For more than half of the world’s population, rice (Oryza sativa L.), the most saltsensitive
cereal, is a dietary staple. Soil salinity is a major constraint to rice
production worldwide. Thus, to feed 9 billion people by 2050, we need to increase
rice production while facing the challenges of rapid global environmental changes.
To meet some of these challenges, there is a vital requirement to significantly
increase rice production in salinized land and improve photosynthetic efficiency.
Exposure of plants to soil salinity rapidly reduces their growth and transpiration
rates (TRs) due to the ‘osmotic component’ of salt stress (sensu Munns and Tester),
which is hypothesized to be related to sensing and signaling mechanisms. Over time,
toxic concentrations of Na+ and Cl− accumulate in the cells of the shoot, known as
the ‘ionic component’ of salt stress, which causes premature leaf senescence. Both
osmotic and ionic components of salinity stress are likely to impact yield. Despite
significant advances in our understanding of the ionic components of salinity
tolerance, little is known about the early responses of plants to salinity stress.
In my PhD project, the aim was to analyze naturally occurring variation in salinity
tolerance of rice and identify key genes related to higher salinity tolerance using
high-throughput phenomics and field trials. I used a forward genetics approach,
with two rice diversity panels (indica and aus) and recently published sequencing
data (McCouch et al., 2017). Indica and aus were phenotyped under controlled
conditions, while the indica diversity panel was also further studied under field
conditions for salinity tolerance. I also examined previously unexplored traits
associated with salinity tolerance, in particular the effects of salinity on transpiration
and transpiration use efficiency. The non-destructive high-throughput experiments
conducted under controlled conditions gave insights into the understudied shoot
ion-independent component of salinity tolerance. In parallel, the field experiments
increased our understanding of the genetic control of further components of salinity
tolerance, including the maintenance of yield under saline conditions. Importantly,
this project also aimed to improve the current association methods of GWAS by
exploring and testing novel Mixed Linear Models. One major benefit of this Ph.D.
project was the development of a more holistic approach that recognizes the
complexity of the genotype–phenotype interaction. The purpose of my work was to
shed more light on the genetic mechanisms of salinity tolerance in rice and discover
genes associated with traits contributing to higher photosynthetic activity under
both controlled and field conditions. This will ultimately lead to further exploration
of the genetic diversity present in the PRAY indica panel, in order to develop higher
yielding rice varieties.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/656786 |
| Date | 05 1900 |
| Creators | Al Tamimi, Nadia |
| Contributors | Tester, Mark A., Biological and Environmental Sciences and Engineering (BESE) Division, Al-Babili, Salim, Gojobori, Takashi, McCouch, Susan |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
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