Santosh Kumar

Morpho-physiological traits associated with reproductive stage drought tolerance of rice (Oryza sativa L.) genotypes under rain-fed condition of eastern Indo-Gangetic Plain

A field experiment was conducted under reproductive stage drought stress condition with the objective to determine the effect of water deficit stress on yield and yield attributes of 75 rice genotypes. The effect of drought stress on various physiological and biochemical traits associated with drought tolerance was also studies at reproductive stage in twelve promising genotypes selected on the basis of yield performance under stress condition. Result revealed that significant yield decline was observed almost in all rice genotypes grown under water deficit stress condition as compared to irrigated situation. Drought stress at reproductive stage caused reduction in relative water content (RWC) (31.57xa0%), membrane stability index (MSI) (25.8xa0%). grain yield (55.31xa0%), number of effective tillers (37.70xa0%), plant biomass (23.65xa0%), and increase in grain sterility (51.5xa0%) and proline content (55.9xa0%) in rice genotypes. However, the responses varied among genotype. Out of the twelve rice genotypes, IR 84895-B-B-127-CRA-5-1-1, IR 83387-B-B-40-1, IR 83376-B-B-24-2, IR55419-04 and IR 83373-B-B-24-3 showed superiority in terms of grain yield, 1000 grain weight, total plant biomass, RWC, leaf area index (LAI), MSI and proline content. Significant and positive correlations were observed between yield and physiological attributes like proline content, LAI, relative water content and plant biomass under drought stress condition. The current study indicated that the physiological and biochemical traits have direct or indirect effect on yield performance of rice genotypes under water stressed environment at reproductive stage.

Depth of soil compaction predominantly affects rice yield reduction by reproductive-stage drought at varietal screening sites in Bangladesh, India, and Nepal

AimsDrought is the major constraint to rainfed rice productivity in South Asia, but few reports provide detailed characterization of the soil properties related to drought stress severity in the region. The aim of the study was to provide a compilation of drought breeding network sites and their respective levels of drought stress, and to relate soil parameters with yield reduction by drought.MethodsThis study characterized levels of drought stress and soil nutrient and physical properties at 18 geographically distributed research station sites involved in rice varietal screening in Bangladesh, India, and Nepal, as well as at farmers’ fields located near the research stations.ResultsBased on soil resistance to penetration profiles, a hardpan was surprisingly absent at about half of the sites characterized. Significant relationships of depth of compaction and yield reduction by drought indicated the effects of soil puddling on susceptibility to cracking, rather than water retention by hardpans, on plant water availability in this region. The main difference between research stations and nearby farmers’ fields was in terms of soil compaction.ConclusionsThese results present an initiative for understanding the range of severities of reproductive-stage drought stress in drought-prone rainfed lowland rice-growing areas in South Asia.

Comprehensive physiological analyses and reactive oxygen species profiling in drought tolerant rice genotypes under salinity stress

Rice being a staple cereal is extremely susceptible towards abiotic stresses. Drought and salinity are two vital factors limiting rice cultivation in Eastern Indo-Gangetic Plains (EIGP). Present study has intended to evaluate the consequences of salinity stress on selected drought tolerant rice genotypes at the most susceptible seedling stage with an aim to identify the potential multi-stress (drought and salt) tolerant rice genotype of this region. Genotypic variation was obvious in all traits related to drought and salt susceptibility. IR84895-B-127-CRA-5-1-1, one of the rice genotypes studied, exhibited exceptional drought and salinity tolerance. IR83373-B-B-25-3-B-B-25-3 also displayed enhanced drought and salt tolerance following IR84895-B-127-CRA-5-1-1. Variations were perceptible in different factors involving photosynthetic performance, proline content, lipid peroxidation, K+/Na+ ratio. Accumulation of reactive oxygen species (ROS) disintegrated cellular and sub-cellular membrane leading to decreased photosynthetic activities. Therefore, accumulation and detoxification of reactive oxygen species was also considered as a major determinant of salt tolerance. IR84895-B-127-CRA-5-1-1 showed improved ROS detoxification mediated by antioxidant enzymes. IR84895-B-127-CRA-5-1-1 seedlings also displayed significant recovery after removal of salt stress. The results established a direct association of ROS scavenging with improved physiological activities and salt tolerance. The study also recommended IR84895-B-127-CRA-5-1-1 for improved crop performance in both drought and saline environments of EIGP. These contrasting rice genotypes may assist in understanding the multiple stress associated factors in concurrent drought and salt tolerant rice genotypes.

Improvement of submergence tolerance in rice through efficient application of potassium under submergence-prone rainfed ecology of Indo-Gangetic Plain

Potassium (K) is one of the limiting factors that negatively influenced rice growth and yield in submergence-prone soils. We conducted an experiment during the wet season of 2014-15 to achieve optimal doses of K and understand the effect of K application on submerged rice in terms of survival, chlorophyll content, non-structural carbohydrates (NSC), anti-oxidant activities and yield. Results revealed that chlorophyll and NSC content were significantly (P≤0.05) lower whereas the activity of anti-oxidants (catalase, superoxide dismutase and total peroxidase) were significantly (P≤0.05) higher after submergence compared with pre-submergence. Further, application of K at a higher basal dose (40kgha-1) was more beneficial to improve survival after de-submergence by maintaining NSC, chlorophyll content and higher activity of anti-oxidants with lower level of lipid peroxidation. Furthermore, results showed superiority of the treatments having application of higher doses with one foliar spray (T9-40kg K2O ha-1 (basal)+one foliar spray at 0.5% K at panicle initiation (PI) stage) for grain yield. We conclude that application of a higher dose of K with one foliar application at PI stage is more beneficial to enhance plant survival, better recovery and yield gain of rice during complete submergence.

Effect of different rice establishment methods on soil physical properties in drought-prone, rainfed lowlands of Bihar, India

To enhance productivity, alleviate environmental and management constraints, and enhance farmers’ incomes in the rice–wheat cropping system of the Indo Gangetic Plains, new approaches that are labour-saving, more productive and sustainable need to be developed. Most systems of rice cultivation use puddling to prepare the seedbed and control weeds in rice fields of rainfed, stress-prone environments. This practice might be helpful to reduce weed pressure and obtain slightly higher productivity, but might have negative impacts on soil physical properties. A better understanding is needed of the comparative advantage of unpuddled rice fields for maintaining good soil physical properties. To study the effect of different rice establishment methods on soil physical properties in a rice–wheat cropping system, we analysed soil samples in 2 years (2012–13 and 2013–14) from an experiment testing puddled and unpuddled rice-establishment methods. The treatments were: (i) puddled, transplanted with best management practices; (ii) puddled, transplanted with the system of rice intensification; (iii) unpuddled, transplanted; and (iv) unpuddled, direct-seeded. Omission of puddling improved soil physical properties such as bulk density, penetration resistance, aggregation stability and cracking behaviour. The absence of soil disturbance also improved soil aggregation, average mean-weight diameter and water-stable aggregates. Thus, unpuddled conditions increased the macro-aggregate fraction by 18–33%. By contrast, the higher frequency of smaller macro-aggregates (0.053–0.25u2009mm diameter) in puddled conditions clearly indicated the breakdown of larger macro-aggregates (>0.25u2009mm) into smaller size fractions. Puddled treatments were also characterised by a hard pan and wider, longer and deeper cracks, with a crack volume more than three times higher in puddled conditions. Unpuddled treatments recorded slightly higher nutrient contents in the topsoil. The study reveals that puddling deteriorates soil health. However, a long-term study is required for a better understanding of the soil changes related to different rice establishment technologies.

Complete mitochondrial genome sequence of Heteropneustes fossilis obtained by paired end next generation sequencing

Abstract In the present study, the complete mitochondrial genome sequence of Heteropneustes fossilis is reported using massive parallel sequence technology. The complete mitogenome of H. fossilis is obtained by de novo assembly of paired end Illumina sequences using CLC Genomics Workbench version 7.0.4, which is 16,489u2009bp in length. It comprised of 13 protein- coding genes, 22 tRNAs, 2 rRNA genes and a putative control region along with the gene order and organization, being similar to most of vertebrates. The mitogenome in the present study has 99% similarity to the complete mitogneome sequence of H. Fossilis, as reported earlier. Phylogenetic analysis of Siluriformes depicted that Heteropneustids were closer to Clariids. The mitogenome sequence of H. fossilis contributes better understanding of population genetics, phylogenetics and evolution of Indian catfish species.

Positive impact of paclobutrazol on gas exchange, chlorophyll fluorescence and yield parameters under submergence stress in rice

Flooding is common in rainfed lowland areas of the world. Several physiological and biochemical plant processes were affected by the flooding, which causes deprivation of O2 in the root zone. Hence, a study was undertaken with four rice varieties, viz., Sita, IR64, FR-13A and Bharani, grown in simulated tanks and subjected to submergence stress. The effect of anti-GA compound paclobutrazol on the recovery of plants including gas exchange, chlorophyll fluorescence and grain yield parameters were measured after submergence stress. Net photosynthesis rate declined in plants subjected to stress at seedling stage. Varieties FR-13A and IR 64 recorded higher photosynthetic rate than Bharani and Sita. However, paclobutrazol application enhanced photosynthesis and transpiration rate in all the varieties after the imposition of stress. Chlorophyll fluorescence parameter, viz., maximum quantum yield of PSII (Fv/Fm) declined under stress at panicle initiation stage in all four varieties. The decline in yield of PSII was less in FR-13A, followed by Bharani and IR 64. Moreover, decline in panicle weight and grain weight was observed in all the varieties under submergence stress; however decline was less when the plants were treated with paclobutrazol. Higher photosynthetic rate coupled with lesser decline in yield of PSII with paclobutrazol application increased the tolerance of variety towards submergence stress. Hence, paclobutrazol application alleviated the negative effect of transient submergence stress by contributing to the recovery of plants and maintenance of yield in rice.

Plant survival, growth and yield attributing traits of rice (Oryza sativa L.) genotypes under submergence stress in rainfed lowland ecosystem

Fourteen rice genotypes comprising of landraces, high yielding varieties (HYVs) carrying Sub1 allele as well as without Sub1 allele contrasting in their tolerance to submergence stress were evaluated for plant survival, growth and yield response under submergence stress during kharif season of 2011 and 2012. Decline in yield was observed almost in all the rice genotypes grown under submergence stress as compared to control condition. Under short term submergence, rice genotypes carrying Sub1 allele survived complete submergence up to 14xa0days, whereas genotypes without Sub1 did not survive significantly and gave very low yield. The decline in yield in rice genotypes under stress (submerged) condition ranged from 1.5 to 97xa0%. Under control condition HYVs with and without Sub1 allele showed non significant differences in grain yield, but showed an average yield advantage of more than 2.5xa0txa0ha−1 over landraces. Non significant difference were observed in landraces for grain yield under submergence and control treatments indicating considerable submergence tolerance. Landraces and HYVs carrying Sub1 showed higher survival percentage after submergence than the susceptible parents and check variety IR 42. Variance studies revealed significant differences among genotypes for yield attributing traits. Correlation studies revealed that genotypes with the capacity to maintain higher biomass, higher chlorophyll and higher starch and sugar concentrations after submergence had higher survival of seedling and grain yield. Present study suggested that submergence tolerance related genes from landraces like Atiranga, Gangasuili and Kalaputia apart from FR 13A need to be identified for introgression into HYVs for successful exploitation of low lying flood prone ecosystem.

Influence of elevated CO2 and temperature on physiological traits and yield attributes of heat tolerant wheat genotype Halna grown inside open top chambers

Both CO2 and temperature caused significant changes in crop productivity. An experiment was conducted wherein wheat was grown inside open top chambers (OTCs) in order to determine the effects of elevated atmospheric carbon dioxide (CO2) and temperature on physiology and yield attributes of wheat genotype Halna. Halna was grown with two levels of carbon dioxide, i.e., ambient (400xa0ppm) and elevated (500xa0±xa020xa0ppm) and two levels of temperature, i.e., ambient, and ambient +2xa0°C during the Rabi (November–April) season of 2014–2015 at ICAR-RCER, Patna, India. The study revealed that elevated CO2 improved water use efficiency by 26.3%, photosynthetic rate by 14.6%, relative water content (RWC) by 15.9%, membrane stability index (MSI) by 6.6%, leaf area (LA) by 4.6%, plant height by 2.53% and grain yield by 26.9% as compared to ambient, while the activity of antioxidant enzymes were decreased, i.e., catalase by −12.59% and peroxidase by −21.04%. However, elevation of temperature by 2xa0°C decreased the photosynthetic rate by 15.9%, LA by 8.7% and grain yield by 11.7% but activity of CAT (+64.8%), and POX (+7.2%) were increased as compared to ambient condition. Simultaneous elevation of both (CO2 and temperature) caused non-significant increase in leaf area, number of grains ear−1, 1000 grain weight and grain yield as compared to ambient condition. The results indicated that elevated CO2 had positive effects, whereas elevated temperature had negative effects and with simultaneous elevation of CO2 and temperature, elevated CO2 nullified the negative effects of elevated temperature on photosynthetic characteristics and yield components of Halna.

RETRACTED ARTICLE: Effect of paclobutrazol on photosynthesis and expression of pyrroline-5-carboxylatesynthase in contrasting wheat genotypes under water deficit stress condition

The corresponding author retracts this article published at online first due to the unreliability of findings arising out of inappropriate handling of the photograph at the bottom right panel of Fig. 2. The authors regret the inappropriate image and thank the anonymous complainant at Pubpeer and the editor of PMBP for bringing it to their notice. The online version of this article contains the full text of the retracted article as electronic supplementary material.