Rhizosphere pH as a result of nitrogen levels and NH4/NO3 ratio and its effect on zinc availability and on growth of rice flower (Ozothamnus diosmifolius)

The effect of modification of the rhizosphere pH, via solution-N concentration and source, on rice flower (Ozothamnus diosmifolius, Astraceae) growth was investigated in two different experiments. In order to simulate a wide range of pHs easily, the plants were grown in an inert artificial substrate (perlite). In the first the rhizosphere pH was modified through variation of N concentrations and the NH₄/NO₃-N ratio in the irrigation water. In the second the rhizosphere pH was modified solely by altering the NH₄/NO₃-N ratio while irrigation-N concentration was held at the level found to be optimal in the first experiment. Cultivation of rice flower, a new crop in Israel, is hampered by lack of knowledge on its Zn nutrition. Because availability of soil Zn largely depends on pH we investigated in the second experiment the effect of Zn foliar application. The growth of rice flower plants under low-N fertilization or low NH₄/NO₃-N ratio was poor and the plants exhibited growth disorders such as tipburn, severe chlorosis and necrosis. These growth disorders could not be ascribed to any direct effect of N nutrition therefore it was suggested that the indirect effect of the treatments, e.g., the rhizosphere pH dominates rice flower growth through its effect on nutrient availability. The only nutrient that was significantly correlated with pH and yield parameters in both experiments was Zn. All irrigation-nutrients concentrations were within the recommended range for hydroponically grown plants; however, the leaf-Mn concentration of plants grown in pH above 7.5 was in the toxic range while that of Zn was deficient. The high preferential uptake of Mn over Zn by rice flower plants and the question of whether high Mn uptake induced Zn deficiency remain open.     

In vitro effects of some herbs used in Egyptian traditional medicine on viability of protoscolices of hydatid cysts

The present work evaluated the effects of alcoholic extracts of salvia (Salvia officinalis), thyme (Thymus vulgaris), and 2 pure compounds (thymol and menthol) on the viability of Echinococcus granulosus protoscolices in vitro. Four different concentrations of each extract (2,500, 1,500, 1,000, and 500 μg/ml) and 3 different concentrations each of thymol and menthol (50, 10, and 1 μg/ml) were used. Concentration of 2,500 μg/ml of both extracts showed a significant protoscolicidal activity on the 6th day. Complete loss of viability of protoscolices occurred with 500 μg/ml concentration of both extracts at day 6 and day 7 post-treatment (PT), respectively. Pure compounds, i.e., menthol and thymol, showed potent effects with 50 μg/ml concentration at day 2 and day 5 PT, respectively. These effects were compared with those of albendazole sulfoxide (800 μg/ml), a commonly used treatment drug for hydatidosis. Krebs-Ringer solution and the hydatid cystic fluid at a ratio of 4:1 was a good preservative solution which kept the protoscolices viable for 15 days.     

An insight into the distribution,genetic diversity,and mycotoxin production of <Emphasis Type="Italic">Aspergillus</Emphasis> section <Emphasis Type="Italic">Flavi</Emphasis> in soils of pistachio orchards

In the present study, 193 Aspergillus strains were isolated from a total of 100 soil samples of pistachio orchards, which all of them were identified as Aspergillus flavus as the most abundant species of Aspergillus section Flavi existing in the environment. Approximately 59%, 81%, and 61% of the isolates were capable of producing aflatoxins (AFs), cyclopiazonic acid (CPA), and sclerotia, respectively. The isolates were classified into four chemotypes (I to IV) based on the ability to produce AFs and CPA. The resulting dendrogram of random amplified polymorphic DNA (RAPD) analysis of 24 selected A. flavus isolates demonstrated the formation of two separate clusters. Cluster 1 contained both aflatoxigenic and non-aflatoxigenic isolates (17 isolates), whereas cluster 2 comprised only aflatoxigenic isolates (7 isolates). All the isolates of cluster 2 produced significantly higher levels of AFs than those of cluster 1 and the isolates that produced both AFB₁ and AFB₂ were found only in cluster 2. RAPD genotyping allowed the differentiation of A. flavus from Aspergillus parasiticus as a closely related species within section Flavi. The present study has provided for the first time the relevant information on distribution and genetic diversity of different A. flavus populations from nontoxigenic to highly toxigenic enable to produce hazardous amounts of AFB₁ and CPA in soils of pistachio orchards. These fungi, either toxigenic or not-toxigenic, should be considered as potential threats for agriculture and public health.