Mutagenesis in wheat: An approach to make saline green!

Abstract

The raising salinity in the soils around the world have been widely studied during the last decades due to the massive loss in agricultural land. Today, nearly 8% of the world’s arable land can no longer be used for crop cultivation due to salt contaminations, and more than half of the countries in the world are affected. Wheat is the second most grown cereal after corn and covers more growth area on the earth than any other crop. Wheat production therefore needs to be increased to meet the demand of a growing world population. Thus, the possibility to grow wheat on salt-effected soil is crucial to feed the population and avoid economic loss for the countries involved. In this thesis, the Bangladeshi wheat variety of BARI Gom-25 that is moderately salt tolerant was used as a source to create a mutagenized population with point mutations, and thereafter it acted as a control to the mutated lines. The benefit of point mutations is that a population with high genetic variation can be created. From such a population novel salt tolerant varieties can be developed, as well as many other valuable traits. From a germination screening of approximately 2000 lines on saline filter paper (200 mM NaCl), 70 lines were identified that exhibited a higher germination rate than the BARI Gom-25 control. These lines were further tested in the field in Bangladesh (Paper I). Thirty-five of those lines were also analyzed in the Australian Plant Phenomics Facility at Adelaide. In these experiments yield, growth, ion content, and water use were determined (Paper II). In Paper III and IV bioinformatic tools were used as an approach to look for transcription factor genes in the wheat genome involved in salt tolerance. The focus was on two different transcription factor families; WRKY (Paper III) and MYB (Paper IV). These studies illustrated the importance of the biological regulation of salt tolerance, and enhanced the understanding behind the mechanisms involved. Moreover, it highlighted putative target genes regulated by WRKY and MYB transcription factors that could be key ones to understand findings from Paper I and II. This thesis points out the importance of salt tolerant crops in general, and wheat in particular, and shows how mutational breeding can be a great asset in the development of salt tolerant varieties. Specific mutagenized wheat lines with strong salt tolerance are identified based on their performance against various parameters, and the importance of WRKY and MYB transcription factor families in the biological regulation of salt tolerance is shown. Finally, downstream candidate genes encoding the observed phenotypes observed.