Communications in agricultural and applied biological sciences最新文献

Fifteen experimental trials were carried out under greenhouse conditions to evaluate the efficacy of preventative treatments based on phosphite salts on the following pathosystems: tomato/Phytophthora nicotianae, zucchini/P. capsici, lettuce/Fusarium oxysporum f.sp. Iactucae, rocket/Fusarium oxysporum f. sp. raphani, wild rocket/Plectosphaerella cucumerina and basii/Peronospora belbahrii. The possible use of phosphite salts in nursery cultivation systems is considered in comparison with chemical fungicides. Phosphites-based products reduced 66-88% and 56-72% the severity of Phytophthora crown root rot of tomato and zucchini, respectively. Four application with the phosphites-based products provided a disease reduction of Fusarium wilt of lettuce from of 33 to 83% and of 45 to 68% on cultivated rocket. These products provide the most constant results when applied in three treatments against Plectosphaerella cucumerina with a disease reduction ranging between 34%-82%. Phosphite-based products showed results statistically similar to mefenoxam when tested against downy mildew of basil. Their contribution to disease management can be very interesting, because they can complement other control measures.

Septoria tritici blotch (STB) caused by Mycosphaerella graminicola is one of the most devastating foliar diseases on wheat. Due to the emergence of fungicide-resistant M. graminicola strains and in an effort to reduce the impact of pesticides on the environment, considerable interest has been devoted to alternative control strategies. The use of natural products, especially through a defense-activating effect on the host, could be considered. Acid ascorbic (AA) is synthesized by plants and most animal cells with antioxidant properties. This study aimed at: (i) assessing the protective effect of an AA-based product on bread (BW) and durum (DW) wheat (Triticum aestivum and T. durum, respectively) susceptible cultivars against M. graminicola and (ii) investigating the mechanisms involved in wheat protection. Therefore, the foliar application of a formulated AA-based product (50 mg L-) on 3-week-old wheat plants reduced the infection level by more than 75% for both BW and DW. In vitro experiments revealed that AA induced a strong inhibition of spore germination (at 50 mg L.(-1)) and hyphal growth (at 16 mg L.(-1)) for both M. graminicola strains, infecting either BW or DW. Used as a preventive foliar spray on wheat leaves, microscopic observations revealed that AA inhibits in planta spore germination, hyphal growth, leaf penetration, substomatal colonization and eventually sporulation. Moreover, AA treatment also decreased fungal protease and cell wall degrading enzyme activities, putative pathogenicity determinants of M. graminicola. In addition to these effects on the fungus, AA induced defence reactions in both BW and DW. Indeed, in non-inoculated context, eliciting effect was observed on (i) stimulation of enzymatic activities such as lipoxygenase, peroxydase and catalase and (ii) transcript accumulation of genes encoding for pathogenesis-related (PR) proteins (chitinase class IV, peroxidase). In inoculated condition, accumulation of H2O2 and phenolic compounds increased at the penetration site in AA-treated leaves. In addition, AA treatment impacted the phenylpropanoid pathway through the induction of phenylalanine ammonia lyase activity. These results show that, in our conditions, AA both presents an antifungal activity and triggers several plant defences in wheat and suggest its use to control M. graminicola on both DW and BW.

Entomotoxic proteins are produced by plants in defence against insect herbivory. Some carbohydrate-binding proteins exhibit strong insecticidal activity affecting the survival, growth, development and feeding behavior of phytophagous insects. The occurrence of entomotoxic lectins is well documented in the Amaryllidaceae, a plant family spread world-wide. In Chile, this family is represented by numerous species, many of which are also of high ornamental value. Protein extracts were obtained from bulbs of five different species of Chilean Amaryllidaceae. A dose-response assay was carried out with two important pests: the greenhouse whitefly Trialeurodes vaporariorum Westwood and the mealybug Pseudococcus viburni Signoret. The extracts were offered to insects in a liquid artificial diet for three days and the mortality was scored. The Phycella australis Ravenna extract caused the highest insecticidal activity (T. vaporariorum LC₅₀: 7200 µg/mL; P. viburni LC₅₀: 9500 µg/mL). Applied at 1000 µg/mL in the diet the P. australis extract did not repel feeding of these pests. A mannose-binding lectin isolated from the bulbs of P. australis proved to be moderately toxic for these pests (T. vaporariorum LC₅₀: 1127 µg/mL; P. viburni LC₅₀: 2320 µg/mL).

Septoria tritici blotch caused by Mycosphaerella graminicola is currently the most devastating disease on wheat crops worldwide. Mycosphaerella graminicola sexual reproduction involves two mating type idiomorphs that were previously studied in several areas around the world, but not in Algeria so far. The objective of this study was thus to determine the frequencies and distribution of M. graminicola mating types in this country. One hundred and twenty monoconidial isolates of this fungus (60 from bread wheat and 60 from durum wheat) were collected during the 2012 growing season from five distinct geographical locations in Algeria. The mating type of each isolate was identified using a multiplex PCR that amplifies either MAT1-1 or MAT1-2 fragment from mating type loci. Both idiomorphs were found at equal frequencies according to the chi-square test at the whole country level (46% MAT1-1 and 54% MAT1-2) and in each of the sampled locations. The two mating types were also detected at equal frequencies on both host species (47% MAT1-1 vs 53% MAT1-2 on bread wheat and 45% MAT1-1 vs 55% MAT1-2 on durum wheat). Our study showed that the two mating types of M. graminicola occur at equal proportions in Algeria and suggests a strong potential for sexual reproduction of the pathogen in this country that may eventually lead to either adaptation to local conditions, plant resistance overcoming or the emergence of resistance to fungicides.

Weed management is critical in hazelnut (Corylus avellana) production. Weeds reduce nutrient availability, interfere with tree growth, and reduce hand-harvesting efficiency. Field experiments were conducted to test effects of cover crops as alternative weed management strategies in hazelnut. The cover crop treatments consisted of Trifolium repens L., Festuca rubra subsp. rubra L., Festuca arundinacea Schreb., Vicia villosa Roth. And Trifolium meneghinianum Celmand fallow with no cover crop. Control plots such as weedy control, herbicide control and mechanical control were added as reference plots. The lowest weed dry biomass was obtained from Vicia villosa plots, and there were no significant differences among all other cover crop treatments. The highest cover crop dry biomass was measured in the Trifolium meneghinianum plots. Regarding the effect of cover crops on hazelnut yields, the lowest yield was ob- tained from weedy control plots, while the highest yield was obtained from F. arundinacea plots. This research indicated that cover crops could be used as living mulch in integrated weed management programs to manage weeds in the hazelnut orchards.

The vinegar fly Drosophila suzukii (Matsumura) (Diptera Drosophilidae), spotted wing drosophila, is a new invasive fruit pest that recently became established in Europe. Unlike other fruit flies that typically only infest overripe and rotten fruit, D. suzukii females oviposit in ripe fruit leading to considerable economic losses of fruit during production. In 2011 and 2012 D. suzukii was detected at several places in Belgium. In 2013, a large-scale monitoring in frame of the project "FLY ALERT" (FOD) was executed using traps with liquid attractant (apple cider vinegar) at more than 100 locations across Belgium during the whole fruit growing season. At 16 locations we also compared the efficacy of a 'bottle type' trap with a 'cup type' trap. The results show that D. suzukii has expanded its distribution in Belgium. Remarkably, in 2013 as well as in 2012 the first detections were made only in the second part of the growing season (August) and the populations reached their peak only at the very end of the season (November). In the bottle type trap the first flies were caught 2-3 weeks earlier than in the cup type trap. In addition, also the population peaks were on average 1 week earlier when monitored with the bottle trap compared to when monitored with the cup trap. In 2014, after an exceptional mild winter adult D. suzukii flies were continuously detected throughout the winter and early spring. The implications of these findings for the phenology of D. suzukii in the Northwest climate region of Europe are discussed.

A perennial switchgrass, (Panicum virgatum L.), (C4) that is native to North America has good potential for biomass production because of its wide geographic distribution and adaptability to diverse environmental conditions. Insects can significantly impact the yield and quality of biofuel crops. If switchgrass are to be grown on marginally arable land or in monoculture, it are likely to be plagued with herbivore pests and plant diseases at a rate that exceeds what would be expected if the plants were not stressed in this manner. This biofuel crop has been under evaluation for commercial growing in Ukraine for eight years. However, insect diversity and the potential impact of pests on biomass production of this feedstock have not been accessed yet. The objective of our study, started in 2011, is a survey of switch grass insects by trophic groups and determine species that have pest status at two sites in the Central part of Ukraine (Kiev and Poltava regions). In Poltava site we investigated the effect of nine varieties of switchgrass (lowland and upland) to insects' diversity. We assessed changes over time in the densities of major insects' trophic groups, identifying potential pests and natural enemies. Obtained results indicates that different life stages of herbivorous insects from Hymenoptera, Homoptera, Diptera and Coleoptera orders were present on switchgrass during the growing season. Our study results suggests that choice of variety has an impact on trophic groups' structure and number of insects from different orders on swicthgrass. Herbivores and beneficial insects were the only groups that showed significant differences across sampling dates. The highest population of herbivores insects we recorded on 'Alamo' variety for studied years, although herbivore diversity tended to increase on 'Shelter', 'Alamo' and 'Cave-in-Rock' during 2012 and 2013. 'Dacotah', 'Nebraska', 'Sunburst', 'Forestburg' and 'Carthage' showed the highest level of beneficial insects during our study.

Ozonation was investigated as a potential post-treatment step for biologically treated landfill leachate to enhance the biodegradability and observe the influence of the initial organic matter concentration and pH. Changes in COD, UV absorption at 254 nm (UVA254) and BOD content were measured during and after ozonation, and the ozone utilisation efficiency at different conditions was calculated. The initial COD concentration was found to influence the absolute removal of UVA254 significantly, but especially changes in pH influenced the ozone reactions. Increased pH (pH 10) most probably increased the overall hydroxyl radical production leading to a higher COD removal and a much better ozone utilisation compared to lower pH. This in contrast to initial COD variations which had little influence on the determined ozone utilisation. Regardless of initial COD content or pH, on average 10% of the initial COD content was converted to BOD, next to 10% COD that was removed.