Response of Leek (Allium porrum L.) to Different Irrigation Water Levels Under Rain Shelter

A pot experiment was conducted to investigate the effects of different water levels on water-use efficiency, yield and growth parameters of leek (Allium porrum L.) and was carried out in the practical research field of Ondokuz May?s University in Turkey. Different irrigation water levels were based on the weight changes of each pot and included 5 irrigation treatments [25% (I₂₅), 50% (I₅₀), 75% (I₇₅), 100% (I₁₀₀) and 118% (I₁₁₈) times of consumed water]. Decreases in irrigation water resulted in decreases in plant height, stem diameter, leaf and stem fresh weights, leaf and stem dry weights and leaf area, but did not significantly affect leaf number or chlorophyll content. A yield-response factor of 1.26 was obtained, implying that the leek crop was sensitive to water stress caused by deficit irrigation. Comprehensive analysis of yield, water use efficiency, and evapotranspiration, the I₇₅ treatment can be suggested for leek production in water-scarce regions.     

Determination of the role of salicylic acid and Benzothiadiazole on physico-chemical alterations caused by <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> in tomato

Shoe-string disease caused by Cucumber mosaic virus (CMV) is one of the major threats to tomato production worldwide. The alteration in some biochemical parameters in leaves of the susceptible tomato genotype (Nagina) associated with CMV infection and the effect of exogenous application of salicylic acid (SA) and benzothiadiazole (BTH) were studied in this paper. Results showed that exogenous treatment with SA and BTH not only led to plants which gave significantly more yield than diseased controls (DC), but also delayed symptom expression and reduced disease severity. Analysis of biochemical parameters indicated that exogenous application of elicitors and viral infection, significantly affected the activity of peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX). Compared to the DC plants, minimum disease severity and maximum number of fruit were recorded after a single dose of SA + BTH. Maximum plant height was recorded after weekly application of SA and maximum fruit yield per plant was gained with single dose of SA. Moreover, the activity of POD was significantly elicited many-fold after weekly application of SA + BTH, while higher amount of SOD was recorded with single dose of SA. The activity of CAT was also significantly accelerated after weekly application of SA + BTH while increased level of APX was noticed with single dose of BTH. In conclusion, the combined application of SA and BTH played an important role in induction of defense mechanism against CMV infection and can be useful in tomato disease management programs.     

Supercritical carbon dioxide micronization of zeaxanthin from moderately thermophilic bacteria Muricauda lutaonensis CC-HSB-11T

Moderately thermophilic bacterial strain CC-HSB-11(T) (Muricauda lutaonensis), which was described recently from a coastal hot spring of Green Island, Taiwan, has been identified to produce zeaxanthin as a predominant xanthophyll by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Cell culture in bioreactor produced 3.12 ± 0.18 mg zeaxanthin L(-1) of culture. Micronization of zeaxanthin was achieved through supercritical carbon dioxide antisolvent precipitation method. Yield of zeaxanthin after the process was 53.4%. Dynamic light scattering assay determined the polydisperse existence of micronized particles of size 3 nm to 2 μm. Field emission scanning electron microscopy revealed distinct morphology and size distribution heterogeneity of particles. Integrity of zeaxanthin after the antisolvent process was assessed by LC-MS/MS. The technique capitalizes on the inherent ability of CC-HSB-11(T) to synthesize zeaxanthin and the work demonstrated feasibility of antisolvent precipitation method to produce microparticles exploiting a bacterial strain.     

Immunomodulatory effect of recombinant RNA‐dependent RNA polymerase protein of Macrobrachium rosenbergii nodavirus in giant freshwater prawn M. rosenbergii

The present study evaluated the role of recombinant RNA‐dependent RNA polymerase (RdRp) protein of Macrobrachium rosenbergii nodavirus (MrNV) in modulating the immune response and in reducing MrNV load in infected prawn. In the first experiment, prawns (25–30 g) were injected with recombinant RdRp protein (RP) at a concentration of 0, 1.0 and 10 μg, and immune parameters and expression of some immune‐related genes were measured up to 14 days post injection (p.i.). In the second experiment, early juveniles were injected with a similar dose of RdRp and animals were challenged by immersion with MrNV. The infection status was detected in muscles by nested RT‐PCR up to 21 days post challenge. Prawn injected with higher concentration of RP showed significantly higher total haemocyte count at different period post injection. Significant up‐regulation of immune‐related genes was observed within 24 h in prawn treated with lower dose of RP and after 7 days p.i. at higher level of RP injection compared with adult control. Most of the tested samples (63%) were found to be RT‐PCR positive for MrNV at 48 h of post‐immersion challenge. After 14 days, MrNV was detected only in control prawn, while both RP‐injected groups were MrNV negative. This study elucidated the potential viral load reduction role played by RdRP in MrNV‐infected prawn.     

Wheat Seed Presoaking for Improved Germination

Seed presoaking improves wheat germination under marginal moisture conditions. The duration of seed presoaking was studied at The University of Arid Agriculture, Rawalpindi, using 10 wheat varieties. Seed presoaking beyond 12 h does not improve germination further, and beyond 21 h, germination rate is drastically reduced.     

Simultaneous effects of plants and earthworms on mineralisation of 15N-labelled organic compounds adsorbed onto soil size fractions

 The simultaneous impact of three successive crops of wheat (Triticum aestivum L.) and of the earthworm (Lumbricus terrestris L.) on the mineralisation of ¹⁵N-labelled organic compounds adsorbed to different soil size fractions (sand and organic residues >50 μm; silt 50–2 μm; coarse clay 2–0.2 μm and fine clay <0.2 μm) was studied under controlled conditions in the greenhouse. Unplanted soils (UPS) were used as controls. In planted soils without earthworm (PS) total plant biomass decreased with each cropping by up to 50%. However, in planted soils with earthworms (PES) the total plant biomass loss was only 17%. This pattern was explained by the earthworm effect. Compared to the unplanted soils, the planted soils had an increased (mean +37%) mineralisation of ¹⁵N adsorbed onto fine clays and a partial transfer of ¹⁵N to silt and coarse clay. The quantities of ¹⁵N mineralised and transferred were higher in the planted soils with earthworms, indicating an amplification of the phenomenon in the presence of earthworms. The simultaneous effect of the rhizosphere and the drilosphere did not lead to increased mineralisation of N adsorbed onto coarse clays and silts but instead a greater transfer of N associated with the fine fractions towards the coarser fractions. Received: 25 April 2000