Developing climate-resilient, lodging-resistant rice requires integrating strong culm and root related genetics, high-throughput and trait-based phenotyping, and optimized agronomic practices. Coordinated use of molecular breeding, gene editing, and management strategies offers sustainable solutions to mitigate lodging under variable environments. Lodging is a major abiotic stress that significantly reduces grain yield and quality in rice, while also increasing vulnerability to pests. Human-induced intensification, including high planting densities, excessive nitrogen application, off-season sowing, and cultivation in upland areas, further increases rice susceptibility to lodging, posing a major management challenge. Sole reliance on the sd1 gene has proven insufficient for ensuring effective lodging resistance. This review examines the diverse factors influencing lodging susceptibility and resistance in rice, including morphological, physiological, biochemical, genetic, agronomic, and environmental aspects, and integrates current advances to guide future research and breeding strategies for lodging-resistant rice. Among these factors, the stem has emerged as a key tissue influencing lodging resistance. Advances in molecular breeding have identified several QTLs and genes, such as SCM1, SCM2, SCM3, SCM4, APO1, and prl4, that are associated with lodging resistance, enabling the use of marker-assisted selection in breeding programs. The review also discusses integrated strategies that combine advanced phenotyping tools, optimized agronomic practices, mathematical modelling, and genetic approaches including molecular breeding and gene editing to effectively develop lodging-resistant rice varieties.

High-density rice planting reduces light quality within the canopy, especially the red to far-red (R: FR) ratio, triggering a physiological shift that enhances elongation growth at the expense of weakened defence mechanisms. This is not a passive consequence but a coordinated regulation controlled by the Phytochrome B (PhyB)-Phytochrome Interacting Factor (PIF) signalling module. Under low R: FR, PhyB becomes inactive, stabilising key PIFs such as OsPIL13 and OsPIF4. These transcription factors promote shade-avoidance growth by enhancing auxin and gibberellin biosynthesis, which in turn suppresses salicylic acid (SA) and jasmonic acid (JA) signalling. They also directly repress the expression of core defence genes. Together, these changes lower immune readiness in shaded rice plants. Here, we propose a rice-specific model in which low R: FR light signals directly suppress immunity through PIF-mediated transcriptional repression, highlighting a monocot-specific mechanism that integrates light perception with immune downregulation.

Low-light (LL) stress caused by persistent cloud cover during the Kharif season significantly reduces rice (Oryza sativa L.) grain yield (GY) by limiting photosynthesis, impairing assimilate production, and affecting reproductive development. To dissect the genetic basis of LL tolerance, 192 diverse rice genotypes were evaluated across contrasting light environments (LL and normal light under Rabi and Kharif seasons) and genotyped using a high-density 44K single nucleotide polymorphism array. Integrating phenotypic and genomic data enabled a multi-tiered analysis from quantitative trait locus (QTL) discovery to gene identification and haplotype dissection. Genome-wide association analysis identified 305 QTLs associated with GY and 11 related traits, including 148 LL-specific and 32 stable QTLs expressed across both seasons. Forty-two candidate genes were localized within major QTL intervals, and 12 were identified as hub genes based on their key roles in photosynthesis, light perception, hormone signaling, and starch biosynthesis. These included Gn1a, OsPsbS1, OsAGPL2, OsLhcb1, OsAUX1, OsSBDCP1, OsNPF5.16, OsPHYA, OsPHYB, OsGIF1, HY5, and OsYUC11. Expression profiling confirmed stronger induction of OsPHYA (∼2.5-fold) and OsPsbS1 (∼2.8-fold) in LL-tolerant genotypes like Purnendu and Swarnaprabha compared to susceptible lines. Haplotype analysis revealed several superior alleles, such as PHYA-Hap2 and OsPsbS1-Hap3, that were consistently associated with higher spikelet fertility, greater grain number, increased biomass, and improved GY under LL, with top-performing haplotypes enhancing yield by 12%-18%. Genotypes carrying these haplotypes (e.g., Purnendu, Swarnaprabha, and Chamarmani) represent valuable breeding donors. Overall, this study provides the first genome-wide identification of LL-specific haplotypes in rice, together with biologically validated hub genes. These findings offer actionable genomic targets and donor resources for developing LL-resilient, high-yielding cultivars suited to changing climate and light-limited environments.

This review provides a comprehensive mechanistic framework for rice adaptation to low-light stress, integrating morpho-physiological adjustments and biochemical plasticity with the phytochrome-PIF signalling network to guide molecular breeding of light-resilient cultivars. Low-light stress (LLS), defined as photosynthetically active radiation below 600 μmol m−2 s−1, is an increasingly important constraint on rice productivity in monsoon-dominated agroecosystems, where persistent cloud cover, dense planting, and atmospheric pollution markedly reduce light availability. Under natural field conditions, pollution-derived seasonal LLS causes yield losses of 10–20

Low light is a major abiotic stress during the wet season, leading to an approximate 35% reduction in rice yield compared to the dry season. Developing rice varieties with improved yields and tolerance to low light conditions is therefore critical. This study aimed to identify low-light-tolerant rice genotypes using a Combined Stress Tolerance and Stability Index (CSTSI). A panel of 192 genotypes was evaluated for 12 agro-morphological traits during the Kharif (wet) seasons of 2021 and 2022. Results showed that low light significantly reduced key traits such as tiller number, grain number, spikelet number, spikelet fertility, panicle number, grain weight, biomass, and grain yield. Two-wayANOVA indicated significant genotypic variation under low light stress, with grain yield and biomass reductions of 41.96 and 28.49%, respectively. Yield Stability Index (YSI) and Relative Yield (RY) were calculated to assess genotype performance. The CSTSI was developed to evaluate overall stress tolerance among the 192 genotypes. Regression analysis revealed strong correlations of CSTSI with RY (0.897) and YSI (0.791), confirming its effectiveness in identifying low-light-tolerant genotypes. Based on the CSTSI, nine genotypes were identified as highly tolerant, outperforming the tolerant check variety, Swarnaprabha. Cluster analysis grouped the 192 genotypes into five clusters. Clusters IV and V included tolerant genotypes such as Purnandu, Ambika, Laxmichura, Chamarmani, Bhasamanik, TRB-468, VL Dhan209, Swarnaprabha, and TRB-451, which exhibited superior performance in YSI, RY, and CSTSI. In contrast, cluster I contained low-performing genotypes like Kunti, Sanwal Basumati, IR8, IR64, Pusa-834, Srabani, Sahabhagi Dhan and Khandagiri. Identifying low-light-tolerant genotypes provides valuable insights for identifying QTLs, genes, and superior haplotypes associated with low-light tolerance. These findings are critical for molecular breeding programs aiming to develop resilient rice varieties for low-light environments. Additionally, the study establishes CSTSI as a reliable parameter for screening genotypes for low-light tolerance.

Low light intensity is a major abiotic stress that severely affects rice yields, particularly in India and Southeast Asia, causing yield reductions of 35–40% during the wet season compared to the dry season. Tolerant rice genotypes exhibit adaptive changes at anatomical, physiological, biochemical, and molecular levels under low-light stress, enabling higher yields compared to susceptible varieties. Our study identified 20 novel QTLs associated with grain yields and nine related traits under low-light and control (normal)-light conditions, using a recombinant inbred line (RIL) population derived from the cross between the low-light-tolerant variety Swarnaprabha and the low-light-susceptible variety IR8. Across the Kharif seasons of 2019 and 2021, 33 stable QTLs were identified, with 11, 13, and 9 QTLs specific to low-light, normal-light, and both conditions, respectively. Of these, Swarnaprabha contributed 28 QTLs, while five were contributed by IR8. Notably, the study identified 11 and 9 novel QTLs under low-light and both conditions, respectively. Three hotspot regions on chromosomes 1, 4, and 8 were identified. These regions harbored 10 novel QTLs and revealed twenty candidate genes, out of which three key hub genes, OsAUX1, OsSBDCP1, and OsNPF5.16, were identified. These hub genes are involved in hormone signaling, starch metabolism, and nitrogen metabolism, respectively. A comprehensive expression analysis of these genes indicated that they are linked to low-light tolerance, offering deeper insights into the genetic and molecular mechanisms underlying low-light resilience. These findings provide valuable genomic resources and potential markers for breeding programs for improving rice productivity under low-light conditions.

Low-light (LL) stress imposes a major constraint on rice yield in densely planted and monsoonal environments, yet the mechanistic basis of shade tolerance remains insufficiently resolved. We investigated four rice genotypes under simulated LL conditions, including two LL-tolerant varieties (Purnendu and Swarnaprabha) and two LL-susceptible varieties (IR64 and IR8). Responses were systematically analysed from the flag leaf to the fourth leaf. Comprehensive evaluation included measurements of light interception, chlorophyll fluorescence, gas exchange, carbohydrate content, chloroplast ultrastructure, and the expression of fourteen photosynthesis-related genes. Our findings demonstrate that LL tolerance in rice cannot be explained by adaptation of a single leaf; rather, it results from a coordinated strategy involving integrated changes at morphological, physiological, biochemical, and gene expression levels throughout the entire canopy. Tolerant genotypes exhibited only 30-35% loss in photons from the flag leaf to the fourth leaf, whereas susceptible genotypes lost up to 75%. Architectural traits such as plant height, leaf area plasticity, and leaf angle accounted for 84% of the variation in radiation use efficiency, while tolerant genotypes sustained higher photosynthetic efficiency, carbohydrate reserves, and robust gene expression across all layers. These insights identify concrete trait targets for breeding LL-resilient rice varieties, supporting stable yield in dense and light-limited environments.

Low light (LL) stress during the grain-filling stage acutely impairs the quality and quantity of starch accumulation in rice grains. Here, we observed that LL-induced poor starch biosynthesis is modulated by auxin homeostasis, which regulates the activities of major carbohydrate metabolism enzymes such as starch synthase (SS) and ADP-glucose pyrophosphorylase (AGPase) in rice. Further, during the grain-filling period under LL, the starch/sucrose ratio increased in leaves but significantly decreased in the developing spikelets. This suggests poor sucrose biosynthesis in leaves and starch in the grains of the rice under LL. A lower grain starch was found to be correlated with the depleted AGPase and SS activities in the developing rice grains under LL. Further, under LL, the endogenous auxin (IAA) level in the spikelets was found to be synchronized with the expression of a heteromeric G protein gene, RGB1. Interestingly, under LL, the expression of OsYUC11 was significantly downregulated, which subsequently resulted in reduced IAA in the developing rice spikelets, followed by poor activation of grain-filling enzymes. This resulted in lowered grain starch accumulation, grain weight, panicle number, spikelet fertility, and eventually grain yield, which was notably higher in the LL-susceptible (GR4, IR8) than in the LL-tolerant (Purnendu, Swarnaprabha) rice genotypes. Therefore, we hypothesize that depletion in auxin biosynthesis under LL stress is associated with the downregulation of RBG1, which discourages the expression and activities of grain-filling enzymes, resulting in lower starch production, panicle formation, and grain yield in rice.

Phytochromes are sensory photoreceptors associated with the photomorphogenesis of plants. Rice has 3 phytochromes (phy); phyA, phyB and phyC. To understand the role of phyA under low light (LL) and normal light (NL) environments in plant growth, photosynthesis, biomass and yield, rice phytochrome A mutant (phyA) along with its wild-type (WT) genotype Akitakomachi were grown in field conditions. To induce LL (∼338 μmole photons m−2 s−1) both WT and phyA were shaded by the agro-shade net that reduced light intensity by ∼75%. The NL intensity (∼1355 μmole photons m−2 s−1) served as the experimental control. The plant height decreased by 8%−10% in phyA mutants both in NL and LL. Other developmental parameters, leaf area index, specific leaf weight, and spikelet fertility declined in the mutants in NL and to a larger extent in the LL. phyA had a lower electron transport rate (ETR), which increased its non-photochemical quenching (NPQ). The photosynthetic rate (PN), stomatal conductance(gs), transpiration rate (E), apparent quantum yield (AQE), maximum carboxylation efficiency (Vcmax) and mesophyll conductance (gm) significantly decreased in phyA than WT in LL. Furthermore, the expression of rice phytochrome-interacting factor-like protein (OsPIL1) was relatively downregulated in phyA under LL, resulting in a reduced total chlorophyll (Chl) and Chl b content and an increased Chl a/b ratio. Additionally, a relatively lower upregulation of Fv/Fm and expression of the isoforms of chlorophyll-a/b-proteins in phyA under LL suggests its inferior light-harvesting capacity compared to WT plants. Reduced PN resulted in a lowered overall carbon budget in phyA that hampered grain yield by 55% more than WT under LL. Our findings demonstrated the critical role of phytochrome A in orchestrating a series of shade-acclimation responses to salvage LL-induced stress and optimize the harvest index in rice.

Photorespiration, which is prevalent under higher temperature and arid conditions, significantly affects crop productivity by reducing yields up to 50% in C3 crops like rice under severe stress conditions. This is primarily attributed to a reduction in net photosynthetic rate (PN). Rice flag leaf photosynthesis is the primary supplier of sugar to the maturing spikelets after anthesis. This study evaluated the grain quality traits and starch content of the wild type (WT) and transgenic rice generated by introducing Escherichia coli (E. coli) glycolate catabolic pathway bypassed (GCPB) through agrobacterium mediated transformation. Leaf soluble protein, photosynthetic CO2 assimilation rate, leaf non-structural carbohydrate content, grain quality traits such as hulling and milling percentages, head rice recovery, water uptake, volume expansion, alkali spreading value, gel consistency, grain breadth, grain starch content and amylose content were affected to a great extent in GCPB transgenic plants (T4). This study indicates the possible role of photorespiratory bypass mechanism in the regulation of source-sink communication, starch biosynthesis and grain quality in rice.

Photorespiration accounts for 20-50 % reduction in grain yield in C3 crops. The process is essential to remove 2-phosphoglycolate produced due to the oxygenation activity of the ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) enzyme. Attempts were made to improve photosynthesis through enriched CO2 concentration by installing numerous photorespiratory bypass modules in the chloroplast of several crops. In this study, we have introduced Escherichia coli glycolate catabolic pathway (ECGC) into rice chloroplast to bypass photorespiration partially (PB) or completely (FB). Five genes encoding glyoxylate carboligase (GCL), tartronic semialdehyde reductase (TSR), and three subunits of glycolate dehydrogenase (GDH) were introduced to get FB plants, whereas only the three subunits of GDH were introduced to get PB plants. Southern analysis confirmed stable integration of the transgenes and their expression was confirmed by RT-qPCR analysis in the T3 progenies. Both FB and PB transformed lines exhibited increased photosynthetic efficiency, biomass, and grain yield than wild type (WT) with empty vector control. The introduction of ECGC pathway favoured the carboxylase activity of RuBisCO while decreasing its oxygenase activity fostering the functioning of Calvin-Benson cycle and resulting in an increased carbon-assimilation that was manifested in their superior architecture and harvest index. These findings will support rice and related cereal crop breeding programs to increase yield under elevated temperature and arid conditions.

The purpose of this study was to determine the impact of low light stress on the morphological parameters and yield of long duration rice genotypes. The experiment was carried out in the field of National Rice Research Institute, and the field layout was done as per the split plot design, with the light in the main plot and the varieties in the sub-plot. During Kharif 2019, the experiment was carried out at plot-4, V-block under the Department of Crop Physiology and Biochemistry at the National Rice Research Institute (NRRI), Cuttack. The experiment was carried out with three different light intensities, namely 100% light as treatment-I (Control), 75% light as treatment-II, and 50% light as treatment-III. Eleven long duration rice varieties were chosen based on yield to investigate the effect of low light on their morphology and yield. It was observed that at 50% flowering stage in 75% and 50% light intensities, plant height and leaf area increases but tiller number, panicle number and yield reduces. At 50% light intensity, yield reduction was significantly greater than 75% light intensity. Among the varieties Nasati Sali, Nalini Sali and Swarnaprabha was recorded highest grain yield in 100% (5.10 t ha-1), 75% (4.27 t ha-1) and 50% light intensity (3.05 t ha-1) respectively.

Seed germination plays cardinal roles in seedling establishment and their successive growth. However, seed germination is retarded by far-red (FR) enrichment under low light stress, and the inhibitory signalling mechanism remains ambiguous. Our results indicated that low light treatment, both in the open and growth chamber conditions, inhibits rice seed germination by decreasing the gibberellin (GA) contents. To explore the mechanism of GA-deficiency under low light stress, differential expression profiling of GA-anabolic, -catabolic, ABA -anabolic, -catabolic, and SLR1 was investigated, revealing that expression of ABA- anabolic, GA-catabolic genes and SLR1 was upregulated with a simultaneous downregulation of ABA-catabolic and GA-anabolic genes under low light treatment. These results suggested that FR-induced GA inadequacy is resulted by upregulation of SLR1 and GA-catabolism genes consequently increase DELLA that further subsided GA-responses in the germinating rice seeds. Moreover, we provided evidence that FR-induced GA inadequacy demotes rice seed germination by decreasing amylase activity, eventually decreasing the carbohydrate solubilization in the germinating seeds. Finally, we suggest that under low light stress, due to a retarded conversion of phytochrome A to their bioactive form, the ABA-catabolic genes were eventually upregulated with a simultaneous downregulation of GA-anabolic genes. Consequently, a lower GA pool fails to leverage the GA-dependent DELLA degradation, further shutting down the expected GA responses that reduce germination efficiency under FR-enriched light.

Low light intensity affects several physiological parameters during the different growth stages in rice. Plants have various regulatory mechanisms to cope with stresses. One of them is the differential and temporal expression of genes, which is governed by post-transcriptional gene expression regulation through endogenous miRNAs. To decipher low light stress-responsive miRNAs in rice, miRNA expression profiling was carried out using next-generation sequencing of low-light-tolerant (Swarnaprabha) and -sensitive (IR8) rice genotypes through Illumina sequencing. Swarnaprabha and IR8 were subjected to 25% low light treatment for one day, three days, and five days at the active tillering stage. More than 43 million raw reads and 9 million clean reads were identified in Swarnaprabha, while more than 41 million raw reads and 8.5 million clean reads were identified in IR8 after NGS. Importantly, 513 new miRNAs in rice were identified, whose targets were mostly regulated by the genes involved in photosynthesis and metabolic pathways. Additionally, 114 known miRNAs were also identified. Five novel (osa-novmiR1, osa-novmiR2, osa-novmiR3, osa-novmiR4, and osa-novmiR5) and three known (osa-miR166c-3p, osa-miR2102-3p, and osa-miR530-3p) miRNAs were selected for their expression validation through miRNA-specific qRT-PCR. The expression analyses of most of the predicted targets of corresponding miRNAs show negative regulation. Hence, miRNAs modulated the expression of genes providing tolerance/susceptibility to low light stress. This information might be useful in the improvement of crop productivity under low light stress.

Light has a significant role in growth and development of plants because of its crucial role in photosynthesis and photo morphogenesis. If the amount of light intensity reaches the plants is reduced than the optimum level then it creates low light stress for plants and this problem is identified in the eastern and north-eastern region of India which is the major rice belt in our country. Therefore the present experiment was conducted during Kharif 2019 at plot no-4, Block-V of Department of Crop Physiology and Biochemistry, NRRI, Cuttack to study the Low light effect on the biochemical changes and grain yield of long duration rice cultivars. In the present research, 9 long duration rice varieties along with 2 check varieties were exposed to 75% light and 50% light condition in comparison to control (100% light) to know the leaf chlorophyll behaviour and yield during kharif (July‒November, 2019). Plants were grown in field condition with shade installation done 15days after transplanting to impose low light stress in plants. Among the varieties, Swarnaprabha was found with the highest total chlorophyll content in 100% L (2.311 mg g-1 fresh weight), 75% L (2.705 mg g-1 fresh weight) and 50% L (3.684 mg g-1 fresh weight) at 50% flowering stage. Similarly, Swarnaprabha was recorded with the highest chlorophyll at 7 days after 50% flowering. In both the cases, low light induced more chlorophyll in plants than normal light. Among the antioxidant enzymes, Peroxidase and Catalase exhibited an increased activity under low light stress, whereas Superoxide dismutase (SOD) exhibited decreased activity in low light stress. Besides, higher yield was recorded in normal light condition than 75% light and 50% light condition. Among the varieties Nasati Sali leads with higher yield in 100% (5.10 t ha-1) and 75% (4.27 t ha-1) light condition. On the other hand Swarnaprabha (3.05 t ha-1) having highest yield at 50% light intensity.

Photosynthesis and respiration are two central and basic physiological processes in regulation to carbon budget and carbon sink in the terrestrial ecosystem, as well as assessment and feedback of highly variable and fluctuating environmental conditions. Elevated CO2, salinity, alkalinity, drought, flood, nutrient deficiency and toxicity, extreme cold and heat, and various natural and anthropogenic pollutants are critical challenges in near future and their primary target is to alteration of photosynthetic and respirational processes, which ultimately influence the final yield potential of major agricultural crops. However, plants adapt themselves to these environmental circumstances via complicated changes at physiochemical and molecular levels. The current chapter highlights the underline mechanisms of photosynthetic and respiration in response to climate change at physiological, biochemical, and molecular levels. This chapter also covers the timely and substantial information regarding the recent progress in photosynthesis and respiration research. First, an outline of future climate change and its impacts on plant processes, functions, and yield potential is presented. Then, responses and adaptation of photosynthesis and respiration mechanisms against multiple stresses are discussed. Globally the present issues are crucial and this chapter helps in better understanding how plants deal with climatic change and their physiological, cellular, and molecular processes to the development of sustainable environment.

Fifty SSR markers were used to assess genetic diversity among 40 drought-tolerant, five moderately drought-tolerant, and three susceptible genotypes to identify new donors for drought tolerance in rice. Out of 50 SSR markers, 17 markers are reported to be linked to major grain yield QTLs under reproductive stage drought stress. 163 (97.7%) out of 167 alleles were found to be polymorphic. The PIC value ranged from 0 to 0.963 with an average of 0.795 per locus. The minor allele frequency varied from 0.312 (RM336) to 0.895 (RM530) with an average of 0.60. The genetic diversity ranged from 0.187 (RM530) to 0.739 (RM336) with an average of 0.51. The cluster analysis grouped all the genotypes into three major clusters at 50% level of genetic dissimilarity. Structure analysis identified two subpopulations among 48 rice genotypes. 81% and 19% of molecular variances were revealed within and among the subpopulations, respectively. The first three principal components explained over 88% of total genetic variation. Two genotypes, Kalakeri and RR-2-6 were identified as new drought-tolerant donors. Kalakeri contributes drought tolerance QTL, qDTY1.1, while RR-2-6 contributes QTLs, qDTY2.2, and qDTY2.3.

Rice grain yield is drastically reduced under low light especially in kharif (wet) season due to cloudy weather during most part of crop growth. Therefore, 50-60% of yield penalty was observed. To overcome this problem, identification of low light tolerant rice genotypes with a high buffering capacity trait such as photosynthetic rate has to be developed. Sedoheptulose-1,7 bisphosphatase, a light-regulated enzyme, plays pivotal role in the Calvin cycle by regenerating the substrate (RuBP) for RuBisCo and therefore, indirectly regulates the influx of CO2 for this crucial process. We found a potential role of SBPase expression and activity in low light tolerant and susceptible rice genotypes by analyzing its influence on net photosynthetic rate and biomass. We observed a significant relationship of yield with photosynthesis, SBPase expression and activity especially under low light conditions. Two tolerant and two susceptible rice genotypes were used for the present study. Tolerant genotypes exhibited significant but least reduction compared to susceptible genotypes in the expression and activity of SBPase, which was also manifested in its photosynthetic rate and finally in the grain yield under low light. However, susceptible genotypes showed significant reduction in SBPase activity along with photosynthesis and grain yield suggesting that tracking the expression and activity of SBPase could form a simple and reliable method to identify the low light tolerant rice cultivars. The data were analyzed using the Indostat 7.5, Tukey-Kramer method through Microsoft Excel 2019 and PAST4.0 software. The significant association of SBPase activity with the grain yield, net assimilation rate, electron transfer rate, biomass and grain weight were observed under low light stress. These traits should be considered while selecting and breeding for low light tolerant cultivars. Thus, SBPase plays a major role in the low light tolerance mechanism in rice.

Low light (LL) intensity is a major abiotic constraint for grain yield in rice during wet season. Phytochromes principally perceive and respond to the red (R) and far-red (FR) region of light and regulate several aspects of photomorphogenesis. Most phytochromes are responsive under R-light and de-activated under FR-light, but phytochrome A (phyA) is biologically functional under both light conditions and plays an important role in the entire life cycle of the plant. Field experiment was conducted on the effect of LL intensity and subsequent exposure to natural light on japonica rice cultivar Akitokomachi (WT) and its phytochrome A mutant (phyA) to understand the role of phyA in the regulation of sink capacity, starch biosynthesis, grain quality, grain yield and related traits during wet season of 2018. Leaf soluble protein, photosynthetic CO2 assimilation rate, leaf non-structural carbohydrate content, sink capacity, grain quality traits such as hulling percentage, milling percentage, head rice recovery, water uptake, volume expansion, alkali spreading value, gel consistency, grain breadth, grain starch content, amylose content and yield attributes such as grain yield, panicle fertility, 1000-grain weight, panicle per plant, spikelets per panicle and grains per panicle along with the expression of starch biosynthesizing enzymes such as such as ADP-glucose pyrophosphorylase (AGPase), starch synthase III (SSIII) and granule bound starch synthase I (GBSSI) were reduced significantly in phyA than WT plants. However, % of grain chalkiness, length and amylopectin content increased in the phyA than WT plants. This study indicates the possible role of phyA in the regulation of source-sink communication, starch biosynthesis and grain quality in rice. Presumably, by participating in the control of several starch synthesizing pathways in the grains, phyA play a crucial role in the regulation of grain quality of rice which depends on the availability of the light intensity during grain-filling stage.