Local and systemic control of powdery mildew (Leveillula taurica) on pepper plants by foliar spray of mono-potassium phosphate

A foliar spray of 1% (w/v) solution of the fertilizer mono-potassium phosphate (MKP) (KH₂PO₄) on the upper surfaces of lower leaves of greenhouse-grown peppers induced local and systemic control against Leveillula taurica, as compared with control plants. This protection was expressed by a reduction in the leaf area covered with sporulating colonies and in conidial production on leaf tissue, 24 or 48 h post-treatment, when MKP was applied on lower leaves of plants that had been exposed to the source of inoculum. Foliar application of MKP, initiated before or after exposure to heavily diseased plants as the source of inoculum, was effective in controlling powdery mildew. Application of MKP efficiently suppressed powdery mildew as expressed by inhibition of the development of new sporulating colonies, as well as the conidial production of the fungus on infected tissue. Microscopic examination indicated destruction of both hyphae and conidial structures on MKP-treated leaves. The efficacy of MKP in controlling powdery mildew on greenhouse-grown plants was compared with a sterol-inhibiting systemic fungicide. Both treatments significantly inhibited powdery mildew as compared with non-treated control plants, although the fungicide-based treatment seemed to be slightly more effective (not significant) in controlling the disease. Phosphate solutions were not phytotoxic to plant tissue and did not affect the yield, as compared with the fungicide treatment. However, a lower yield was recorded for the non-treated control plots because of mildew infection on leaves. These data indicate that MKP spray may be applied as an alternative practice for the control of powdery mildew in peppers.     

Control of tomato powdery mildew (Leveillula taurica) in the Comarca Lagunera, Coahuila State, Mexico, supported by the spray forecast model Tomato.PM

Tomato powdery mildew [Leveillula taurica (Lev.) Arm.] is a common disease of tomato crops in the Comarca Lagunera region of the state of Coahuila, Mexico. To control the disease, fungicides are commonly sprayed up to 18 times on a weekly basis in this region. Effectiveness of the spray forecast model Tomato.PM, developed for California conditions, to reduce fungicide spraying, was evaluated. Disease dynamics on plants treated with three different fungicides (azoxystrobin, myclobutanil and wettable sulfur), with and without model recommendations, was analyzed in three experiments at three locations. When spraying followed model recommendations, it was possible to eliminate 11-16 fungicide applications with no significant effect on fruit yield. All three fungicides reduced the severity of disease but their effects varied with the cropping cycle. A significant increase in total yield due to fungicide spraying was observed in one out of three experiments.     

Grape powdery mildew (Erysiphe necator) risk assessment based on airborne conidium concentration

Atmospheric concentrations of Erysiphe necator conidia were monitored for 2 years in a vineyard planted with cultivars susceptible to powdery mildew in the vine production area of Quebec, Canada. The concentrations of airborne conidia were determined and compared using two types of samplers: a Burkard volumetric sampler and a rotating-arm sampler. The coefficients of correlation between the volumetric and rotating-arm sampler placed at 45 cm from the ground was r = 0.81 and 0.82 in 2000 and 2001, respectively. The relationship between incidence of powdery mildew on the leaves of three cultivars (Chancellor, Geisenheim, and Frontenac) and the cumulative concentration of airborne conidia (based on 3 d of sampling weekly) was then studied. This relationship was similar for the three cultivars, (R² = 0.97, 0.95, 0.97, for cvs Chancellor, Geisenheim, and Frontenac respectively) and was well described using the cumulative form of the Weibull model. Based on this model, it was possible to establish the period of high risk (highest rate of increase in powdery mildew incidence) from 645 to 5614, 2437 to 2951, and 1052 to 3061 conidia m⁻³ of air for the cvs Chancellor, Geisenheim, and Frontenac, respectively. An action threshold, for timing interval between fungicide sprays, of 50 conidia m⁻³ d⁻¹ was evaluated under field conditions with cv Chancellor and was as good as a calendar-based program with fewer fungicide sprays under unfavourable weather conditions. Monitoring airborne inoculum could be used as a component of a risk management system for grape powdery mildew to time intervals between fungicide sprays.     

Effects of propylene oxide doses on Cyperus and Belonolaimus control and nutrient absorption in tomato

Among the current methyl bromide alternatives under study, propylene oxide has shown potential to control soilborne diseases, nematodes, and weeds in polyethylene-mulched tomato (Lycopersicon esculentum Mill.). Therefore, field trials were conducted to determine the most effective propylene oxide doses against populations for the nematode Belonolaimus spp. and the weed Cyperus spp. and their effect on nutrient uptake. Propylene oxide doses were 0, 190, 380, 570, 760, and 950 L/ha. Data indicated that populations of Belonolaimus and Cyperus rapidly decreased with 570 L/ha of propylene oxide. Propylene oxide doses also affected foliar concentrations of phosphorus and potassium. There was a linear increase of phosphorus concentration as dose increased, whereas potassium concentration increased rapidly after 190 L/ha of propylene oxide. The highest tomato yields were obtained with application of 760 and 950 L/ha of propylene oxide.     

Effects of sulfosulfuron soil residues on barley (Hordeum vulgare), sunflower (Helianthus annuus) and common vetch (vicia sativa)

The phytotoxicity and sensitivity of succeeding crops to the new sulfonylurea, sulfosulfuron, have been reported although there is insufficient data on the phytotoxic effect of field soil residues. Growth chamber bioassays were conducted to detect the presence of residues in soil samples previously treated with sulfosulfuron at the recommended rate and double rate (20 and 40 g a.i./ha) that could affect the succeeding crop. Soil samples were collected between 7 and 9 months after sulfosulfuron application in field selectivity assays at nine different locations in Northern and Central Spain. The bioassay test species were barley (Hordeum vulgare L.) ‘Graphic’, sunflower (Helianthus annuus L.) ‘Albasol’ and common vetch (Vicia sativa L.) ‘Neska’, typical crops grown in rotation with wheat (Triticum aestivum L.) in this area. Sulfosulfuron residues did not affect barley and common vetch, but inhibited shoot length, root length and root dry weight of sunflower seeded into some soils treated with the 2× rate (40 g a.i/ha) 9 months earlier.     

Effects of chrysophanol, parietin, and nepodin of Rumex crispus on barley and cucumber powdery mildews

Three substances that show antifungal activity against Blumeria graminis f. sp. hordei were isolated from roots of Rumex crispus and identified as chrysophanol, parietin, and nepodin. The substances were tested for plant disease control activity in vivo against six plant pathogenic fungi. All specifically reduced the development of barley powdery mildew. The concentrations required for 50% disease control were 4.7 μg/ml for chrysophanol, 0.48 μg/ml for parietin, and 20 μg/ml for nepodin. These agents showed both curative and protective activity against barley powdery mildew. Chrysophanol (100 μg/ml) and nepodin (400 μg/ml) were more effective than the fungicides fenarimol (30 μg/ml) and polyoxin B (100 μg/ml), under glasshouse conditions, against cucumber powdery mildew, which is caused by Podosphaera xanthii. Parietin (30 and 10 μg/ml) reduced the development of cucumber powdery mildew as efficiently as fenarimol (30 μg/ml) and more effectively than polyoxin B (100 μg/ml).     

Identification of powdery mildew resistance loci in wheat by integrating genome-wide association study(GWAS) and linkage mapping

Wheat powdery mildew(Blumeria graminis f.sp.tritici, Bgt) is a disease of increasing importance globally due to the adoption of high yielding varieties and modern sustainable farming technologies.Growing resistant cultivars is a preferred approach to managing this disease, and novel powdery mildew resistance genes are urgently needed for new cultivar development.A genome-wide association study was performed on a panel of 1292 wheat landraces and historical cultivars using 5011 single nucleotide polymorphism(SNP)markers.The association panel was evaluated for reactions to three Bgt inoculants, OKS(14)-B-3-1, OKS(14)-C-2-1, and Bgt15.Linkage disequilibrum(LD) analysis indicated that genome-wide LD decayed to 0.1 at 23 Mb, and population structure analysis revealed seven subgroups in the panel.Association analysis using a mixed linear model(MLM) identified three loci for powdery mildew resistance on chromosome 2 B, designated QPm.stars-2BL1,QPm.stars-2BL2, and QPm.stars-2BL3.To evaluate the efficacy of GWAS in gene discovery,QPm.stars-2BL2 was validated using F2 and F2:3 populations derived from PI420646 × OK1059060-126135-3.Linkage analysis delimited the powdery mildew resistance gene in PI 420646 to an interval where QPm.stars-2BL2 was located, lending credence to the GWAS results.QPm.stars-2BL1 and QPm.stars-2BL3, which were associated with four SNPs located at 457.7–461.7 Mb and two SNPs located at 696.6–715.9 Mb in the Chinese Spring reference IWGSC RefSeq v1.0, respectively, are likely novel loci for powdery mildew resistance and can be used in wheat breeding to improve powdery mildew resistance.     

温度对短额负蝗生长发育及种群趋势的影响

为明确温度对短额负蝗Atractomorpha sinensis（I.Bolivar）种群生长发育、生殖力及种群趋势的影响。本试 验设置16℃、20℃、24℃、28℃和32℃等5个恒温梯度,在实验室条件下（H:D = 16:8,RH 70%±5%）,以大豆叶片为食 物饲养,系统观测短额负蝗实验种群各虫态发育历期、发育速率及繁殖等情况,测算其发育起点温度和有效积温, 并利用生命表技术分析各温度条件下的种群趋势。结果表明,短额负蝗各虫态的发育历期均随温度的升高而缩 短,其发育速率与温度呈显著正相关。短额负蝗卵、若虫和成虫的发育起点温度分别为9.58℃、10.55℃、11.40℃,有 效积温依次为449.80、540.03、430.94日·度。在试验条件下,短额负蝗单雌产卵量28℃时最高,为66.12粒,24℃时次 之,为 60.30粒,16℃时最低,为 28粒;各试验温度条件下实验种群趋势指数均>1,其中 24℃时最大,为 18.97。该结 果为短额负蝗的田间预测及综合防控提供了科学依据。      

种植年限对香草兰生理状况及根际土壤微生物区系的影响

对不同种植年限香草兰园植株生理指标及根际土壤微生物区系进行测定分析。结果表明:10 a以上园龄的香草兰叶片净光合速率、蒸腾速率和叶绿素含量显著降低,而0～5 a园龄香草兰叶片各生理指标并无显著性差异。平板稀释涂布结果显示:5、10和20 a园龄香草兰根际可培养细菌和放线菌数量显著低于新植园,根际细菌与新植园相比分别降低了58.4%、91.6%、96.7%;根际真菌及尖孢镰刀菌数量呈相反趋势,与新植园相比,真菌数量分别是新植园的1.6、2.1和3.4倍。综上所述,种植10 a以上的香草兰园植株生长代谢缓慢,土壤微生物由细菌型向真菌型转变,微生物区系失衡。     

Effects of azoxystrobin, difenoconazole, polyoxin B (polar) and trifloxystrobin on germination and growth of Alternaria alternata and decay in red delicious apple fruit

Alternaria alternata is the predominant fungal pathogen responsible for moldy-core in red delicious strains of apple. In this study, we report on the effects of the polyoxin B compound Polar, the strobilurin fungicides, azoxystrobin and trifloxystrobin, and the sterol inhibitor difenoconazole on spore germination, mycelial growth and fruit decay on detached fruits caused by A. alternata. Germination was most sensitive to polyoxin B and trifloxystrobin among the tested compounds. The 50% and 95% effective concentration (EC₅₀, and EC₉₅), values for in vitro inhibition of conidial germination of the fungus were lowest for polyoxin B and trifloxystrobin, ranging from <0.01 to 0.15 μg/ml and 180 μg/ml, respectively. Germination was least sensitive to difenoconazole and azoxystrobin (EC₅₀ and EC₉₅ values ranging from 25 to 72 μg/ml and 720 μg/ml, respectively). Mycelial growth in vitro of A. alternata was most sensitive to difenoconazole (EC₅₀ and EC₉₅ values of 0.8 and 12 μg/ml, respectively) and least sensitive to both strobilurin fungicides (EC₉₅>1000 μg/ml). Decay formation by A. alternata on mature detached fruits was most affected by trifloxystrobin and azoxystrobin (EC₅₀ and EC₉₅ values of 0.015–0.087 μg/ml and 8 μg/ml, respectively), intermidiate in sensitivity to Polyoxin B (EC₅₀ and EC₉₅ from 1 to 33 μg/ml, respectively), and difenoconazole was the least effective (EC₅₀ and EC₉₅ from 20 to 490 μg/ml, respectively). Polyoxin B applied at 24 or 48 h post-inoculation inhibited fruit decay development. Difenoconazole and trifloxystrobin were less effective and azoxystrobin was ineffective when applied at 48 h post inoculation. The activity of azoxystrobin, difenoconazole, Polyoxin B and trifloxystrobin on one or more stages of the life cycle of A. alternata and on decay development in fruits suggests that these compounds potentially could provide control of moldy-core disease in apple.     

玉米和小麦对黏虫生长发育和繁殖的影响

在室内温度15℃～25℃(平均18℃)、相对湿度70％、光周期12 L:12 D条件下,测定黏虫在玉米和小麦上各发育阶段的历期、存活率和产卵量,组建黏虫在两种寄主植物上的生命表.结果表明,与幼虫期取食小麦相比,取食玉米的幼虫发育历期极显著缩短(1.168±0.337)d;成虫产卵前期和产卵历期分别显著缩短和延长(1.0...     

Effect of wheat (Triticum aestivum) cultivars and seeding rate on yield loss from Galium aparine (cleavers)

Galium aparine L. is a troublesome broadleaved weed in winter wheat fields and other winter-sown crops in Eurasia and North America. Field experiments were conducted in Havza and Kavak, Samsun-Turkey, to evaluate the effect of different densities of G. aparine on the productivity of four wheat cultivars and to determine the effects of different seeding rates of wheat cultivars on the competitive ability of G. aparine. In experiments over 3 years, the wheat cultivar Panda was taller at maturity than other cultivars at both sites. Although Bezostaja was naturally shorter than other cultivars, its height decreased less due to competition from G. aparine than other cultivars. Wheat grain yields increased with seeding rate, either in the presence or in the absence of G. aparine at both locations. Based on wheat yields the relative competitiveness of the wheat cultivars was Bezostaja>Momtchill=Panda>Kate A-l. G. aparine biomass and seed numbers were reduced by an increase in the wheat seeding rate and by cultivar effects.     

Effects of germination and kilning on the phenolic compounds and nutritional properties of quinoa (Chenopodium quinoa) and kiwicha (Amaranthus caudatus)

Quinoa (Chenopodium quinoa) and kiwicha (Amaranthus caudatus) are nutritious pseudocereals that originate from the Andean region. The aim of this research was to study the effect of germination and the subsequent kilning on the phenolic compounds and proximate composition in selected Peruvian varieties of quinoa (“Chullpi”) and kiwicha (“Oscar Blanco”). The germination process was carried out for 24, 48 and 72 h at 22 °C, and the kilning was performed with samples germinated for 72 h by drying the seeds at 90 °C for 5 min. Both processes increased the protein content of the samples. However, lipid content was reduced during germination. On the other hand, germination and kilning clearly increased the concentration of total phenolic compounds in both quinoa and kiwicha. Germination for 72 h either with or without kilning process resulted in a significant (p < 0.05) increase in the total content of phenolics compared to untreated materials, which was especially due to coumaric acid and a kaempferol tri-glycoside in quinoa and caffeoylquinic acid in kiwicha. Based on the results, germination and kilning may improve the nutritional quality of the Andean grains, encouraging the usage of the processed grains as ingredients in functional products for people with special gluten-free or vegetarian diets.     

Influence of growth temperature on content, viscosity and relative molecular weight of water-soluble β-glucans in barley (Hordeum vulgare L.)

β-Glucan content and viscosity of water-soluble β-glucans have a considerable impact on the digestion of barley. Eight different 2-row barley (Hordeum vulgare L.) cultivars were grown in controlled environment chambers at five different temperatures until maturity. The samples were pearled, milled and analysed for their content of total, insoluble and soluble β-glucan. The water-soluble fraction was extracted at 37 °C, subjected to amylase treatment and freeze-dried. Water-soluble crude β-glucans were solubilised in distilled water, analysed for viscosity and their purity was checked by nuclear magnetic resonance. Molecular weights were profiled by size exclusion chromatography with RI detection. The content of total β-glucan varied from 4.0% to 7.4%, and was significantly affected by the growth temperature. An interaction between cultivar and growth temperature was observed for the total β-glucan content. The extractability was significantly affected by growth temperature, as there was recorded an increasing amount of water-soluble β-glucan with increasing growth temperature. Both the viscosity and the molecular weight of the water-soluble β-glucans increased with the growth temperature.     

Effects of light, hydropriming and abiotic stress on seed germination, and shoot and root growth of pyrethrum (Tanacetum cinerariifolium)

Poor germination and seedling establishment are major problems in arid and semi-arid environments, and these characteristics are considered to be important factors in later plant growth and yield. Laboratory experiments were conducted on freshly harvested pyrethrum (Tanacetum cinerariifolium) seeds to investigate the effects of light (influenced by the seeding method) and seed hydropriming on germination, and shoot and root growth at 25 °C. Exposure to light could reduce germination from 52% to 22% and increase the mean germination time (MGT) from 7 to 12 days. The responses of hydroprimed and unprimed seeds to salt and drought stress were determined at osmotic potentials of 0 (distilled water), −0.3, −0.6, −0.9, −1.2 MPa in NaCl and PEG6000. Seed germination and seedling growth were inhibited by increasing salt and drought stress. The germination percentage of unprimed seeds was reduced from 52% to 16% in −1.2 MPa NaCl, and no seeds germinated at osmotic potentials ≤−0.9 MPa PEG. Both shoot and root growth were inhibited at osmotic potentials ≤−0.9 MPa NaCl and ≤−0.6 MPa PEG. Hydropriming shortened the delay of MGT at all osmotic potentials, and improved the germination percentage in distilled water (from 52% to 59%) and resistance to salt stress with nearly double germination (from 16% to 29%) at the highest salt concentration. When non-germinated seeds were transferred to distilled water after 20 days of incubation in total up to 12-15% of NaCl and 25-27% of PEG stressed seeds did not recover. These results show that the inhibition of the germination and seedling growth at the same osmotic potential of NaCl and PEG resulted from drought stress rather than salt toxicity, and that hydropriming is an effective tool to improve the quality of pyrethrum seeds.     

Effects of cooking,germination and fermentation on the chemical composition of Nigerian Cowpea (Vigna unguiculata)

The effects of cooking, germination, and fermentation on the chemical composition of cowpea were studied. There were noticeable trends in the protein, carbohydrate and crude fiber as a result of the different treatments. Both the germinated and fermented samples contained more ether extractable lipids than the raw and cooked samples. Untreated raw cowpea contained 5.9 mg/g phytic acid, 1.66 mg/g phytate phosphorus, 3.3 mg/g total phosphorus, 56.8 mg/g total sugar, and no reducing sugar. Cooking the dry beans at 100°C for 1 1/2 hours had little effect on the phytic acid and phytate phosphorus. There were, however, significant decreases in total phosphorus and sugars of the cooked beans. After germination for 24 hours, 48 hours and 72 hours respectively, there was a significant decrease in phytic acid and total sugar and increase in total phosphorus and reducing sugar. Similar results were also obtained when the dry beans was fermented for 24 hours, 48 hours and 72 hours respectively.     

Effects of piperonyl butoxide on Bemisia tabaci Genn. (Homoptera: Aleyrodidae): mortality, development, parasitism and predation in Israeli cotton fields

In field trials in Israel, piperonyl butoxide (PB) alone, at concentrations of 2000 and 5000 ppm exerted good control over nymphal Bemisia tabaci populations on cotton. Weekly doses of these concentrations exerted greater control than a recommended oil and were as effective as the standard single application of buprofezin. Cypermethrin caused marked resurgence within the plots, probably as a consequence of its detrimental effects on natural enemies. Neither PB, buprofezin nor the oil reduced the incidence of natural enemies. Treatment with 2000 or 5000 ppm PB resulted in a shift in age structure toward a greater proportion of young instars than in other treatments. There was some evidence that these effects facilitated a greater level of parasitism in PB-treated plots.     

不同测报工具对吉林省粘虫监测效果研究

通过比较3种测报工具(诱蛾器、虫情测报灯、高空探照灯)对吉林省粘虫成虫的诱捕效果,结合卵巢解剖技术确定粘虫虫源类型,探讨适用于吉林省各虫源类型粘虫的监测工具。结果表明,吉林省的粘虫成虫可分为迁入型、混合型、迁出型3种虫源类型。3种测报工具均能有效监测粘虫成虫发生的相对高峰期。以诱集数量为标准,针对迁入型虫源,选择诱蛾器、高空探照灯为测报工具;针对混合型虫源,虫情测报灯诱捕效果较好;针对迁出型虫源,选择虫情测报灯、诱蛾器为适宜的测报工具。     

Effect of irrigation frequency and planting density on herbage biomass and oil production of thyme (Thymus vulgaris) and hyssop (Hyssopus officinalis)

An experiment was undertaken to determine the herbage biomass and oil production of thyme (Thymus vulgaris Linn.) and hyssop (Hyssopus officinalis Linn.) in 2003 and 2004 in the semi-arid region of Khorasan in Iran. The experiment was a split plot with three irrigation intervals as main plots and three planting densities as subplots, all of which replicated three times. Irrigation intervals consisted of 7, 14, and 21 days for both crops and planting densities of 6.6, 8, and 10 (plants m⁻²) for thyme and 5, 6.6, and 8 (plants m⁻²) for hyssop. Different planting densities were employed by changing planting distances on cultivation rows. Herbage biomass and oil production of shoots, harvested at flowering were measured as annual production of each crop. Irrigation intervals did not change total harvested herbage biomass and oil production of both crops. Averaged across both years of the experiment, thyme produced higher oil than hyssop. Both crops produced higher biomass and oil in the second year of the experiment compared to the first year. While thyme plants biomass and oil production were lower at the highest planting density, hyssop plants showed no response to planting density. Herbage biomass and oil production of hyssop did not show a clear trend in response to interaction of irrigation intervals and planting densities in both years of the experiment. Our results showed that there is a high potential for saving water through longer irrigation intervals (e.g. 14 days) using locally adapted plants in the semi-arid conditions of Khorasan. These crops serve as alternative sources of income in dry years.     

橡胶叶水浸提液对花生幼苗早期根系形态及其生理特性的影响

为深入理解橡胶树的化感抑制作用,采用适当浓度的橡胶叶水浸提液处理刚萌动的花生种子10 d,测定花生幼苗早期根系形态及其生理指标。结果表明:橡胶叶水浸提液能显著降低花生幼苗胚根长度、苗高、根鲜重、地上部鲜重以及根冠比,对根生长的抑制作用比地上部强烈;能显著降低根系总长、根表面积、根体积和根尖数,但对根平均直径有轻微的促进作用,与对照相比,差异不显著;能显著降低根系SOD、POD、CAT活性、可溶性蛋白质、可溶性糖、脯氨酸含量以及根系活力,却明显增加根系MDA含量和相对电导率。说明橡胶叶水浸提液可通过破坏花生幼苗的抗氧化防御机制,降低其渗透调节能力,减少根系的吸收面积,抑制根系的吸收活性来抑制花生幼苗的生长。