JWSS - Journal of Water and Soil Science

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A major limitation for higher yield of rice plant is water availability. Water use efficient varieties tolerant to upland conditions could help to relax this limitation. Three separate experiments were conducted to study the effects of water regimes on growth, aerenchyma formation, and nutrient absorption of Iranian rice varieties. In the first experiment, five varieties of rice were grown under three different irrigation levels. The second experiment involved the study of nutrient uptake by Sazandagee and Tarom varieties under four different water regimes, and in the third experiment, the effect of aeration on growth characteristics of Sazandagee rice was assessed in a hydroponics system. Results of the first experiment showed that submerged conditions continuously or after four weeks of initial growth had a significant effect on plant growth. Aerenchyma formation was affected by rice varieties and was less affected by irrigation status. In the second experiment, plant growth characteristics were affected similar to experiment one. Also it was shown that nutrients such as P, Mg, and Fe were absorbed with higher efficiency under submerged conditions. Results of the third experiment revealed that aeration had no significant effect on plant growth characteristics. Based on the results of these three experiments, it can be concluded that better performance of rice plant under continuous or partial flooding is mainly related to higher absorption of some macro - and micronutrients. Therefore, this parameter should be considered in water management programs for rice.

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Endophytic fungi, Neotyphodium spp. symbiotically infect host grasses, Fescue arundinacea Schreb. and F. pratensis Huds. and Mealybug, Phenococcus solani Ferris attacks some forage plants. To evaluate the role of these fungi to control this pest, four genotypes of F. arundinacea and two genotypes of F. pratensis were used. Plant tillers were split into two sections, one section of which was freed from endophyte using a fungicide mixture. The mixture contained 2 grams of active ingredients of Propiconazol and 1 ml of Folicur per liter of water. New tillers from endophyte-infected and endophyte-free plants were transferred into the field. The number of mealybugs was measured after the first visible sign of infestation on roots. To count mealybug, one plant hill of each plot was randomly selected. Hay yield of each plot was measured by clipping the plants 5 cm above ground level. Correlation of hay yield and other growth characteristics with the number of mealybugs on roots as an index for mealybug damage on infested plants was determined. The results indicated that endophyte-free plants were highly infested with mealybug, P. solani compared with endophyte-infected plants that were completely free of P. solani, correlation coefficients showed that there was significant negative correlation between forage yield and mealybug numbers, indicating mealybug damage on infested plants. It seems that endophytic fungi are effective biocontrol factors for some root feeding pest such as mealybug, P. solani.

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In order to evaluate endophyte effect on plant earliness, compatible host-endophyte combinations including four genotypes of tall fescue and two genotypes of meadow fescue were selected and used in this study. One tiller-part of each genotype was treated using a fungicide mixture of Propiconazole and Folicur. New tillers of endophyte-infected and endophyte-free plants were planted in the field according to a complete block design with three replications. The traits including days to head emergence, days to 50% anthesis, days to maturity initiation, number of heads (as a weekly measurement), total seed weight, net seed weight and empty seed weigh were measured. Results showed that endophytes can enhance head emergence, maturity initiation and periodical seed yield. Days to 50% anthesis, and days to maturity initiation were also reduced. Head numbers in some genotypes increased up to 2 times. Increase in net seed yield may show some physiological alterations in plant such as hormonal balance alteration which may provide better seed setting in infected plants. Based on this study, we concluded that endophytic fungi can induce earliness in infected host plants.

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Fescues (Festuca spp) are widely distributed in the temperate regions and are used for turf, forage and soil conservation. Though seed traits are important measures of the effects of endophytic fungi on their host, little information is available in this respect for Festuca. In this study, endophyte-infected (E⁺) and endophyte-free (E^-) clones of the six fescue genotypes were used to investigate the effects of endophyte on seed production. The relationships between seed traits plus direct and indirect effects of components on seed yield were also studied. Endophyte infection resulted in 38.1% to 249% more seed yields in some genotypes, though some were not affected by this symbiotic relationship. Correlations between traits and also results of stepwise regression were influenced by the presence of the symbiotic fungi. Path analysis showed that endophytic fungi changed direct and indirect effects of components on seed yield. In endophyte containing clones, panicle fertility had the most direct effects and number of panicle per plant and seed per panicle the most indirect effects on seed yield. In E- clones, panicle fertility had the highest indirect effects and other components had direct effects on seed yield. The results suggested that breeding strategies for increasing seed yield in fescue should consider the presence or absence of endophyte in germplasm.

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During recent years, several genotypes have been selected from Isfahan land race Kouseh. The performance of safflower selected genotypes was studied in the field conditions, at Agriculture Research Station, Isfahan University of Technology during 2003. The experiment was carried out using a split plot arrangement according to a randomized complete block design with three replications. Planting dates (March 11, April 20, May 22 and June 23) were considered as the main plots and subplots consisted of 20 genotypes of safflower including 19 selections from Kouseh and Arak-2811 genotype. Days from planting to emergence and emergence to stem elongation were reduced as planting was delayed until the fourth planting date. Days from stem elongation to head visible was reduced with delay from the first to the third planting date, and then increased. Days from head visible to 50% flowering was reduced with delay from the first date to the third planting date, but increased in the fourth planting date. Days from 50 percent flowering to physiological maturity was increased with delay in planting. Days from planting to emergence, emergence to stem elongation, stem elongation to head visible and 50 percent flowering to physiological maturity were not influenced by genotypes. Genotype DP7 had the highest and genotype C111 and genotype DP25 had the lowest days from head visible to 50% flowering. The interaction between planting date and genotype in regard to days from stem elongation to head visible was also significant. Seed weight per plant was reduced with delay in planting date. Genotype ISF66 had the highest and genotype Arak-2811 had lowest seed weight per plant. The number of days from emergence to head visible in ISF66, DP5, C128 and Arak-2811 was affected by maximum temperature (Tmax), in genotype DP7 by Tmax², in genotypes DP17, DP1 and C41100 by Tmin² and in genotypes DP9, DP25, ISF28, ISF22, and C111 was affected by day length. It seems that development period from emergence to head visible was affected by temperature in the most genotypes. On March 11 planting date, genotypes had the maximum response to temperature and day length and the minimum response was observed in the fourth planting date. The genotype ISF66 had the highest seed yield on March 11 planting date. The result of this study showed that safflower should be planted in late March under condition similar to this experiment for maximum yield production.

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Safflower having oil with high unsaturated fatty acids is a very valuable plant. However the sensitivity of safflower to some pests as safflower fly (Acanthiophilus helianthi), particularly in drought stress conditions has limited its production. In order to evaluate the effect of drought stress on population density and damage of important safflower pests, especially safflower fly, an experiment was conducted in the field using 5 irrigation treatments including 50, 70, 90, 110 and 130 mm evaporation from class A pan in a randomized complete block design with three replications. The local safflower variety used in this study was Isfahan land variety, Kooseh. In each irrigation regime, the half of one plot was locally sprayed by Chlorpyrifos in 2ml per liter of water to be compared with non-sprayed part. During 8 weeks of sampling, population of aphids, Uroleucon carthami, leafhopper, Empoasca decipiens and safflower fly, A. helianthi and also percentage of damaged heads by safflower fly were measured. The results showed that in non-sprayed conditions, the highest safflower fly (2.38 flies per net) and aphid population (165.57 aphids per plant) was observed at 130 mm evaporation regime. Drought stress also decreased (30.23 %) safflower seed yield. Severe drought stress together with non-spaying may increase safflower pests population particularly safflower fly and reduce seed yield. However low level of drought stress (70 mm evaporation from class A pan) may decrease relative number of insects and save irrigation water. Drought stress also decrease the population of leafhopper. In this study, 70 mm evaporation regime was the optimum irrigation treatment regarding lower aphid and fly damage (15.86% damaged heads in non-sprayed condition) and higher safflower seed yield (1687.5 kg/ha in sprayed condition).

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Soil water repellency can affect several soil properties such as aggregate stability. Soil texture and organic matter are two main internal factors responsible for the variability of soil water repellency. Major sources of organic matter in soil include plant residues, and exudates of plant roots and soil microorganisms. Tall fescue (Festuca arundinacea Schreb.) as an important cool-season perennial forage grass is usually infected by a fungal endophyte (Epichloë coenophiala) which often enhances resistance to biotic and abiotic stresses as well as altering the litter decomposition rate and soil properties. In this study, the effects of endophyte-infected (E+) and endophyte-free (E−) tall fescue residues (in three different levels of 0, 1 and 2%) on soil organic carbon, basal microbial respiration, water-dispersible clay and water repellency index (determined by intrinsic sorptivity method) were investigated in four texturally-different soils in the laboratory. E+ and E− tall fescue residues were completely mixed with moist soil samples and then were incubated at 25 °C. During two months of incubation period, the amended soil samples were subjected to 10 wetting and drying cycles and then, the above-mentioned soil properties were measured. The results indicated that soil organic carbon and water-dispersible clay were greater, while basal soil respiration and repellency index were lower in fine-textured soils. Water repellency index was increased by production of hydrophobic substances (for the rate of 1%) and was reduced by induced greater soil porosity (for the rate of 2%). Presence of endophyte in plant residues had no significant effect on water sorptivity, ethanol sorptivity and water repellency index; nevertheless, E+ residues increased soil organic carbon and decreased water-dispersible clay significantly. Overall, it is concluded that tall fescue residues, especially those with E+, can improve soil physical quality due to improving soil organic carbon storage and water repellency index and decreasing water-dispersible clay (as an index for aggregate instability). These E+ species and the residues have great potential to be used in sustainable soil conservational managements.