicide (Fitosporin-M) and this must be considered when using biofungicide for wheat cultivation.


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