Abstract
Wheat is one of the most important crops worldwide. The use of plant growth promoting microorganisms, such as those of the genus Trichoderma, constitutes an alternative to chemical fertilizers, since they are cheaper and are not detrimental to the environment. However, the interaction between Trichoderma and wheat plants has been scarcely studied, at least at a molecular level. In the present work, a microarray approach was used to study the early transcriptomic changes induced in wheat roots by Trichoderma harzianum, applied alone or in combination with different concentrations of calcium nitrate [Ca(NO3)2], which was last used as nitrogen (N) source. Our results show that T. harzianum causes larger transcriptomic changes than Ca(NO3)2 in wheat roots, and such changes are different when plants are challenged with Trichoderma alone or treated with a combination of T. harzianum and Ca(NO3)2. Overall, T. harzianum activates the expression of defense-related genes at early stages of the interaction with the roots, while this fungus reduces the expression of genes related to plant growth and development. Moreover, the current study in wheat roots, subjected to the different T. harzianum and Ca(NO3)2 combinations, reveals that the number of transcriptomic changes was higher when compared against those caused by the different Ca(NO3)2 concentrations than when it was compared against those caused by T. harzianum. N metabolism gene expression changes were in agreement with the levels of nitrate reductase activity measured in plants from Trichoderma plus Ca(NO3)2 conditions. Results were also concordant with plant phenotypes, which showed reduced growth at early interaction stages when inoculated with T. harzianum or with its combination with Ca(NO3)2 at the lowest dosage. These results were in a good agreement with the recognized role of Trichoderma as an inducer of plant defense.
Highlights
Wheat (Triticum aestivum L.) is one of the most important crops on Earth, with an area harvested of 220 million ha and a global production of 770 million tons, China and India being the major producers followed by Russia and United States (FAOSTAT, 2018)
Out of a total of 61,127 probe sets deposited on the microarray, only 226 genes showed at least a twofold significant change in expression using a P-value < 0.015 in at least one of the eight assayed conditions (Supplementary Table S2)
No Gene Ontology (GO) categories were significantly over-represented after comparing the expression changes detected in the eight considered growth conditions
Summary
Wheat (Triticum aestivum L.) is one of the most important crops on Earth, with an area harvested of 220 million ha and a global production of 770 million tons, China and India being the major producers followed by Russia and United States (FAOSTAT, 2018). It has been reported that the human processes -primarily the manufacture of fertilizer for food production- have converted around 120 million tons of N2 from the atmosphere per year into reactive forms, and most of them end up polluting the environment. This value has overcame by four times the capacity of recycling that our planet possesses (Rockström et al, 2009). Currently in Spain, 2.4 million ha are devoted to wheat crops employing 200 kg/ha/year This drastic situation is a suitable scenario for developing novel strategies to increase crop yields. This need has led to the search for biostimulants for plant nutrition as biological and environmentally friendly alternatives to reduce or substitute the use of inorganic fertilizers, while ensuring the yield and high quality of crops (Vita et al, 2018)
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