Multi-Omics and Integrative Approach towards Understanding Salinity Tolerance in Rice: A Review.

Rice (Oryza sativa L.) plants are simultaneously encountered by environmental stressors, most importantly salinity stress. Salinity is the major hurdle that can negatively impact growth and crop yield. Understanding the salt stress and its associated complex trait mechanisms for enhancing salt tolerance in rice plants would ensure future food security. The main aim of this review is to provide insights and impacts of molecular-physiological responses, biochemical alterations, and plant hormonal signal transduction pathways in rice under saline stress. Furthermore, the review highlights the emerging breakthrough in multi-omics and computational biology in identifying the saline stress-responsive candidate genes and transcription factors (TFs). In addition, the review also summarizes the biotechnological tools, genetic engineering, breeding, and agricultural practicing factors that can be implemented to realize the bottlenecks and opportunities to enhance salt tolerance and develop salinity tolerant rice varieties. Future studies pinpointed the augmentation of powerful tools to dissect the salinity stress-related novel players, reveal in-depth mechanisms and ways to incorporate the available literature, and recent advancements to throw more light on salinity responsive transduction pathways in plants. Particularly, this review unravels the whole picture of salinity stress tolerance in rice by expanding knowledge that focuses on molecular aspects.

Early flowering, good grain quality mutants through gamma rays and EMS for enhancing per day productivity in rice (Oryza sativa L.).

PURPOSE: Rice is the prominent crop of world and it frames the important component of food chain. But, long duration of highly preferred rice varieties requires more water and are prone to biotic and abiotic stresses. Short duration rice varieties serve as a promising alternative in such cases. Hence, the present study was taken up to induce early flowering mutants in popular rice variety Bapatla 2231 (BPT 2231), a long duration medium slender rice variety using gamma rays and Ethyl Methane Sulfonate (EMS) treatment combinations. MATERIALS AND METHODS: Five hundred well filled and viable grains of optimum moisture content (12%) were subjected to irradiation with 8 doses comprising 100 Gy, 200 Gy, 300 Gy, 350 Gy, 400 Gy, 450 Gy, 500 Gy and 600 Gy treatments. For combination treatments, the irradiated seeds of gamma rays were further treated with 30 mM concentrations of Ethyl Methane sulfonate (EMS). The irradiated population were raised up to M3 generation for the identification of early maturing mutants. The isolated early maturing mutants in M3 generation were characterized for phenotypic, biochemical and grain qualities. RESULTS: The frequency of desirable early maturing mutants was observed more in combination treatments than the individual treatments of gamma rays. A total of 34 early maturing mutants (M) with variation for grain quality and biochemical traits were obtained. The mutants M-1, M-3, M-5, M-32, and M-34 were high yielding with fine grain type. The mutants M-4, M-17, M-18, M-19, M-20, and M-26 were high yielding with bold grain type. The mutants M-22, M-23, M-24, M-27, and M-28 were high in nutrient content. The early mutants matured 40-50 days earlier than control. CONCLUSION: In this variety, the combination treatments showed higher mutation frequency, mutagenic effectiveness and efficiency than the gamma rays in induction of both chlorophyll and viable mutants. This study revealed that the combination treatments were more effective in inducing early mutants than the gamma ray treatments alone. The early maturing mutants can be released as variety after evaluation under different yield trials and the mutants with increased nutrient content and varied grain quality can be utilized in hybridization/heterosis breeding programs for rice crop improvement.

Comparative Profiling of Volatile Compounds in Popular South Indian Traditional and Modern Rice Varieties by Gas Chromatography-Mass Spectrometry Analysis.

Rice (Oryza sativa L.) is one of the major cereal crops cultivated across the world, particularly in Southeast Asia with 95% of global production. The present study was aimed to evaluate the total phenolic content (TPC) and to profile all the volatile organic compounds (VOCs) of eight popular traditional and two modern rice varieties cultivated in South India. Thirty-one VOCs were estimated by gas chromatography-mass spectrometry (GC-MS). The identified volatile compounds in the 10 rice varieties belong to the chemical classes of fatty acids, terpenes, alkanes, alkenes, alcohols, phenols, esters, amides, and others. Interestingly, most of the identified predominant components were not identical, which indicate the latent variation among the rice varieties. Significant variations exist for fatty acids (46.9-76.2%), total terpenes (12.6-30.7%), total phenols (0.9-10.0%), total aliphatic alcohols (0.8-5.9%), total alkanes (0.5-5.1%), and total alkenes (1.0-4.9%) among the rice varieties. Of all the fatty acid compounds, palmitic acid, elaidic acid, linoleic acid, and oleic acid predominantly varied in the range of 11.1-33.7, 6.1-31.1, 6.0-28.0, and 0.7-15.1%, respectively. The modern varieties recorded the highest palmitic acid contents (28.7-33.7%) than the traditional varieties (11.1-20.6%). However, all the traditional varieties had higher linoleic acid (10.0-28.0%) than the modern varieties (6.0-8.5%). Traditional varieties had key phenolic compounds, stearic acid, butyric acid, and glycidyl oleate, which are absent in the modern varieties. The traditional varieties Seeraga samba and Kichilli samba had the highest azulene and oleic acid, respectively. All these indicate the higher variability for nutrients and aroma in traditional varieties. These varieties can be used as potential parents to improve the largely cultivated high-yielding varieties for the evolving nutritional market. The hierarchical cluster analysis showed three different clusters implying the distinctness of the traditional and modern varieties. This study provided a comprehensive volatile profile of traditional and modern rice as a staple food for energy as well as for aroma with nutrition.