Rice Cv Research Articles

Evaluation of Organic Matter for Enhancing the Agro-physiological Traits of Rice cv. Banyuasin Planted under Saline Conditions

Evaluation of Organic Matter for Enhancing the Agro-physiological Traits of Rice cv. Banyuasin Planted under Saline Conditions

Quantifying chlorophyll content index for efficient nitrogen management in rice (Oryza sativa L.)

Applying nitrogen fertilizer strategically enhances rice productivity in nitrogen-deficient soils. Splitting fertilizer doses across growth stages optimizes nutrient use efficiency. Monitoring chlorophyll levels correlates closely with leaf nitrogen content, crucial for assessing crop health. Non-destructive chlorophyll content meter techniques, such as the Chlorophyll Content Index (CCI), allow for precise nitrogen management adjustments in the field. However, its critical value may differ depending on crops and varieties. Hence, to find out the critical CCI value for rice cv. ADT 43, observational trials were conducted at the Experimental Farm of Annamalai University during two seasons Kuruvai (June-Oct 2023) and Navarai (Dec-March 2024). The pooled data of the present study indicated that the average LNC (maximum tillering, panicle initiation and booting stages) has a linear relationship (R2=0.8545) with the yield of rice crop. The corresponding higher yield ( greater than 7t/ha) coincided with LNC of 3.1%. Likewise, the average CCI has a linear relationship (R2=0.9031) with the LNC of rice plants. The corresponding LNC ( greater than 7t/ha) was matched with the CCI value of 29. This CCI value of 29 is considered as the critical CCI value. CCI can be used as a decision-support tool for N-fertilization of short duration rice crop, and when CCI reduced below this critical value the farmers can fertilise the field with adequate N.

Growth and yield of basmati rice (Oryza sativa L.) cv. Pusa Basmati-1728 as influenced by different levels of nitrogen and bio-inoculants

Growth and yield of basmati rice (Oryza sativa L.) cv. Pusa Basmati-1728 as influenced by different levels of nitrogen and bio-inoculants

Effectiveness of local isolates of Trichoderma spp. in imparting drought tolerance in rice, Oryza sativa

Rice is a crop that requires high amount of water, and the drought is a major constraint in paddy cultivation. Water stress condition frequently prevails due to shortage of rain which results in significantly reduced plant growth and yield of rice. In the present study capability of Trichoderma spp. in imparting drought tolerance to rice, Oryza sativa was explored. Eleven local strains of Trichoderma spp. were applied to rice cv. Swarna Sub-1 through soil application (2 g/kg soil) and seed treatment (20 g/kg seed) under 0, 25, 50 and 75% less watering of the recommended amount. The soil application of T. harzianum AMUTHZ84 significantly promoted the shoot and root length (23.6 and 21.3%) followed by seed treatment (19.7 and 18.2%) under recommended level of irrigation condition (100% irrigation). Next in effectiveness was T. viride AMUTVR73 (21.5 and 18.1%) over untreated control. However, under 75% water availability, soil application with T. harzianum AMUTHZ82 was found superior over other isolates in enhancing shoot and root length (17.7 and 16.4%). The same isolate was also recorded to be superior under 50% (12.4 and 10.1%) and 25% water availability (9.3 and 8.1%) in enhancing the plant growth and biomass of rice cv. Swarna Sub-1. The isolate also significantly enhanced the leaf pigments, and photosynthesis in the rice plants grown under 25–75% water stress condition. In general, soil application of Trichoderma isolates was found more effective than seed treatment, and the T. harzianum AMUTHZ82 provided 8–17% enhancement in the plant growth, biomass, leaf pigments and photosynthesis of rice cv. Swarna Sub-1 grown under 25–75% water stress condition.

Enhancing rice productivity through holistic nutrient management: integrating vermicompost and Azolla for improved agronomic performance and sustainability

A three-year multi-location trial on the farmer’s field was conducted in West Bengal, India to evaluate the impact of integrated nutrient management (INM) on the performance of kharif rice cv. Swarna Sub 1. The experiment employed a randomized block design (RBD) across eleven farmers’ fields with similar soil properties, texture, topography, and historical fertilizer application patterns. Three treatments were tested: T1 – common practice of applying N:P:K @ 55:32:27 kg ha−1, T2 – soil test-based application (STA) of ∼75% recommended N dose through chemical fertilizer + ∼ 25% through Azolla, and T3 – soil test-based application of ∼ 75% recommended N dose through chemical fertilizer + 20% N from vermi-compost + 5% N through Azolla. The result of the experiment revealed that the T3 exhibited significant improvements in plant height, leaf area index (LAI), effective tillers meter−2, number of panicles plant−1, and 1000-grain weight compared to T2 and T1. Among the different nutrient management practices, the T3 recorded maximum rice grain productivity than the T1, and T2, Further, the benefit-cost ratio was noticed significantly higher under T3 (1.29) followed by T2 (1.27) and T1 (1.23). The soil organic carbon (SOC), available nutrient was enhanced by the soil test-based application of ∼75% recommended N dose through chemical fertilizer + 20% N from vermicompost + 5% N through Azolla. Thus, our study indicated that the balanced nutrient application through combined sources (T3) could improve crop growth; and sustain rice productivity, besides enhancing the farm income, and soil different soil properties.

Effect of Varying Level of Nitrogen and Spacing on the Yield of Boro Rice Cv. BRRI Dhan47

Effect of Varying Level of Nitrogen and Spacing on the Yield of Boro Rice Cv. BRRI Dhan47

Incidence of Rice Stem Borers in Coastal Andhra Pradesh with Emphasis on <i>Sesamia inferens</i> (Walker)

A roving survey was conducted in the rice crop grown in coastal districts of Andhra Pradesh during rabi, 2021-22 and 2022-23. Overall mean stem borer incidence varied from 13.59% - 14.83% in both the seasons. Larvae of Scirpophaga incertulas (Walker), Sesamia inferens (Walker), Chilo polychrysus (Meyers) and Chilo auricilius (Dudgeon), were recorded from four districts during the survey. Among the stem borers, S. incertulas was the most predominant species (53.37%) followed by S. inferens (44.7%). Natural larval parasitization (21%) of S. inferens by Cotesia flavipes Cameron was observed in West Godavari district. The biology of S. inferens was studied on rice cv. MTU 1121. The average larval period recorded was 32.40± 0.35 days. Total life cycle of S. inferens ranged between 41-65 and 46-73 days for male and female moths, respectively. Current study suggests that S. inferens could be a potential threat to rice cultivation in coastal Andhra Pradesh.

Loss-of-function of PGL10 impairs photosynthesis and tolerance to high-temperature stress in rice.

High temperature (HT) affects the production of chlorophyll (Chl) pigment and inhibits cellular processes that impair photosynthesis, and growth and development in plants. However, the molecular mechanisms underlying heat stress in rice are not fully understood yet. In this study, we identified two mutants varying in leaf color from the ethylmethanesulfonate mutant library of indica rice cv. Zhongjiazao-17, which showed pale-green leaf color and variegated leaf phenotype under HT conditions. Mut-map revealed that both mutants were allelic, and their phenotype was controlled by a single recessive gene PALE GREEN LEAF 10 (PGL10) that encodes NADPH:protochlorophyllide oxidoreductase B, which is required for the reduction of protochlorophyllide into chlorophyllide in light-dependent tetrapyrrole biosynthetic pathway-based Chl synthesis. Overexpression-based complementation and CRISPR/Cas9-based knockout analyses confirmed the results of Mut-map. Moreover, qRT-PCR-based expression analysis of PGL10 showed that it expresses in almost all plant parts with the lowest expression in root, followed by seed, third leaf, and then other green tissues in both mutants, pgl10a and pgl10b. Its protein localizes in chloroplasts, and the first 17 amino acids from N-terminus are responsible for signals in chloroplasts. Moreover, transcriptome analysis performed under HT conditions revealed that the genes involved in the Chl biosynthesis and degradation, photosynthesis, and reactive oxygen species detoxification were differentially expressed in mutants compared to WT. Thus, these results indicate that PGL10 is required for maintaining chloroplast function and plays an important role in rice adaptation to HT stress conditions by controlling photosynthetic activity.

Constructed Rice Tracers Identify the Major Virulent Transcription Activator-Like Effectors of the Bacterial Leaf Blight Pathogen

Xanthomonas oryzae pv. oryzae (Xoo) injects major transcription activator-like effectors (TALEs) into plant cells to activate susceptibility (S) genes for promoting bacterial leaf blight in rice. Numerous resistance (R) genes have been used to construct differential cultivars of rice to identify races of Xoo, but the S genes were rarely considered. Different edited lines of rice cv. Kitaake were constructed using CRISPR/Cas9 gene-editing, including single, double and triple edits in the effector-binding elements (EBEs) located in the promoters of rice S genes OsSWEET11a, OsSWEET13 and OsSWEET14. The near-isogenic lines (NILs) were used as tracers to detect major TALEs (PthXo1, PthXo2, PthXo3 and their variants) in 50 Xoo strains. The pathotypes produced on the tracers determined six major TALE types in the 50 Xoo strains. The presence of the major TALEs in Xoo strains was consistent with the expression of S genes in the tracers, and it was also by known genome sequences. The EBE editing had little effect on agronomic traits, which was conducive to balancing yield and resistance. The rice-tracers generated here provide a valuable tool to track major TALEs of Xoo in Asia which then shows what rice cultivars are needed to combat Xoo in the field.

Nutrient remobilization and C:N:P stoichiometry in response to elevated CO2 and low phosphorus availability in rice cultivars introgressed with and without Pup1

The continuously rising atmospheric CO2 concentration potentially increase plant growth through stimulating C metabolism; however, plant C:N:P stoichiometry in response to elevated CO2 (eCO2) under low P stress remains largely unknown. We investigated the combined effect of eCO2 and low phosphorus on growth, yield, C:N:P stoichiometry, and remobilization in rice cv. Kasalath (aus type), IR64 (a mega rice variety), and IR64-Pup1 (Pup1 QTL introgressed IR64). In response to eCO2 and low P, the C accumulation increased significantly (particularly at anthesis stage) while N and P concentration decreased leading to higher C:N and C:P ratios in all plant components (leaf, sheath, stem, and grain) than ambient CO2. The remobilization efficiencies of N and P were also reduced under low P with eCO2 as compared to control conditions. Among cultivars, the combined effect of eCO2 and low P was greater in IR64-Pup1 and produced higher biomass and grain yield as compared to IR64. However, IR64-Pup1 exhibited a lower N but higher P concentration than IR64, indicating that the Pup1 QTL improved P uptake but did not influence N uptake. Our study suggests that the P availability along with eCO2 would alter the C:N:P ratios due to their differential partitioning, thereby affecting growth and yield.

Development of activation-tagged gain-of-functional mutants in indica rice line (BPT 5204) for sheath blight resistance.

The development of sheath blight (ShB) resistance varieties has been a challenge for scientists for long time in rice. Activation tagging is an efficient gain-of-function mutation approach to create novel phenotypes and to identify their underlying genes. In this study, a mutant population was developed employing activation tagging in the recalcitrant indica rice (Oryza sativa L.) cv. BPT 5204 (Samba Mahsuri) through activation tagging. In this study, we have generated more than 1000 activation tagged lines in indica rice, from these mutant population 38 (GFP- RFP+) stable Ds plants were generated through germinal transposition at T2 generation based on molecular analysis and seeds selected on hygromycin (50mg/L) containing medium segregation analyses confirmed that the transgene inherited as mendelian segregation ratio of 3:1 (3 resistant: 1 susceptible). Of them, five stable activation tagged Ds lines (M-Ds-1, M-Ds-2, M-Ds-3, M-Ds-4 and M-Ds-5) were selected based on phenotypic observation through screening for sheath blight (ShB) resistance caused by fungal pathogen Rhizoctonia solani (R. solani),. Among them, M-Ds-3 and M-Ds-5 lines showed significant resistance for ShB over other tagged lines and wild type (WT) plants. Furthermore, analysed for launch pad insertion through TAIL-PCR results and mapped on corresponding rice chromosomes. Flanking sequence and gene expression analysis revealed that the upregulation of glycoside hydrolase-OsGH or similar to Class III chitinase homologue (LOC_Os08g40680) in M-Ds-3 and a hypothetical protein gene (LOC_Os01g55000) in M-Ds-5 are potential candidate genes for sheath blight resistance in rice. In the present study, we developed Ac-Ds based ShB resistance gain-of-functional mutants through activation tagging in rice. These activation tagged mutant lines can be excellent sources for the development of ShB resistant cultivars in rice.

Fluidized Bed Heat Treatment for Controlling the Lesser Grain Borer (Rhyzopertha dominica) and Sawtoothed Grain Beetle (Oryzaephilus surinamensis) on Paddy cv. Khao Dawk Mali 105

The efficacy of fluidized bed (FDB) heating was studied for controlling stored product insects on rough rice using laboratorial heat-fluidized bed equipment, and the milling quality of rice was later examined. Rough rice cv. Khao Dawk Mali 105 (13% wb) infested with insects was treated with FDB. The lesser grain borer (Rhyzopertha dominica, Fabricius) (internal feeders) had a higher tolerance for heat than the sawtoothed grain beetle (Oryzaephilus surinamensis Linnaeus, external feeders). At a hot air velocity of 3.7 m/s at 55°C for 90 s, the mortality of the lesser grain borer treated by FDB significantly differed (P <0.05) between all stages and from the untreated control. The pulpal stage, as an FDB-tolerant stage of the lesser grain borer, was treated with 55–65 °C for 60–150 s. FDB heat treatment at 55°C for 150 s, 60°C for 90 s, and 65°C for 60 s caused 100% mortality. At a hot air velocity of 3.7 m/s at 40°C for 120 s, the mortality of the sawtoothed grain beetle significantly differed (P <0.05) between all stages and the untreated control. The egg stage, as the FDB-tolerant stage, was treated at 40–50 °C for 60–150 s. FDB heat treatment at 45°C for 150 s and 50°C for 60 s caused 100% mortality. Some of the adults that survived FDB exposure were able to reproduce, but there were significantly less progeny than in the untreated control. Heat FDB slightly affected rice quality in terms of physical and chemical properties. Keywords: Heat, Fluidized bed heat, Paddy, Stored insect pests

Effects of elevated CO2 concentration gradients on rice grain quality under two cultivation practices in cold region

AbstractBackground and ObjectivesThe effect of elevated atmospheric CO2 (eCO2) on rice (Oryza sativa L.) grain quality has been widely studied, but mostly under two contrasting levels of CO2 concentration. Our study was conducted in a new version of CO2 Gradient Tunnel (CGT) to study the responses of grain quality of japonica rice cv. Wuyoudao no.4 (WYD4) and Songjing no.9 (SJ9) to five CO2 concentrations (390–600 μmol·mol−1) gradient levels at two cultivation practices: traditional flooding (TF) and non‐flooded plastic film mulching (PM).FindingsThe results showed that the response of SJ9 to eCO2 was more pronounced under TF cultivation. When the CO2 concentration increased to 450 μmol·mol−1, the brown rice ratio and milled rice ratio of SJ9 decreased by 4.2% and 17.7%, respectively. However, when CO2 concentration increased to 600 μmol·mol−1, the brown rice ratio increased by 3.7%. These results reveal that different gradients of eCO2 have different effects on rice quality. Besides that, eCO2 decreased the nutritional quality of SJ9 by decreasing the protein content and amylose content, while eCO2 improved rice appearance and eating quality. Different from SJ9, when CO2 concentration increased to 500–600 μmol·mol–1, the milled rice ratio and head rice ratio of WYD4 increased by 5.9%–7.5% and 16.7%–19.5% under PM cultivation. Furthermore, eCO2 decreased the chalky grain rate or chalkiness by 34.5%–80.5% and 53.1%–77.1%, respectively.ConclusionsUnder PM cultivation, the rice milling quality and appearance quality of WYD4 were promoted by eCO2. Rice nutritional quality was significantly decreased in both cultivation practices. In the comparison of rice quality between the two cultivations, except for rice eating quality, the other grain quality parameters of SJ9 under PM cultivation were better than those under TF cultivation. The opposite was true for WYD4.Significance and NoveltyUnder future production conditions with eCO2, the high‐yielding SJ9 cultivar is more suitable for water‐saving cultivation with mulching film, while the high‐quality WYD4 is suitable for TF cultivation.

REDUCTION OF CHEMICAL FERTILIZER APPLICATION BY USING BIOCHAR FOR THE GROWTH AND YIELD OF RICE CV. BRRI dhan 29

A field experiment was carried out at research field, Hajee Mohammad Danesh Science and Technology University, Dinajpur to assess the reduction of chemical fertilizer application by using biochar for the growth and yield of rice cv. BRRI dhan 29. The experiment was performed with five treatments viz. T1 = Recommended doses of N, P, K and S, T2 = Biochar 10 t ha-1, T3 = Biochar 7.5 t ha-1 + half recommended doses of N, P, K and S, T4 = Biochar 5 t ha-1 + half recommended doses of N, P, K and S and T5 = Biochar 2.5 t ha-1 + half recommended doses of N, P, K and S. The experiment was laid out in Randomized Complete Block Design (RCBD) with four replications. The highest plant height (102.35 cm) and the number of tillers hill-1 (26.35) was found in the treatment T1 which was statistically similar to the treatment T3 with the values 99.93 cm and 25.89, respectively. The panicle length (25.01 cm), number of spikelets hill-1 (14.30), number of grains panicle-1 (194.50) and 1000-grain weight (25.03 g) were found maximum in the treatment T3 which was statistically similar to the treatment T1 with the values 24.89 cm, 13.87, 193.50 and 24.37 g; respectively. The highest grain yield (7.46 t ha-1) and straw yield (9.92 t ha-1) was found on T1 treatment which was statistically similar to the treatments T3 (7.42 and 9.86 t ha-1). The highest biological yield (17.28 t ha-1) was measured in the treatment T3. These results suggest that application of 7.5 t ha-1 biochar with half recommended doses of N, P, K and S may reduce 50% of N, P, K and S for rice cultivation (cv. BRRI dhan 29) as these treatments acquire statistically similar production to solely chemical fertilizer applications. However, further research is needed on biochar production, cost efficiency for biochar application and environmental aspects of biochar application.

Cloning of maize chitinase 1 gene and its expression in genetically transformed rice to confer resistance against rice blast caused by Pyricularia oryzae.

Fungal pathogens are one of the major reasons for biotic stress on rice (Oryza sativa L.), causing severe productivity losses every year. Breeding for host resistance is a mainstay of rice disease management, but conventional development of commercial resistant varieties is often slow. In contrast, the development of disease resistance by targeted genome manipulation has the potential to deliver resistant varieties more rapidly. The present study reports the first cloning of a synthetic maize chitinase 1 gene and its insertion in rice cv. (Basmati 385) via Agrobacterium-mediated transformation to confer resistance to the rice blast pathogen, Pyricularia oryzae. Several factors for transformation were optimized; we found that 4-week-old calli and an infection time of 15 minutes with Agrobacterium before colonization on co-cultivation media were the best-suited conditions. Moreover, 300 μM of acetosyringone in co-cultivation media for two days was exceptional in achieving the highest callus transformation frequency. Transgenic lines were analyzed using molecular and functional techniques. Successful integration of the gene into rice lines was confirmed by polymerase chain reaction with primer sets specific to chitinase and hpt genes. Furthermore, real-time PCR analysis of transformants indicated a strong association between transgene expression and elevated levels of resistance to rice blast. Functional validation of the integrated gene was performed by a detached leaf bioassay, which validated the efficacy of chitinase-mediated resistance in all transgenic Basmati 385 plants with variable levels of enhanced resistance against the P. oryzae. We concluded that overexpression of the maize chitinase 1 gene in Basmati 385 improved resistance against the pathogen. These findings will add new options to resistant germplasm resources for disease resistance breeding. The maize chitinase 1 gene demonstrated potential for genetic improvement of rice varieties against biotic stresses in future transformation programs.

Overexpression of black rice OsC1 confers tissue-specific anthocyanin accumulation in indica rice cv. Kasalath and its potential use as a visible marker in rice transformation

Anthocyanin biosynthesis, a process regulated by distinct MYB and MYC transcription factors, plays a crucial role in determining pigmentation in various tissue of plants. This study aimed to investigate the impact of overexpressing the OsC1 gene from black rice, encoding a MYB transcription factor, on anthocyanin pigmentation in red indica rice cv. Kasalath. Anthocyanin pigmentation was readily observed as purple spots in calli and as purple shoot tips and purple leaf sheath in transgenic seedlings. We confirmed the presence of the transgene using GUS assay and PCR analysis, and the pigmentation segregated following a 3:1 Mendelian ratio. T0 and T1 transgenic plants exhibits anthocyanin accumulation in various tissues including leaf sheaths, auricles, nodes, stigma, apiculus and awns, excluding the pericarp. Notably, the pigmentation in node tissues has not been previously reported for the OsC1 gene, and this gene does not involve in pericarp pigmentation. RT-PCR analysis of transgenic seedlings demonstrated that the overexpression of the OsC1 gene upregulated anthocyanin structural genes, particularly OsDFR, leading to anthocyanin accumulation. Intriguingly, the absence of OsB2 expression, encoding a MYC transcription factor, in transgenic seedlings suggests the involvement of alternative MYC factors in purple leaf sheaths. This study not only expands our understanding of OsC1's role in tissue specific anthocyanin pigmentation but also proposes OsC1 as a potential visible marker in rice transformation. Utilizing OsC1 as a marker provides an alternative approach to address concerns related to antibiotic-resistant genes while providing visually striking pigmentation.

Enhancing rice growth and yield with weed endophytic bacteria Alcaligenes faecalis and Metabacillus indicus under reduced chemical fertilization.

Endophytic bacteria, recognized as eco-friendly biofertilizers, have demonstrated the potential to enhance crop growth and yield. While the plant growth-promoting effects of endophytic bacteria have been extensively studied, the impact of weed endophytes remains less explored. In this study, we aimed to isolate endophytic bacteria from native weeds and assess their plant growth-promoting abilities in rice under varying chemical fertilization. The evaluation encompassed measurements of mineral phosphate and potash solubilization, as well as indole-3-acetic acid (IAA) production activity by the selected isolates. Two promising strains, tentatively identified as Alcaligenes faecalis (BTCP01) from Eleusine indica (Goose grass) and Metabacillus indicus (BTDR03) from Cynodon dactylon (Bermuda grass) based on 16S rRNA gene phylogeny, exhibited noteworthy phosphate and potassium solubilization activity, respectively. BTCP01 demonstrated superior phosphate solubilizing activity, while BTDR03 exhibited the highest potassium (K) solubilizing activity. Both isolates synthesized IAA in the presence of L-tryptophan, with the detection of nifH and ipdC genes in their genomes. Application of isolates BTCP01 and BTDR03 through root dipping and spraying at the flowering stage significantly enhanced the agronomic performance of rice variety CV. BRRI dhan29. Notably, combining both strains with 50% of recommended N, P, and K fertilizer doses led to a substantial increase in rice grain yields compared to control plants receiving 100% of recommended doses. Taken together, our results indicate that weed endophytic bacterial strains BTCP01 and BTDR03 hold promise as biofertilizers, potentially reducing the dependency on chemical fertilizers by up to 50%, thereby fostering sustainable rice production.

Enhancing resistance to blast disease through CRISPR/Cas9 gene editing technology in OsHDT701 gene in RPBio-226 rice cv. (Oryza sativa L.)

Enhancing resistance to blast disease through CRISPR/Cas9 gene editing technology in OsHDT701 gene in RPBio-226 rice cv. (Oryza sativa L.)

Phosphorus management and suitability of rice cultivar on system yield augmentation under rice-fallow area of Mid-Central Table Land Zone of Odisha

A field experiment was carried out during 2018-19 and 2019-20 to study the effect of phosphorus doses and rice varieties on system efficiency in rice-green gram cropping system under Mid-Central Table Land Zone of Odisha. The experiment was conducted in split-plot design with three replications. Four main plots viz., P1: P100 of soil test dose (STD)to rice and no P to green gram, P2: P100 of STD to both the crops separately, P3 : P50 of STD to rice &P100 of STD to green gram, P4: P100 of STD of both the crops applied to rice only, were allotted to the main plots and three rice varieties viz., V1 - Mandakini, V2 - Lalat and V3 - Pratikhya to the sub plots. Application of P100 of STD to both the crops separately (P2)resulted in the highest pooled system yield of 6.87 tha-1 however amongst rice cultivars highest system yield of 6.51 t ha-1 was recorded with treatment where green gram was sown after rice cultivar "Mandakini". Similarly, thesame system P-management practice (P2) and the sowing window of rice cultivars (Mandakini) recorded the highest system nutrient uptake, gross and net returns and B: C ratio. But the available soil nutrient status was the maximum with P1 where P100 of STD as basal was applied to riceand green gram was sown after rice cv. 'Mandakini'. However, the available P of the system in the post harvest soil was estimated higher in treatment P2.

Interactive effects of selenium and arsenic on phenolic constituents and antioxidant activity in rice (Oryza sativa L.)

Arsenic (As) is a heavy toxic metalloid found in air, water and soil that adversely affects the plant growth by inducing oxidative stress in plants. Its contamination of rice is a serious problem throughout the world. Selenium (Se) is a beneficial micronutrient for plants that acts as an antioxidant at low doses and protect the plants against number of environmental stresses either by modulating the primary metabolic pathways or regulating the production of phenolic compounds. In the present investigation, effect of Se on different phenolics, enzymes related to their metabolism and antioxidative potential were studied in As stressed rice leaves. Rice plants were grown in pots containing sodium arsenate (2–10 mg As(V) kg−1 soil) and sodium selenate (0.5–1 mg Se kg−1 soil), both alone and in combination and leaf samples were analyzed for various biochemical parameters. Phenolic constituents increased in rice leaves with As(V) treatment from 2 to 5 mg kg−1 soil and leaves exposed to As(V) @ 5 mg kg−1 soil exhibited 1.7, 1.9 and 2.5 fold increase in total phenolics, o-dihydroxyphenols and flavonols, respectively at grain filling stage. Binary application of Se + As improved various phenolic constituents, FRAP, reducing power and antioxidant activities as compared to control. PAL, TAL and PPO activities increased from 1.3 to 4.6 fold in combined As + Se treatment at both the stages. Anthocyanin contents showed a decline (10.8 fold) with increasing As doses and its content improved at both the stages with maximum increase of 3.76 fold with As5+Se1 combination. Binary application of As + Se improved gallic acid, chlorogenic acid, 3-hydroxy benzoic acid and kaempferol contents than control whereas catechin and coumaric acid showed the reverse trend. Application of Se can modulate phenolic constituents in leaf and grains of rice Cv PR126 due to As stress that helped plants to adapt to excess As and resulted in improved plant growth.