Present Status and Future Prospects of Drought Tolerance in Rice

Rice is an important staple food crop across the world. It is mainly cultivated under irrigated lowland and also rain-fed upland conditions where drought stress is often noticed. Global climate change predicts an intensification of drought stress in future due to uneven rainfall which was witnessed for the last few years. Confronting drought stress can deliver fruitful crop returns in rice and scope for research extents. Drought stress affects the overall plant growth and yield. A prominent improvement has been made during last two decades in our understanding of the mechanisms involved in adaptation and tolerance to drought stress in rice. In order to achieve the marked crop returns from rainfed areas, there is a requisite of drought tolerant rice varieties, and genetic improvement for drought tolerance should be a prime area of concern in the future. A huge rice germplasm is available and good number of the germplasm possess drought tolerance and these genomic regions have been exploited in developing some drought tolerant rice varieties. The application of available genotyping methodologies, the identification of traits of interest, and key genetic regions associated with the drought tolerance have opened new prospects to successfully develop new drought tolerant varieties. This chapter deals with the importance of drought tolerance in rice crop followed by the evolution of molecular markers and breeding techniques in identifying drought tolerant QTL’s/genes and their utilization in the improvement of drought tolerant rice varieties

Deep sequencing of small RNAs reveals ribosomal origin of microRNAs in Oryza sativa and their regulatory role in high temperature

MicroRNAs are small noncoding regulatory RNAs which control gene expression by mRNA degradation or translational repression. They are significant molecular players regulating important biological processes such as developmental timing and stress response. We report here the discovery of miRNAs derived from ribosomal DNA using the small RNA datasets of 16 deep sequencing libraries of rice. Twelve putative miRNAs were identified based on highly stringent criteria of novel miRNA prediction. Surprisingly, 10 putative miRNAs (mi_7403, mi_8435, mi_12675, mi_4266, mi_4758, mi_4218, mi_8200, mi_4644, mi_14291, mi_16235) originated from rDNA of rice chromosome 9. Expression analysis of putative miRNAs and their target genes in heat tolerant and susceptible rice cultivars in control and high temperature treated seedlings revealed differential regulation of rDNA derived miRNAs. This is the first report of rDNA derived miRNAs in rice which indicates their role in gene regulation during high temperature stress in plants. Further studies in this area will open new research challenges and opportunities to broaden our knowledge on gene regulation mechanisms

Rice biofortification: breeding and genomic approaches for genetic enhancement of grain zinc and iron contents

Rice is a highly consumed staple cereal cultivated predominantly in Asian countries, which share 90% of global rice production. Rice is a primary calorie provider for more than 3.5 billion people across the world. Preference and consumption of polished rice have increased manifold, which resulted in the loss of inherent nutrition. The prevalence of micronutrient deficiencies (Zn and Fe) are major human health challenges in the 21st century. Biofortification of staples is a sustainable approach to alleviating malnutrition. Globally, significant progress has been made in rice for enhancing grain Zn, Fe, and protein. To date, 37 biofortified Fe, Zn, Protein and Provitamin A rich rice varieties are available for commercial cultivation (16 from India and 21 from the rest of the world; Fe > 10 mg/kg, Zn > 24 mg/kg, protein > 10% in polished rice as India target while Zn > 28 mg/kg in polished rice as international target). However, understanding the micronutrient genetics, mechanisms of uptake, translocation, and bioavailability are the prime areas that need to be strengthened. The successful development of these lines through integrated-genomic technologies can accelerate deployment and scaling in future breeding programs to address the key challenges of malnutrition and hidden hunger

Development of early maturing salt-tolerant rice variety KKL(R) 3 using a combination of conventional and molecular breeding approaches

Introduction: Soil salinity poses a severe threat to rice production, resulting in stunted growth, leaf damage, and substantial yield losses. This study focuses on developing an early maturing seedling stage salinity tolerant rice variety by integrating conventional breeding methods with marker assisted breeding (MAB) approaches.Methods: Seedling-stage salinity tolerance Quantitative Trait Locus (QTL) “Saltol” from the salt-tolerant parent FL478 was introduced into the high-yielding but salt-sensitive rice variety ADT 45. This was achieved through a combination of conventional breeding and MAB. The breeding process involved rigorous selection, screening, and physiological parameter assessments.Results: KKL(R) 3 (KR 15066) identified as the top performing Recombinant Inbred Line (RIL), consistently demonstrating maximum mean grain yields under both salinity (3435.6 kg/ha) and normal (6421.8 kg/ha) conditions. In comparison to the early maturing, salt-tolerant national check variety CSR 10, KKL(R) 3 exhibited a substantial yield increase over 50%.Discussion: The notable improvement observed in KKL(R) 3 positions it as a promising variety for release, offering a reliable solution to maximize yields, ensure food security, and promote agricultural sustainability in both saline and non-saline environments. The study highlights the effectiveness of MAB in developing salt-tolerant rice varieties and emphasizes the significance of the Saltol QTL in enhancing seedling stage salinity tolerance. The potential release of KKL(R) 3 has the capacity to revolutionize rice production in salt affected regions, providing farmers with a reliable solution to maximize yields and contribute to food security while ensuring agricultural sustainability

Development and evaluation of introgression lines with yield enhancing genes of the Indian mega-variety of rice, MTU1010

MTU 1010 is an early maturing and high-yielding mega rice variety widely grown in an area of 3 Mha. It is characterised by limited grain number and panicle branching. To improve the grain number in MTU 1010, an IRRI breeding line, IR121055-2-10-5 was utilized as donor to transfer yield-enhancing genes Gn1a and OsSPL14 (associated with increased grain number and better panicle branching, respectively) into MTU1010 by Marker-Assisted Backcross Breeding (MABB). At each backcross generation, foreground selection was carried out with Gn1a and OsSPL14- specific molecular markers, whilst background selection was done with a set of SSR markers polymorphic between the IR121055-2-10-5 and MTU1010. With the use of a gene-specific marker, homozygous BC2 F2 plants carrying the yield-enhancing gene were identified and advanced through pedigree-method of selection till BC2 F6 and best performing ten lines were selected and evaluated in replicated station trials for yield contributing traits, where grain number and brancing per panicle exhibited high significant and positive correlation with single plant yield. Three promising lines namely RP6353-5-8-13-24, RP6353-26-13-39-5 and RP6353-32-12-8-16 with higher grain number and yield than MTU1010 were identified and nominated for evaluation in Initial Varietal Trial-Aerobic (IVT-Aerobic) of All India Crop Improvement Programme on Rice (AICRP), of which RP6353-26-13-39-5 (IET28674), was promoted for further testing

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Not AvailableThis paper presents the results of studies conducted in India to enhance the yield potential of improved Samba Mahsuri (ISM) using marker-assisted selection for the presence of yield target traits, i.e. high grain number, strong culm and panicle branching, which are governed by the genes Gn1a, SCM2 and OsSPL14, respectively. Phenotypic evaluation of the F4 population derived from the cross ISM Ã x YPK-267 was carried out for growth and yield related traits. Promising lines were identified for further use in rice breeding programmes.Not Availabl

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Not AvailableA study was conducted to evaluate the genetic variability parameters, correlation and path coefficient analysis for eight yield related traits in segregating F2 population of an aerobic restorer AR 9-18 × YPK 198 (Donor for yield enhancing genes Gn1a and OsSPL14) at ICAR-IIRR, Hyderabad during the kharif, 2019. The results indicated that, productive tiller number, grain number per panicle and plant yield showed high PCV and GCV. Height of plant, productive tiller number, grain number per panicle and plant yield exhibited a high heritability and also high genetic advance as per cent of mean which indicates simple selection would be effective for enhancement of these traits. Correlation studies indicated that plant yield was associated significantly positive with height of plant, productive tiller number, length of panicle and grain number per panicle. High positive direct effect on plant yield was recorded by productive tiller number, grain number per panicle and height of plant.Not Availabl

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Not AvailableHybrids commercially grown in the country gives 15-20% yield advantage over the best inbred varieties. There is a need to increase the magnitude of heterosis level to 20-30% besides improving grain quality and other desirable traits like plant type, number of productive tillers, flowering duration, desirable plant height, grain type, yield, maintenance ability, disease and insect pest resistance etc. In present study we developed base composite populations suitable to local conditions using original gene pool obtained from International Rice Research Institute (IRRI) by adding 10 component lines for above mentioned different traits. More than 950 productive segregants selections were made and stabilized through pedigree method for desirable traits. The developed lines are superior for different traits. This indicates population improvement strategy is bringing the superior allele into one line in short period of time from different genotypes. This method is very useful to increase diversity in hybrid rice parental lines within known timeICAR-Indian Institute of Rice Researc

Breeding Novel Rice Hybrids for Aerobic Ecology: A Way Out from Global Warming and Water Crisis

The development of novel rice hybrids is a prospectus area of research for enhancing grain yield to meet the growing population demands. An experiment was conducted in 2016–2017 to develop novel rice hybrids for aerobic ecology with lesser yield penalties than irrigated ecosystems, with the added advantage of reduced methane emissions and water budget as witnessed in irrigated systems. Based on the restorer-maintainer reaction and spikelet fertility (%), ten restorer lines were selected to cross with three CMS (Cytoplasmic male sterile) lines in the Line by Tester fashion in Yasangi (summer) season 2016–2017. They resulted in 30 experimental hybrids besides 13 parental lines (10 restorer lines and 3 B—lines of akin CMS lines) and checks (GK 5022, CR Dhan 201) assessed during the Vankalam (rainy) season 2017 at three different places/locations viz., Rajendranagar, Warangal, and Kampasagar. The outcome of the experiment was that two experimental hybrids viz., APMS-6A × HRSV-7 and IR-79156A × ATR-372, were categorized as stable hybrids with desirable sca (Specific combining ability) effects, heterosis (ranging from 7% to 13%) over best check GK 5022, along with an in-essence performance for yield and other yield attributing characters