Irfan Afzal

Enhancing the Performance of Direct Seeded Fine Rice by Seed Priming

Abstract Higher water requirements and increasing labor costs are the major problems of the traditional rice production system. Direct seeded rice culture, growing rice without standing water, can be an attractive alternate. However, poor emergence and seedling establishment, and weed infestation are the main hindrances in the adoption of this culture. An attempt to improve the performance of direct seeded rice by seed priming was made in the present study. Priming tools employed were traditional soaking (soaking in tap water up to radicle protrusion), hydropriming for 48 h, osmohardening with KCl or CaCl2 (osmotic potential of – 1.25 MPa) for 24 h, vitamin priming (ascorbate 10 ppm) for 48 h and seed hardening for 24 h. All the priming techniques improved crop stand establishment, growth, yield and quality except traditional soaking, which resulted in impaired germination and seedling establishment that ended in reduced kernel yield and lower harvest index than that of control. Early and synchronized germination was accompanied by enhanced amylase activity and total sugars. Osmohardening with CaCl2 resulted in the best performance, followed by hardening and osmohardening with KCl. Osmohardening with CaCl2 produced 2.96 t ha-1 (vs 2.11 t ha-1 from untreated control) kernel yield, 10.13 t ha-1 (vs 9.35 t ha-1 from untreated control) straw yield and 22.61% (vs 18.91% from untreated control) harvest index. Mean emergence time and emergence to heading days, germination percentage and panicle bearing tillers; plant height and straw yield, 1000-kernel weight and kernel yield, α-amylase activity and total sugars, kernel proteins and kernel water absorption were correlated positively.

Seed Priming Influence on Early Crop Growth, Phenological Development and Yield Performance of Linola (Linum usitatissimum L.)

Reduced early crop growth and limited branching are amongst yield limiting factors of linola. Field response of seed priming treatments viz. 50 mmol L−1 salicylic acid (SA), 2.2% CaCl2 and 3.3% moringa leaf extract (MLE) including untreated dry and hydropriming controls was evaluated on early crop growth and yield performance of linola. Osmopriming with CaCl2 reduced emergence time and produced the highest seedling fresh and dry weights including Chl. a contents. Osmopriming with CaCl2 reduced crop branching and flowering and maturity times and had the maximum plant height, number of branches, tillers, pods and seeds per pod followed by MLE. Increase in seed weight, biological and seed yields was 9.30, 34.16 and 39.49%, harvest index (4.12%) and oil contents (13.39%) for CaCl2 osmopriming. Positive relationship between emergence and seedling vigor traits, 100-seed weight, seed yield with maturity time, 100-seed weight and seed yield were found. The study concludes that seed osmopriming with CaCl2 or MLE can play significant role to improve early crop growth and seed yields of linola.

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

Abstract 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), CaCl2 (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 CaCl2 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.

Physiological Strategies to Improve the Performance of Spring Maize (Zea mays L.) Planted under Early and Optimum Sowing Conditions

Low temperature at stand establishment and high temperature at reproductive stage are involved in reduction of grain yield of spring maize. A field study was therefore conducted to evaluate different physiological strategies for improving performance of spring maize under temperature extremes. Seed priming and foliar spray with 3% moringa leaf extract (MLE) and 100 mg L-1 kinetin solution alone or in all possible combinations with each other at three growth stages (knee height, tasseling and grain filling stage) and hydropriming was compared with control. Seed priming plus foliar spray of MLE and kinetin significantly improved stand establishment especially under early sown crop as indicated by reduced mean emergence time (MET), improved emergence index (EI) and final emergence percentage (FEP). Similarly increased chlorophyll contents, crop growth rate, leaf area index, photosynthetic rate, transpiration rate, relative water content and decreased membrane permeability were recorded in both early and optimum sowing conditions in MLE priming plus foliar spray treatment. All these improvements were harvested in the form of increased yield and harvest index compared with control treatment. Overall crop sown at optimum time performed best but exogenous application of MLE through seed priming and foliar spray maximally improved the performance of early sown maize crop which is attributed more likely due to improved stand establishment, chlorophyll and phenolic contents, increased leaf area duration and grain filling period. It can be concluded that seed priming with MLE along with its foliar spray could increase production of maize under temperature extremes.

Transgenic plants for abiotic stress tolerance: current status

Abiotic stress is one of the primary causes of crop losses worldwide (Bray et al. 2000. Responses to abiotic stresses. In: Buchanana BB, Gruissem W, Jones RL, editors. Biochemistry and Molecular Biology of Plants. Rockville (MD): American Society of Plant Physiologists. p. 1158–1249). To cope with the detrimental effects of stress, plants have evolved many biochemical and molecular mechanisms. One of the well-documented stress responses in plants is accumulation of osmolytes during stress. Although their actual roles in plant-stress tolerance remain controversial, these molecules are thought to have positive effects on enzyme and membrane integrity, along with adaptive roles in mediating osmotic adjustment in plants grown under drought conditions. Recent studies have demonstrated that the manipulation of genes involved in the biosynthesis of these osmolytes have improved plant tolerance to drought and salinity in a number of crops. There is renewed hope of understanding the molecular basis of osmolyte accumulation under stress and manipulating these processes via genetic engineering. For future work on generating transgenic plants with still higher levels of tolerance, the new knowledge may be used via guided genetic engineering of multiple genes to create crop plants with significantly increased productivity under drought stress. This review surveys the current advances in engineering abiotic stress-tolerant plants, particularly the genetic engineering of osmolyte genes (osmoprotectants) for imparting drought stress tolerance in plants.

Enhancement of Antioxidant Defense System Induced by Hormonal Priming in Wheat

Use of plant hormones as seed priming agents is known to improve the field performance especially under stressful conditions like salinity. A pot experiment was conducted to study the effects of seed priming of two wheat (Triticum aestivum L.) cultivars Auqab-2000 (salt tolerant) and MH-97 (salt sensitive) under saline (15 dS m−1) and non-saline (2.75 dS m−1) conditions. For priming seeds were soaked in aerated water (hydropriming), and solutions of kinetin (Kin; 25 mg L−1), or salicylic acid (SA; 50 mg L−1) for 12 h. All the priming treatments significantly reduced the adverse effects of salinity in terms of improving final emergence, growth and grain yield of both cultivars. Seed priming with SA and Kin improved salt tolerance in both wheat cultivars by the activation of antioxidants, i.e. superoxide dismutase (SOD) and catalase (CAT) to counterbalance the oxidative damage. Albeit, Na+ and Cl− contents increased due to salinity, all priming strategies lowered the accumulation of Na+ and enhanced the acc...

Effect of nitrogen regimes on combining ability variation in oil and protein contents in cottonseed (Gossypium hirsutum L.).

Abstract Eight parental cultivars and 56 hybrids of cotton (Gossypium hirsutum) were grown in normal and nitrogen-deficient conditions in the field to investigate the effect of nitrogen regime on the oil and protein contents and their combining ability. The mean oil and protein contents of the parental cultivars greatly varied with the nitrogen regime, which indicated their nitrogen sensitivity. The genetic variability of oil and protein contents was low in the same nitrogen regime, but was high in the comparison between the normal and nitrogen-deficient conditions. The nitrogen regime affected not only the oil and protein contents and ranking of parental cultivars, but also the combining ability. A normal nitrogen level was found to be more useful for selecting the additive type of gene action in breeding of cotton.

Recent Advances in Seed Enhancements

Seed quality is vital to sustainable crop production and food security. Seed enhance‐ ments include physical, physiological and biological treatments to overcome germina‐ tion constraints by uniform stands, earlier crop development and better yields. Improved germination rates and seedling vigour are due to reduced emergence time by earlier start of metabolic activities of hydrolytic enzymes and resource mobiliza‐ tion. Nutrient homeostasis, ion uptake, hormonal regulation, activation of antioxidant defence system, reduced lipid peroxidation and accumulation of compatible solutes are some mechanisms conferring biotic and abiotic stress tolerance. Several transcription factors for aquaporins, imbibitions, osmotic adjustment, antioxidant defence and phenylpropanoid pathway have been identified. However, the knowledge of molecu‐ lar pathways elucidating mode of action of these effects, reduced longevity of primed or other physical and biological agents for seed treatments and market availability of high-quality seeds are some of the challenges for scientists and seed industry. In this scenario, there is need to minimize the factors associated with reduced vigour during seed production, improve seed storage and handling, develop high-tech seeds by seed industry at appropriate rates and integrate agronomic, physiological and molecular seed research for the effective regulation of high-quality seed delivery over next generations.

Sodium exclusion is a reliable trait for the improvement of salinity tolerance in bread wheat

ABSTRACT Identification of novel wheat (Triticum aestivum L.) germplasm is imperative to develop salt tolerant varieties. In the first phase, 400 accessions were screened against high salt stress (200 mM NaCl) on the basis of Na+ accumulation in leaf blade, and 40 genotypes with contrast reaction to salinity were selected. Salt tolerant group (25 genotypes) had higher leaf K+/Na+ ratio, maximum root and shoot lengths, leaf fresh/dry weights and chlorophyll content as compared to the salt sensitive group (15 genotypes). In second phase, physiologically based screening was performed on selected genotypes against varying salinity levels (0, 100 and 200 mM NaCl). GGE biplot analysis indicates that genotypes TURACO, V-03094, V0005, V-04178, Kharchia 65 and V-05121 were the most salt-tolerant and declared winners as depicted by more gaseous exchange relations and growth potential which was strongly correlated with proper Na+, K+ discrimination in leaf and root tissues. Genotypes PBW343*2, NING MAI 50, PGO, PFAU, V-04181, PUNJAB 85, KIRITATI, TAM200/TUI and TAM200 were poor performer due to more Na+ accumulation in leaf ultimately retarded growth. In conclusion, low Na+ accumulation in leaf can be used as the best screening criteria, employing a large set of genotypes in a breeding program.

Seed Enhancement of Silybum marianum and Optimization of Silymarin Extraction

The present study elucidates the impact of different priming strategies on seed emergence and growth of milk thistle [Silybum marianum (L.) Gaertn.] and also evaluation of the efficacy of various extraction methods for optimal extraction of silymarin from milk thistle seeds. Seeds were primed with distilled water, Humic acid (2%), potassium chloride (2%) and moringa leaf extract (3%) for 24 h. Untreated seeds were used as control. Primed and non-primed seeds were sown in plastic pots. Seed priming treatments significantly improved the performance of milk thistle seeds as indicated by higher values of final emergence and lower values of mean emergence time and time taken to 50% emergence as compared to non-primed seeds. Silymarin was extracted from seeds of milk thistle by applying various techniques like Reflux, Soxhlet, maceration and microwave assisted extraction by using various solvents. Extraction with Soxhlet and microwave assisted techniques were proved better as compared to the others. The results indicated that in both spectrophotometric and HPLC quantification, silymarin contents were found maximum in extracts prepared with methanol by microwave assisted extraction technique followed by Soxhlet.