Different Levels Of Salinity Research Articles

Impact of Salinity Stress on Morpho-physiology of Four Rice (Oryza sativa L.) Varieties

Abiotic stress, especially salinity, is one of the major restraints for attaining self-sufficiency in the food grain production. The saline soils affect the crop growth both directly and indirectly by interfering with plant metabolism resulting in reduction in yield potential of various crops. Rice (Oryza sativa L.), the staple food of much of the world’s population, is categorized as a salt-susceptible crop. Improving the salt tolerance of rice would increase the potential of saline-alkali land and ensure food security. To investigate the effect of different levels of salinity on morpho-physiological characters and yield of four rice variety viz. Pokkali, Narendra Ushar Dhan 3, IR 28 and IR 29. A pot experiment was conducted during Kharif 2011 and 2012 at the Department of Crop Physiology, Narendra Deva University of Agriculture and Technology, Kumarganj, Faizabad (U.P.) under normal soil and saline conditions with EC 6.0 and EC 10.0 dS/m. Gradual increase on plant height as well as biomass with the advancement in the age of crop up to dough grain in all the varities under both normal and salinity treatment. Maximum grain yield recorded in tolerant varieties Narendra Usar Dhan 3 followed by Pokkali, whereas minimum in IR 28. Under saline conditions regarding sink potential, the tolerant varieties recorded less reduction in yield attributes like length of panicle (cm), number of panicle per plant, number grain panicle-1 and grain yield plant-1 as compared to normal condition. The salinity tolerance capacity of tolerance varieties was associated with increased the activity of catalase and superoxide dismutase enzyme batter accumulation of proline and total carbohydrate as compared to normal condition.

Evaluation of Probiotics Ability to Enhance Population Density, Growth Rate, and Neonates Production of Moina micrura in Different Environmental Parameters

Salinity, light intensity, and oxygen concentration are key environmental factors that significantly affect biological processes and the composition and dispersion of Moina biomass. Evaluating the effectiveness of probiotic enrichment in improving population density, growth rate, and neonate production can provide valuable details on the effectiveness of probiotics in enhancing the resilience and viability of Moina micrura under suboptimal circumstances. The purpose of this research project is to assess the efficacy of two probiotics, Bacillus pocheonensis strain S2 and Lysinibacillus fusiformis strain A1, in improving the population density, growth rate, and reproductive output in M. micrura across various environmental conditions. Moina micrura were treated with each probiotic at a volume of 5 x 105 CFU/ml under different levels of salinity (0, 2, 4, and 6 ppt), light intensity (800, 1,000, 1,500, and 2,000 lux), and oxygen concentration (80, 70, 60, and 50%). The results indicated that M. micrura treated with L. fusiformis A1 at 0 ppt attained the highest population density (6 ± 0.90 Ind./ml), growth rate (0.355 ± 0.030 µ), and number of offspring production (5 ± 0.75 Ind./ml). The highest point of population density (5 ± 0.07 Ind./ml), growth rate (0.381 ± 0.002 µ) and number of offspring (7 ± 0.41 Ind./ml) of M. micrura were obtained while treated with B. pocheonensis S2 at light intensity of 1,500 lux. Similarly, the highest population density (5 ± 0.60 Ind./ml), growth rate (0.365 ± 0.190 µ), and offspring production (2 ± 0.25 Ind./ml) of M. micrura were observed during enrichment with B. pocheonensis S2 at 70% oxygen concentration. Therefore, these results suggested that the optimum conditions for enriching M. micrura with B. pocheonensis S2 are salinity of 0 ppt, 70% oxygen concentration, and a light intensity level of 1,500 lux.

Study on heavy metal leaching from steel slag in coastal soft soil and its environmental impact

ABSTRACT To explore the environmental impact of steel slag deposited within a coastal soft soil foundation, the steel slag produced by a steel plant in Fangchenggang city was chosen as a case study. Seawater was collected from the coastal foundation, and water with different levels of salinity was obtained by low-temperature evaporation, filtration, sterilisation, and dilution. Leaching tests of steel slag in artificial seawater with different levels of salinity were carried out according to the Toxicity Characteristic Leaching Procedure (TCLP). The results showed that with the increase in the leaching time and salinity of the solution, the concentration of heavy metals in solution displayed an upward trend; however, the rate of increase decreased once the concentration reached a certain level. From an environmental perspective, it is not advisable to use steel slag as a filler near drinking water, and steel slag should not be used as a foundation material in the high-salinity coastal soft soil layer.

New surfactants based on soybean oil triglycerides, hexamethylenediamine and alkyl dihalides

The interaction of soybean oil triglycerides with hexamethylenediamine resulted in a nonionic surfactant – hexamethyleneamide of a mixture of soybean oil acids, which was then modified using alkyl dihalides (1,2-dibromoethane, 1,3-dibromopropane, and 1,5-dibromopentane). These reactions synthesized ionic surfactants. The composition and structure of the resulting amidoamine and its modifications with alkyl dihalides were identified using infrared spectroscopy. The obtained products were characterized by key physicochemical parameters. Conductometric measurements of aqueous solutions of the obtained salts with varying concentrations were also performed. It was found that with increasing concentration, the specific conductivity value increases, and these values are significantly higher than the specific conductivity of distilled water, indicating the ionic structure of the obtained substances. Surface activity was measured with a tensiometer using the Du Nouy ring method at the air-water interface. According to the determined surface tension values, surface tension isotherms were constructed. The stabilization of surface tension values for the nonionic surfactant occurs at 35.2 mN/m, while for the ionic surfactants, it occurs at values of 34.2, 34.0, and 33.2 mN/m, respectively. The colloid-chemical properties of the synthesized surfactants were studied, their adsorption characteristics were experimentally determined, and the most important colloid-chemical parameters were calculated, such as the critical micelle concentration, surface tension, maximum adsorption, minimum cross-sectional area of the molecule, surface pressure, adsorption efficiency, and the change in Gibbs free energy of the micellization and adsorption processes. Under laboratory conditions, the relative oil-collecting and oil-dispersing abilities of the obtained products were investigated using thin films (thickness <1 mm) of Balakhani oil on the water surface with different levels of salinity (seawater, freshwater, and distilled water). The synthesized surfactants were used in undiluted form and as 5% aqueous solutions. It was found that in seawater, the maximum oil dispersion coefficient, which indicates the degree of cleaning the water surface, is 91.1%. It is worth noting that transitioning from nonionic to ionic surfactants increases the duration of the reagents’ action.

Effect of Humic Acid and Ascorbic Acid on Seed Germination and Growth of Cucumber (Cucumis sativus L.) under Salinity Stress

The aim of this study was to investigate the effects of Humic Acid (HA) and Ascorbic Acid (AsA) on cucumber growth under different levels of soil salinity. The experiment was designed as a factorial, using a completely randomized design in the laboratory of Samangan University in Afghanistan. The levels of salinity stress were set at (0, 50, and 100mM sodium chloride) while AsA and HA were set at (0, 30, and 60mM and 0, 1 and 2. L-l) respectively. The results of the analysis showed that the effect of all factors were significant on all studied traits. The highest mean daily germination (19%), root length (56.22mm), shoot length (39,06mm), fresh shoot weight (183.7mg), and seed vigor index were obtained from the (0mM salinity+60mM AsA+ 2g.L-l HA) treatment. Also the most germination percentage (95%), fresh root (45.88mg) and dry root (13.76mg), observed in (50mM salinity+0mM AsA+ 2g.L-l HA) treatment. However, the combined amounts of (60mM AsA+ 2g.L-l HA) were more effective for reducing different levels of salinity and increasing the growth characteristics of cucumber. Also, 2g L-l HA and 60mM AsA alone, were more effective. Treatments without AsA and HA showed the lowest growth in most traits. These findings suggest that the application of HA and AsA can help to improve cucumber growth under salt stress conditions.

Enhancing Bean (Phaseolus vulgaris L.) Resilience: Unveiling the Role of Halopriming against Saltwater Stress

Common bean (Phaseolus vulgaris L.), one of the most important cultivated legumes, requires a high level of water. It is included among the most sensitive species to climate change; drought and salinity cause a reduction in photosynthesis, metabolic and enzymatic alterations, and oxidative stress. To improve crop tolerance to salt, seed priming and acclimation can be useful tools. To test the salt tolerance of beans, a preliminary screening was undertaken on four cultivars of P. vulgaris (Black Turtle, Cargamanto, Bola Roja, Borlotto) by exposing the seeds to different levels of salinity. The salt-sensitive cultivar Borlotto was chosen for experimental greenhouse trials to study the effects of halopriming and acclimation. Primed and non-primed seeds were sown in non-saline soil and acclimated for 2 weeks; then, the plants were watered with non-saline and saline solutions for 4 weeks. At the end of this growth period, the primed plants showed a marked increase in salt stress tolerance, improving the chlorophyll content, phenolic compounds, and many enzymes’ activities, in turn reducing the effect of salt on growth and fruit production compared to the non-primed controls. In conclusion, halopriming can be considered a useful tool to enhance salinity tolerance in beans and other salt-sensitive crops.

Yield and Bio-Chemical Parameters of Onion (Allium Cepa L.) and Consequences of Saline Irrigation Water on It

At Department of Agricultural Chemistry and Soil Science a pot experiment was conducted during the rabi, season of 2017-18. Department of Agricultural Chemistry and Soil Science situated at College of Agriculture, Junagadh Agricultural University, Junagadh, Gujarat. The objective of the study is to assess the consequences of saline irrigation water on yield of Onion (Allium Cepa L.) varieties. The study also possess the growth and nutrients composition of Onion (Allium Cepa L.) varieties and effect of saline irrigation water on it. Four levels of salinity are contained viz., < 2.0, 4.0, 6.0 and 8.0 dS m-1. GJWO-3, GJRO-11, Talaj red, Pilli patti and PWF-131 these five varieties comprised in factorial completely randomized design with three replications. It found that the yield of chlorophyll a (5.77 mg/gf.wt), chlorophyll-b (4.22 mg/gf.wt), and total chlorophyll were significantly influenced by different levels of salinity, whereas; yield of fresh straw (37.03 g/pot), bulb (37.49 g/pot), RWC, proline (0.96 µmole/gf.wt), were significantly influenced among different varieties of onion tested.

Physiological responses, ion accumulation and yield performance of wheat (Triticum aestivum L.) to salt stress

Wheat is affected by various biotic and abiotic stresses, especially salinity, which reduces the growth and yield drastically. High salinity is a major constraint for wheat productivity in many countries, including Bangladesh. With this view, here, an experiment was conducted to observe genotypic differences in physiological, ion accumulation, agro-morphological and yield performance of wheat against different levels of salinity. Experimental variables consisted of five salt tolerant genotypes (G 20–2–2, G 20–1–2, G 13–2, G 22–2, G 9–2), one susceptible genotype (G 24–2) and one standard check variety (BARI ghom 25), which assigned to four levels of salinity with electrical conductivities control (0.3), 4, 8 and 12 dS m−1. Irrespective of genotypes, salinity stress significantly decreased the yield and yield attributes. Results of analyses based on salt tolerance indices of plant growth related and yield contributing parameters, ionic balance (Na+, K+ and Na+ /K+ ratio), and stress indicators such as chlorophyll content, photosynthetic rate (Pn), stomatal conductance (gs) and transpiration rate (Tr) revealed genotypes G 20–2–2, G 13–2 and G 20–1–2 as salt tolerant, genotype G 9–2 as moderately salt-tolerant and G 24–2 and G 22–2 as salt-sensitive genotypes. Additionally, lower accumulations of hydrogen peroxide and malondialdehyde, and higher activities of antioxidant enzymes in the salt-tolerant genotypes G 20–2–2 and G 13–2 than in the salt-sensitive genotype G 24–2 indicated reduced oxidative damage in genotypes G 20–2–2 and G 13–2 relative to that in genotype G 24–2. Collectively, our findings suggest that the optimum growth and yield of salt tolerant genotypes are associated with decreased Na+/K+ ratio, increased antioxidant enzymes activity and reduced oxidative stress.

Effect of Salinity Stress on the Morphological and Physiological Characteristics of Peppermint under Greenhouse Condition

Peppermint is a rich source of valuable compounds with therapeutic, coloring, preservative and other uses for humans. Peppermint is used in food, perfumery and medicine all over the world. Higher plants experience salt stress due to an excessive buildup of sodium chloride; salinity impacts plants through osmotic stress and toxicity. Salinity impacts every major activity in plants, including growth, photosynthesis, lipid metabolism, protein synthesis, energy production, and germination through biomass and seed formation. The experiment was carried out in the research farm of agriculture faculty of Lorestan University, Iran. The aim of the current research was to examine the effect of different levels of salinity (0, 50 and 100 mM) on the morphological and physiological characteristics of peppermint in the greenhouse. The result showed that salinity stress at 50 and 100 millimole (mM), decreased plant height (11.76%, 23.53%), number of leaves (25.11%, 33.92%), leaf surface (24.76%, 56.37%), crown diameter (14.15%, 25.47%), root length (20.61%, 31.58%), leaf fresh weight (14.47%, 30.47%), leaf dry weight (1.16%, 12.69%), fresh weight of stem (10.78%, 21.11%), dry weight of stem (16.32%, 37.76%), chlorophyll a (46.08% and 61.09%), Chlorophyll b (32.48% and 41.65%), total chlorophyll (40.84% and 53.59%) and carotenoid (34.67% and 67.02%) compared to the control conditions respectively. Hence, increase in salinity concentration at 50 and 100 mM, increased the amount of malondialdehyde (MDA) (37.06% and 73.63%), leaf proline (301.50% and 382.09%) and essential oil (100.40% and 80.32% compared to control. The results of this study showed that, the salinity stress had a significant effect on the morphological, physiological and biochemical characteristics of peppermint. The results showed that, increases in the salinity stress, significantly increased the amount of electrolyte leakage, production of essential oil, malondialdehyde and proline. Moreover, increase salinity levels in irrigation water, caused reduction in growth characteristics of peppermint. It is to be concluded that, Peppermint is a semi-salt resistant plant, cultivation of peppermint in the medium saline soil is recommended.

The role of endophytic bacteria in increasing nitrogen concentration, root length, and dry weight of rice plants (Oryza sativa L.) in saline soil

Soil salinity can interfere with the absorption of water and plant nutrients, causing a decrease in growth and yield of rice plants in saline soil. This negative effect can be reduced by the application of endophytic bacteria biofertilizer. Endophytic bacteria live in plant tissues and play a role in increasing plant growth through nitrogen fixation or growth hormone production. The purpose of this study was to determine the effect of endophytic bacterial biofertilizer application on N concentration, root length, and dry weight of rice seedlings (Oryza sativa L.) in soils with different salinities. This research was conducted in the greenhouse of the Faculty of Agriculture, Universitas Padjadjaran. The experimental design used was a Randomized Block Design (RBD) with 8 combinations. The treatments were with and without endophytic bacterial biofertilizers, and soils with different levels of salinity (non-saline soil and saline soil with salinities of 2, 4, and 6 mmhos cm-1) and repeated 4 times. The experimental results showed that the combination treatment of endophytic bacterial biofertilizer in saline soil of 2 mmhos cm-1 was able to increase the N concentration, root length, and dry weight of rice plants which were higher than the treatment of endophytic bacterial biofertilizer in soil with salinity of 4 and 6 mmhos cm-1. The application of endophytic bacteria biofertilizer has higher dry weight of rice plants than without endophytic bacteria at each different salinity level.

Bacterial Endophytes from Legumes Native to Arid Environments Are Promising Tools to Improve Mesorhizobium-Chickpea Symbiosis under Salinity.

Symbiotic nitrogen fixation is a major contributor of N in agricultural ecosystems, but the establishment of legume-rhizobium symbiosis is highly affected by soil salinity. Our interest is focused on the use of non-rhizobial endophytes to assist the symbiosis between chickpea and its microsymbiont under salinity to avoid loss of production and fertility. Our aims were (1) to investigate the impact of salinity on both symbiotic partners; including on early events of the Mesorhizobium-chickpea symbiosis, and (2) to evaluate the potential of four non-rhizobial endophytes isolated from legumes native to arid regions (Phyllobacterium salinisoli, P. ifriqiyense, Xanthomonas translucens, and Cupriavidus respiraculi) to promote chickpea growth and nodulation under salinity. Our results show a significant reduction in chickpea seed germination rate and in the microsymbiont Mesorhizobium ciceri LMS-1 growth under different levels of salinity. The composition of phenolic compounds in chickpea root exudates significantly changed when the plants were subjected to salinity, which in turn affected the nod genes expression in LMS-1. Furthermore, the LMS-1 response to root exudate stimuli was suppressed by the presence of salinity (250 mM NaCl). On the contrary, a significant upregulation of exoY and otsA genes, which are involved in exopolysaccharide and trehalose biosynthesis, respectively, was registered in salt-stressed LMS-1 cells. In addition, chickpea co-inoculation with LMS-1 along with the consortium containing two non-rhizobial bacterial endophytes, P. salinisoli and X. translucens, resulted in significant improvement of the chickpea growth and the symbiotic performance of LMS-1 under salinity. These results indicate that this non-rhizobial endophytic consortium may be an appropriate ecological and safe tool to improve chickpea growth and its adaptation to salt-degraded soils.

The impact of Saccharomyces cerevisiae stimulation on various physiological indicators of oats (Avena sativa) exposed to salinity

Abstract. Abdulfatah HF, Naji EF. 2023. The impact of Saccharomyces cerevisiae stimulation on various physiological indicators of oats (Avena sativa) exposed to salinity. Biodiversitas 24: 6753-6760. The objective of the current study is to examine the effects of different levels of salinity, specifically 0, 2.5, and 4.5 ds m-1(S1, S2, S3), on diverse physiological parameters in two principal oat cultivars (Avena sativa L.), Pimula (A1), and Genzania (A2), priming with Saccharomyces cerevisiae for 24 hours at a concentration of 0 and 6 g.L-1. The study employed a completely randomized design with three repetitions for each treatment and was conducted at the laboratory of the College of Science, University of Anbar. The Genzania cultivar that was not stimulated with yeast demonstrated the highest percentage of total chlorophyll content (2.28 mg. g. plant-1), statistically significant (P?0.05) compared to the lowest rate recorded by the Pimula cultivar (1.94 mg. g. plant-1). While no significant differences appeared between both cultivars stimulated with yeast under the influence of the salinity concentrations, the S2 treatment had the highest rate and significantly more than the S3 treatment. This demonstrates increased tolerance of the yeast priming cultivars to salinity treatment. The A2 cultivar was characterized by the highest rate of proline in plants stimulated and not stimulated with yeast, with significant differences from the A1 cultivar. However, the S3 treatment had the highest rate of proline (20.96?mole g plant-1) in the stimulated plants, with a higher significance than treatment S2. There was a statistically significant in the electrolyte leakage rate between the non-stimulated cultivars. In contrast, no significant differences appeared for the plants stimulated with yeast, indicating an increase in their tolerance to salinity. Priming seeds with yeast extract has been shown to improve important physiological characteristics in plants, such as total chlorophyll content, proline content, and electrolyte leakage, indicating the effectiveness of yeast in increasing plant resilience to salt stress.

Reducing heavy metal (Zn, Cu) toxicity in a semi-arid area by halophytes

This work is the subject of a study of the effect of Atriplexhalimus on the variability of the percentage of certain heavy metals in the region of Boukhadra-Ouanza north of Tébessa, which is characterized by the proximity of an ancient mining area and with different levels of salinity. Where we made field trips, the first to know the area and determine the sampling locations, and the second to take samples. The latter (soil surrounding the roots of the cut plant and soil without vegetation at a distance of one meter), then after we measured the salinity standards (electrical conductivity and the percentages of certain heavy metals. The samples were analyzed at the Geology Laboratory, Faculty of Nature and Life Sciences, University of Tébéssa, where soil CE calculated and compared to the percentage of heavy metals (zinc and copper) in the soil. The results showed the presence of a significant proportion of heavy metals such as zinc and copper, especially in the third study area, which is considered high by World Health Organization standards and to acceptable standards, because the latter is located near an abandoned mining area, unlike the high salinity factor in the first and second areas.

Quantitative and Qualitative Responses of Hydroponic Tomato Production to Different Levels of Salinity

Quantitative and Qualitative Responses of Hydroponic Tomato Production to Different Levels of Salinity

β-Aminobutyric acid enhances salt tolerance of African marigold by increasing accumulation rate of salicylic acid, γ-Aminobutyric acid and proline

African marigold (Tagetes erecta L.) is one of most cultivated warm-season flowers which is used as cut flower, potted flower or margin flower. Nowadays, one of the most common issues of landscaping is sensitivity of ornamental plants to salinity of soil or irrigation water. In order to investigate the role of β-Aminobutyric acid (BABA) treatments in alleviation of adverse effects of salt stress on African marigold, a factorial experiment was conducted based on completely randomized design with 3 replications during 2022–2023. The experimental treatments included different concentrations of BABA (0, 4, 8 and 12 mM) and different levels of salinity (0, 50, 100 and 150 mM NaCl). Results demonstrated that the negative effects of salinity on marigold characteristics increased by increasing the salinity level, but BABA treatments effectively alleviated the adverse effects. Fresh and dry weight of shoots and root, leaf relative water content, total chlorophyll and carotenoid content, the activity rate of phenylalanine ammonia lyase, catalase and superoxide dismutase, and the accumulation rate of salicylic acid, γ-Aminobutyric acid (GABA) and proline were significantly increased by treatment of marigold plants with BABA 8 mM. Also, this treatment maintained plant phenol and protein content, and reduced H2O2 content, malondialdehyde content and electrolyte leakage under salinity conditions. Accumulation of salicylic acid, GABA and proline caused by BABA treatment could probably be one of most important mechanisms of enhancing salt tolerance rate of marigold plants in this study, therefore, it is recommended to use this treatment as innovative and efficient technique to overcome salinity effects on African marigold plants.

Reducing heavy metal (Zn, Cu) toxicity in a semi-arid area by halophytes

This work is the subject of a study of the effect of Atriplexhalimus on the variability of the percentage of certain heavy metals in the region of Boukhadra-Ouanza north of Tébessa, which is characterized by the proximity of an ancient mining area and with different levels of salinity. Where we made field trips, the first to know the area and determine the sampling locations, and the second to take samples. The latter (soil surrounding the roots of the cut plant and soil without vegetation at a distance of one meter), then after we measured the salinity standards (electrical conductivity and the percentages of certain heavy metals. The samples were analyzed at the Geology Laboratory, Faculty of Nature and Life Sciences, University of Tébéssa, where soil CE calculated and compared to the percentage of heavy metals (zinc and copper) in the soil. The results showed the presence of a significant proportion of heavy metals such as zinc and copper, especially in the third study area, which is considered high by World Health Organization standards and to acceptable standards, because the latter is located near an abandoned mining area, unlike the high salinity factor in the first and second areas.

Asymmetric Nanoporous Alumina Membranes for Nanofluidic Osmotic Energy Conversion.

The potential of harnessing osmotic energy from the interaction between seawater and river water has been recognized as a promising, eco-friendly, renewable, and sustainable source of power. The reverse electrodialysis (RED) technology has gained significant interest for its ability to generate electricity by combining concentrated and diluted streams with different levels of salinity. Nanofluidic membranes with tailored ion transport dynamics enable efficient harvesting of renewable osmotic energy. In this regard, anodic aluminum oxide (AAO) membranes with abundant nanochannels provide a cost-effective nanofluidic platform to obtain structures with a high density of ordered pores. AAO can be utilized in constructing asymmetric composite membranes with enhanced ion flux and selectivity to improve output power generation. In this review, we first present the fundamental structure and properties of AAO, followed by summarizing the fabrication techniques for asymmetric membranes using AAO and other nanostructured materials. Subsequently, we discuss the materials employed in constructing asymmetric structures incorporating AAO while emphasizing how material selection and design can resist and promote efficient energy conversion. Finally, we provide an outlook on future applications and address the challenges that need to be overcome for successful osmotic energy conversion.

Salinity Tolerance, Seasonal and Multiyear Dynamics of Biting Midges (Diptera, Ceratopogonidae) in Macrozoobenthos Communities of Saline Rivers (the Lake Elton Basin, Russia)

The results of long-term studies of biting midges (Diptera, Ceratopogonidae) in macrozoobenthos communities of five saline rivers of the hyperhaline Lake Elton basin are presented. The fauna of Ceratopogonidae includes 5 halophilic and euryhaline species, among which representatives of the tribe Palpomyiinae predominate. Taxonomic composition of the family differs in rivers with different levels of salinity. Species Sphaeromias miricornis and Culicoides riethi are widely distributed in mesohaline the Khara, the Lantsug and the Bolshaya Samoroda rivers, and P. schmidti widely distributed in polyhaline the Chernavka and the Solyanka rivers. Two generations of S. miricornis and three generations of P. schmidti were recorded. Departure of the first generation of P. schmidti occurs in mid-May, S. miricornis in late May–early June. There is an increase in mean annual abundance and biomass of biting midges in polyhaline rivers compared to mesohaline rivers.

In Vitro Assessment of Eight Selected Indigenous Fungal Isolates Tolerance to Various Abiotic Stresses and their Effects on Seed Germination

Fungal bio-control agents (BCA) can minimize use of agro-chemicals while increasing plant productivity and tolerance to biotic-abiotic stressors. Ideally, BCA should tolerate varying environmental conditions they are introduced into, to successfully dominate and protect plants from stressors. However, BCA are living micro-organisms, their survival and efficacy can be impeded by extreme conditions. The current study aimed at evaluating whether indigenous fungal isolates, viz, Aspergillus flavus, A. terreus, Penicillium sp. AL-38 IRH-2012b, Talaromyces minioluteus, T. purpureogenus, T. sayulitensis, Trichoderma ghanense and T. viride can tolerate different levels of salinity, pH, nutrient and temperature. Certain fungal species are pests with potential of destroying many crops; the pathogenic effects of the aforementioned fungal isolates were further assessed on different crops’ seeds. The results showed that, although being indigenous, Aspergillus, T. sayulitensis and T. ghanense failed to thrive in high salinity and pH. While Penicillium sp. AL-38 IRH-2012b failed to thrive under reduced nutrient level and all fungal isolates failed to grow at 10–20 °C. Furthermore, it was noted species within the same genus could affect crops in both favorable and unfavorable ways. The study demonstrated that the selected indigenous fungal isolates can tolerate different abiotic conditions and have potential to improve seed germination and seedling growth.

Salinity and Variety Effects on Yield, Yield Attributes and Soil of Tomato under Greenhouse Conditions of Central Fiji

Background: Tomato (Lycopersicon esculentum Mill) is a widely cultivated vegetable crop worldwide, including in Fiji. However, the suitability of tomato cultivation under greenhouse conditions in the central region of Fiji, which experiences salinity issues, remains unclear. Methods: A pot experiment was conducted at the Instructional Agricultural Farm Complex of the College of Agriculture, Fisheries and Forestry, Fiji National University, Fiji, to determine the effect of different levels of salinity on the growth and yield of tomato (Lycopersicon esculentum Mill) varieties. The experiment included two factors: three tomato varieties (V1= Melrose; V2= Alton; V3= Alafua Large) and four levels of NaCl salinity (T1= Control; T2= 2 dSm-1; T3= 4 dSm-1 and T4= 8 dSm-1) randomized thrice in a randomized complete block design. The effects of various varieties and salinity levels on tomato yield were studied in this experiment. Result: The results revealed that variety Alafua Large performed comparatively better in all cases. This recorded maximum fruit length (4.22 cm), fruit breadth (3.31 cm), individual fruit weight (45.60 g), number of fruits (7.83) and fruit yield (352.10 g) whereas Alton recorded the minimum of the above yield attributes. In the case of the combined effect of variety and salinity, Alafua Large showed better yield (432.17 g and 394.51 g) per plant than the other varieties when combined with the lower salinity level i.e., EC 2 dSm-1 and 4 dSm-1, respectively. The yield of tomato varieties declined with the increasing salinity level condition. The yield of Alafua Large was 194.54 g when applied with the highest level of salinity i.e., EC 8 dSm-1 and the yield of Alton was 64.69 g which was the lowest yield among the varieties with the highest level of salinity condition. Therefore, from the results, Alafua Large is comparatively more salt tolerant than the other varieties which were studied in this experiment.