Versuche zur Reduzierung der Population von Tetranychus arabicus (Attiah) mittels Sprühens anorganischer Salzlösungen auf die Blätter

Effect of some nutritional plant sprays on the population of Tetranychus arabicus (Attiah) (Acarina, Tetranychidae) Studies on the effect of inorganic compounds on the population density ofT. arabicus indicated that all materials gave over 50% reduction after 15 days except chromic chloride and magnesium oxide which gave only 33% each, while potassium iodine built up mites population. As such, these compounds are potentially important mites-control chemicals. Also data showed conclusively that inorganic compounds may be used as well to manipulate host plant resistance, as to correct crop nutritional difficiency. However, the mode of action and the time of application of these compounds under natural field conditions still need further investigations.      

An evaluation of methods for characterising and monitoring gum arabic of commerce and related Acacia gums

Summary Three methods that have been suggested as inexpensive for characterisation of gum arabic were evaluated in characterising and monitoring gum arabic of commerce. The methods were; physico-chemical and carbohydrate analysis (analytical), determination of molecular mass by gel permeation chromatography (gpc) and an Enzyme Linked Immunosorbent Assay (ELISA). The results revealed that gpc provides quick and consistent information on gum arabic of commerce from Acacia senegal. It was able to detect the three chemical species; Arabinogalactan protein complex (AGP), Arabinogalactan (AG) and Glycoprotein (GP) fractions that are typical of A. senegal and could differentiate gum from the two varieties of A. senegal, i.e., var. senegal and var. kerensis on the basis of the enhanced UV peaks in the later. It was able to distinguish gums from different Acacia species as well as suspected contaminants. The analytical method could differentiate between the two varieties of A. senegal on the basis of optical rotation, protein content and viscosity which were noted as basic parameters for comparison. However, where the proposed FAO (1990) specifiction was applied in its present form, it failed to adequately characterise gum from var. kerensis as gum arabic. Secondly, natural product variability i.e., the observed between sample variation made the method to have limited application in adequately characterising gum arabic from even a single source. The method was able to distinguish gums from the other Acacia species purely on the basis of optical rotation though information on nitrogen and sugar composition was also invaluable. Generating data on the composition of sugars requires time that militates against the method as a slow process. Because of the overlap in the analytical parameters for some samples, it could be adequately characterise two of the samples that were presented as suspected contaminants. Nonetheless, by combining information of gpc and analytical data, a better evaluation of the gums was achieved. The method of Elisa has a future scope but will require refining it by utilising monoclonal antibodies to be developed for it to be more specifc in characterising gum arabic from A. senegal. The authors wish to thank Dr. P. A. Williams of the North East Wales Institute, Deeside, Clwyd, UK for the use of the gpc and Elisa facilities. B.N.C. is grateful to the Kenyan and British governments for financial support.     

Über nematizide Wirkungen der Henna-PflanzeLawsonia inermis gegen den WurzelnematodenMeloidogyne incognita

A suppressive effect was obtained by the henna plant (Lawsonia inermis) againstM. incognita development. Henna reduced tomato root gall numbers, number of the egg-laying females and rate of the nematode reproduction, when tomato and henna were grown together. Also, same, reduction in these nematode biological processes was found, when tomato plants were grown in soil containing root exudates of henna, but with less amount. When henna was grown alone, root gall index and the rate of nematode reproduction reduced to 75 and 99%, respectively, compared with those of tomato grown alone.     

Effectiveness of tagetes natural exudates onMeloidogyne javanica (Chitwood) nematode

The effectiveness of intercropping tagetes with tomato in comparison with the natural root exudates of tagetes onMeloidogyne javanica nematode population and galls on tomato cultivated in sandy soil was studied. Both tagetes roots extracts and intercropping tagetes with tomato significantly reducedM. javanica nematode population, egg masses and galls on tomato. Intercropping tagetes with tomato was more effective in reducing root-knot nematode population and galls than treating tomato with natural root extracts of tagetes.Therefore, intercropping resistant plant with susceptible host to nematode is a new and good approach to nematode control.

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Zusammenfassung Es wurde die Wirkung des Pflanzens vonTagetes zwischen Tomaten im Vergleich zur Beigabe von Wurzel-Exudaten vonTagetes zu den Tomaten auf den NematodenMeloidogyne javanica in Sandboden untersucht. Beide Verfahren reduzierten signifikant die Zahl der Nematoden, die Eigelege und Gallenbildungen an den Tomaten. Jedoch wirkte die Zwischenpflanzung vonTagetes besser als die Hinzufügung vonTagetes-Wurzelexudaten.Auf Grund der Ergebnisse bietet das Zwischenpflanzen einer resistenten Pflanzenart zu einer nematoden-empfindlichen Pflanzenart einen neuen Weg der Nematodenbekämpfung.

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With one table     

Bio-efficacy of sincocin AGTM to controlTylenchulus semipenetrans (Tylenchida,Nematoda) in citrus orchard

Field experiment was conducted at a site naturally infested withTylenchulus semipenetrans to explore the effect of sincocin AGTM as a biocidal agent at 2000 ppm in controlling citrus nematodes. Sincocin AGTM significantly reduced citrus nematode population in both soil and roots ofCitrus sinesis, and enhanced both growth of orange trees and soil mites especially the mesostigmatide mites. In treated soil, the nature nematode feeders, mesostigmatide mites were increased by 140% and 243%, one month and two months, respectively, post application.     

Interaction of root-knot nematode and mycorrhizal fungi on common beanPhaseolus vulgaris L.

The interactions of root-knot nematode and VAM fungus on common bean plants (Phaseolus vulgaris L.), and the sequence of nematode infection were studied in the greenhouse. The inoculation with VAM fungus caused a significant increase in plant height and fresh weight compared with non treated plants.Meloidogyne infection unsignificantly decreased plant height and dry weight. When fungus was inoculated at 15 and 30 days prior toM. incognita infection, a significant increase in fresh weight was observed. There were no significant differences in total nitrogen (mg/plant) between plants inoculated withM. incognita alone or those inoculated with bothM. incognita and VAM fungus at the same time or 15 days after the fungus inoculation. Plants preinoculated with VAM fungus 30 days prior to nematode infection had a significant increase in total nitrogen. The inoculation with VAM fungus caused a significant increase in phosphorus content. However, it was significantly decreased in plants inoculated with nematode alone and in plants inoculated with VAM fungus andM. incognita at the same time. Gall index and final nematode population were significantly increased when nematodes were treated at the same time with fungus, although there were significant decrease in nematode final population and gall index when the plants were treated with nematodes at 15 and 30 days after mycorrhizal infection. A decrease in percentage of fungal colonization was observed when nematodes were inoculated with fungus at the same time.     

Are specific testing protocols required for organic onion varieties? Analysis of onion variety testing under conventional and organic growing conditions

Organic growers need information on variety performance under their growing conditions. A 4-year onion variety research project was carried out to investigate whether setting up a variety testing system combining conventional and organic variety trials is feasible and efficient rather than organizing separate variety trials under the two management systems. During 4 years commercial onion cultivars were tested at a certified organic and a non-organic location. Both systems were managed without chemical pest, disease and sprouting control, but differed in fertility management (organic manure in autumn versus synthetic fertilizer), soil cultivation and weed management (mechanical weeding versus application of herbicide). Management system significantly affected plant density, thickness of neck, and proportion of small and large bulbs. Variety × management system interactions were significant for bulb uniformity, earliness, proportion of large bulbs, dormancy and relative storage success but did not change the ranking of the varieties. We conclude that organic growers can profit from a more conscious variety choice when conventionally fertilised trials would refrain from using pesticides, fungicides, herbicides and sprout inhibitors. However, this would require an adaptation of the management protocol in such a way that trials might no longer represent conditions of conventional farmers. Furthermore, assessments of leaf erectness, disease resistance to downy mildew and leaf blight should be included in the protocols for organic use. We advocate better communication between breeders and growers on specific variety characteristics contributing to improving yield stability under low-input, organic growing conditions.     

SSR markers for marker assisted selection of root-knot nematode (<Emphasis Type="Italic">Meloidogyne incognita</Emphasis>) resistant plants in cotton (<Emphasis Type="Italic">Gossypium hirsutum</Emphasis> L)

Cotton (Gossypium hirsutum L) cultivars highly resistant to the southern root-knot nematode (RKN) [Meloidogyne incognita (Kofoid and White) Chitwood] are not available. Resistant germplasm lines are available; however, the difficulty of selecting true breeding lines has hindered applied breeding and no highly resistant cultivars are available to growers. Recently, molecular markers on chromosomes 11 and 14 have been associated with RKN resistance, thus opening the way for marker assisted selection (MAS) in applied breeding. Our study aimed to determine the utility of these markers for MAS. Cross one was RKN resistant germplasm M240 RNR × the susceptible cultivar, FM966 and is representative of the initial cross a breeder would make to develop a RKN resistant cultivar. Cross two consists of Clevewilt 6 × Mexico Wild (PI563649), which are the two lines originally used to develop the first highly RKN resistant germplasm. Mexico Wild is photoperiodic. We phenotyped the F₂ of cross one for gall index and number of RKN eggs per plant and genotyped each plant for CIR 316 (chromosome 11) and BNL 3661 (chromosome 14). From this, we verified that MAS was effective, and the QTL on chromosome 14 was primarily associated with a dominant RKN resistance gene affecting reproduction. In the first F₂ population of cross two, we used MAS to identify 11 plants homozygous for the markers on chromosomes 11 and 14, and which also flowered in long days. Progeny of these 11 plants were phenotyped for RKN gall index and egg number and confirmed as RKN highly resistant plants. Generally about 7–10 generations of RKN phenotyping and progeny testing were required to develop the original RKN highly resistant germplasms. Our results show that commercial breeders should be able to use the markers in MAS to rapidly develop RKN resistant cultivars.     

Validation and application of a high fidelity mRNA linear amplification procedure for profiling gene expression

The need for microgram quantities of RNA for microarray experiments has hindered application of this novel technology in cell types/tissue samples with limited abundance of RNA. In this study, potential application of T7-based linear RNA amplification was investigated for use in gene expression profiling experiments where starting material is limited. Yield and integrity of amplified antisense RNA (aaRNA), microarray hybridization intensities, and fidelity of differential gene expression detected were determined for arrays generated for unamplified versus amplified RNA from the same homogenous starting pools. Total RNA was extracted from bovine spleen and fetal ovary, serially diluted to concentrations ranging from 2 microg to 500 pg and amplified. Quality and quantity of total input RNA and aaRNA were assessed by spectrophotometry, gel electrophoresis and bioanalyzer. In experiment 1, we determined the optimal amounts of aaRNA generated from 20, 40, 200 ng and 2 microg input total RNA for use in cDNA synthesis, labeling and array hybridization that would yield robust and consistent hybridization signals on a bovine oocyte cDNA microarray. In experiment 2, comparison of microarray hybridization intensities and fidelity of differential gene expression between aaRNA generated from 2, 20 and 40 ng input total RNA versus unamplified RNA (uRNA) were conducted. The hybridization intensities for each of the 7000 spots per slide for microarrays conducted using aaRNA versus uRNA were highly correlated (2 ng = 0.84, 20 ng = 0.88, 40 ng = 0.90; P < 0.01). The false positive rate was low and similar (4.0% versus 4.4%) for arrays done with uRNA and aaRNA. Ninety-seven ESTs were detected as differentially expressed in the fetal ovary versus spleen at > 1.5- or < 0.5-fold using uRNA (P < 0.05). However, the number of genes detected in arrays using aaRNA was approximately 1.5-2.5 times greater than with uRNA. Approximately, 65-70% of differentially expressed genes were common between uRNA and aaRNA arrays. Relative fold-expression (Cy3/Cy5 ratios) for 25 overlapping abundant genes was comparable for uRNA versus aaRNA arrays with 2 and 20 ng total RNA as input. Results demonstrate that T7-based linear amplification of small amounts of input RNA and use of aaRNA in microarray experiments retains fidelity of detection of differential gene expression that is relatively comparable to experiments done with uRNA and provides a potentially viable approach to facilitate gene expression profiling using limited amounts of starting material.