Iran Agricultural Research
Volume:32 Issue: 1, Summer and Autumn 2013

In this study، texture profile analysis and a creep test were used to determine the textural quality attributes of fish protein isolates and conventional surimi. These isolates were made from raw materials obtained from filleting processes of Silver carp (Hypophthalmichthys molitrix) using acid and alkaline aided treatments. Texture profile analysis was performed in order to obtain hardness، cohesiveness، springiness and chewiness of the samples. Added to this، a creep test was applied to measure the elasticity value of the samples. Results were compared to the attributes of conventional surimi produced from the fish. Textural assessment was performed on gel samples formed by heating in hot water at 85 °C for 30 min. Comparison of fish protein isolate gels and the conventional surimi indicated significant differences in texture profile analysis parameters except for springiness value. Furthermore، the results of the creep test revealed that conventional surimi had significantly lower elasticity (29. 8±0. 9%) than fish protein isolate gels.

Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae)، is one of the most important pest of vegetable and fruit crops. This polyphagous pest has a range of natural enemies including the parasitoid Eretmocerus mundus (Merect) (Hymenoptera: Aphelinidae). To determine the molecular profile and taxonomic status of Iranian isolates of E. mundus، parasitized B. tabaci samples were collected from cotton crops in Maharlu region (Shiraz، Fars province). DNA was extracted from samples and subjected to polymerase chain reaction using a pair of mitochondrial cytochrome oxidase subunit I (mtCOI) gene specific primers. A DNA fragment of approximately 850 bp in size was amplified، cloned and sequenced. Comparison of the DNA nucleotide (nt) sequence of the mtCOI gene of three Iranian isolates with the same region of Chalcidoid species (Hymenoptera) available in the GenBank indicated that the mtCOI gene of Iranian isolates of E. mundus shares 98. 8-99. 5 % sequence homology. Among the Chalcidoid species compared، the Iranian isolates of E. mundus were more closely related to two Moroccan isolates of E. mundus; their mtCOI gene shared 96. 7-97. 7 % homology، being more distantly related to a Heterandrium species (family Agaonidae)، and their mtCOI gene nt sequence sharing 81. 2-83. 8 % homology.

In order to study the effects of different salinity levels on turnip (Brassica rapa L.)، an investigation was conducted at Yasouj University، Iran، in 2010. The effects of four salinity levels including 1. 92، 9. 87، 19. 6 and 21. 94 ds m-1 (20:1 ratio of NaCl: CaCl2 in Hoagland solution) on germination، vegetative and maturity stages of turnip (Baherghan landrace) were investigated. The results revealed that the measured traits at the germination stage were significantly affected by salinity treatments. The effect of salinity stress was only significant for leaf area، sodium and potassium contents at the vegetative stage. Salinity had significant effects on all the recorded traits of turnip roots، except for Ca2+، Zn and Fe contents. Based on stress intensity values، salinity affected germination percentage (SI=1. 0) on the second day and the seedling root length (SI=0. 93) more than other measured traits. The results of SI (stress intensity) showed that salinity affected Na+ content more than other traits at the maturity stage (SI=0. 74). Ca2+ showed an inverse response and had the lowest SI (SI=0. 001). Based on this study، vegetative growth and root elongation stages were more tolerant and sensitive to salinity، respectively. In addition، seedling root length at germination stage and tissue Na+ content at subsequent growth stages were the most important traits، recommended to be used as selection criteria in turnip breeding programs.

Understanding the relationship between sink and source in maize is of prime importance in maize growing regions. In this study، a field experiment was carried out during spring and summer 2007 in the experimental field of the College of Agriculture، Shiraz University، to examine the effects of source restriction (defoliation) on sink size (yield and its components) of SC704 maize hybrid. A factorial arrangement in a randomized complete block design with four replications was used. Treatments composed of four stages of source restriction including defoliation at half-silking and 3 consecutive 10 day intervals، as well as three defoliation intensities (zero، half and all leaf removal). It was found that delay in source limitation was associated with a lower mean kernel weight achievement. The highest mean kernel weight was attained in defoliation at half- silking (208. 14 g)، which also resulted in the lowest grain yield reduction، compared to no defoliation treatment. Increase in defoliation intensity was associated with a decrease in grain yield; however، delay in defoliation after mid- silking had no significant effect on grain yield. It was concluded that the grain yield of SC704 maize hybrid was more sensitive to source limitation (i. e. defoliation) intensity than defoliation time.

The effects of arbuscular mycorrhizal (AM) fungi on growth and phosphorus (P) inflow into two species of clover plant with different root morphology were studied. The experiment was arranged as a randomized complete block design consisting of a 2×3×3 factorial combination of two clover species (Trifolium alexandrinum L. and Trifolium pratense L.)، three mycorrhiza states (without mycorrhiza، Glomus intraradices and Glomus mosseae) and three harvests (20، 40 and 60 days after transplanting) with 4 replications. In this experiment، plant dry matter، root colonization and P uptake in terms of P inflow and mycorrhizal P response (MPR) were determined. Results showed that mycorrhizal growth response (MGR) of T. alexandrinum was greater than that of T. pratense. This was mainly attributed to the higher root length of T. alexandrinum which provides a greater surface area for colonization compared to T. pratense. The highest P inflow was observed during the first harvest period (0-20 d). In this harvest period and during the treatment with T. alexandrinum، P inflow into non-colonized roots، roots colonized by G. mosseae and G. intraradices were 1. 9، 6. 8 and 8. 01 pM m-1 s-1، respectively being 3. 6 and 4. 2 times greater than the control plants. The greater effect of G. intraradices compared to G. mosseae on increasing P inflow might be due to the superior ability of G. intraradices to spread into the soil and absorb more P beyond the P depletion zones around the roots and/or might be due to the higher intensity of arbuscules and intra-radical hyphae per unit length of colonized root. In conclusion، T. alexandrinum was more responsive to mycorrhizal colonization than T. pratense which، in turn، resulted in better P nutrition of T. alexandrinum colonized by G. intraradices.

The possible alleviating effects of salicylic acid on protection of cowpea (Vigna unguiculata) cv. Parastu under water stress conditions were investigated in the University of Zanjan Agriculture Research Station during 2008. Water stress was imposed by withholding irrigation at 50% flowering (flowering water stress، FWS) and when 50% of the pods grew 2-3cm (pod-formation water stress، PFWS). Salicylic acid (SA) was sprayed when plants had approximately ten fully expanded leaves with different concentrations of 0، 150، 300، 450 and 600 µM. Water stress was found to affect net photosynthesis rate، relative water content and Chlorophyll index. Proline content and leaf temperature increased in response to water stress. In both water stress treatments، plants treated with 300µM SA showed the highest values for net photosynthesis rate، transpiration rate and proline concentration. In FWS، the lowest leaf temperature was recorded in the control plants. However، in PFWS، leaf temperature was not affected by SA treatment. In FWS condition، the application of 300 µM SA showed the highest leaf area. It seems that the application of SA in 300 µM concentration may improve plant functions in both normal and stress conditions.