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. 2011;6(11):e28091.
doi: 10.1371/journal.pone.0028091. Epub 2011 Nov 23.

Competitive Performance of Transgenic Wheat Resistant to Powdery Mildew

Free PMC article

Competitive Performance of Transgenic Wheat Resistant to Powdery Mildew

Olena Kalinina et al. PLoS One. .
Free PMC article


Genetically modified (GM) plants offer an ideal model system to study the influence of single genes that confer constitutive resistance to pathogens on the ecological behaviour of plants. We used phytometers to study competitive interactions between GM lines of spring wheat Triticum aestivum carrying such genes and control lines. We hypothesized that competitive performance of GM lines would be reduced due to enhanced transgene expression under pathogen levels typically encountered in the field. The transgenes pm3b from wheat (resistance against powdery mildew Blumeria graminis) or chitinase and glucanase genes from barley (resistance against fungi in general) were introduced with the ubiquitin promoter from maize (pm3b and chitinase genes) or the actin promoter from rice (glucanase gene). Phytometers of 15 transgenic and non-transgenic wheat lines were transplanted as seedlings into plots sown with the same 15 lines as competitive environments and subject to two soil nutrient levels. Pm3b lines had reduced mildew incidence compared with control lines. Chitinase and chitinase/glucanase lines showed the same high resistance to mildew as their control in low-nutrient treatment and slightly lower mildew rates than the control in high-nutrient environment. Pm3b lines were weaker competitors than control lines. This resulted in reduced yield and seed number. The Pm3b line with the highest transgene expression had 53.2% lower yield than the control whereas the Pm3b line which segregated in resistance and had higher mildew rates showed only minor costs under competition. The line expressing both chitinase and glucanase genes also showed reduced yield and seed number under competition compared with its control. Our results suggest that single transgenes conferring constitutive resistance to pathogens can have ecological costs and can weaken plant competitiveness even in the presence of the pathogen. The magnitude of these costs appears related to the degree of expression of the transgenes.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.


Figure 1
Figure 1. Mildew incidence in phytometers of 15 wheat lines grown with the same lines as competitive environments.
Left chart (A): soil with low nutrient level. Right column (B): soil with high nutrient level (fertilized subplots). The mildew incidence in phytometers is plotted as a function of the mildew incidence of the competitive environments (linear regression lines), demonstrating differences among phytometer lines and increased infection in phytometer plants in pathogen-susceptible environments. Mildew incidence is the percentage of plants infected with the pathogen. Solid black lines: lines Pm3b#1–4; dashed black lines: lines Sb#1–4 and Bobwhite; solid grey lines: transgenic A9 Chi and A13 Chi/Glu lines; dashed grey lines: Frisal control line; dotted grey lines: three Swiss conventional wheat varieties (Casana, Toronit and Fiorina).
Figure 2
Figure 2. Performance of the 15 wheat lines grown with the same lines as competitive environments.
Left column (A): average performance of the transgenic and conventional lines across 15 competitive environments. Right column (B): relative performance of the investigated wheat lines under competition with other lines expressed as a percentage of the estimates in their own environment. The data for high and low nutrient treatments are pooled. Dashed lines denote 100% (i.e. log-ratio = 0: same performance in own and foreign competitive environment). Bars represent means ± standard errors back-transformed from log scale. Five grades of the grey scale indicate groups of wheat lines; from dark to light: transgenic lines, the genetically closest control (sister lines), wheat varieties used for transgene insertion and modern conventional wheat varieties. The significant differences between the Pm3b and corresponding control Sb lines, between Frisal and A9 Chi line, Frisal and A13 Chi/Glu line and among the three conventional varieties Fiorina, Casana and Toronit are shown with asterisks: *** – P<0.001, ** – P<0.01, * – P<0.05.
Figure 3
Figure 3. The relationship between mildew incidence and yield in 15 wheat lines.
Left chart (A): soil with low nutrient level. Right column (B): soil with high nutrient level (fertilized subplots). The solid and dotted lines are linear regression lines for the groups of means for transgenic Pm3b lines and for control Sb lines and variety Bobwhite. Mildew incidence is a percentage of plants infected with the pathogen. The data for 15 wheat competitive environments are pooled.

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