Variety improvement in rice (Oryza sativa L.): proteomic, hormonal and in vitro studies

Rice (Oryza sativa L.) is without doubt one of the major crops worldwide, as its consumption is continuously increasing, especially in less developed coun-tries where it is the most important staple. This cereal has been domesticated for a long time, fruit of which several species and varieties are now available. Moreover, it was key during the green revolution where its production more than doubled and has a deep cultural background in all the regions it is grown. Hence, it is of uttermost importance for researchers and breeders to broaden and expand the knowledge we have on this cereal on all the study and re-search areas, especially now that we are living in the 21st century, which is marked by climate change. This natural phenomena is one of the most menac-ing as it will reduce the quantity and quality of arable land due to salinization of soil as well as water scarcity which is the single most important factor that determines global crop yields. In this sense, this thesis addressed three im-portant topics on rice that will help researchers and breeders for the improve-ment of rice varieties in the forthcoming future: (i) Analysis of salinity tolerant rice plants subjected to high salt concentration through a combined approach of shotgun proteomics and physiological char-acterization for the identification of new key proteins involved in the tolerance to this stress. In this study we provide a huge database for future studies of the salinity-stress response in rice varieties harboring the Saltol region, as we de-tected more than 2000 proteins during the early stages of salinity stress in the shoots and roots of the FL478 rice line. Moreover, this study highlights the im-portance of examining both the shoots and roots because their salinity toler-ance traits are different and respond to different requirements of the rice plant. Finally, the information presented here expands our knowledge on adaptive processes under high salinity in rice plants and notably, in rice roots. (ii) Phytohormones analysis in dwarf varieties through a broad phytohormone profiling method developed during this thesis for the characterization of phyto-hormone levels during the development of plants with contrasting heights that will allow have more information for developing new dwarf mutant varieties. In this work, we reported that GA19 seems to have a crucial role in gibberellin availability in rice as its levels were much higher than all the other gibberellins in all tissues. In addition, it has been demonstrated that the GA20ox-2 mutation is not the only factor affecting height in rice, as a mutated variety had an in-creased growth during the half of its development period. Finally, we estab-lished for the first time a simple and broad phytohormone extraction and detec-tion protocol that allows to identify 13 gibberellins and ABA, JA and IAA in several tissues at different phenological stages. (iii) Improvement and enhancement of anther culture protocols in rice for ob-taining higher rates of stabilized green double haploid plants using different cold-pretreatments, hormones and antimitotics in the growing media for their subsequent commercialization. It was evidenced that the best cold-pretreatment was 10oC for 9 days, and that colchicine addition greatly en-hances the production of green double haploid plantlets. Moreover, we have introduced for the first time a post-anther culture treatment with good pro-spects. Finally, several of the rice lines produced were assayed in rice paddy fields where they showed good agronomical behavior.