12/28/2023 0 Comments Banner effect joomlaIt has been reported that Pokkali maintains lower shoot Na + accumulation and lower shoot Na +/K + ratio under high salinity compared to sensitive genotypes 19, 20. Munns and Tester 3 and Roy 18 have proposed several physiological mechanisms of seedling tolerance such as sodium exclusion, compartmentalization of excessive sodium ions (tissue tolerance) and shoot-ion independent tolerance for early stage tolerance. The physiological basis of salt tolerance during the early seedling stage is well understood. This emphasizes the importance of discovering the contributing traits of these two very important growth stages of rice. 17 have shown that salinity tolerance at the seedling and reproductive stages is only weakly associated. At the reproductive stage, salinity stress produces a significant decrease in panicle weight, panicle length, primary branches per panicle, filled grains per panicle, total seeds per panicle, total seed weight per panicle, 1000-seed weight and total seed weight per plant 15, 16. During salt stress at the early seedling stage, there is a significant decrease of dry matter as well as quantum yield of PSII and a significant increase of sodium concentration in root, stem and shoot tissue 14. It is most sensitive to salinity at the early seedling stage and during panicle formation, and relatively tolerant during early germination, active tillering and maturity 8, 9, 10, 11, 12, 13. The effect of salinity on rice growth varies across various developmental stages 8. Therefore, it is important for breeders to identify genetic variants of salt stress responses in these naturally adapted landraces in order to design highly salt tolerant elite rice. However, studies of these adapted landraces to understand their salt tolerant mechanisms can help to incorporate desired traits into commercial rice. Unfortunately, these landraces suffer from low yield, poor grain quality and longer duration to reach maturity and therefore not suitable as commercial varieties. Many other salt-tolerant landraces such as Horkuch, Ashfal, Jatai and Balam from the coastal region of southern Bangladesh have been identified and are currently grown by farmers in these salt-affected regions 6, 7. The rice landrace, Pokkali, has long been used as a salt tolerant landrace reference. However, the coastal belt of Bangladesh is enriched with many local rice landraces, among which a handful are adapted to high-to-moderate soil salinities. Recent studies have shown that production of high yielding rice varieties in Bangladesh will decrease by 15.6% in coastal districts where soil salinity is predicted to exceed 4 deciSiemens per meter (dSm −1) by 2050 5. High yielding “elite” rice cultivars are especially susceptible to salinity stress. In Bangladesh, about 30% of the cultivable land along the coast is affected by salinity due to tidal flood during the wet season resulting in direct inundation by saline water, and upward or lateral movement of saline ground water during the dry season 4. Bangladesh and other locales at or near sea level are particularly vulnerable to climate change-induced salinity. Among these abiotic stresses, salinity has already affected 45 million hectares of irrigated land worldwide and 1.5 million additional hectares are impacted each year 3. Rice ( Oryza sativa L.) production, which feeds almost half of the world population, is under threat from global environmental changes such as increasing salinity, heat and drought 1, 2. Finally, we identified QTLs co-localization for multiple traits that highlights the possible constraint of multiple QTL selection for breeding programs due to different contributions of a donor allele for different traits. This underscores the importance of considering cytoplasm-nuclear interaction for breeding programs. In addition, we detected a significant effect of the cytoplasmic genome on the QTL model for some traits such as leaf total potassium and filled grain weight. We identified 14 QTLs for 9 traits and found that most are unique to specific developmental stages. Our aim was to detect genetic loci that contributes to the salt adaptive responses of the two different developmental stages of rice which are very sensitive to salinity stress. In this study, we implemented a QTL analysis framework with a reciprocal mapping population developed from a salt tolerant landrace Horkuch and a high yielding rice variety IR29. Rice landraces indigenous to coastal Bangladesh can be a great resource to study the genetic basis of salt adaptation. To cope with the increased soil salinity due to climate change, we need to develop salt tolerant rice varieties that can maintain their high yield. Salinity has a significant negative impact on production of rice.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |