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951.
Antonio Ippolito Leonardo Schena Franco Nigro Vincenza Soleti ligorio Thaer Yaseen 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(8):833-843
Two primers, specific for Phytophthora nicotianae (Pn6) and P. citrophthora (Pc2B), were modified to obtain Scorpion primers for real-time identification and detection of both pathogens in citrus nursery soils and roots. Multiplex PCR with dual-labelled fluorogenic probes allowed concurrent identification of both species ofPhytophthora among 150 fungal isolates, including 14 species of Phytophthora. Using P. nicotianaespecific primers a delayed and lower fluorescence increase was also obtained from P. cactorumDNA. However, in separate real-time amplifications, the aspecific increase of fluorescence from P. cactorum was avoided by increasing the annealing temperature. In multiplex PCR, with a series of 10-fold DNA dilutions, the detection limit was 10 pg l-1 for P. nicotianaeand 100 pg l–1 for P. citrophthora, whereas in separate reaction DNA up to 1 pg l-1 was detected for both pathogens.Simple and rapid procedures for direct DNA extraction from soil and roots were utilised to yield DNA whose purity and quality was suitable for PCR assays. By combining these protocols with a double amplification (nested Scorpion-PCR) using primers Ph2-ITS4 amplifying DNA from the main Phytophthora species (first round) and PnB5-Pn6 Scorpion and Pc2B Scorpion-Pc7 (second round), it was possible to achieve real-time detection of P. nicotianaeand P. citrophthora from roots and soil. The degree of sensitivity was similar to that of traditional detection methods based on the use of selective media. The analyses of artificially and naturally infested soil showed a high and significant correlation between the concentration of pathogen propagules and the real-time PCR cycle threshold. 相似文献
952.
Greenhouses in Turkey under integrated pest management can be colonized by a high number predatory flies of the species Coenosia attenuata Stein, 1903 (Muscidae: Coenosia Meigen, 1826). Studies have shown that Coenosia predators do not simply colonize greenhouses from the outside for short periods but instead they are able to complete their
developmental cycle in the greenhouse soil and can become established there for a long period of time. C. attenuata is indigenous to the Palaeotropical region. Its prey spectrum includes whiteflies, black fungus gnats and leaf-mining flies.
Studies of the natural occurrence of these predaceous flies in greenhouses led to a recognition of the significance of this
complex of beneficials for the control of important greenhouse pests. They can build up effective populations under greenhouse
conditions, and as non-specific predators can feed on a variety of pest groups and on innocuous species. 相似文献
953.
Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is an exotic species native to the USA, damaging cotton and other plant families. The
feeding potential of different development stages of Cryptolaemus montrouzieri Mulsant, a biological control agent against mealybugs, was investigated on different development stages of P. solenopsis. Fourth instar grubs and adults of C. montrouzieri were the most voracious feeders on different instars of mealybug. The number of 1st instar nymphs of mealybug consumed by 1st, 2nd, 3rd and 4th instar larvae and adult beetles of C. montrouzieri was 15.56, 41.01, 125.38, 162.69 and 1613.81, respectively. The respective numbers of 2nd and 3rd instar nymphs of mealybug consumed were 11.15 and 1.80, 26.35 and 6.36, 73.66 and 13.32, 76.04 and 21.16, 787.95 and 114.66.
The corresponding figures for adult female mealybugs were 0.94, 3.23, 8.47, 12.71 and 73.40, respectively. The results indicate
that C. montrouzieri has the potential to be exploited as a biocontrol agent in North India; inoculative releases of 4th instar larvae and adults may provide instant control of P. solenopsis. Field experiments should be conducted to determine the efficiency of the ladybird on this mealybug. 相似文献
954.
During 2010, yellowing symptoms were frequently observed in cultivated squash fields in Egypt. A total of 717 symptomatic
squash leaf samples were collected from four regions where squash cultivation is of economic importance for the country: Kafrelsheikh,
El-Behira, El-Sharkia and El-Ismailia. Serological analysis showed that 95.6% of the symptomatic squash samples were infected
by Cucurbit aphid-borne yellows virus (CABYV), and visual estimation of the incidence of yellowing symptoms suggested a very high incidence of CABYV in the fields.
Twelve CABYV isolates were characterized by sequencing two regions of the viral genome, open reading frame (ORF) 3 and ORFs
4/5. Overall, Egyptian isolates were very similar among them, and had higher similarity values with a French than with a Chinese
isolate. The average nucleotide diversity for ORF 3 was significantly higher than for the other two regions, indicating that
variability is not evenly distributed along the viral genome. The ratios between nucleotide diversity values in non-synonymous
(d
N
) and synonymous (d
S) positions (d
N
/d
S) for each ORF showed that the three ORFs are evolving under different pressures, although predominantly under purifying selection.
Phylogenetic analyses revealed that these Egyptian isolates, with only one exception, shared the same clade with a French
isolate. Moreover, these analyses suggested that Egyptian isolates belong to the Mediterranean group described previously. 相似文献
955.
Powdery mildew fungi are parasitized by strains of the genetically distinct Ampelomyces quisqualis. To investigate whether differences in the phylogeny and other cultural, morphological and physiological characteristics
of these different strains are related to differences in their geographic origins or the host species from which they were
isolated, several A. quisqualis strains isolated from different species of Erysiphaceae collected in different countries and possessing different ITS rDNA
sequences were selected and characterized. The results revealed some significant variation among the selected strains, which
provides evidence for the existence of different physiological forms within the A. quisqualis species. Two groups that display differential growth on artificial media were identified. These groups also differ in the
morphology of their mycelium, but not in the morphology of their pycnidia and conidia. Temperature greatly affected the in vitro growth of the A. quisqualis strains and growth rate was closely correlated to colony color. Differences in the conidial germination of distinct strains
were observed during the recognition phase of the parasitic relationship. The germination of each of the investigated strains
was greatly stimulated by all of the examined powdery mildew species and not only by the conidia of their original hosts.
An Italian strain isolated from grapevine in the Trentino Alto-Adige region was identified as the strain that germinates the
most quickly in the presence of powdery mildew conidia. Phylogenetic analysis revealed that these A. quisqualis strains can be classified into five different genetic groups, which generally correlate with the fungal host of origin and
morphological and growth characteristics. 相似文献
956.
Black nightshade (Solanum nigrum L.) is a troublesome weed worldwide, affecting a large number of crops. As weed development is affected by a variety of factors,
advanced knowledge on the plant’s biological and ecological qualities can support favorable management strategies. Seed density
is an ecological factor affecting emergence and early growth of many weed species. For that reason, the current study characterizes
and quantifies the seed density impact on black nightshade seedling-emergence and early growth, and the interaction between
seed density and burial depth on these growth parameters. Greenhouse studies conducted in 2005, 2006 and 2010 examined black
nightshade seed densities of 1, 5, 10, 25 and 50 seeds per pot, buried at, 1, 2, 3, 4 and 5 cm. Impact of seed density on
weed emergence and growth was characterized by number of emerged plants and leaves, followed by biomass measurements. Seed
density had no impact on emergence at the tested burial depths. There was a strong logistic relationship (P < 0.001, and R
2
> 0.97) between time and emergence, and a strong linear relationship (P < 0.002 and R
2
> 0.86) between time and number of leaves produced in all depths and seed densities. A negative relationship was observed
between seed density and plant development and growth rate. Results of this study extend the knowledge on black nightshade
biology and support decision-making concerning rational weed management. 相似文献
957.
Mónica Berbegal Luis Armando Álvarez Ana Pérez-Sierra Josep Armengol 《Phytoparasitica》2012,40(1):1-4
Pythium isolates were recovered from endive plants (Cichorium endivia) showing vascular necrosis collected from commercial fields located in Castellón province (eastern Spain). They were identified
as Pythium tracheiphilum on the basis of their phenotypical and molecular profile. Pathogenicity tests conducted with two P. tracheiphilum isolates, obtained from endive and lettuce (Lactuca sativa), respectively, in this region, confirmed that both isolates were pathogenic to endive, with no significant differences in
virulence between them. This is the first report of vascular necrosis caused by P. tracheiphilum on endive in Spain. 相似文献
958.
M. I. Tajul Takayuki Motoyama Akikazu Hatanaka M. Sariah Hiroyuki Osada 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(1):91-100
Four green-odour compounds—trans-2-hexenal, cis-3-hexenol, n-hexanal, and cis-3-hexenal—were applied (0.85 μg ml−1 as vapour) to rice plants in laboratory conditions to observe their biological activity against the phytopathogenic fungus
Maganporthe oryzae, which causes rice blast disease worldwide. Two compounds, trans-2-hexenal and cis-3-hexenal, showed remarkable disease suppression efficacy (99.7% and 100% suppression, respectively), while n-hexanal had moderate (86.5%) and cis-3-hexenol had weak (20.8%) disease-suppressing effects. Pre-application and post-application of trans-2-hexenal or cis-3-hexenal had slight effects on blast incidence, suggesting that these compounds had direct effects to suppress M. oryzae infection. In fact, trans-2-hexenal and cis-3-hexenal exhibited a growth suppression effect on M. oryzae. Interestingly, these two compounds inhibited appressorium formation at lower concentrations than the growth suppression.
Studies on the hypersensitive response (HR)-like reaction and plant β-1,3-glucanase activity in rice plant confirmed that
induced resistance was not the major factor involved in the disease suppression mechanism. Results of this study conclusively
showed that trans-2-hexenal and cis-3-hexenal possess potent inhibitory activities against the growth and the appressorium formation of M. oryzae and could be used as antifungal agents to significantly reduce M. oryzae infections in rice. 相似文献
959.
Michel Almaguer Teresa Irene Rojas Francisco Javier Rodríguez-Rajo María Jesús Aira 《European journal of plant pathology / European Foundation for Plant Pathology》2012,133(2):473-482
This study characterised the airborne mycobiota of a rice plantation in Bauta (Havana, Cuba), with a view to improving crop
quality. Culturable airborne fungi were sampled between March 2007 and February 2008 using a volumetric method (SAS Super
100) with potato dextrose agar as culture medium. The total fungal count was 51,425 cfu/m3. The 39 filamentous genera identified included several major rice pathogens (Bipolaris, Curvularia, Alternaria, Pyricularia, Cercospora and Fusarium) as well as potentially mycotoxigenic species of Fusarium, Penicillium and Aspergillus. Analysis of the influence of weather-related factors on spore counts revealed that total counts and Penicillium counts correlated positively with daily relative humidity, mean temperature and dew point. 相似文献
960.
Nalini Mallikarjuna Deepak R. Jadhav Kanaka Reddy Fatema Husain Kumkum Das 《European journal of plant pathology / European Foundation for Plant Pathology》2012,132(1):17-21
Cultivated groundnut is susceptible to late leaf spot (LLS) caused by Phaeoisariopsis personata [(Berk. & M.A. Curtis) Aex] and resistance is low to moderate in the primary gene pool of groundnut. Closely related wild
species in the secondary gene pool are highly resistant to the disease. All the closely related Arachis species are diploid and cultivated groundnut is a tetraploid. Utilization of diploid Arachis species to transfer LLS resistance is time consuming and cumbersome. New sources of Arachis hypogaea (also called synthetic groundnut) were developed at ICRISAT. These are tetraploids and the present investigation has shown
that they are resistant to LLS. 相似文献