The effect of take-all disease on gas-exchange rates and biomass
in two winter wheat lines with different drought response |
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Authors: | Maria Balota CM Rush WA Payne MD Lazar |
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Institution: | (1) Texas A&M University System, Texas Agricultural Experiment Station Amarillo, 6500 Amarillo Blvd. West, Amarillo, TX 79106, USA |
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Abstract: | There have been no studies of the effect of take-all on leaf gas-exchange rates, despite the fact that take-all severely restricts
plant water and nutrient uptake, which results in significant biomass and grain yield reduction. Here we describe the effect
of inoculation with Gaeumannomyces graminis (Sacc.) var. tritici (Ggt) on carbon assimilation rate (A) and biomass production of wheat plants grown under two water regimes. We show that
the impact of Ggt inoculation on plant growth and leaf A may be through reduced photosynthetic capacity of the leaves and
not water stress per se. The nature of this reduced photosynthetic capacity remains uncertain but may involve nutrient deficiency and different enzymes
produced by the fungus. In each of the 3 years the experiment was conducted, Ggt significantly reduced A, i.e. at anthesis
by 18% in 2000, 15% in 2001, and 12% in 2002. In agreement with other field studies, Ggt reduced tiller number and production
of all plant components, mostly root dry mass and grain mass per plant. Highly significant negative correlations were found
between disease rating and A in all years, showing that at disease ratings equal or higher than 3 (on a scale from 1 to 4)
A could practically be zero. While A decreased, intercellular CO2 concentration increased or did not change, and stomatal conductance was relatively high. In addition, A was more reduced
under high than under low soil moisture content. These results support the idea that water stress per se did not contribute to the observed reduction of A. The mechanism of photosynthetic capacity reduction due to the Ggt root-rotting
fungus is of interest as it may lead to the molecular mechanisms of plant resistance and ultimately to the development of
take-all resistant plants. |
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Keywords: | Gaeumannomyces graminis (Sacc ) var tritici photosynthesis Triticum aestivum (L ) water stress |
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