Rising air temperature is a major constraint for crop productivity under the current climate change scenario. Rice crops are known to be sensitive to high-temperature (HT) stress at anthesis and post-anthesis stages. Photosynthesis is an important metabolic process and is affected by HT stress. A pot study was planned to screen a set of seventy-three Indian rice accessions based upon changes in the rate of photosynthesis (Pn) and related gas exchange traits under HT, and to characterize the contrasting rice accessions for component traits of HT stress tolerance. All accessions were raised under ambient temperature (AT) until the booting stage and exposed to HT using controlled chambers at anthesis and post-anthesis. HT exposure led to a large reduction (up to 50%) in Pn, but stomatal conductance (gs) and the rate of transpiration (E) increased significantly across the rice accessions. Based on the photosynthetic response under HT, two contrasting rice accessions (IRGC 135883, tolerant, and IRGC 127222, sensitive) were selected and characterized for HT tolerance, along with an NL-44 check. Among them, Pn decreased marginally but gs and E showed significant increases under HT in the tolerant accession, while sensitive accession showed an up to 50% reduction in Pn and marginal increase in gs and E. No significant changes were recorded for chlorophyll fluorescence (Fv/Fm) in both the genotypes, but tissue temperature depression (TTD) was higher in IRGC 135883 accession under HT. Endogenous abscisic acid (ABA) content increased under HT in the flag leaf of both the accessions, and the highest increase was observed in the sensitive accession. Similarly, spikelet fertility and grain yield showed large reductions in sensitive rice accession under HT. A large increase in ABA concentration in the leaves of the sensitive rice accession might be affecting its gs and cooling capacity under an HT environment. Finally, the study concludes that tolerant rice accessions can be recommended as donors and exploited in future rice breeding programs for developing climate-resilient rice genotypes.
One hundred and sixty two genotypes of different Lens species were screened for salinity tolerance in hydroponics at 40, 80 and 120 mM sodium chloride (NaCl) for 30 d. The germination, seedling growth, biomass accumulation, seedling survivability, salinity scores, root and shoot anatomy, sodium ion (Na+), chloride ion (Cl-) and potassium ion (K+) concentrations, proline and antioxidant activities were measured to evaluate the performance of all the genotypes. The results were compared in respect of physiological (Na+, K+ and Cl-) and seed yield components obtained from field trials for salinity stress conducted during two years. Expression of salt tolerance in hydroponics was found to be reliable indicator for similarity in salt tolerance between genotypes and was evident in saline soil based comparisons. Impressive genotypic variation for salinity tolerance was observed among the genotypes screened under hydroponic and saline field conditions. Plant concentrations of Na+ and Cl- at 120 mM NaCl were found significantly correlated with germination, root and shoot length, fresh and dry weight of roots and shoots, seedling survivability, salinity scores and K+ under controlled conditions and ranked the genotypes along with their seed yield in the field. Root and shoot anatomy of tolerant line (PDL-1) and wild accession (ILWL-137) showed restricted uptake of Na+ and Cl- due to thick layer of their epidermis and endodermis as compared to sensitive cultigen (L-4076). All the genotypes were scanned using SSR markers for genetic diversity, which generated high polymorphism. On the basis of cluster analysis and population structure the contrasting genotypes were grouped into different classes. These markers may further be tested to explore their potential in marker-assisted selection.
Abstract An investigation was conducted to understand the genetics and molecular mapping for salinity stress tolerance in lentil at the seedling stage. The populations were developed through crossing between salt sensitive (L‐4147 and L‐4076) and salt‐tolerant (PDL‐1 and PSL‐9) genotypes. The parents, F 1 , F 2 , F 3 and backcross populations were assayed in salt solution at 120 mM NaCl for assessing salinity stress tolerance based on seedling survival and a Fluorescein diacetate (FDA) signal. The F 1s were found tolerant to salinity stress indicating their dominance over the sensitive ones. The F 2 segregation fitted well with the expected monogenic frequency ratio of salt‐tolerant: salt‐sensitive plants, which indicates that salinity stress tolerance is governed by a single dominant gene. This was also confirmed in F 3 and backcross segregation data. Allelism test supported the hypothesis that the same gene was conferring stress tolerance in tolerant genotypes (PDL‐1 and PSL‐9). This matched with major QTL of seedling survival under salinity stress. Four hundred and ninety‐five SSR markers were analyzed for polymorphism and 11 of them were found polymorphic between the parents. Among eleven polymorphic markers, seven were associated with seedling survival under salinity stress. The QTL of this trait was mapped within a map distance of 133.02 cM in F 2 mapping population (L‐4147 × PDL‐1) and it was found located on linkage group 1 (LG_1) and explained phenotypic variance of 65.6%. This report on QTL mapping should be useful for dissection of candidate genes and development of molecular markers for improvement of salinity stress tolerance in lentil.
While both water and nitrogen (N) are necessary for crop output and quality, excessive N application increases production costs and environmental degradation. Recent years have seen the development of NUE and WUE assessment tools, which have shown value. This chapter discusses the properties of next-generation phenomics that are critical for recognising rice genotypes during periods of water scarcity. In addition to the newly proposed one, the experiment featured non-imaging hyperspectral remote sensing, thermal imaging, and colour and multispectral imaging sensors from the ground and aerial platforms. Numerous multivariate models for the non-invasive evaluation of rice plants' relative water content (RWC) and sugar content were examined using spectral reflectance data gathered in the 350–2500 nm spectral region. Differentiating rice genotypes was accomplished using spectral data. A crop water stress score developed from thermal imaging of selected rice genotypes may be used to identify rice with high drought resistance and low drought sensitivity. The researchers used multispectral and RGB sensors mounted on a drone for field remote sensing and heat map mapping to record the distinct responses of various genotypes and characteristics. The procedures established are rapid, low-cost, and non-invasive, providing a viable alternative to traditional approaches. These techniques are now being used to do high-throughput plant phenotyping in water scarcity and nutrient deficiency conditions.
Rice productivity is severely hampered by heat stress (HS) which induces oxidative stress in this crop. This oxidative stress can be alleviated using various exogenous chemicals, including spermidine (Spd). Therefore, the present study was carried out to characterize HS components and to elucidate the role of exogenous Spd application in rice at the flowering stage.Two contrasting rice genotypes, i.e. Nagina22 (N22) and Pusa Basmati-1121 (PB-1121) were placed in temperature tunnels and exposed to HS (38-43°C) with and without Spd (1.5 mM) foliar application during the heading stage till the end of the anthesis stage.Heat stress induced the production of H2O2 and thiobarbituric acid reactive substances, which resulted in lower photosynthesis, spikelet sterility, and reduced grain yield. Interestingly, foliar application of Spd induced antioxidant enzyme activities and thus increased total antioxidant capacity resulting in higher photosynthesis, spikelet fertility, and improved grain yield under HS in both genotypes. Under HS with Spd, higher sugar content was recorded as compared to HS alone, which maintained the osmotic equilibrium in leaf and spikelets. Spd application initiated in vivo polyamine biosynthesis, which increased endogenous polyamine levels.This study corroborates that the exogenous application of Spd is promising in induction of antioxidant defence and ameliorating HS tolerance in rice via improved photosynthesis and transpiration. Thereby, the study proposes the potential application of Spd to reduce HS in rice under current global warming scenario.
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