Effects of bovine spermatozoa preparation on embryonic development in vitro

The aim of our research was to examine the ability of density gradient preparation BoviPure^? and swim up method on bull sperm separation and in vitro embryo production (IVP) systems. Frozen/thawed semen from six Simmental bulls was pooled and treated using both methods. The sperm motility, concentration, membrane activity, membrane integrity and acrosomal status were evaluated and compared before and after sperm processing using BoviPure^? and swim up methods. We also evaluated and compared cleavage rates, embryo yield and quality between the methods. There were significant differences (P < 0.05) between the sperm characteristics before and after BoviPure^?, but not after swim up method. However, there were significant differences for sperm results among those two mentioned methods. A total of 641 oocytes were matured and fertilized in vitro and cultured in SOFaaBSA. The percentage of cleavage (Day 2) and the percentage of hatched embryos (Day 9) were similar for both methods. However, embryo production rate (Day 7) was significantly higher using BoviPure^? method (P < 0.05). Also, total cell number and embryo differential staining (inner cell mass and trophectoderm cells) of Day 7 morulas and blastocysts showed that BoviPure^? treated sperm displayed higher quality embryos compared to swim up method (P < 0.05). Our results indicate that BoviPure^? method has an enhanced capacity in sperm selection for in vitro embryo production when compared with swim up method. So, we concluded that BoviPure^? could be considered as a better alternative to swim up method for separating bull spermatozoa from frozen/thawed semen for IVP of bovine embryos.     

Early events responsible for aluminum toxicity symptoms in suspension-cultured tobacco cells

We investigated the aluminum (Al)-induced alterations in zeta potential, plasma membrane (PM) potential and intracellular calcium levels to elucidate their interaction with callose production induced by Al toxicity. A noninvasive confocal laser microscopy has been used to analyse the live tobacco (Nicotiana tabacum) cell events by means of fluorescent probes Fluo-3 acetoxymethyl ester (intracellular calcium) and DiBAC4 (PM potential) as well as to monitor callose accumulation. Log-phase cells showed no detectable changes in the PM potential during the first 30 min of Al treatment, but sustained large depolarization from 60 min onwards. Measurement of zeta potential confirmed the depolarization effect of Al, but the kinetics were different. The Al-treated cells showed a moderate increase in intracellular Ca2+ levels and callose production in 1 h, which coincided with the time course of PM depolarization. Compared with the Al treatment, cyclopiazonic acid, an inhibitor of endoplasmic reticulum Ca(2+)-ATPase, facilitated a higher increase in intracellular Ca2+ levels, but resulted in accumulation of only moderate levels of callose. Calcium channel modulators and Al induced similar levels of callose in the initial 1 h of treatment. Callose production induced by Al toxicity is dependent on both depolarization of the PM and an increase in intracellular Ca2+ levels.     

Chickpea facilitates phosphorus uptake by intercropped wheat from an organic phosphorus source

Pot experiments were conducted to investigate interspecific complementation in utilization of phytate and FePO₄ by plants in the wheat (Triticum aestivum L.)/chickpea (Cicer arietinum L.) intercropping under sterile and non-sterile conditions. The pots were separated into two compartments by either a solid root barrier to eliminate root contact and solute movement, by a nylon mesh (30 M) to prevent root contact but permit solute exchange, or not separated between the compartments. Wheat plants were grown in one compartment and chickpea in the other. Two P sources were tested at 60 mg P kg^–1 soil (sodium phytate or FePO₄). Under non-sterile conditions, the biomass of wheat was significantly greater when the roots were intermingled with chickpea than when the roots were separated from chickpea roots by a solid root barrier or nylon mesh. When phytate–P was applied, P concentrations in wheat (2.9 g kg^–1 in shoots and 1.4 g kg^–1 in roots) without root barrier between the two species were higher than those in the treatments with nylon mesh or with the solid root barrier separation (1.9 g kg^–1 in shoots and 1.0 g kg^–1 in roots). In contrast, P concentrations in wheat supplied with FePO₄ were similar between the root separation treatments. There was no significant difference in P uptake by chickpea between the P sources or between the root separation treatments, except that P uptake was greater in the phytate treatment with the root barrier. Total P uptake from phytate was increased by 25% without root separation compared to the root separation treatments. Under sterile conditions and supply of phytate–P, the biomass of wheat was doubled when the roots were intermingled with chickpea and increased by a third with the nylon mesh separation compared to that with the solid root barrier. Biomass production in wheat at various treatments correlated with P concentration in shoot. Biomass production and P concentration in chickpea were unaffected by root separation. Total P uptake by plants was 68% greater with root intermingling and 37% greater with nylon mesh separation than that with the solid root barrier. The results suggest that chickpea roots facilitate P utilization from the organic P by wheat.     

Time-course of Biosynthesis of Phenolics and Lignin in Roots of Wheat Genotypes Differing in Manganese Efficiency and Resistance to Take-all Fungus

Inhibition of lignin biosynthesis in Triticum aestivum L. rootsby Mn deficiency has been suggested as the mechanism of reducedresistance of Mn-deficient wheat roots to infection by the take-allfungus (Gaeumannomyces graminis var. tritici). This study evaluatedphenolics and lignin accumulation in roots of wheat genotypesdiffering in Mn efficiency (measured as growth and yield inMn-deficient soils) and take-all resistance. Seedlings of theMn-inefficient, take-all sensitive genotype Bayonet and theMn-efficient, more take-all resistant genotype C8MM were grownin nutrient solution without added Mn for 18 d and then transferredto a Mn-deficient sandy soil fertilized with Mn at 0 or 30 mgkg^-1. Both genotypes had Mn-deficient roots and shoots at thetime of transfer to the soil. Roots of both genotypes were inoculatedwith the take-all fungus 0, 1, 3 and 7 d after transfer. Twenty-fourhours after inoculation, take-all fungus penetrated the rootstele of take-all sensitive Bayonet but not of more resistantC8MM wheat. Rates of phenolics and lignin accumulation in rootsdeclined steadily during growth in soil for up to 8 d, werehigher in mature, fully differentiated parts of the root systemcompared to distal, younger root tissue, and were higher inBayonet than in C8MM. Manganese fertilization did not significantlyinfluence rates of phenolics and lignin accumulation but reduceddepth of radial penetration by hyphae in both genotypes. Therate of phenolics accumulation was positively (r = 0·91to 0·96) correlated with the rate of lignin accumulation.Mn-efficient C8MM had a higher rate of lignin accumulation perunit of phenolics than Mn-inefficient Bayonet over a wide rangeof phenolics synthesis rates. From this we suggest that C8MMhas a more efficient mechanism for conversion of phenolics tolignin, the trait which appears related to higher take-all resistanceof this genotype.Copyright 1994, 1999 Academic Press Gaeumannomyces graminis var. tritici, lignin, manganese, phenolics, resistance, roots, Triticum aestivum     

Zinc fertilisation increases tolerance to Rhizoctonia solani (AG 8) in Medicago truncatula

The effect of Zn fertilisation on tolerance of Medicago truncatula to infection by the root-rotting pathogen Rhizoctonia solani (AG 8) was studied in a field survey and in two experiments in controlled conditions. From the field survey, the concentration of Zn in the shoots of medics was found to be inversely related to the severity of disease on the root. Overall, the addition of Zn to Zn-deficient soil in controlled environment experiments resulted in reduced yield loss in the presence of R. solani, a reduction in disease score and no change in the concentration of nutrients in the shoots. However, under Zn deficiency, increasing levels of added R. solani resulted in significant yield loss, an increase in disease score and a reduction in concentration of Zn in the roots. This occurred despite a decrease in the number of infection sites caused by the fungus on the root and a lower amount of R. solani DNA extracted in medics deficient in Zn compared with plants supplied with Zn. While plants supplied with Zn were able to maintain a stable concentration of Zn in the shoots, the concentration of Zn in the roots also declined with increasing levels of R. solani. In conclusion, Zn application does not directly inhibit infection by R. solani, nor reduce its pathogenicity, but it does strongly increase root growth. The net result is that Zn-sufficient plants are more tolerant to the effects of root pruning by the fungus than Zn-deficient plants.     

Red-shifted light-harvesting system of freshwater eukaryotic alga Trachydiscus minutus (Eustigmatophyta,Stramenopila)

Photosynthesis Research - Survival of phototrophic organisms depends on their ability to collect and convert enough light energy to support their metabolism. Phototrophs can extend their absorption...     

Genotypic variation in zinc efficiency and resistance to crown rot disease (Fusarium graminearum Schw. Group 1) in wheat

A crown rot disease in wheat caused by the fungusFusarium graminearum Schw. Group 1 is a widespread problem in chronically Zn-deficient Australian soils. A link between crown rot and Zn deficiency was established by Sparrow and Graham (1988). This paper reports a test of a further hypothesis, that wheat genotypes more efficient at extracting zinc from low-zinc soils are more resistant to infection by this pathogen. Three wheat cultivars (Excalibur, Songlen and Durati) of differential Zn efficiency were tested at three zinc levels (0.05, 0.5 and 2.0 mg Zn kg⁻¹ of soil) and three levels ofF. graminearum S. Group 1 inoculum (0.1 g and 0.3 g kg⁻¹ live chaff-inoculum and control having 0.1 g kg⁻¹ dead chaff inoculum). Six weeks after sowing dry matter production of shoots and roots was decreased byFusarium inoculation at 0.05 mg and 0.5 mg kg⁻¹ applied Zn.Fusarium inoculum at 0.1 g was as effective as 0.3 g kg⁻¹ for infection and decreasing dry matter. The infection at the basal part of culm decreased significantly by increasing the rate of Zn application. Excalibur, a Zn-efficient cultivar (tolerant to Zn deficiency) produced significantly more shoot and root dry matter, and showed less disease infection compared with Zn-inefficient cultivars (Durati and Songlen) at low (0.05 mg Zn kg⁻¹ soil) and medium (0.5 mg Zn kg⁻¹ soil) Zn fertilization rates. Higher rate of Zn fertilization (2.0 mg Zn kg⁻¹ soil) reduced the disease level in Durati to the level of Excalibur but the disease level of Songlen was still high, indicating its high Zn requirement and or sensitivity to crown rot. The data on Zn uptake show that Excalibur, being Zn-efficient, was able to scavenge enough Zn from Zn-deficient soil, we suggest that besides sustaining growth Excalibur was able to build and maintain resistance to the pathogen; inefficient cultivars needed extra Zn fertilization to achieve performance comparable to that of Excalibur. The present study indicates that growing Zn-efficient cultivars of wheat along with judicious use of Zn fertilizer in Zn-deficient areas where crown rot is a problem may sustain wheat production by reducing the severity of the disease as well as by increasing the plant vigour through improved Zn nutrition. ei]Section editor: R Rodriques-Kalana