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Title: Genetic, phenomic and molecular analysis of drought avoidance and recovery traits in rice for the improvement of plant breeding
Author: Alshugeairy, Zaniab
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2013
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Rice (Oryza sativa L.) is one of the main staple foods of the world. With the increase of population and the deficit of irrigated water, the increase in rice production that is predicted will be dependent on areas prone to drought. Root depth is important for plant growth and survival during drought because of its role in facilitating water uptake from deep soil layers. By advances in genomics, the plant root systems can be linked to quantitative trait locus (QTL) information to achieve a most beneficial design of root system architecture. There is a demand to develop and validate techniques that permit estimation of the root system. Therefore, two techniques (root penetration ability to non-woven fabric and a buried herbicide method at depth 30 cm) were used in this study to assess root traits in a total of 36 rice cultivars. The results from these screens were assessed with root traits measured on the same cultivars in the rhizotrons and hydroponic experiment. Correlations between these methods showed that herbicide score at day 35 was most strongly related to traits of the rhizotron experiment, especially number of roots passed 50 cm at 35 days, root angle at day 21, root thickness, water use and % root mass. Using all of these traits obtained in the rhizotron in a best subset regression suggests that up to 71% of the variation in herbicide score can be explained. These data strongly imply that symptoms are related to root development and transpiration demand and are therefore ideal for assessing water extraction by roots at depth. The herbicide method has been applied to screen root depth in 138 recombinant inbred lines derived from crossing between two subspecies Indica Bala and Japonica Azucena. Analysis of mapping population revealed two putative QTLs on chromosome 6 near marker RZ682 and one on chromosome 7 near marker RG351 and two significant QTLs near marker G1010b and G1073 for root depth on chromosome 8. The same method has been used to evaluate root depth in 325 rice diversity panel allowing high resolution genetic mapping. Using efficient mixed model (statistical analyses for genome wide association), four associations were detected, two on chromosome 1 and one on each of chromosome 4 and 6. In addition, the same rice diversity panel has been evaluated for drought avoidance by assessing leaf rolling (as one plant mechanism against drought stress) and drought recovery. A total of three significant associations, on chromosomes 4, 6 and 7 were identified for leaf rolling while only one significant association on chromosome 2 for drought recovery was found. Positional candidate genes underneath QTLs were examined bioinformatically and through the literature revealing several interesting genes which may offer potential for developing drought resistant rice cultivars. Therefore, developing a cost effective high-throughput system that can measure traits related to drought avoidance and drought recovery on a large number of plants would aid genetic studies in breeding and gene identification.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Rice