Communications in agricultural and applied biological sciences最新文献

Hydroponic systems used for growing potted ornamentals in greenhouses are commonly ebb-and-flow irrigation systems. The drainage water is usually recycled to save water and nutrients. To avoid the spread of pathogens in these closed irrigation systems, disinfection of the recycled water is standard practice. Growers can use slow sand filtration or UV-radiation techniques, but these methods are often either not sulted for specific problems or they require an excessively large investment. The objective of this study was to test less expensive but effective alternative disinfection systems. The efficacy of five disinfection systems against fungi and oomycetes was determined: Aqua-Hort (based on Cu-ions), Reciclean (performic acid), D1-OX Forte (CIO2), ECA (electrochemically activated water = anodic oxidation: hypochlorite and free radicals) and Newtec (also anodic oxidation). These five systems and a no-sterilization control were integrated in small closed ebb-and-flow circuits with nutrient solution reservoirs of 400 L each. Activity against Fusarium was excellent with ECA, good with Newtec and DI-OX Forte, moderate with high doses of Reciclean (250 ppm H2O2 and poor with the Aqua-Hort. There was no Pythium in the ECA and Newtec systems, while still so in the Aqua-Hort system, even at high doses (up to 7 ppm Cu++). Although the Reciclean (up to 100 ppm H2O2) and Aqua-Hort systems did not perform well against the pathogens, they did very well against algae; especially Reciclean was also useful against duckweed in water and liverwort on soil substrates. Concentrations of total Cl were elevated in water, substrate and plants after treatments with ECA and Newtec; other accumulations were Cu (Aqua-Hort), Na and SO4 (DI-OX Forte). However, only on a limited number of plant species these accumulations produced phytotoxic effects.

A total of 40 actinomycetes isolated from rhizosphere soils of Ononis angustissima Lam. were in vitro tested for their antagonism against deferent pathogenic microorganisms by streak assay. Among the isolates, four (21, 2A26, 1B10 and 2C34) present a potent antagonism against both pathogenic bacteria and fungi, they were selected, identified by 16S rDNA sequence analysis and phenotypic properties, and tested for their antimicrobial activity as well as their biocontrol potential against Chickpea (Cicer arietinum L.) pathogenic fungus (Fusarium oxysporum). Cultural characteristic studies strongly suggested that these strains belong to the genus Streptomyces. The four Streptomyces sp., solubilize phosphate and produce extracellular fungal cell-wall degrading enzymes chitinase and protease, as well as a marked production of acid-β-indole acetic (AIA). The nucleotide sequence of the 16S rRNA gene of Streptomyces sp. strains 21, 2A26, 1B10 and 2C34 exhibited close similarity (62-75%) with Streptomyces parvulus MARS 16S rRNA genes. The inhibition was higher against fungi and Gram+ bacteria, while Gram- bacteria were less inhibited. The growth of the plant pathogenic fungus Fusarium oxysporum was considerably inhibited in the presence of the strains 21, 2A26, 1B10 and 2C34 culture supernatant. These studies revealed that the presence of the Streptomyces strains in the soil significantly promoted the growth of the Chickpea plants. These results indicate that the Streptomyces strains isolated for rhizosphere from Ononis angustissima Lam. growing in arid conditions in southern Algeria (Sahara) could be an interesting source for antimicrobial bioactive substances and as biocontrol agents.

Sustainable production of food, feed and fiberwarrants sustainable soil management and crop protection. The tools available to achieve this are both in the realm of the plants and of the soil, with a key role for plant-soil interactions. At the plant level we have vast knowledge of variation within plant species with respect to pests and diseases, based on which we can breed for resistance. However, given that systems evolve this resistance is bound to be temporarily, hence also other strategies are needed. Here I plea for an integrative approach for sustainable production using ecological principles. Ecology, the study of how organisms interact with their environment, teaches us that diversity promotes productivity and yield stability. These effects are thought to be governed through resource use complementarity and reduced build-up of pests and diseases both above- and belowground. In recent years especially the role of soil biotic interactions has revealed new insights in how plant diversity and productivity are related to soil biodiversity and the functions soil biota govern. In our grassland biodiversity studies we found that root feeders can promote plant diversity and succession without reducing plant community productivity, this illustrates the role of diversity to maintain productivity. Also diversity within species offers scope for sustainable production, for example through awareness of differences between plant genotypes in chemical defense compounds that can attract natural enemies of pests aboveground- and belowground thereby providing plant protection. Plant breeding can also benefit from using complementarity between plant species in the selection for new varieties, as our work demonstrated that when growing in species mixtures plant species adapt to each other over time such that their resource acquisition traits become more complementing. Finally, in a recent meta-analysis we show that earthworms can stimulate crop yield with on average 25%, but also that the effect size is conditional on fertilizer management and crop type. Together these examples illustrate the role of soil ecology in plant growth and the potential of its use for sustainable crop productivity through judicious management of plant-soil interactions.

Investigation throughout the subsequent years of 2011-2012 and 2012-2013 indicated that chaff scale, P. pegandii is an important economic pest on citrus trees in Abou El-Matamer area, El-Beheira Governorate, Egypt. It has been recorded in relatively high rates all over the year on three citrus varieties called Succari, Baladi and Navel oranges. Field observation and recorded data revealed that the common abundance was recorded for chaff scale on Succari oranges followed by Navel oranges then the least abundant on Baladi oranges. Generally, the calculated data on Succari oranges showed that, the population of P. pergandii reached the maximum during July and there were five highly variation periods in both the growing seasons of 2011-2012 and 2012-2013. The maximal percent of pre and adult females was observed during Spring and early Summer and reached 100% of the total counted individuals during October and December in the first year, but in the second one a higher population was recorded during Summer and early Winter months. The adult males were observed during Summer and Autumn months. Results showed also that the relationship between daily mean temperature and population density of chaff scale was weak, insignificantly negative in the two growing seasons (2011-2012 and 2012-2013) and also insignificantly but positive with relative humidity. That relationship with wind speed indicated weak positive significance in the first year and strong in the second season. The relationship between dew point and insect population was weak of positive significance in both growing seasons.

Azadirachtin is a known botanical insecticide with multiple modes of action. Whether these effects have any relation with the modes of application, specifically during ecdysis process, has been the objective of the present study and accordingly the impairment, if any, among cuticular proteins of Spodoptera litura (Fab.) was determined. Azadirachtin was applied topically, via injection or oral administration. Azadirachtin administered via injection and topical applications severely impaired the ecdysis by 86.67 and 80.0%, respectively. However, this impairment via oral administration was significantly lower (73.33%). Using SDS-PAGE, the cuticular proteins were determined for treated insects under all the three modes of application. In all cases 6 protein bands (MW 9-34 kDa) were identified using markers as standard. In all treatments 3 induced proteins (MW. ~16, 20 and 23 kDa) and 1 reduced protein (~19 kDa) were observed. In case of the topical treatment a different induced protein of ~18 kDa was identified. The change in cuticular proteins, their possible role in ecdysis impairment vis-a-vis the mode of application of azadirachtin is being correlated. This will help in understanding the mode-of-action at cuticular level and also will allow developing a suitable application strategy under field conditions in insect pest management.

Iran is one of the most important potato-producing countries in Asia and Oceania. Approximately 20 percent of potato cultivation in Iran occurs in the North-western provinces. Pectobacterium and Dickeya species cause important diseases in potato crop. They may incite blackleg and are responsible for tuber soft rot in storage, thereby reducing yield and quality. In order to identify and differentiate the species of soft rot bacteria, potato stems and tubers showing soft rot symptoms were collected from potato fields in North-western Iran. A total of fifty strains belonging to Pectobacterium and Dickeya species were isolated and identified from the infected tissues. Phenotypic characterization revealed a considerable variation among strains thus dividing them into five separate groups. Group 1 strains belonged to Dickeya chrysanthemi that were different from the type strain in malonate utilization. Group 2 strains were similar to Pectobacterium betavascularum but were different from the type strain in utilization of raffinose, citrate and D-sorbitol. Group 3 strains showed more resemblance to P. wasabiae but were different from the type strain with respect to acetoin production. Group 4 strains belonged to P. carotovorum subsp. carotovorum (Pcc) and group 5 strains were identified as intersubspecific of Pcc and P. carotovorum subsp. odoriferum. Polymerase chain reaction using pelY primers identified strains belonging to Pectobacterium species but not P. betavascularum.

Pollen microbial content of 15 samples was investigated. Pollen was collected by honeybees. Total aerobic mesophilic count ranged from 3.00 to 5.48 Log CFU/g. Total mold and yeast count ranged from 2.3 to 6.99 Log CFU/g. Selected strains of isolated molds from pollen samples were characterized by conventional methods. Potent phytopathogenic and food spoilage species such as Penicillium sp., Alternaria alternata, Alternaria sp., Cladosporium werneckii, Mucor hiemalis, Rhizomucor pusillus, Aspergillus flavus, Aspergillus niger, Drechslera tritici-repentis, Verticillium albo-atrum, and Aspergillus alliaceus were recovered. Other fungal species with valuable biotechnological and plant diseases control purposes were isolated. They were characterized as Geotrichum candidum, Monilia sitophilia, and Sepedonium chrysospermum. Animal pathogenic molds were also isolated. Bee pollen may be considered as a source for a highly diverse fungal flora with different applications.

Internal fruit rot of sweet pepper grown in glasshouses has been an increasing problem worldwide since around 2000. In the UK, surveys in 2007 showed infected fruits were present in many crops at levels from 1 to 37%. The disease causes some losses on production nurseries but more importantly also causes rejection by packers and complaints by supermarkets. Losses vary greatly between crops and seasons, and growers are generally unaware a problem may be present until harvest or postharvest. The fruit rot arises through infection of flowers (Yang et al., 2010). Several Fusarium species have been associated with the disease in the UK, notably F. lactis and F. oxysporum. Observations in commercial crops indicate the disease is favoured by high humidity. At present there is no effective method of control. This experimental work aimed to reduce losses to Fusarium internal fruit rot through increased knowledge of factors associated with a high incidence of the disease and use of biofungicides and fungicides to control flower infection.

In modern agriculture, most farmers rely on herbicides for weed control. The intensive use of herbicides in crops has led to the development of herbicide resistance in numerous weeds worldwide. In Belgium, farmers have encountered problems with controlling populations of Alopecurus myosuroides, Matricaria recutita, Stellaria media and Popover rhoeas in some wheat fields with the conventionally used acetolactate synthase (ALS)-inhibiting herbicides. Dose response assays were conducted in the greenhouse to test the sensitivity of these populations to the key ALS-inhibiting herbicides mesosulfuron-methyl + iodosulfuron-methyl for A. myosuroides and metsulfuron-methyl and florasulam for M. recutita, S. media and P. rhoeas. The ED₉₀- and ED₅₀-values (effective dose for resp. 90% and 50% biomass reduction) were compared with those of sensitive reference populations and the resistance index (RI) was calculated. High levels of resistance were detected forA. myosuroides (RI: 24.3) after treatment with mesosulfuron-methyl and for M. recutita (RI: 36.4 to 49.5), S. media (RI > 20) and P. rhoeas (RI: 23.6) after treatment with metsulfuron-methyl. However, the metsulfuron-methyl resistant populations of M. recutita and S. media were sufficiently controlled with florasulam at the maximum authorised field dose. This was not the case for P. rhoeas. The metsulfuron-methyl resistant P. rhoeas population were also high-level resistant against florasulam (RI: 29.5). Integrated weed management practices (crop rotation, herbicide mixing, ...) should be applied to reduce the selection pressure for resistant weeds.

The droplet size distribution of agricultural sprays is a key parameter during the plant protection product applications. Therefore, measurement of the drop size distribution is an important concern for spray users as well as nozzle manufacturers. The present work assessed the capability of a shadowgraphy technique to distinguish correctly the 6 spray class boundaries defined in the ISO draft standard (ISO 25358). The measurement set-up is composed by a high speed camera synchronized with a LED backlighting. The tested spray is positioned between the camera and the light. The droplets appear on the images as shadows on a brighter background. For each acquisition, two frames are recorded within a small time laps (38 μI. The droplet diameter and velocity are retrieved by using advanced image analysis algorithm on each pair of frames. Then, the drop size distribution is obtained by gathering the data retrieved from all the images. The global results showed that the 6 drop size distributions were correctly separated highlighting the ability of the method to measure small as well as large droplets using the same set-up configuration. The spatial analysis showed that the spray scanning should be extended in the minor axis direction in order to catch the whole spray.