title: Estimation of the genetic diversity in wheat (<i>Triticum aestivum<i> L.) regarding mycorrhization of roots and its impact on drought stress tolerance
Creators: name: Lehnert, Heike
Publisher: name: Dissertationen aus dem Julius Kühn-Institut
Year: 2019

description: Bread wheat is one of the major staple food crops worldwide, which is increasing constantly in demand due to the earth´s growing population. Besides this, in the majority of wheat growing areas worldwide, the incidence of drought stress has increased significantly resulting in a negative impact on plant development and grain yield. Arbuscular mycorrhizal symbiosis are associations between specialized soil fungi and plants. The positive effects of arbuscular mycorrhizal symbiosis on plant performance under drought stress conditions by improving drought stress tolerance are widely known. Nevertheless, no extensive knowledge associated with genotypic differences in root colonization of wheat by mycorrhizal fungi and the response of wheat to mycorhizae under drought stress conditions is available. Furthermore, quantitative trait loci (QTL) involved in root colonization of wheat by mycorrhizal fungi and in the response to drought stress conditions in the presence of mycorrhizae are largely unknown. Therefore, a diverse set consisting of 94 bread wheat genotypes was phenotyped under drought stress and well watered conditions in the presence and absence of mycorrhizae. Root colonization by mycorrhizal fungi, grain yield and yield components, drought stress related traits as well as response to mycorrhizae were assessed. Significant genotypic differences (p&lt;0.0001) were detected in root colonization of wheat by mycorrhizal fungi. Drought stress tolerance of wheat was significantly increased in the presence of mycorrhizae compared to drought stress tolerance in the absence of mycorrhizae. However, genotypes differed in their response to mycorrhizae under drought stress conditions. Interestingly, root colonization by mycorrhizal fungi and response to mycorrhizae under drought stress conditions were not correlated, indicating that both traits are independent and under control of different genomic regions. In parallel to phenotyping, wheat accessions were genotyped by using the 90K iSelect chip, resulting in a set of polymorphic single nucleotide polymorphism (SNP) markers. At the beginning of the work, no reference sequence of wheat was available. Therefore, the set of SNP markers was mapped based on the 90K consensus map, resulting in 17,823 polymorphic mapped markers, which were used for genome-wide association studies. In total, six QTL regions associated with root colonization by mycorrhizal fungi were detected on chromosomes 3A, 4A and 7A. Since the wheat reference sequence of Chinese Spring is available, all further genome-wide association studies were conducted by using a set of 15,511 markers mapped against the reference sequence. Several QTL regions on different chromosomes were detected associated with grain yield and yield components under drought stress conditions. Furthermore, two genomic regions on chromosomes 3D and 7D were found to be significantly associated with the response to mycorrhizae under drought stress conditions. Overall, the results reveal that inoculation of wheat with mycorrhizal fungi significantly improves drought stress tolerance and that QTL regions associated with root colonization of wheat by mycorrhizal fungi and the response to mycorrhizae under drought stress conditions exist, which are independently. The results reported here provide key insight into the genetics of root colonization by mycorrhizal fungi and the response to mycorrhizae under drought stress conditions in wheat. Maybe in the future, these initial results will help to contribute to use mycorrhizal fungi effectively in bread wheat production and combine new approaches i.e. use of genotypic variation in response to mycorrhizae under drought stress conditions with existing breeding programs for drought tolerance to develop new drought stress tolerant genotypes.
description: Dissertationen aus dem Julius Kühn-Institut, 2019