The role of allelopathy in agricultural pest management

Allelopathy is a naturally occurring ecological phenomenon of interference among organisms that may be employed for managing weeds, insect pests and diseases in field crops. In field crops, allelopathy can be used following rotation, using cover crops, mulching and plant extracts for natural pest management. Application of allelopathic plant extracts can effectively control weeds and insect pests. However, mixtures of allelopathic water extracts are more effective than the application of single-plant extract in this regard. Combined application of allelopathic extract and reduced herbicide dose (up to half the standard dose) give as much weed control as the standard herbicide dose in several field crops. Lower doses of herbicides may help to reduce the development of herbicide resistance in weed ecotypes. Allelopathy thus offers an attractive environmentally friendly alternative to pesticides in agricultural pest management. In this review, application of allelopathy for natural pest management, particularly in small-farm intensive agricultural systems, is discussed.     

Evaluation of Germplasm Using SSR Markers of Functional Genes in Rice

16 SSR (Simple sequence repeats) primers of functional genes in rice were used to detect genetic diversity among 23 accessions of rice germplasm from 5 countries in the world. The average number of alleles per SSR locus was 5.2 with a range from 2 to 10. Genetic similarities among the 23 rice accessions ranged from 0.13 to 0.64. UPGMA cluster analysis showed that the 23 rice accessions could be classified into two distinct classes at similarities with a coefficient of 0.13. The Japonicas from Brazil, Japan and China were classified into Class I, along with upland rice from Brazil. The Indicas from Pakistan and Korea were classified into Class Ⅱ. Consequently, the function of genes SSR markers could be used as a useful tool for measuring genetic diversity, assigning rice to geographical distribution, ecotype, and pedigree relationship.     

Nutritional Quality Characteristics of Different Wild and Underutilized Fruits of Terai Region,Uttarakhand (India)

The present study was carried out to analyze the nutritional potential of 25 of the most commonly consumed wild and underutilized fruits in the Terai region of Uttarakhand, India. The result of the different fruits analyzed revealed the richness of different phytochemicals among them. The protein content was found to be higher in Solanum nigrum, Broussonetia papyrifera, and Aegle marmelos, while Terminalia bellerica, Ficus racemosa, and Artocarpus heterophyllus were rich in lipid content. The reducing sugars ranged from 1.1–68.2% and non-reducing sugars varied from 0–6.4%. Vitamin analysis revealed higher ascorbic acid content in Emblica officinalis and Pithecellobium dulce, high riboflavin content in Broussonetia papyrifera and Ficus palmata, and high thiamine content in Artocarpus lakoocha and Solanum nigrum. The phenolic content varied from 32.9–2662.4 mg/100 g, the flavonoids between 1.2–93.8 mg/100 g, and carotenoids ranged between 0–85.7 mg/100 g. These wild fruits proved to be a good source of nutrients. Moreover, these fruit species act as a pool of genetic resources for crop improvement by breeding experiments. It can be suggested to commercialize these fruit species for enhancing the socioeconomic status of weaker section of society.     

Seed Priming with Ascorbic Acid Improves Drought Resistance of Wheat

The study, consisting of two independent experiments, was conducted to evaluate the role of seed priming with ascorbic acid (AsA) in drought resistance of wheat. In the first experiment, seeds of wheat cultivars Mairaj‐2008 and Lasani‐2008 were either soaked in aerated water (hydropriming) for 10 h or not soaked (control). In the second experiment, seeds of same wheat cultivars were soaked in aerated (2 mm ) AsA solution (osmopriming) or water (hydropriming) for 10 h. In both experiments, seeds were sown in plastic pots (10 kg) maintained at 70 % and 35 % of water‐holding capacity designated as well watered and drought stressed, respectively. Both experiments were laid out in a completely randomized design with six replications. Drought caused delayed and erratic emergence and disturbed the plant water relations, chlorophyll contents and membranes because of oxidative damage; however, root length in cultivar Lasani‐2008 was increased under drought. Hydropriming significantly improved the seedling emergence and early growth under drought and well‐watered conditions; however, improvement was substantially higher from osmopriming with AsA. Similarly, osmopriming with AsA significantly improved the leaf emergence and elongation, leaf area, specific leaf area, chlorophyll contents, root length and seedling dry weight. Owing to increase in proline accumulation, phenolics and AsA, by seed priming with AsA, plant water status was improved with simultaneous decrease in oxidative damages. These improved the leaf emergence and elongation, and shoot and root growth under drought. However, there was no difference between the cultivars in this regard. In conclusion, osmopriming with AsA improved the drought resistance of wheat owing to proline accumulation and antioxidant action of AsA and phenolics, leading to tissue water maintenance, membrane stability, and better and uniform seedling stand and growth.     

DROUGHT STRESS: Comparative Time Course Action of the Foliar Applied Glycinebetaine,Salicylic Acid,Nitrous Oxide,Brassinosteroids and Spermine in Improving Drought Resistance of Rice

Worldwide rice productivity is being threatened by increased endeavours of drought stress. Among the visible symptoms of drought stress, hampered water relations and disrupted cellular membrane functions are the most important. Exogenous use of polyamines (PAs), salicylic acid (SA), brassinosteroids (BRs), glycinebetaine (GB) and nitrous oxide (NO) can induce abiotic stresses tolerance in many crops. In this time course study, we appraised the comparative role of all these substances to improve the drought tolerance in rice (Oryza sativa L.) cultivar Super‐Basmati. Plants were subjected to drought stress at four leaf stage (4 weeks after emergence) by maintaining soil moisture at 50 % of field capacity. Pre‐optimized concentrations of GB (150 mg l^?1), SA (100 mg l^?1), NO (100 μmol l^?1 sodium nitroprusside as NO donor), BR (0.01 μm 24‐epibrassinolide) and spermine (Spm; 10 μm ) were foliar sprayed at five‐leaf stage (5 weeks after emergence). There were two controls both receiving no foliar spray, viz. well watered (CK1) and drought stressed (CK2). There was substantial reduction in allometric response of rice, gas exchange and water relation attributes by drought stress. While drought stress enhanced the H₂O₂, malondialdehyde (MDA) and relative membrane permeability, foliar spray of all the chemicals improved growth possibly because of the improved carbon assimilation, enhanced synthesis of metabolites and maintenance of tissue water status. Simultaneous reduction in H₂O₂ and MDA production was also noted in the plants treated with these substances. Drought tolerance was sturdily associated with the greater tissue water potential, increased synthesis of metabolites and enhanced capacity of antioxidant system. Of all the chemicals, foliar spray with Spm was the most effective followed by BR.