Differential response to paraquat induced oxidative stress in two rice cultivars on antioxidants and chlorophyll a fluorescence

The responses of antioxidative system and photosystem II photochemistry of rice (Oryza sativa L.) to paraquat induced oxidative stress were investigated in a chilling-tolerant cultivar Xiangnuo no. 1, and a chilling-susceptible cultivar, IR-50. Electrolyte leakage and malondialdehyde (MDA) content of Xiangnuo no. 1 were little affected by paraquat, but they increased in IR-50. After paraquat treatment, superoxide dismutase (SOD) activity remained high in Xiangnuo no. 1, while it declined in IR-50. Activities of catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) declined with oxidative stress in both cultivars, but Xiangnuo no. 1 had higher GR activity than IR-50. Under paraquat induced oxidative stress, ascorbic acid (AsA) and reduced glutathione (GSH) concentrations remained high in Xiangnuo no. 1, but decreased in IR-50. The results indicated that higher activities of SOD and GR and higher contents of AsA and GSH in Xiangnuo no. 1 under paraquat induced oxidative stress were associated with its tolerance to paraquat, while paraquat induced damage to IR-50 was related to decreased activities of SOD, APX and GR and contents of AsA and GSH. F _v/F _m, Φ _PSII, and qP remained high in Xiangnuo no. 1, while they decreased greatly in IR-50 under paraquat induced oxidative stress.     

An inductive pulse of hydrogen peroxide pretreatment restores redox-homeostasis and oxidative membrane damage under extremes of temperature in two rice cultivars

Imbibitional heat and chilling stress caused disruption of redox-homeostasis and oxidative damage to newly assembled membrane system by aggravating membrane lipid peroxidation and protein oxidation [measured in terms of thiobarbituric acid reactive substances (TBARS), free carbonyl content (C=O groups) and membrane protein thiol level (MPTL)] along with concomitant increase in accumulation of reactive oxygen species (superoxide and hydrogen peroxide) and significant reduction of antioxidative defense (assessed in terms of total thiol content and activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) in both the salt sensitive (Ratna) and resistant (SR 26B) germinating tissues of rice cultivars. When compared, salt resistant cultivar SR 26B found to suffer significantly less oxidative membrane damage as compared to salt sensitive cultivar Ratna. Treatment with low titer of hydrogen peroxide caused significant reversal in oxidative damages to the newly assembled membrane system imposed by imbibitional heat and chilling stress (evident from the data of TBARS, C=O, MPTL, ROS accumulation, membrane permeability status, membrane injury index and oxidative stress index) in seedlings of both the cultivars of rice (Ratna and SR 26B). Imbibitional H₂O₂ pretreatment also caused up-regulation of antioxidative defense (activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and total thiol content) in the heat and chilling stress-raised seedlings of experimental rice cultivars. When the parameters of early growth performances were assessed (in terms of relative growth index, biomass accumulation and vigor index), it clearly exhibited significant improvement of early growth performances of both the rice cultivars. Better response towards H₂O₂-mediated acclamatory performances and restoration of redox- homeostasis under extremes of temperature were noticed in salt sensitive rice cultivar Ratna compared to salt resistant SR 26B. Taken as a whole, the result suggests the significance of the role of ‘inductive pulse’ of H₂O₂ in acclimatizing adverse temperature stress by restoration of redox-homeostasis and mitigation of oxidative membrane protein and lipid damages during the recovery phase of post-germination event.     

Characteristics of chlorophyll fluorescence and antioxidative system in super-hybrid rice and its parental cultivars under chilling stress

Characteristics of chlorophyll fluorescence and antioxidative system were investigated in rice (Oryza sativa L.) super-hybrid Liangyoupeijiu (LYPJ), maternal cultivar Peiai64s, and paternal cultivar indica rice 9311 under chilling stress. During 6-d chilling treatment, chlorophyll content of all three genotypes was gradually declined. However, the decrease in photosystem 2 (PS 2) maximum photochemical efficiency (F_v/F_m) and quantum yield of PS 2 (Φ_PS2) was less expressive in LYPJ than in parental cultivars The electrolyte leakage and malondialdehyde content in all cultivars increased after chilling treatment, but LYPJ exhibited the least increasing tendency. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) were higher in LYPJ than in parental cultivars. The results demonstrated that tolerance to chilling stress in LYPJ might be adopted mostly from its maternal cultivar.     

Assessment of yield based selection under managed field stress condition for breeding for rice yield improvement under drought

The progress in development and dissemination of drought tolerant lines has been slow as compared to the increasing drought prevalence in the rice growing regions. Significant amount of work has been done in the past on drought resistance traits in rice crop, still the benefit of improved drought tolerant rice cultivars reaching the farmer’s field is not very high and ways to expedite the development of drought tolerant and productive rice cultivars needs to be addressed. In this article, an assessment of easily practicable approach of managed stress screening and prospect of direct selection for yield under drought stress is discussed. Also the large effect yield QTLs identified for grain yield under drought stress field conditions is being reviewed for successful introgression into elite genetic background for developing drought tolerant cultivars with improved yield for the drought prone target environment.     

Different effects of chilling on respiration in leaves and roots of cucumber (Cucumis sativus)

The effects of chilling on respiration (SHAM-resistant, cytochrome pathway and KCN-resistant, alternative pathway), temperature sensitivity, relative electrolyte conductivity, and degrees of oxidative stress (H(2)O(2) and malonaldehyde (MDA) contents) were separately examined in leaves and roots of cucumber (Cucumis sativus L.). After chilling at 8 degrees C for 4 days, both total respiration and KCN-resistant respiration in roots increased at different measurement temperatures. In contrast, SHAM-resistant respiration remained unchanged. In comparison, chilling significantly decreased the total respiration in leaves and this decrease was mostly due to a decrease in SHAM-resistant respiration. Chilling apparently decreased the sensitivity of KCN-resistant respiration to changes of temperature. The reduction levels of ubiquinone pool (UQr/UQt) increased both in chilled leaves and roots whilst pyruvate content increased only in chilled roots, but not in chilled leaves. Furthermore increases of H(2)O(2) and MDA contents were much greater in leaves than in roots. The same trend was also observed for ion leakage from tissues. Taken together, the results suggested that the higher chilling tolerance of roots was associated with their high total respiration and KCN-resistant respiration.     

Heat and chilling induced disruption of redox homeostasis and its regulation by hydrogen peroxide in germinating rice seeds (Oryza sativa L., Cultivar Ratna)

Extremes of temperature (both heat and chilling) during early inbibitional phase of germination caused disruption of redox-homeostasis by increasing accumulation of reactive oxygen species (superoxide and hydrogen peroxide) and significant reduction of antioxidative defense (assessed in terms of total thiol content and activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) in germinating tissues of rice (Oryza sativa L., cultivar Ratna). Imbibitional heat and chilling stress also induced oxidative damage to newly assembled membrane system by aggravating membrane lipid peroxidation and protein oxidation [measured in terms of thiobarbituric acid reactive substances (TBARS), free carbonyl content (C = O groups) and membrane protein thiol level (MPTL)]. Treatment with standardized low titer hydrogen peroxide during early imbibitional phase of germination caused significant reversal in oxidative damages to the newly assembled membrane system imposed by heat and chilling stress [evident from the data of TBARS, C = O, MPTL, ROS accumulation, membrane permeability status, membrane injury index and oxidative stress index] in seedlings of experimental rice cultivar. Imbibitional H₂O₂ pretreatment also caused up-regulation of antioxidative defense (activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and total thiol content) in the heat and chilling stress-raised rice seedlings. When the parameters of early growth performances were assessed (in terms of relative growth index, biomass accumulation, relative germination performance, mean daily germination, T₅₀ value), it clearly exhibited significant improvement of early growth performances of the experimental rice cultivar. The result proposes that an ‘inductive pulse’ of H₂O₂ is required to switch on some stress acclimatory metabolism through which plant restores redox homeostasis and prevents or repairs oxidative damages to newly assembled membrane system caused by unfavorable environmental cues during early germination to the rice cultivar Ratna. The importance of mitigating oxidative damages to membrane lipid and protein necessary for post-germinative growth under extremes of temperature is also suggested.     

Redox metabolic and molecular parameters for screening drought tolerant indigenous aromatic rice cultivars

The present work makes an effort to assess and standardize some redox metabolic and molecular parameters for screening drought tolerant indigenous aromatic rice cultivars of West Bengal, India. PEG-induced dehydration stress during early germination caused disruption of redox-homeostasis and oxidative damage in four IARVs (Jamainadu, Tulaipanji, Sitabhog and Badshabhog) by enhancing the accumulation of pro-oxidants [assessed in terms of oxidation of 2′,7′-dichlorofluorescindiacetate (DCFDA), accumulation of \({\text{O}}_{2}^{ \cdot - }\) and H₂O₂ and in situ staining of reactive oxygen species (ROS) in germinating tissue], significant reduction of antioxidative defence (total antioxidant and radical scavenging capacity, total thiol content and activities of antioxidative defence enzymes) and aggravating protein oxidation and lipid peroxidation (assessed in terms of free carbonyl content and accumulation of thiobarbituric acid reactive substances). When compared between the indigenous aromatic rice cultivars, a clear trend in differential redox regulatory properties in which ROS-antioxidant interaction acts at metabolic interface for redox homeostasis was observed in the order Badshabhog > Tulaipanji > Sitabhog > Jamainadu. Moreover, when the efficacy of ascorbate–glutathione cycle for scavenging H₂O₂ generated during dehydration stress was assessed and compared between the landraces exposed to PEG-induced dehydration stress in germinating tissue, it also exhibited almost the same trend with the landrace Tulaipanji and Badsabhog exhibiting maximum and Jamainadu the minimum efficiencies of the redox cycle. The indigenous aromatic rice cultivars Tulaipanji and Badsabhog resist dehydration stress better than the other two landraces due to its early preparedness to combat oxidative stress by up-regulating expression of genes of some enzymes of ascorbate–glutathione cycle along with some other antioxidative enzymes. A model of redox homeostasis in which ROS-antioxidant (ascorbate–glutathione system) acts at metabolic interface for up-regulation of antioxidative gene expression necessary for differential drought stress tolerance among the indigenous aromatic rice varieties is suggested.     

Relationship of photosynthetic efficiency and seed-setting rate in two contrasting rice cultivars under chilling stress

Low temperature during the vegetative stage affects rice (Oryza sativa L.) seed-setting rate in Heilongjiang province at Northeast China. However, little is known about changes of the photosynthetic rate and physiological response in contrasting rice cultivars during chilling periods. In this study, two rice cultivars with different chilling tolerance were treated with 15°C from June 27 to July 7. The chilling-susceptive cultivar, Longjing11 (LJ11), showed a significant decrease in a ripening rate and seed-setting rate after being treated for four days, whilst chilling-tolerant cultivar, Kongyu131 (KY131), was only slightly affected after 4-d treatment. The photosynthetic activities, chlorophyll contents, and antioxidative enzyme activities in LJ11 decreased significantly along with the chilling treatment. The decrease in ß-carotene contents might play a role as it could cause direct photooxidation of chlorophylls and lead to the inhibition of the photosynthetic apparatus. In the meantime, no significant damage was found in leaves of KY131 from June 27 to July 11. In conclusion, the chilling-tolerance mechanism of rice is tightly related to the photosynthetic rate, metabolism of reactive oxygen species, and scavenging system in the vegetative stage.     

Variation of physiological and antioxidative responses in tea cultivars subjected to elevated water stress followed by rehydration recovery

Water stress is a major limitation for plant survival and growth. Several physiological and antioxidative mechanisms are involved in the adaptation to water stress by plants. In this experiment, tea cultivars (TV-1, TV-20, TV-29 and TV-30) were subjected to drought stress by withholding water for 20 days followed by rehydration. An experiment was thus performed to test and compare the effect of dehydration and rehydration in growing seedlings of tea cultivars. The effect of drought stress and post stress rehydration was measured by studying the reactive oxygen species (ROS) metabolism in tea. Water stress decreased nonenzymic antioxidants like ascorbate and glutathione contents with differential responses of enzymic antioxidants in selected clones of Camellia sinensis indicating an oxidative stress situation. This was also apparent from increased lipid peroxidation, O₂ ⁻ and H₂O₂ content in water stress imposed plants. But the oxidative damage was not permanent as the plants recovered after rehydration. Comparatively less decrease in antioxidants, higher activities of POX, GR, CAT with higher phenolic contents suggested better drought tolerance of TV-1, which was also visible from the recovery study, where it showed lower ROS level and higher recovery of antioxidant property in response to rehydration, thus proving its better recovery potential. On the other hand, highest H₂O₂ and lipid peroxidation with decrease in phenolic content during stress in TV-29 suggested its sensitivity to drought. The antioxidant efficiency and biochemical tolerance in response to drought stress thus observed in the tested clones of Camellia sinensis can be arranged in the order as TV-30 > TV-1 > TV-29 > TV-20.     

Cold sensitivity in rice (Oryza sativa L.) is strongly correlated with a naturally occurring I99V mutation in the multifunctional glutathione transferase isoenzyme GSTZ2

GSTZs [Zeta class GSTs (glutathione transferases)] are multifunctional enzymes that belong to a highly conserved subfamily of soluble GSTs found in species ranging from fungi and plants to animals. GSTZs are known to function as MAAIs [MAA (maleylacetoacetate) isomerases], which play a role in tyrosine catabolism by catalysing the isomerization of MAA to FAA (fumarylacetoacetate). As tyrosine metabolism in plants differs from animals, the significance of GSTZ/MAAI is unclear. In rice (Oryza sativa L.), a major QTL (quantitative trait locus) for seedling cold tolerance has been fine mapped to a region containing the genes OsGSTZ1 and OsGSTZ2. Sequencing of tolerant (ssp. japonica cv. M-202) and sensitive (ssp. indica cv. IR50) cultivars revealed two SNPs (single nucleotide polymorphisms) in OsGSTZ2 that result in amino acid differences (I99V and N184I). Recombinant OsGSTZ2 containing the Val99 residue found in IR50 had significantly reduced activity on MAA and DCA (dichloroacetic acid), but the Ile184 residue had no effect. The distribution of the SNP (c.295A>G) among various rice accessions indicates a significant association with chilling sensitivity in rice seedlings. The results of the present study show that naturally occurring OsGSTZ2 isoforms differ in their enzymatic properties, which may contribute to the differential response to chilling stress generally exhibited by the two major rice subspecies.     

Pre-treating paclobutrazol enhanced chilling tolerance of sweetpotato

The objective of this work was to study changes in low molecular weight antioxidants and antioxidative enzymes in chilling-stressed sweetpotato, as affected by paclobutrazol (PBZ) pre-treatment 24 h prior to exposure to chilling conditions. Sweetpotato ‘TN71’ and ‘TN65’ were treated with 300 mg PBZ/5 ml/plant, after which plants were subjected to 7°C/7°C (day/night) for periods of 1, 3 and 5 days, followed by a 3-day recovery period at 24°C/20°C (day/night). A factorial experiment in completely randomized design with four replications was used in this study. Young fully expanded leaves at each temperature and period of time were clipped for antioxidative system measurement. We concluded that different varieties displayed variations in their oxidative system, and the differential expressions of each genotype were associated with chilling stress response. Plants with various antioxidative systems responded differently to chilling stress according to the duration of the chilling period and subsequent re-warming period. ASA, GSH and GSSG contents were enhanced in TN71 prior to chilling stress. Increased APX, GR, ASA and MDA activities accounted for chilling tolerance in TN65. Furthermore, our results indicate that the elevated levels of the antioxidative system observed after PBZ pre-treatments afforded the sweetpotato leaf improved chilling-stress tolerance. The levels of ASA and GSSG of both TN71 and TN65 under chilling were significantly raised by pre-treating with PBZ. PBZ pre-treatment exhibited the important function of enhancing the restoration of leaf oxidative damage under chilling stress and increasing the chilling tolerance of plants to mitigate chilling stress effects.     

Differential antioxidative responses of indica rice cultivars to drought stress

The present study investigated the linkages between drought stress, oxidative damages and variations in antioxidants in the three rice varieties IR-29 (salt-sensitive), Pokkali (salt-tolerant) and aromatic Pusa Basmati (PB), to elucidate the antioxidative protective mechanism governing differential drought tolerance. Water deficit, induced by 20% (w/v) polyethylene glycol (PEG-6000), provoked severe damages in IR-29 and PB in the form of huge chlorophyll degradation and elevated H₂O₂, malondialdehyde and lipoxygenase (LOX, EC 1.13.11.12) levels as compared to Pokkali. The protein oxidation was more conspicuous in IR-29. Increment in antioxidants, particularly flavonoids and phenolics was several folds higher over control in Pokkali, while much lesser in IR-29 and PB. The activity of catalase (CAT, EC 1.11.1.6) and superoxide dismutase (SOD, EC 1.15.1.1) were decreased in IR-29 and PB, but unaltered in Pokkali. However, marked drought-induced increase in guaiacol peroxidase (GPX, EC 1.11.1.7) activity was noted in both IR-29 and PB. Induction in radical scavenging activity, being the maximum in IR-29, and increased reducing power ability in all the cultivars, accompanied with drought stress, were observed as a defense mechanism. The novelty of our work is that it showed the aromatic rice PB behaving more closely to IR-29 in greater susceptibility to dehydration stress, while the salt-tolerant Pokkali also showed effective drought tolerance properties.     

水稻幼苗叶绿体保护系统对干旱的反应

干旱条件下水稻耐旱品种湘中籼２号比不耐旱品种湘早籼１２号具有较低的质膜相对透性、叶绿素含量降低较少,表明耐旱品种受伤害较轻,两个品种的抗坏血酸。过氧化物酶（ＡｓＡ－ＰＯＤ）均降低,但耐旱品种降低较少。耐旱品种的谷胱甘肽还原酶（ＧＲ）活性在干旱初期提高,不耐旱品种的则变化不大。０．０１ｍｍｏｌ／Ｌ的百草枯和０．１ｍｍｏｌ／Ｌ的Ｈ２Ｏ２亦能诱导耐旱品种的ＧＲ活性,但对不耐旱品种的ＧＲ活性不受影响,说明可能是干旱诱导的氧化胁迫诱导了ＧＲ活性。干旱条件下两品种的抗坏血酸（ＡｓＡ）和还原型谷胱甘肽（ＧＳＨ）含量均是先升后降,但耐旱品种提高幅度较大。结果表明,耐旱品种的叶绿体保护系统的活性比不耐旱品种的高。     

不同耐旱性水稻幼苗对氧化胁迫的反应

干旱条件下水稻(Oryza sativa L.)耐旱性较强的“湘中籼2号”比耐旱性较弱的“湘早釉12号”O_2~-的产生速率低。百草枯(0.01mmol/L)和H_2O_2(10mmol/L)处理促进干旱对水稻幼苗的伤害,但耐旱性较强的品种伤害较轻。单独用百草枯处理后,耐旱性较强的品种比耐旱性较弱的品种能更大幅度地提高超氧物歧化酶和过氧化物酶的活性;而H_2O_2处理后耐旱性较强的品种能提高过氧化氢酶活性。这些结果表明,耐旱性较强的水稻品种有较强的抗氧化胁迫能力。     

Manganese-excess induces oxidative stress,lowers the pool of antioxidants and elevates activities of key antioxidative enzymes in rice seedlings

Manganese (Mn) is an essential element for plant growth but in excess, specially in acidic soils, it can become phytotoxic. In order to investigate whether oxidative stress is associated with the expression of Mn toxicity during early seedling establishment of rice plants, we examined the changes in the level of reactive oxygen species (ROS), oxidative stress induced an alteration in the level of non-enzymic antioxidants and activities of antioxidative enzymes in rice seedlings grown in sand cultures containing 3 and 6 mM MnCl₂. Mn treatment inhibited growth of rice seedlings, the metal increasingly accumulated in roots and shoots and caused damage to membranes. Mn treated plants showed increased generation of superoxide anion (O₂ ^.−), elevated levels of H₂O₂ and thiobarbituric acid reactive substances (TBARS) and decline in protein thiol. The level of nonprotein thiol, however, increased due to Mn treatment. A decline in contents of reduced ascorbate (AsA) and glutathione (GSH) as well as decline in ratios of their reduced to oxidize forms was observed in Mn-treated seedlings. The activities of antioxidative enzymes superoxide dismutase (SOD) and its isoforms Mn SOD, Cu/Zn SOD, Fe SOD as well as guaiacol peroxidase (GPX) increased in the seedlings due to Mn treatment however, catalase (CAT) activity increased in 10 days old seedlings but it declined by 20 days under Mn treatment. The enzymes of Halliwell-Asada cycle, ascorbate peroxidase (APX) monodehydoascorbate reductase (MDHAR), dehyroascorbate reductase (DHAR) and glutathione reductase (GR) increased significantly in Mn treated seedlings over controls. Results suggest that in rice seedlings excess Mn induces oxidative stress, imbalances the levels of antioxidants and the antioxidative enzymes SOD, GPX, APX and GR appear to play an important role in scavenging ROS and withstanding oxidative stress induced by Mn.     

Proteomic analysis of rice leaves during drought stress and recovery

Three-week old plants of rice (Oryza sativa L. cv CT9993 and cv IR62266) developed gradual water stress over 23 days of transpiration without watering, during which period the mid-day leaf water potential declined to approximately -2.4 MPa, compared with approximately -1.0 MPa in well-watered controls. More than 1000 protein spots that were detected in leaf extracts by proteomic analysis showed reproducible abundance within replications. Of these proteins, 42 spots showed a significant change in abundance under stress, with 27 of them exhibiting a different response pattern in the two cultivars. However, only one protein (chloroplast Cu-Zn superoxide dismutase) changed significantly in opposite directions in the two cultivars in response to drought. The most common difference was for proteins to be up-regulated by drought in CT9993 and unaffected in IR62266; or down-regulated by drought in IR62266 and unaffected in CT9993. By 10 days after rewatering, all proteins had returned completely or largely to the abundance of the well-watered control. Mass spectrometry helped to identify 16 of the drought-responsive proteins, including an actin depolymerizing factor, which was one of three proteins detectable under stress in both cultivars but undetectable in well-watered plants or in plants 10 days after rewatering. The most abundant protein up-regulated by drought in CT9993 and IR62266 was identified only after cloning of the corresponding cDNA. It was found to be an S-like RNase homologue but it lacked the two active site histidines required for RNase activity. Four novel drought-responsive mechanisms were revealed by this work: up-regulation of S-like RNase homologue, actin depolymerizing factor and rubisco activase, and down-regulation of isoflavone reductase-like protein.     

Differential down-regulation of zeaxanthin epoxidation in two rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) cultivars with different chilling sensitivities

When the leaf segments of rice (Oryza sativa L.) plants were subjected to chilling in the moderate light, zeaxanthin (Zx) formation was faster in a chilling-tolerant Dongjin-byeo (DJ) than in a chilling-sensitive IR841. Although the rate of Zx formation was accelerated by the treatment of 5 mM salicylaldoxime, an inhibitor of Zx epoxidase (ZE), there was almost no changes in DJ. A similar result was observed when leaf segments were treated with 50 mM sodium fluoride, a potent inhibitor of chloroplast phosphatase. The slow Zx epoxidation in IR841 during light-chilling was confirmed in leaf segments treated with 10 mM dithiothreitol, an inhibitor of violaxanthin de-epoxidase (VDE). However, the differences between the two cultivars were not observed at 25oC. These results suggest that compared with IR841 the higher rate of Zx formation in DJ is not due to the higher VDE activity in DJ but is due to more rapid down-regulation of ZE in DJ, possibly by its phosphorylation. Compared with DJ, IR841 accumulated more superoxide with PSI inactivation during light-chilling, which eliminates the possibility of increased ZE down-regulation in DJ leaves by photo-oxidation. In vitro study with alkaline phosphatase supports the idea of down-regulation of ZE by phosphorylation under light-chilling condition. We propose that this reversible down-regulation of Zx epoxidation possibly by the phosphorylation of ZE is an important regulation mechanism of violaxanthin cycle that confers chilling tolerance of a rice cultivar under chilling stress in the light with moderate intensities.     

QTLs linked to leaf epicuticular wax,physio-morphological and plant production traits under drought stress in rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Drought stress is the major constraint to rice (Oryza sativa L.) production and yield stability in rainfed ecosystems. Identifying genomic regions contributing to drought resistance will help to develop rice cultivars suitable for rainfed regions through marker-assisted breeding. Quantitative trait loci (QTLs) linked to leaf epicuticular wax, physio-morphological and plant production traits under water stress and irrigated conditions were mapped in a doubled haploid (DH) line population from the cross CT9993-5-10-1-M/IR62266-42-6-2. The DH lines were subjected to water stress during anthesis. The DH lines showed significant variation for epicuticular wax (EW), physio-morphological and plant production traits under stress and irrigated conditions. A total of 19 QTLs were identified for the various traits under drought stress and irrigated conditions in the field, which individually explained 9.6%–65.6% of the phenotypic variation. A region EM15_10-ME8_4-R1394A-G2132 on chromosome 8 was identified for leaf EW and rate of water loss i.e., time taken to reach 70% RWC from excised leaves in rice lines subjected to drought stress. A large effect QTL (65.6%) was detected on chromosome 2 for harvest index under stress. QTLs identified for EW, rate of water loss from excised leaves and harvest index under stress in this study co-located with QTLs linked to shoot and root-related drought resistance traits in these rice lines and might be useful for rainfed rice improvement.