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1.
Reduced lignin concentration in brown mid-rib mutants in both maize and sorghum have resulted in improved dry matter digestibility, increased milk yield and higher energy in lactating cows. However, the mutations were not widely deployed due to concern that reduced lignin concentration might increase vulnerability to lodging and stalk rot incidence. The objective of this study was to determine the effects of the mutations on stalk strength and stalk rot resistance in both sorghum and maize. Six brown midrib (bmr) sorghum, four brown midrib (bm) maize, and their normal isolines were evaluated for stalk strength and stalk rot disease reaction at two locations in four replications. Three randomly selected plants in each plot were inoculated with Macrophomina phaseolina at 14 d after flowering by using the toothpick inoculation technique. On 28 d after inoculation, the plants were rated for disease severity by measuring the length of necrotic lesions in the stalks. Stalk strength was determined from another three random plants in each plot by using a rind penetrometer. The mutations had no effect on stalk rot disease severity in either sorghum or maize though stalks strength was markedly affected by the mutations in both species. While maize bm entries broke easily in response to mild mechanical stress, bmr sorghums did not exhibit sign of stalk collapse in all backgrounds. The result suggests that the bmr genes in both maize and sorghum can be deployed without incurring losses to stalk rot disease.  相似文献   

2.
The ability of hydrolytic enzyme production by two different isolates of Macrophomina phaseolina was studied on apple pomace as a substrate for solid state fermentation (SSF). Initial moisture level, temperature and fermentation period was optimized so as to achieve higher output. Among the two different isolates, microsclerotial (MphP) and mycelial (MphM), MphP was observed as a potential source of different hydrolytic enzymes as compared to MphM. MphP gave higher enzyme activities (IU/gram dry substrate (gds): filter paper cellulase (FPase) activity 196.21 ± 16.3 (120 h), carboxymethyl cellulase (CMCase) 279.34 ± 28.25 (72 h), β-glucosidase (BGL) 129.82 ± 12.41 (96 h), xylanase 2527.88 ± 46.15 (120 h), and amylase 2780.72 ± 38.13 (96 h), respectively at 70% (v/w) IML. The incubation temperature was also found to have impact on the enzyme production ability of Macrophomina strains. The higher enzyme activities were achieved (IU/gds) as follows FPase 276.13 ± 25.02 (40 °C, 120 h), CMCase 278.11 ± 24.47 (35 °C, 144 h), BGL 189.47 ± 15.05 (30 °C, 144 h), xylanase 3845.77 ± 43.38 (35 °C, 144 h) and amylase activity of 3309.45 ± 29.22 (35 °C, 120 h), respectively using MphP at 70% (v/w) IML. This study reports for the first time the potential of carbohydrate degrading enzyme bioproduction by different isolates of M. phaseolina.  相似文献   

3.
Five bacterial strains (TR1 to TR5) isolated from root nodules of fenugreek (Trigonella foenum-graecum) were tested for their plant growth promotory traits and biocontrol potential against Fusarium oxysporum. On the basis of morphological, physiological, biochemical and molecular characteristics, strains TR1 and TR3 - TR5 were identified as Ensifer meliloti, and TR2 as Rhizobium leguminosarum. All bacterial isolates utilized phosphate in vitro. Except TR5, all isolates produced IAA and none of them showed volatile cyanogens production. Except TR3, all isolates produced in vitro siderophore. Isolate TR1 and TR4 showed chitinase production while only TR2 showed β-1,3-glucanase activity. Isolates TR1, TR2 and TR5 exhibited ACC deaminase activity. Isolates TR1, TR2 and TR4 inhibited the growth of F. oxysporum, causing loss of structural integrity of the mycelium, hyphal perforation, lysis, fragmentation and degradation. The potential for nodulation and nitrogen fixation of the strains were confirmed by amplification of 500 bp nodC and 781 bp nifH fragments. The application of the TR1 + TR2 combination resulted in increased grain yield by 35% and 36% of fenugreek in two consecutive field trials, respectively as compared to control. Maximum increments in vigour index, nodule number and root and shoot biomass were recorded with seed inoculated with consortium (TR1 + TR2) followed by single inoculation as compared to control. The antibiotic resistant marker strain of E. meliloti TR1strep+ and R. leguminosarum TR2tet+ confirmed the efficient colonization of fenugreek roots. This study showed that these rhizobial isolates have properties of biocontrol agents and may be applied to promote the growth of fenugreek.  相似文献   

4.
The full whole culture (FWC), containing parasporal protein toxins of Bacillus thuringiensis israelinsis (Bti) and Bacillus sphaericus 2362 (Bs), either singly or in combination with plant oils and commercial insecticides, was tested against larval and adult stages of Culex pipiens mosquitoes under controlled laboratory conditions. In terms of LC50 values recorded after 24, 48, 72 and 96 h, the bacterial toxins showed high potency towards both larvae and adults of mosquitoes in a dose-dependent manner. Generally, the Bti toxin seemed to be more potent than the Bs toxin. For example, the Bti toxin showed a 24 h LC50 of 8.2 ppm against mosquito larvae compared to 13.6 ppm for the Bs toxin. In the adult bioassay, the obtained 24 h LC50 values were 0.064 and 0.085 mg/cm2, respectively for the two bacterial toxins. The bacterial toxins mixed with plant oils or insecticides at equitoxic doses (e.g., LC25 values) mostly showed potentiation effects, either against larvae or adults of the tested insect. Among a total of 14 paired mixtures, only the joint action estimated for the mixture of malathion + Bti or Bs was accounted as additively. Combining Bti or Bs endotoxins at LC0 with different plant oils and insecticides at LC50 concentration levels each, has resulted in considerable synergism against either larvae or adults. In the case of larval bioassays, the maximum synergistic factor (SF) obtained (ca. 2.0) was entitled to the mixture of Bti + spinosad. In the adult bioassays, the mixtures containing Curcuma longa or Melia azedarach oil extracts with Bti or Bs toxins achieved a SF accounted to 2.0. The results of the present study may be considered as an additional contribution to the area of joint toxicity of biocidal agents combining bacterial toxins, plant oils and traditional insecticides. The reached findings may encourage future research to elucidate its performance under practical field conditions.  相似文献   

5.
Ritu Mawar  Satish Lodha   《Crop Protection》2009,28(10):812-817
In a two year field study, the effect of varying intensities of sub-lethal heating on the efficiency of Brassica amendments in controlling viable populations of Macrophomina phaseolina and Fusarium oxysporum f sp. cumini was determined in an arid region of India. After 30 d of dry summer exposure of pathogen infested soil, incorporation of mustard residues and oil cake (0.18% and 0.04% w/w) and then applying one irrigation caused significant reduction by 75.3–81.3% in viable counts of M. phaseolina that causes dry root rot of legumes and by 93.9% in counts of F.o. f. sp. cumini causing wilt of cumin (Cuminum cyminum L.) at 0–15 and 16–30 cm depths. Increasing duration of summer exposure to 60 d improved the reductions in viable propagules of M. phaseolina by 83.6–90.4% and in F.o. f. sp. cumini by 78.2–94.8% at same soil depths. At certain heat levels, reduction in viable population of Fusarium due to amendments and irrigation was greater than that recorded in Macrophomina. Significantly low levels of reduction in pathogenic propagules of Macrophomina (63.9–71.4%) and Fusarium (48.0–57.2%) under shade compared to unshaded conditions indicated that mild heating did not cause discernible weakening effect. In second season also, 89.2–91.5% and 78.5–95.8% reduction in counts of Macrophomina and Fusarium, respectively was achieved by the application of amendments after 60 d of summer exposure at 0–30 cm soil depth. These results suggested a new approach to improve the control of soil-borne plant pathogens in hot arid regions by combining prolonged sub-lethal heating, effective naturally available on-farm wastes as soil amendments and one summer irrigation.  相似文献   

6.
Arbuscular mycorrhizal fungi (AMF) and members of the genus Trichoderma have emerged as promising groups of microbial inoculants that can induce plant growth and resistance to disease. This study aimed at investigating the potential of AMF and a strain (PR11) of Trichoderma asperellum to promote cacao growth and induce resistance against Phytophthora megakarya. Cacao seedlings were either non-inoculated, or inoculated with the saprophytic fungus T. asperellum and/or a mixture of two different mycorrhizal fungi, Gigaspora margarita and Acaulospora tuberculata. Eighteen weeks after planting, a series of morphological as well as biochemical changes, which are considered to be part of the plant defense response, were measured after a challenge inoculation of the leaves with zoospores of P. megakarya. Inoculation with AMF and T. asperellum alone was essential for the promotion of plant growth. Significant increase in plant height, root and shoot fresh weights, as well as phosphorous uptake was recorded in comparison to non-inoculated control plants. However, dual inoculation of cacao seedlings with T. asperellum and AMF did not always positively benefit the plants. Leaf inoculation showed variation among the treatments, with the lowest disease index (highest level of resistance) recorded in plants inoculated with either AMF or T. asperellum only. This came along with a high synthesis of amino acids and phenolic compounds in both healthy and infected leaves, suggesting that these metabolites are implicated in disease resistance.  相似文献   

7.
In vitro clonal propagation of Clitoria ternatea has been achieved by employing decapitated embryonic axes (DEAs) explants. The explants induced multiple shoots on cytokinin-containing medium. Several cytokinins [6-benzylaminopurine (BAP), 6-furfuryl aminopurine (KIN) and thidiazuron (TDZ)] were assayed. The best response was achieved with 2 mg l−1 BAP in which 100% of cultures produced 6.0 ± 0.14 shoots per explant. MS + 1 mg l−1 gibberellic acid (GA3) was the most suitable for shoot elongation. Regenerated shoots were rooted in half-strength Murashige and Skoog (MS) medium with 0.2 mg l−1 indole-3-butyric acid (IBA). Plantlets were successfully acclimatized and established in soil, and they were morphologically indistinguishable from the source plant. The plantlets attained maturity and flowered normally. The efficient regeneration protocol reported here provides an important method of micropropagation of this plant. Furthermore, this protocol may be used for genetic transformation of this valuable medicinal plant for its further improvement.  相似文献   

8.
The aphids Macrosiphum euphorbiae (Thomas) and Myzus persicae (Sulzer) (Hemiptera: Aphididae) are responsible for yield reduction in potato (Solanum tuberosum) production by direct phloem feeding and by spreading viruses. Breeding resistant traits from Solanum chomatophilum into the potato germplasm provides alternative means to control aphid infestations. Integrated pest management strategy, using plant resistance, benefits from the characterization of the resistance and of its impact on aphid biology. Our objective was to characterize the resistance of S. chomatophilum by assessing the effects of accessions, plant parts on aphid performance, and by assessing the impact of the resistance factors on different aphid developmental stages and on alate morph production. Detailed aphid performance was obtained by measuring fecundity, survival, percentage of nymphs that reached adult moult, and population growth using whole plant and clip cage experimental designs. Accession and plant physiological age, but not aphid developmental stage, influenced all life-history parameters, except for alate morph production which was not induced on the resistant accessions. Plant part influence was independent of plant species and accession. Both experimental designs resulted in congruent resistance levels at the accession level for each of the two aphid species, supporting the use of any of them in S. chomatophilum resistance screening. PI243340 was resistant to both aphid species, while PI365324 and PI310990 were also resistant to M. euphorbiae and M. persicae, respectively.  相似文献   

9.
The fungitoxic effects of 66 medicinal plants belonging to different families were evaluated in vitro on Pythium aphanidermatum, the causal agent of chilli damping-off. Of these, Zimmu leaf extract (Allium sativum L. × Allium cepa L.) showed the highest inhibition of mycelial growth of P. aphanidermatum (13.7 mm). The antimicrobial compounds were isolated from Zimmu leaf extract and 22 compounds were identified through gas chromatography mass spectroscopy (GC–MS). Biocontrol agents Trichoderma viride and Pseudomonas fluorescens and Zimmu extract were also tested alone and together in vitro and in vivo experiments for control of P. aphanidermatum. The in vitro studies revealed that combination of T. viride + P. fluorescens + Zimmu leaf extract showed the highest mycelial growth inhibition over the control. Both antagonists were compatible with each other and with Zimmu leaf extract. The pot culture studies revealed that seed treatment with combined application of T. viride + P. fluorescens + Zimmu leaf extract was superior in reducing the pre and post-emergence damping-off incidence (8.3 and 17.0%, respectively), and increased the plant growth and yield (shoot length and root length of 13.7 and 6.3 cm, 146 g/plant, respectively) of chilli when compared to control.  相似文献   

10.
Hybanthus parviflorus is a perennial shrub, widely distributed in the tropical and subtropical regions of America, and is known as ‘violetilla’ in Argentina. Previous phytochemical studies of this species led us to the isolation and determination of the primary structure of a novel macrocyclic polypeptide, the cyclotide hypa A. Here the insecticidal activities of extracts of H. parviflorus were determined against Ceratitis capitata Wied., the Mediterranean fruit fly or ‘Medfly’. Mortality in the different life stages of Medfly, total mortality and modifications of the insect’s physiology caused by 50% EtOH and CH2Cl2 extracts of H. parviflorus were evaluated. In addition, we determined the occurrence of ursolic acid, β-sitosterol and the polyphenols quercetin, quercetin-3-methyl ether, apigenin, luteolin, kaempferol, rutin, caffeic acid and chlorogenic acid. The promising insecticidal activity of 50% EtOH extracts of H. parviflorus and its purified fractions was related to the presence of cyclotides. The insecticidal activity of CH2Cl2 extracts could be related to the presence of polyphenols, ursolic acid and β-sitosterol.  相似文献   

11.
Transgenic corn hybrids that express toxins from Bacillus thuringiensis (Bt) are highly effective against the European corn borer, Ostrinia nubilalis (Hübner), and the closely related Asian corn borer, Ostrinia furnacalis (Guenée). Since the registration of Bt corn hybrids in the U.S. in 1996, there has been a great deal of information generated on O. nubilalis. However, relatively little information exists for O. furnacalis. To help determine whether the information generated for O. nubilalis can be leveraged for decisions regarding the use of transgenic Bt corn against O. furnacalis, experiments were designed to determine whether the pattern of sensitivity to various Bt Cry1 toxins is similar between the two species. Test insects included laboratory-reared O. furnacalis originating from Malaysia, a Bt-susceptible laboratory colony of O. nubilalis maintained at the University of Nebraska-Lincoln (UNL) and an out-group consisting of the sugarcane borer, Diatraea saccharalis (F.), from Louisiana which represents a different genus from the same family. O. furnacalis and O. nubilalis exhibited a similar pattern of susceptibility to all the Cry1 toxins and were highly susceptible to the range of Bt toxins tested including Cry1Aa, Cry1Ab, Cry1Ac and Cry1F. Both of the Ostrinia species were more tolerant to Cry1Ba compared with D. saccharalis, although sensitivity of O. furnacalis was intermediate and did not differ significantly from that of O. nubilalis and D. saccharalis. D. saccharalis was also susceptible to the range of toxins tested but unlike the two Ostrinia species, was more tolerant to Cry1F and more susceptible to Cry1Ba. These results indicate that both of the Ostrinia corn borer species are similar in sensitivity to the Cry1Aa, Cry1Ab, Cry1Ac, Cry1Ba and Cry1F toxins, thus suggesting shared toxin receptors and mechanisms of toxicity for the two species.  相似文献   

12.
The legume pod borer Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) has developed high levels of resistance to conventional insecticides, and therefore, efforts are being made to develop transgenic chickpea expressing toxin genes from the bacterium Bacillus thuringiensis (Bt) for controlling this pest. However, there is an apprehension that acid exudates in chickpea might interfere with the biological activity of Bt. Therefore, we studied the biological activity of Bt (BiolepR) on four chickpea genotypes with different levels of resistance to H. armigera under field conditions, and by incorporating lyophilized leaf and pod tissue into the artificial diet with and without Bt. The pH of the acid exudates varied from 2.1 to 2.9, and malic and oxalic acids were the major components of the acid exudates in different chickpea genotypes. There was no survival of H. armigera larvae in chickpea plants sprayed with 0.1, 0.2 and 0.5% Bt. There was a significant reduction in larval survival, larval and pupal weights and fecundity, and prolongation of larval and pupal periods in chickpea plots sprayed with Bt (0.05%) as compared to the unsprayed plots. Biological activity of Bt was lower on artificial diets with leaf or pod powder of chickpea genotypes, which might be because of a low intake of Bt toxins due to the antifeedant effects of acid exudates in the chickpea or reduction in biological activity of Bt due to the interaction of biochemical constituents in chickpea with the Bt toxins. Larval survival, larval and pupal weights, pupation and adult emergence were significantly lower on diets with leaf or pod powder of the H. armigera-resistant genotypes than on the susceptible check. Chickpea genotypes with resistance to H. armigera acted in concert with Bt to cause adverse effects on the survival and development of this insect. The results suggested that development of transgenic chickpeas expressing toxin genes form Bt will be quite effective for controlling of the pod borer, H. armigera.  相似文献   

13.
Three hundred (300) methanol extracts of barks, leaves, flowers and stems of 200 plant species from Alto Rio Grande and Vale do São Francisco regions, State of Minas Gerais, Brazil, were prepared and submitted to an in vitro growth test with the fungus Colletotrichum lindemuthianum, causal agent of anthracnose in common bean. Extracts from 13 plant species (Astronium fraxinifolium, Inga marginata, Malva sylvestris, Matayba elaeagnoides, Miconia argyrophylla, Myrcia fallax, Ocimum gratissimum, Origanum vulgare, Rollinia emarginata, Siparuna arianeae, Styrax pohlii, Tabebuia serratifolia and Trichilia pallida) presented antifungal activity and were used in other in vitro assays. Extracts from M. argyrophylla, M. fallax, O. vulgare, S. arianeae and S. pohlii were the most promising for the inhibition of the mycelial growth while the extracts of M. argyrophylla, M. elaeagnoides and O. gratissimum presented the best results for the inhibition of conidial germination. Under greenhouse conditions, the extracts of M. argyrophylla and O. vulgare caused the greatest reductions (41.82% and 37.65%, respectively) in disease severity when a local effect assay was carried out. In the systemic effect assay, also in a greenhouse, the most promising extracts were those from I. marginata, M. argyrophylla, M. fallax, M. sylvestris, O. gratissimum, O. vulgare and S. arianeae, which reduced the severity of the anthracnose to values below 35% of the observed for the control. Therefore, future studies with these plant species should be carried out to develop new products to control the common bean anthracnose.  相似文献   

14.
Trichoderma viride was proved as an effective biocontrol agent against two fungal pathogens, Fusarium oxysporum f. sp. adzuki and Pythium arrhenomanes, infecting soybean. During an in vitro biocontrol test, Trichoderma showed mycoparasitism and destructive control against the tested fungal pathogens. Both the pathogens significantly influence the germination and P. arrhenomanes had a severe effect (only 5% germination). The root system of the soybean plant was poorly developed due to the infection and it exerted a negative influence on the nodulation and further growth phases of the plant. During pot assay along with biocontrol activity, Trichoderma showed growth promoting action on the soybean plant. Trichoderma enhanced growth of shoot and root systems and fruit yield after 12 weeks of growth. Pythium and Fusarium infected plants treated with Trichoderma had ∼194% and 141% more height than pathogens alone. The fruit yield treated with Trichoderma was ∼66 per plant whereas the yield was only 41 for a control plant. The plants infected with Pythium and Fusarium and treated with Trichoderma had fruit yields of 43 and 53 respectively and those were 5 and 1.6 times higher than plants infected with pathogens.  相似文献   

15.
Two antimicrobial alkaloids, palmatine and jatrorrhizine, were isolated from tubers of traditional Chinese medicinal plant Tinospora capillipes using activity-guided isolation method and chromatography. Their antimicrobial activity was determined in vitro. The results showed that palmatine and jatrorrhizine had inhibitory activity against plant pathogens Colletotrichum gloeosporioides, Fusarium oxysporum f. sp. niveum, Mycosphaerella sentina, Pestalotia mangiferae, Cercospora kaki, Gymnosporangium haraeanum, Rhizoctonia solani and Colletotrichum graminicola, with the EC50 values of 0.0348-0.8356 g L−1 and 0.0240-0.8649 g L−1, respectively. Palmatine and jatrorrhizine also exhibited inhibition against animal pathogens Bacillus cereus, Bacillus megaterium, Bacillus subtilis, Staphyloccocus aureus, Staphylococcus epidermidi, Micrococcus lysodeikticus, Proteus vulgaris, Salmonella typhi and Escherichia coli, with the MIC values of 0.1-0.8 g L−1 and 0.1-0.6 g L−1, respectively. These results suggested that palmatine and jatrorrhizine showed relatively broad spectrum antimicrobial activity against plant and animal pathogens.  相似文献   

16.
The population dynamics of Xanthomonas campestris pv. vitians (Xcv) was studied both externally and internally in lettuce, tomato and pepper plants. In addition, the application of bactericides during transplant production period was carried out for the management of bacterial leaf spot of lettuce under greenhouse conditions. Epiphytic populations of Xcv were recovered on leaves of lettuce plants (105 CFU/g) 5 weeks after sprayed than the other plant species when inoculated with 108 CFU/ml of Xcv. When plants of each crop species infiltrated with the bacterium at 105 CFU/ml, the highest populations were developed in lettuce (108 CFU/cm2) followed by pepper with 106 CFU/cm2 and tomato with 105 CFU/cm2 10-days after infiltration. Application of a mixture of Maneb and Kocide or Kocide alone as a foliar spray on lettuce significantly reduced the incidence and disease severity of bacterial leaf spot by 29 and 27% respectively. Spread of the bacterium and development of the disease may partly be managed by avoiding intercropping of these plants commonly grown in close proximity to lettuce. For the management of leaf-associated populations of Xcv in lettuce, use of a mixture of Maneb and Kocide is advocated to minimize the effect of attacks.  相似文献   

17.
Secondary plant compounds are recognised as important components of plant defence system against herbivores and pathogens. Five monoterpenoids, (R)-linalool, 1,8-cineole, (S)-2-heptyl acetate, (S)-2-heptanol and citral, which are natural components of the essential oils of Aframomum melegueta (K. Schum) and Zingiber officinale (Roscoe), were tested at the ratios in which they occur naturally for repellent activity against Tribolium castaneum (Herbst.) and Rhyzopertha dominica (F.) in a 4-way olfactometer. The results showed the repellent properties of the compounds as both beetles spent less time in the olfactometer arm containing the test stimuli. (R)-linalool and (S)-2-heptanol were stronger repellent compounds than the others. Linalool showed good repellent activity against T. castaneum (P = 0.001) as the insect spent 1.22 min in the test arm compared to the control arms (2.78 min), and R. dominica (P = 0.001) with 0.89 min in the test arm compared to 2.87 min in the control arms. With (S)-2-heptanol, T. castaneum spent 1.23 min in the test arm compared to 2.83 min in the control arms. R. dominica spent 1.61 min in the test arm and 2.69 min in the control arms. For the number of entries or visits made, while both insects were significantly repelled (P < 0.05) by the linalool-treated arm than the control, only R. dominica was repelled by the (S)-2-heptanol-treated arm (P = 0.038) compared to the control arms. The results indicate that A. melegueta and Z. officinale essential oils and their components could be suitable as safer repellents or fumigants against T. castaneum and R. dominica.  相似文献   

18.
Sclerotinia rot caused by the fungus Sclerotinia sclerotiorum is one of the most serious and damaging diseases of oilseed rape and there is keen worldwide interest to identify Brassica genotypes with resistance to this pathogen. Complete resistance against this pathogen has not been reported in the field, with only partial resistance being observed in some Brassica genotypes. Introgression lines were developed following hybridization of three wild crucifers (viz. Erucastrum cardaminoides, Diplotaxis tenuisiliqua and E. abyssinicum) with B. napus or B. juncea. Their resistance responses were characterized by using a stem inoculation test. Seed of 54 lines of B. napus and B. juncea obtained from Australia, India and China through an Australian Centre for International Agricultural Research (ACIAR) collaboration programme were used as susceptible check comparisons. Introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum had much higher levels (P < 0.001) of resistance compared with the ACIAR germplasm. Median values of stem lesion length of introgression lines derived from the wild species were 1.2, 1.7 and 2.0 cm, respectively, as compared with the ACIAR germplasm where the median value for stem lesion length was 8.7 cm. This is the first report of high levels of resistance against S. sclerotiorum in introgression lines derived from E. cardaminoides, D. tenuisiliqua and E. abyssinicum. The novel sources of resistance identified in this study are a highly valuable resource that can be used in oilseed Brassica breeding programmes to enhance resistance in future B. napus and B. juncea cultivars against Sclerotinia stem rot.  相似文献   

19.
Prohexadione-calcium and trinexapac-ethyl, inhibitors of 2-oxoglutaric acid-dependent dioxygenases, were tested for their efficacy in controlling scab infection on apple (cv. Golden Delicious) scions under greenhouse and field conditions. Their effectiveness was compared with other types of growth inhibitors (chlormequat chloride and paclobutrazol). Furthermore, to determine the time required to build-up plant resistance against scab, the compounds were applied at different concentrations and timings prior the inoculation with Venturia inaequalis. Prohexadione-calcium and trinexapac-ethyl significantly reduced scab incidence starting approximately 10 and lasting for approximately 25 days after application. In field conditions, the practical application of these compounds may result valuable both to control the vegetative/reproductive balance of the trees and to effectively reduce the amount of fungicides used to control scab.  相似文献   

20.
Laboratory and field/pot experiments were conducted to determine the effect of two insecticides, fipronil and pyriproxyfen, on growth, symbiotic properties (nodulation and leghaemoglobin content), amount of N and P nutrients in plant organs, seed yield and seed protein of pea plants. In addition, the role of the most promising fipronil and pyriproxyfen tolerant Rhizobium leguminosarum strain MRP1 having plant growth promoting traits such as, production of phytohormones and siderophores, was also assessed in the presence and absence of both insecticides. Generally, fipronil and pyriproxyfen at the tested rates (recommended and higher doses) decreased the growth of both R. leguminosarum inoculated or uninoculated pea plants. Of the various concentrations of the two insecticides, pyriproxyfen at all concentrations in general, showed comparatively more severe toxicity to pea plants by decreasing plant biomass, symbiotic attributes, nutrients (nitrogen and phosphorus) uptake, seed yield and grain protein over the uninoculated control. The sole application of 3900 μg pyriproxyfen kg−1 soil (three times the recommended dose) showed the highest toxicity and decreased the root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, seed yield and grain protein by 20%, 27%, 25%, 29%, 15% and 2% respectively, compared to the control. Interestingly, when the inoculant strain MRP1 was used with any concentration of the two insecticides, it significantly (P ≤ 0.05) increased the measured variables (plant dry weight, nodule numbers, dry nodule biomass, leghaemoglobin, nitrogen and phosphorus uptake, seed yield and grain protein) when compared to the plants grown in sandy clay loam soils treated solely (without inoculant) with the same individual treatment of each insecticide. For instance, three times the recommended dose of pyriproxyfen with strain MRP1 showed a highest stimulatory effect and increased the root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, seed yield and grain protein by 108%, 124%, 119%, 153%, 112% and 6% respectively, compared to the plants grown in soil treated solely with three times the recommended dose of pyriproxyfen.  相似文献   

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