Seed pre-treatment in rice reduces damage, enhances carbohydrate mobilization and improves emergence and seedling establishment under flooded conditions

Priming rice seeds (soaking followed by drying) or soaking just before sowing improved emergence from flooded soil, reduced membrane damage from ROS and hastened carbohydrate mobilization. Most benefit was to lines with a superior ability to germinate in flooded soil even when untreated

Nitrogen Use Efficiency in Rice under Abiotic Stress: Plant Breeding Approach

Nitrogenous fertilizer has remarkably improved rice (Oryza sativa L.) yield across the world since its discovery by Haber-Bosch process. Due to climate change, future rice production will likely experience a wide range of environmental plasticity. Nitrogen use efficiency (NUE) is an important trait to confer adaptability across various abiotic stresses such as flooding, drought and salinity. The problem with the increased N application often leads to a reduction in NUE. New solutions are needed to simultaneously increase yield and maximize the NUE of rice. Despite the differences among flooding, salinity and drought, these three abiotic stresses lead to similar responses in rice plants. To develop abiotic stress tolerant rice varieties, speed breeding seems a plausible novel approach. Approximately 22 single quantitative trait loci (QTLs) and 58 pairs of epistatic QTLs are known to be closely associated with NUE in rice. The QTLs/genes for submergence (SUB1A) tolerance, anaerobic germination (AG, TPP7) potential and deepwater flooding tolerance (SK1, SK2) are identified. Furthermore, phytochrome-interacting factor-like14 (OsPIL14), or loss of function of the slender rice1 (SLR1) genes enhance salinity tolerance in rice seedlings. This review updates our understanding of the molecular mechanisms of abiotic stress tolerance and discusses possible approaches for developing N-efficient rice variety

Morpho-Physiological Changes in Roots of Rice Seedling upon Submergence

Submergence is a serious environmental condition that causes large loss in rice production in rain fed lowland and flood affected area. This study evaluated morphological and physiological responses of rice roots to submergence using two tolerant rice genotypes FR13A and Swarna-Sub 1 and two sensitive ones Swarna and IR42. The tolerant genotypes had higher survival rate and less shoot elongation but greater root elongation during submergence than the sensitive ones. After submergence, the tolerant genotypes also had higher root dry weight and more active roots than the sensitive ones. Tolerant genotypes exhibited less root injury, with less malondialdehyde production and slower electrolyte leakage after submergence. Tolerant genotypes also maintained higher concentrations of soluble sugar and starch in roots and shoots and higher chlorophyll retention after submergence than the sensitive ones. Our data showed that root traits such as root activity and root growth are associated with survival rate after submergence. This is probably accomplished through higher energy supply, and membrane integrity is necessary to preserve root function and reduce injury during submergence. These root traits are important for submergence tolerance in rice. Keywords: peroxidase, root activity, submergence, rice seedling, Sub1a gen

Enhancement of submergence tolerance in transgenic ice overproducing pyruvate decarboxylase

Transgenic rice (Oryza sativa L.) lines were produced through transformation with rice pdc1 gene coding for pyruvate decarboxylase (PDC), one of the enzymes involved in alcohol fermentation. The over-expression of PDC was used not only to assess the role of alcohol fermentation but also to produce lines with enhanced metabolic capacity under anaerobiosis conferring submergence tolerance to these lines. Tillers of confirmed T0 transgenic lines showed higher PDC activities and ethanol production compared to the untransformed control. Consequently, ethanol production of tillers of T0 transgenic plants was positively correlated with survival after submergence. This is the first known report of transformation of an economically-important crop resulting in increased submergence tolerance