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1.
Tomato fruits are susceptible to infection by Alternaria species. In addition, Alternaria species may contaminate the fruits with mycotoxins. There is thus interest in control systems to minimise pathogenicity and control toxin production. The objectives of this study were to examine the effect of plant extracts of Eucalyptus globulus and Calendula officinalis on the growth of strains of Alternaria alternata and A. arborescens, on pathogenicity of tomato fruits and mycotoxin production. The growth bioassays showed that the ethanolic and chloroformic fractions of E. globulus were the most effective in reducing growth of A. alternata (66–74 %) and A. arborescens (86–88 %), respectively at 2500 μg/g. The effects of plant extracts on mycotoxin biosynthesis were variable and strain dependent. The most effective fractions in decreasing mycotoxin accumulation were the ethanolic and chloroformic extracts of E. globulus, which reduced tenuazonic acid by 89 %, alternariol by 75–94 % and almost complete inhibition of alternariol monomethyl ether. All the tested fractions reduced percentage of infected tomato fruits when compared to the controls. The ethanolic and chloroformic fractions of E. globulus completely inhibited growth of A. alternata and A. arborescens on unwounded fruits and reduced the aggressiveness on wounded fruits of strains of both species significantly.  相似文献   

2.
The ability to control soil-borne pathogens in agriculture is highly conditioned by the restricted use of synthetic pesticides. Allelopathy, the antimicrobial activity of plant extracts, is a promising option against crop pathogens. Extracts from Lycium spp. such as L. barbarum, L. chinense and L. intricatum possess biological and therapeutic properties. Individual methanolic extracts from leaves and stems of the Mediterranean medicinal species L. europaeum collected in two locations of Tunisia were each evaluated in vitro against Verticillium dahliae (Vd), Sclerotinia sclerotiorum (Ss) and Harpophora maydis (Hm). The mycelial growth of the three fungi was significantly reduced by all the extracts at doses of 10 and 30 μl mL?1 (equivalent to 1 and 3 mg plant tissue mL?1). The sporulation of Hm was almost completely inhibited in all the amendments, but that of Vd was stimulated by one of the leaf extracts when 1 and 3 mg dried plant tissue mL?1 were used. Sclerotia of Ss were formed in a smaller number, their total weight increasing at extract doses equivalent to 1 mg plant tissue mL?1 and higher. In greenhouse, the pathogenicity of Hm was confirmed as early as 6 weeks after inoculation, since it caused significant decreases of weights in both roots and aboveground parts of maize. The detrimental effect of Hm on maize root weight in greenhouse was significantly counteracted by one of the leaf extracts added by watering. In total, 11 phenolic compounds were separated in the four extracts. The hydroxycinnamic acid family, including chlorogenic acid as a major compound, represented more than 50% of the total content in all the samples. Rutin was the most abundant flavonoid. The results of this work show the detrimental effect of L. europaeum extracts against the soil-borne pathogens Hm, Ss and Vd, and highlight their potential in crop protection if adequately developed into final products and used in combination with other tools.  相似文献   

3.
Nine insecticides, namely, imidacloprid, thiamethoxam, chlorantraniliprole, clothianidin, pymetrozine, ethofenprox, BPMC, endosulfan, acephate, and the product Virtako® (Syngenta; chlorantraniliprole 20%?+?thiamethoxam 20%) were tested to determine their toxicity to the parasitoid Trichogramma chilonis using an insecticide-coated vial (scintillation) residue bioassay. All the insecticides tested showed different degrees of toxicity to the parasitoid. Thiamethoxam showed the highest toxicity to T. chilonis with an LC50 of 0.0014 mg a.i. l ?1, followed by imidacloprid (0.0027 mg a.i. l ?1). The LC50 values of acephate and endosulfan were 4.4703 and 1.8501 mg a.i. l ?1, exhibiting low toxicity when compared with other insecticides tested. Thiamethoxam was found to be 3,195, 1,395 and 1,322 times more toxic than acephate, chlorantraniliprole and endosulfan, respectively, as revealed by the LC50 values to T. chilonis. Based on risk quotient, which is the ratio between the field-recommended doses and the LC50 of the beneficial, only chlorantraniliprole was found to be harmless to T. chilonis. The insecticides thiamethoxam, imidacloprid, Virtako®, ethofenprox and BPMC were found to be dangerous to the parasitoid. Since T. chilonis is an important egg parasitoid of leaf folders, reported to reduce the pest population considerably and often released augmentatively in rice IPM programs, the above noted dangerous chemicals should be avoided in the rice ecosystem.  相似文献   

4.
Brinjal shoot and fruit borer Leucinodes orbonalis Guen. is a major pest of brinjal in India. The field collected larvae of L.orbonalis were tested for their susceptibility to three diamide insecticides by fruit dip bioassay technique. Cyantraniliprole and chlorantraniliprole were 5.23 and 2.80 times more toxic to L. orbonalis as compared to flubendiamide. Large variation in the susceptibility of L. orbonalis to cyantraniliprole, chlorantraniliprole, flubendiamide was observed and the LC50 values were 0.084, 0.157 and 0.439 mg a.i. L?1, respectively. In span of two years there was a significant increase in the LC50 values of cyantraniliprole (0.062 to 0.085 mg a.i. L?1), chlorantraniliprole (0.097 to 0.157 mg a.i. L?1), flubendiamide (0.284 to 0.439 mg a.i. L?1) to population of L. orbonalis, which showed 1.35, 1.62 and 1.55 fold resistance, respectively indicating faster development of resistance to diamide insecticides.  相似文献   

5.
In this investigation, leaf extracts of Ocimum basilicum and Mangifira indica were used as reducing agents for biosynthesis of silver nanoparticles (AgNPs). The biosynthesized AgNPs were authorized by UV-vis spectrophotometry and X?ray diffraction (XRD) analysis. AgNPs were obtained after 5?min of reaction at 80oC. The formation of AgNPs was confirmed by the presence of absorption peaks at 439?nm using extract from O. basilicum and at 442.5?nm from M. indica. X?ray spectra showed strong peaks for the crystalline Ag. Shape and size of the biosynthesized AgNPs were studied using high resolution transmission electron microscope (HR-TEM). Size of the produced AgNPs was found to be 9–35?nm. Effect of the synthesized nanosilver was then investigated on some biochemical attributes of wheat plant (Triticum aestivum cultivar saka 92). The growth parameters such as shoot lengths, fresh and dry weight of shoot, chlorophyll, carbohydrate and protein contents in shoot of wheat plant were investigated. Application of AgNPs synthesized from Ocimum basilicum and from Mangifira indica at the concentrations of 20,40?ppm showed an increase in shoot length, fresh and dry weight of shoot, chlorophyll, total carbohydrate and protein content in shoot of wheat plants, beyond these concentrations an inhibitory effects were shown.  相似文献   

6.
White grubs, Leucopholis spp. are subterranean pests of arecanut grown in South India. Grub infestation leads to yellowing, stem tapering, and crown size and yield reduction. Use of chemical insecticide to mage the white grubs gives varying degree of success. Hence an attempt was made to screen newer and safer insecticides. Imidacloprid (LC50 at 120 h = 16.849 ppm on III instar larvae), chlorpyriphos (LC50 = 14.242) and bifenthrin (LC50 = 12.797 ppm) were identified as effective insecticides. Evaluation of these insecticide in the field over two year period indicated the following efficacy in reducing larval population: chlorpyriphos @ 4 kg a.i/ha (83.31%) > bifenthrin @ 4 kg a.i./ha (82.83%) > imidacloprid @ 0.24 kg a.i./ha (75.84%) > bifenthrin @ 2 kg a.i./ ha (74.26%) > chlorpyriphos @ 2 kg a.i./ha (69.15%) > chlorpyriphos @ 1 kg a.i./ha (61.79%) > imidacloprid @ 0.12 kg a.i./ha (56.54%) > bifenthrin @ 1 kg a.i./ha (54.34%) > imidacloprid @ 0.06 kg a.i./ha (41.47%). Bifenthrin in soil persisted for a longer period than chlorpyriphos. On the day of application, 59.46 ppm bifenthrin residue was recovered from soil. On 10th day, it was 7.29 ppm which decreased to 2.59 ppm on 30th day and was beyond detection limit on 65th day. Chlorpyriphos exhibited a rapid degradation in the initial stage; 27.46 ppm residue on the day of application, which further reduced to 0.964 ppm on 10th day, and was below the detection limit on the 30th day. Growth of Trichoderma harzianum was not affected by bifenthrin even up to 40 ppm concentration. However, chlorpyriphos affected the growth of Trichoderma at higher than 5 ppm dose. Similarly, imidacloprid inhibited the colony growth from 2 ppm onwards. Having high lipophylic property and contact toxicity, bifenthrin would be an ideal alternative insecticide to chlorpyriphos for the management of white grubs in palm garden, which is safe and long persisting.  相似文献   

7.
The feeding preference by Thaumastocoris peregrinus, Carpintero and Dellapé (Heteroptera: Thaumastocoridae) on different Eucalyptus species was evaluated through choice tests in a paired comparisons design. Twenty individuals per combination were tested over a 48 h period, and each one was offered leaves of two species at a time, in all possible combinations. Preference was determined by counting the number of insect excrements on each plant as a proxy for effective feeding, and then ranked through a paired comparison matrix. A linearity index was calculated to test for hierarchy preferences and, after that, a cardinal index (David’s score) was calculated to assign a preference value for each species. The essential oils were extracted from leaves of each Eucalyptus species, and their chemical composition determined through GC-MS. The results show a significant and strictly linear feeding preference ranking between the species tested. The order of preference between species was E. viminalis > E. grandis > E. tereticornis > E. dunnii > E. maidenii > E. globulus. The qualitative and quantitative chemical compositions of the essential oils of these Eucalyptus species differed. A significant correlation was found between the feeding preferences and the concentrations of 1,8-cineole as a repellent and p-cymene as a feeding stimulant. These results underline the importance of selecting the right Eucalyptus species in areas infested by T. peregrinus.  相似文献   

8.
Plant response to one type of stress can be affected by simultaneous exposure to a second stress, for example when abiotic and biotic stresses occur together. Ten rice genotypes comprising those with bacterial blight (BB) resistance (R) genes, drought quantitative trait loci (QTLs) plus a BB R gene, and BB susceptible genotypes, were subjected to mild and moderate drought stress and plants were inoculated with two Xoo strains (PXO99 and PXO145) to simulate the challenges rice crops face under simultaneous stress of drought and BB. Plant height and dry shoot biomass were significantly reduced by drought stress treatments. The BB disease lesion lengths varied according to rice genotypes and PXO99 Xoo multiplication and spread in planta was higher compared to that of PXO145, which generally decreased under mild drought stress. Rice genotype IRBB7 (Xa7) showed less Xoo spread and a reduced Xoo multiplication under drought stress compared to the well-watered control with PXO145. In contrast, in genotypes with a different BB R gene and/or drought QTLs [IRBB4 (Xa4), IR87705–6-9-B (Xa4 + qDYT 2.2 ), IR87707–445-B-B-B (Xa4 + qDYT 2.2  + qDYT 4.1 ) and IR87707–446-B-B-B (Xa4 + qDYT 2.2  + qDYT 4.1 )], Xoo multiplication and spread in planta was higher with drought stress. This study has shown that drought stress affected rice response to the BB pathogen and the response varied according to the rice genotype. It is concluded that evaluating rice varieties under combined abiotic and biotic stresses will be the best strategy to determine biotic stress resistance durability under climate change.  相似文献   

9.
Entomopathogenic nematodes in the genus Steinernema are associated with Xenorhabdus spp. bacteria. When steinernematid colonise an insect host the nematode-bacterium association overcomes the insect immune system and kills the host within 48 h. Xenorhabdus spp. produce secondary metabolites that are antifungal to protect nematode-infected cadavers from fungal colonization. The concentrated, or cell-free metabolites of X. szentirmaii exhibit high toxicity against various fungal plant pathogens and show potential as natural bio-fungicides. In the current study, we determined 1) thermo-stability, 2) dose-response, and 3) shelf-life of antifungal metabolites of X. szentirmaii against Monilinia fructicola (cause of brown rot of peach and other stone fruit) and Glomerella cingulata (cause of antharacnose). Thermo-stability was determined by autoclaving bacterial culture broths (121 °C and 15 psi for 15 min) and measuring fungal growth on in potato dextrose agar (PDA) containing 10% of the supernatants. Autoclaving had no impact on the antifungal activity of the secondary metabolites. Over a test period of 9 months, the activity of both extract types did not decline when stored at 4 or 20 °C. A dose-response study (10, 20, 40, 60, 80 and 100% supernatant-containing metabolite) using both phytopathogens demonstrated that a greater dose of supernatant increased antifungal activity. The antifungal-metabolite containing supernatant of X. szentirmaii has potential as a bio-fungicide. These results demonstrate the metabolite(s) are thermo-stable, they have a long shelf-life and require no stabilizing formulation, even at room temperature.  相似文献   

10.
We evaluated the chemical composition of thirteen commercially available plant essential oils and their insecticidal activity against the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Gas chromatography-mass spectrometry was used to characterize the chemical components of the essential oils. A total of 113 compounds were identified, with terpenes (>80%) and aromatic compounds as primary constituents. The toxicity of each pure essential oil was tested separately on third instar larvae and adult beet armyworms by topical application of 0.5 μl oil/ insect. All plant essential oils were found to be harmful to S. exigua, with third instar larvae showing significantly more susceptibility than adults. Essential oils of Cinnamomum zeylanicum and Juniperus virginiana showed the highest toxicity (mortality above 90%) to larvae, while C. zeylanicum and Pogostemon cablin oils were the most harmful compounds (95% mortality) to adults. Cymbopogon winterianus oil caused delayed mortality (similar to the effects of insect growth regulators) as well as malformations in pupae. C. winterianus, Ocimum basilicum and Rosmarinus officinalis oils significantly reduced fecundity, whereas no significant effects were observed on fertility.  相似文献   

11.
The Rhizoctonia solani species consists of multinucleate isolates that belong to anastomosis groups AG1–AG3 and differ in virulence and host affinity. R. cerealis is a binucleate species of anastomosis group AG-D which causes sharp eyespot, a common plant disease in Poland. Rhizoctonia spp. is a ubiquitous soil pathogen that poses a significant threat for global crop production due to the absence of effective crop protection products. The aim of this study was to determine the virulence of R. solani and R. cerealis isolates towards Beta vulgaris, Zea mays, Triticum spelta and T. aestivum seedlings, to confirm the presence of endopolygalacturonase genes pg1 and pg5 in the genomes of the tested isolates and to evaluate the tested isolates’ sensitivity to triazole, strobilurin, imidazole and carboxamide fungicides. All tested isolates infected B. vulgaris seedlings. but none of them were virulent against Z. mays plants. R. solani isolates AG4 PL and AG2-2IIIB PL were characterized by the highest virulence (average infestation score of 2.37 and 2.53 points on a scale of 0–3 points) against sugar beet seedlings. The prevalence of infections caused by most of the analysed isolates (in particular R. solani AG4 J—11.8, and R. cerealis RC2—0.78) was higher in spelt than in bread wheat. The virulence of the analysed isolates was not correlated with the presence of pg1 and pg5 genes. The efficacy of the tested fungicides in controlling Rhizoctonia spp. infections was estimated at 100% (propiconazole + cyproconazole), 98.8% (penthiopyrad), 95.4% (tebuconazole) and 78.3% (azoxystrobin).  相似文献   

12.
Chamomile Matricaria recutita (L.) is an ancient healing plant; it is used for a sore stomach, a mild laxative, anti-inflammatory and a gentle sleep aid. Chamomile plants are infested by chamomile stem-weevil Microplontus rugulosus (Col., Curculionidae) and chamomile smooth beetle Olibrus aeneus (Col., Phalacridae), and can lead to a high reduction in chamomile yield. This work aimed to survey M. rugulosus and O. aeneus by different monitoring methods as well as to manage them by using entomopathogenic nematodes.  相似文献   

13.
Fusarium oxysporum f. sp. melongenae (Fomg), causal agent of Fusarium wilt of eggplant, is a serious pathogen in open fields and greenhouses. Inter-simple sequence repeat (ISSR) banding profiles, sequence analyses of inter-transcribed-spacer (ITS), translation elongation factor 1-alpha (TEF-1α), and actin (actA) DNA regions were employed in this study to determine genetic diversity and population structure of Fomg isolates obtained from Turkey. For ISSR study, (ACTG)5, (GACAC)3, (GACA)4, (GATA)4, HVH(TG)7 and (CA)8RG primers were selected from a set of 16. Discriminative ability of the primers revealed with various indices including polymorphic information content (PIC), and mean PIC value was calculated as 0.26. The ISSR data revealed 31 loci belonging to 202 Fomg isolates and 14 of them were found to be polymorphic. The isolates on neighbor joining ISSR tree were grouped into two major clusters which separated Fomg and outgroup isolates. Population structure was investigated based on bayesian modeling and results indicated five subpopulations (K = 5, ?K = 205.42). Mean genetic and geographical distances among sampling locations revealed only a weak and insignificant correlation (r = 0.583, P = 0.06). Phylogenetic analyses were carried out with ITS, TEF-1α and actA DNA regions with a selected subset of 30 Fomg, along with one non-host and one outgroup isolates. Since ITS region were not able to provide a meaningful separation, TEF-1α and actA sequences of each organism were concatenated individually to build a dendrogram. The clustering tree successfully separated the Fomg, non-host and outgroup isolates in which all Fomg were located on the same branch, forming a monophyletic group in the dendrogram.  相似文献   

14.
Locomotory behaviour of insecticide-resistant and susceptible populations of diamondback moth, Plutella xylostella (Linnaeus), a challenging insect-pest of cruciferous vegetable crops round the globe, was studied with the help of Ethovision. Larvae from the susceptible population of P. xylostella travelled more distance on insecticide-treated or untreated surface and consequently their speed was also more as compared to those taken from the insecticide-resistant population.Whereas, the turn angle of larvae from insecticide-resistant population was significantly higher as compared to those from susceptible population. The resistant larvae travelled significantly less distance (260.68 cm/5 min) on treated-surface (with LC50 value of endosulfan, quinalphos, fenvalerate and spinosad) with more value of turn angle (231.16°) than the susceptible ones which moved faster (517.23 cm/5 min) with less value of turn angle (100.63°). Influence of varying temperatures on locomotory behaviour of larvae from the susceptible and resistant population of P. xylostella was also studied and observed that susceptible P. xylostella larvae travelled significantly greater distance as compared to the larvae from insecticide-resistant population, at different temperatures. Locomotory behaviour of larvae of P. xylostella also changes with food conditions. Resistant larvae starved for 24 h travelled significantly lesser distance (147.29 cm) as compared to unstarved ones (332.50 cm). Similar trend in behaviour was also recorded with respect to speed of larvae of P. xylostella. Larvae turn more frequently when kept without food (starved) than those fed normally; the turn angle was significantly higher (290.07°) for resistant larvae and for susceptible larvae it was lesser i.e. 151.55°, when kept at starved conditions. Hence, certain pronounced behavioural differences were registered in locomotion of insecticide-resistant P. xylostella as compared to the susceptible one and this knowledge would help to find effective management solutions to P. xylostella.  相似文献   

15.
The occurrence and geographic distribution of longidorid nematode species inhabiting the rhizosphere of cultivated olive (cvs. Chemlali and Chétoui) in Tunisia were investigated. Morphological and morphometrical studies identified three Longidorus and six Xiphinema species, with frequencies of prevalence as following: Longidorus africanus (23.0 %), L. euonymus (4.5 %), L. glycines (13.7 %), Xiphinema conurum (13.7 %), X. italiae (36.4 %), X. meridianum (13.7 %), X. pachtaicum (18.2 %), X. robbinsi (9.1 %), and Xiphinema sp. (4.5 %). The three Longidorus species were reported for the first time in Tunisia, in addition to two species of Xiphinema (viz. X. meridianum and X. robbinsi). Molecular characterisation using D2-D3 expansion regions of 28S rRNA and ITS1-rRNA was carried out and Bayesian inference analysis was used to reconstruct phylogenetic relationships among these species and with other longidorids. Twenty-five new D2-D3 of 28S rRNA gene sequences were obtained in the present study, seven for Longidorus and 18 for Xiphinema spp., as well as 14 new ITS1 rRNA gene sequences (seven for Longidorus and seven for Xiphinema spp.).  相似文献   

16.
Real-Time PCR assay was used to quantify the expression of marker genes of the salicylic acid, jasmonic acid and ethylene signaling pathways in seven Solanum lines after inoculation with a Ralstonia solanacearum phylotype I strain, R008. Four Solanum lycopersicum lines (CRA 66, Hawaii 7996, MST 32/1, Quatre carrées), one S. tuberosum line (Spunta), the wild Lycopersicon cerasiforme and Solanum commersonii were used for this investigation. Results revealed very little activation of the jasmonic acid pathway marker genes, lipoxygenase A (LoxA) and protease inhibitor II (Pin2), with no significant difference (p > 0.05) in fold change expression among the Solanum lines. In contrast the salicylic acid pathway marker genes, glucanase A (GluA) and PR-1a, and the ethylene pathway marker genes, osmotin-like (Osm) and PR-1b, were expressed at higher levels with a statistically significant difference (p < 0.05) in fold change expression among the Solanum lines. The resistant lines L. cerasiforme, CRA 66, Hawaii 7996 and S. commersonii showed stronger activation of the salicylic acid and ethylene marker genes than the moderately resistant cultivar (MST 32/1) and the susceptible lines (Quatre carrées and Spunta). The marker genes reached their highest expression levels earlier (4 h.p.i) in the resistant and moderately resistant lines than in the susceptible lines (48 h.p.i.). These results indicate that salicylic acid and ethylene signaling pathways have a significant role in defense against R. solanacearum. The timing and magnitude of the upregulation of gene expression may determine the plant ability to put up a defense response against the pathogen.  相似文献   

17.
An enrichment microsphere immunoassay (MIA) was developed, based on the Luminex xMAP® technology, for the simultaneous (duplex) detection of Pectobacterium atrosepticum (former name Erwinia carotovora subsp. atroseptica) (Pca) and Dickeya dianthicola (former name Erwinia chrysanthemi) (Dcd) in potato plant extracts. Target bacteria in the extracts were enriched for 48 h in a semi-selective broth containing polypectate under low oxygen conditions. Samples were subsequently incubated with antibody-coated colour-coded microspheres (beads) and with secondary antibodies conjugated with Alexa Fluor® 532, a reporter dye. Samples were analyzed with the Luminex analyzer, in which one laser identified each microsphere and another laser the reporter dye conjugated to the secondary antibodies. The assay required minimal sample preparation, could be completed in 1 h, was performed in 96 wells microtitreplates and required no wash steps. The limit of detection for the duplex enrichment MIA was 100–1000 cfu ml?1, which was a hundred times lower than of an enrichment-ELISA. Without enrichment, the sensitivity of MIA and ELISA was largely similar and ranged between 106 and 107 cells ml?1. No difference in sensitivity was found between a MIA in a single or duplex format. In a comparative test with non-infected potato plant extracts and extracts from plants infected with Pca or Dcd, results of the enrichment MIA correlated well with those of the enrichment ELISA and enrichment PCR. These results indicate that MIA can be reliably used for multiplex detection of soft rot Enterbacteriaceae in crude potato plant extracts. The technology is an attractive and cost-effective alternative to other detection methods, including ELISA.  相似文献   

18.
Fusarium proliferatum has been identified as the main causal agent of bulb rot of garlic (Allium sativum L.). This disease occurs after the drying process and can rot almost 30 % of the bulbs. Few studies are available regarding the effectiveness of chemical treatments to reduce F. proliferatum incidence in garlic. The efficacy of three commercial fungicides of different chemical groups to reduce seven strains of F. proliferatum mycelial growth was tested in vitro. These three fungicides were also evaluated by foliar spreading of aqueous suspension in a field crop. Fluopyram 20 % + tebuconazole 20 % and tebuconazole 50 % + trifloxystrobin 50 % were highly effective at reducing mycelial growth in F. proliferatum with EC50 values <2 ppm. In general, the effectiveness of the fungicides was enhanced with increasing dosage. Our results indicate that the fungicides evaluated in this study may lead to a risk of resistance appearing in F. proliferatum at low concentrations and this risk is maintained at higher doses for the fungicide dimethomorph 7.2 % + pyraclostrobin 4 %. Although several of the fungicides affected in vitro mycelial growth of F. proliferatum, as a part of an strategy to measure the efficacy of resistance management it is necessary to monitor the ongoing efficacy of fungicides under commercial conditions. All fungicidal treatments tested in field application failed to control garlic bulb rot during storage.  相似文献   

19.
Infection by Pyrenophora teres f. teres (Ptt) or P. teres f. maculata (Ptm), the causal agents of the net and spot forms of net blotch of barley, respectively, can result in significant yield losses. The genetic structure of a collection of 128 Ptt and 92 Ptm isolates from the western Canadian provinces of Alberta (55 Ptt, 27 Ptm), Saskatchewan (58 Ptt, 46 Ptm) and Manitoba (15 Ptt, 19 Ptm) were analyzed by simple sequence repeat (SSR) marker analysis. Thirteen SSR loci were examined and found to be polymorphic within both Ptt and Ptm populations. In total, 110 distinct alleles were identified, with 19 of these shared between Ptt and Ptm, 75 specific to Ptt, and 16 specific to Ptm. Genotypic diversity was relatively high, with a clonal fraction of approximately 10 % within Ptt and Ptm populations. Significant genetic differentiation (PhiPT = 0.230, P = 0.001) was found among all populations; 77 % of genetic variation occurred within populations and 23 % between populations. Lower, but still significant genetic differentiation (PhiPT = 0.038, P = 0.001) was detected in Ptt, with 96 % of genetic variation occurring within populations. No significant genetic differentiation (PhiPT = 0.010, P = 0.177) was observed among Ptm populations. Isolates clustered in two distinct groups conforming to Ptt or Ptm, with no intermediate cluster. The high number of haplotypes observed, combined with an equal mating type ratio for both forms of the fungus, suggests that P. teres goes through regular cycles of sexual recombination in western Canada.  相似文献   

20.
The development, reproduction, and population growth parameters of cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), were studied on three different Cucumis sativus cultivars (Beith Alpha Bal?kesir, B.T. Bursaalpha, Beith Alpha MR,) under controlled conditions (25?±?1 °C, 65?±?5% RH, and a photoperiod of 16:8 (L:D) h. Life table parameters were estimated according to age-stage, two-sex life table method. Results indicated that the Bt Bal?kesir are favorable hosts for A. gossypii because of the shorter preadult developmental time, lower preadult mortality rate, and higher total fecundity on this cultivar. The intrinsic rate of increase (r?=?0.4214 d-1), the net reproduction rate (R0?=?51.80 offspring), and the finite rate of increase (λ?=?1.5242 d-1) values were higher on the Bt Bal?kesir. The effect of cucumber cultivars on the biology of A. gossypii was determined as significant and it was found that cv. Bt Bal?kesir was the most convenient cucumber cultivar in terms of the life cycle of A. gossypii. For an ecological and economic pest control, against aphids use of resistant or less favourable crop cultivars is considered one of the important components of integrated pest management. Therefore, results acquired might be used in pest management program that will be prepared for this aphid.  相似文献   

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