Irrigation and Zn fertilizer management improves Zn phyto‐availability in various rice production systems

Zinc (Zn) is an important micronutrient for rice (Oryza sativa L.) production and its deficiency has been observed in various production systems. High grain Zn concentration is equally important for high rice yield and human health. In this work, the effects of Zn fertilization on seedling growth, grain yield, grain Zn concentration, and their association with root traits were studied under alternate wetting and drying (AWD), aerobic rice (AR), system of rice intensification (SRI), and continuous flooding (CF). Zinc fertilization (15 kg ha^?1) improved nursery seedlings chlorophyll and Zn concentrations, root length, and number of roots with highest values observed in CF. At harvesting, maximum plant height, panicle length, total and panicle bearing tillers, and kernel yield were found with Zn addition in AWD and CF rice systems. Mid season drainage provided at maximum tillering and Zn fertilization increased its concentration in leaves, culms, panicles, and grains under CF and AR at physiological maturity. Most of Zn applied was allocated into culms and panicles, nevertheless, a significant increase in grain Zn concentration was also observed in all production systems. Association of leaf Zn with grain Zn concentration was stronger than with culm and panicle Zn. The results indicate that Zn application after rice nursery transplanting is more important for grain Zn enrichment in all rice systems than for increase in grain yield in all systems except AWD where grain yield was also increased. More grain yield in CF and AWD as compared to SRI and AR can also be attributed to decreased spikelet sterility and to better Zn phyto‐availability in these rice systems at physiological maturity.     

Perspectives of folate biofortification of cereal grains

One sixth of the world’s population is suffering from hidden hunger that indicates a gross malnutrition particularly among children and women of third world countries. The deficiency of micro nutrients, especially iron (Fe) causes a number of ailments such as megaloblastic anemia and neural tube defects in poor population. There is a dire need to supplement iron in the diet. Current efforts implicate fortification of wheat flour and other grains with different iron formulations such as ethylenediaminetetraacetic acid (EDTA), FeSO₄ and elemental iron. However, all such interventions are not sustainable due to logistic and quality assurance problems in resource-limited settings. For a long term solution, development of crop plants with increased micronutrients and iron bioavailability is essential. Therefore, biofortification of cereal grains using translational genomics approaches for enhancement of folate through genome editing in cereals is inevitable to mitigate the folate deficiency in poor remote population in a cost effective manner.     

Genetic dissection of root architectural traits by QTL and genome‐wide association mapping in rapeseed (Brassica napus)

Variation in root architecture is essential for the adaptation of plants to target environments. A non‐destructive gel‐based mini‐rhizotron system was used for root architecture trait phenotyping. This system has facilitated the visualization of root architectural traits in large genotype collection of rapeseed including 94 double haploid (DH) lines from “Express617” x “V8” and 439 inbred lines (ASSYST diversity set). A high‐density Express617‐V8 linkage map was used for quantitative trait loci (QTLs) identification in DH population based on standard composite interval mapping. 6K SNPs were analysed for association mapping of root traits in ASSYST diversity set. A large variation, broad segregation and medium–low heritability of root architectural traits, primary root length and growth rate, lateral root number, lateral root length and lateral root density, were observed. In the double haploid population, 11 QTL regions, and in the diversity set, 38 significant marker–trait associations were detected. Significant marker–trait associations proved that these are quantitatively inherited traits controlled by multiple genes which revealed to proceed for genetic improvement and selection of rapeseed lines with improved root system.     

Potassium–sodium interactions in soil and plant under saline‐sodic conditions

About 7% of the total land around the globe is salt‐affected causing a great loss to agriculture. Salt stress refers to the excessive amount of soluble salts in the root zone which induce osmotic stress and ion toxicity in the growing plant. Among toxic ions, sodium (Na⁺) has the most adverse effects on plant growth by its detrimental influence on plant metabolism in inhibiting enzyme activities. An optimal potassium (K⁺) : Na⁺ ratio is vital to activate enzymatic reactions in the cytoplasm necessary for maintenance of plant growth and yield development. Although most soils have adequate amounts of K⁺, in many soils available K⁺ has become insufficient because of large amounts of K⁺ removal by high‐yielding crops. This problem is exacerbated under sodic or saline‐sodic soil conditions as a consequence of K⁺‐Na⁺ antagonism. Here K⁺ uptake by plants is severely affected by the presence of Na⁺ in the nutrient medium. Due to its similar physicochemical properties, Na⁺ competes with K⁺ in plant uptake specifically through high‐affinity potassium transporters (HKTs) and nonselective cation channels (NSCCs). Membrane depolarization caused by Na⁺ makes it difficult for K⁺ to be taken up by K⁺ inward‐rectifying channels (KIRs) and increases K⁺ leakage from the cell by activating potassium outward‐rectifying channels (KORs). Minimizing Na⁺ uptake and preventing K⁺ losses from the cell may help to maintain a K⁺ : Na⁺ ratio optimum for plant metabolism in the cytoplasm under salt‐stress conditions. It would seem a reasonable assumption therefore that an increase in the concentration of K⁺ in salt‐affected soils may support enhanced K⁺ uptake and reduce Na⁺ influx via HKTs and NCCSs. Although very useful information is available regarding K⁺‐Na⁺ homeostasis indicating their antagonistic effect in plants, current knowledge in applied research is still inadequate to recommend application of potassium fertilizers to alleviate Na⁺ stress in plants under sodic and saline‐sodic conditions. Nevertheless some encouraging results regarding alleviation of Na⁺ stress by potassium fertilization provide the motivation for conducting further studies to improve our understanding and perspectives for potassium fertilization in sodic and saline‐sodic environments.     

Seed priming improves early seedling vigor,growth and productivity of spring maize

Potential of seed priming treatments in improving the performance of early planted maize was evaluated against timely planting. Seeds of maize hybrid FH-810 were soaked in water(hydropriming), Ca Cl2(2.2%, osmopriming), moringa leaf extracts(MLE 3.3%, osmopriming) and salicylic acid(SA, 50 mg L–1, hormonal priming) each for 18 h. Untreated and hydroprimed seeds were taken as control. Seeds primed with SA took less time in emergence and had high vigor in early planted maize. Amongst treatments, hormonal priming, reduced the electrical conductivity, increased the leaf relative and chlorophyll contents followed by osmopriming with Ca Cl2 at seedling stage. Likewise, plant height, grain rows and 1 000-grain weight, grain and biological yield and harvest index were also improved by seed priming; however hormonal priming and osmopriming with MLE were more effective in this regard. Improved yield performance by hormonal priming or osmopriming with MLE in early planting primarily owed to increased leaf area index, crop growth and net assimilation rates, and maintenance of green leaf area at maturity. In conclusion, osmopriming with MLE and hormonal priming with SA were the most economical treatments in improving productivity of early planted spring maize through stimulation of early seedling growth at low temperature.     

Co-induction of glutathione-S-transferases and multidrug resistance associated protein by xenobiotics in wheat

Herbicide safeners are known to protect monocotyledonous crops from herbicide injury by accelerating the metabolism of herbicides. We have investigated the effects of the safener cloquintocetmexyl, which protects small-grain cereals against the graminicidal herbicide, clodinafop-propargyl. Subtractive suppression hybridisation was used to identify wheat genes which are up-regulated by treatment not only with cloquintocet-mexyl but also with phenobarbital, which is known to stimulate xenobiotic metabolism in animals and plants. DNA sequences of five glutathione transferases (GSTs) belonging to three different classes and a multidrug resistance associated protein (MRP) homologue were identified in the screen. The chemical inducibility of these clones was confirmed by Northern analysis. The MRP protein was shown to be induced by treatments with cloquintocet-mexyl and phenobarbital and to be localised to the tonoplast. Since clodinafop-propargyl is not known to be metabolised by glutathionylation, the significance of GST induction is interpreted in terms of a generalised response to chemical stress, particularly the generation of active oxygen species. This work establishes herbicide safeners as useful tools for the identification of genes encoding herbicide-metabolising enzymes.     

Nitrogen use efficiency,water saving and yield of rice transplanting on raised bed over traditional flat method

Flat transplanting with flooded irrigation is commonly used for growing rice, but it results in ineffective use of applied fertilizer and water. The objective of this study was to compare nitrogen use efficiency and water saving of rice transplanted on beds and on flat ground. This field experiment was performed in randomized complete design for three continuous years and all treatments were repeated three times. Results showed that transplanting of four lines of rice nursery on bed and one line in furrow and nitrogen application at 150 kg ha^?1 recorded 16.06, 21.81, 16.0 and 20.21% higher paddy yield, nitrogen (N) uptake in paddy, N use efficiency and N agronomic efficiency than traditional flat method at same N level. Without loss in yield, about 25 kg ha ^?1 of N fertilizer and 24% of water can be saved with bed transplanting of rice as compared to flat method.