Cucumber Plants (cucumber + plant)

Distribution by Scientific Domains

Selected Abstracts

An ecological cost of plant defence: attractiveness of bitter cucumber plants to natural enemies of herbivores

Anurag A. Agrawal
Abstract Plants produce defences that act directly on herbivores and indirectly via the attraction of natural enemies of herbivores. We examined the pleiotropic effects of direct chemical defence production on indirect defence employing near-isogenic varieties of cucumber plants (Cucumis sativus) that differ qualitatively in the production of terpenoid cucurbitacins, the most bitter compounds known. In release,recapture experiments conducted in greenhouse common gardens, blind predatory mites were attracted to plants infested by herbivorous mites. Infested sweet plants (lacking cucurbitacins), however, attracted 37% more predatory mites than infested bitter plants (that produce constitutive and inducible cucurbitacins). Analysis of the headspace of plants revealed that production of cucurbitacins was genetically correlated with large increases in the qualitative and quantitative spectrum of volatile compounds produced by plants, including induced production of (E,)-,-ocimene (3E,)-4,8-dimethyl-1,3,7-nonatriene, (E,E)-,-farnesene, and methyl salicylate, all known to be attractants of predators. Nevertheless, plants that produced cucurbitacins were less attractive to predatory mites than plants that lacked cucurbitacins and predators were also half as fecund on these bitter plants. Thus, we provide novel evidence for an ecological trade-off between direct and indirect plant defence. This cost of defence is mediated by the effects of cucurbitacins on predator fecundity and potentially by the production of volatile compounds that may be repellent to predators. [source]

Dispersion of flightless adults of the Asian lady beetle, Harmonia axyridis, in greenhouses containing cucumbers infested with the aphid Aphis gossypii: effect of the presence of conspecific larvae

Lionel Gil
Abstract Most females of the Asian lady beetle, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), stop laying eggs if conspecific larvae are present. We studied the effect of this inhibition on the dispersion of this insect in a greenhouse containing cucumbers uniformly infested with the aphid Aphis gossypii Glover (Homoptera: Aphididae). In the absence of conspecific larvae, the adults moved around at random, sinuously, and independently. They spent most of their time walking on the ground and only a little time on the aphid-infested plants. When the cucumber plants in one half of the greenhouse had conspecific larvae on them, the whole adult population migrated to the larva-free half of the greenhouse. Consequently, most eggs were laid in that part of the greenhouse which was devoid of larvae. The consequences of this spatio-temporal interaction between larvae and adults for the biological control of aphids is discussed. [source]

Plant growth promotion and biological control of Pythium aphanidermatum, a pathogen of cucumber, by endophytic actinomycetes

K.A. El-Tarabily
Abstract Aims:, To evaluate the potential of Actinoplanes campanulatus, Micromonospora chalcea and Streptomyces spiralis endophytic in cucumber roots, to promote plant growth and to protect seedlings and mature plants of cucumber from diseases caused by Pythium aphanidermatum, under greenhouse conditions. Methods and Results:, Three endophytic isolates, out of 29, were selected through tests aimed at understanding their mechanisms of action as biocontrol agents and plant growth promoters. When applied individually or in combination, they significantly promoted plant growth and reduced damping-off and crown and root rot of cucumber. The combination of the three isolates resulted in significantly better suppression of diseases and plant growth promotion, than where the plants were exposed to individual strains. Conclusions:, The three selected actinomycete isolates colonized cucumber roots endophytically for 8 weeks, promoted plant growth and suppressed pathogenic activities of P. aphanidermatum on seedling and mature cucumber plants. Significance and Impact of the Study:, The results clearly show that the endophytic, glucanase-producing actinomycetes used, especially as a combined treatment, could replace metalaxyl, which is the currently recommended fungicide for Pythium diseases in the United Arab Emirates. These endophytic isolates also have the potential to perform as plant growth promoters, which is a useful attribute for crop production in nutrient impoverished soils. [source]

Chilling tolerance of maize, cucumber and rice seedling leaves and roots are differentially affected by salicylic acid

Ho-Min Kang
Salicylic acid (SA) is one component of a complex signalling pathway that is induced by a number of biotic and abiotic stresses. Exposing seedling radicles to aqueous solutions of 0.5 mM salicylic acid for 24 h before chilling at 2.5C for 1,4 days reduced the chilling-induced increase in electrolyte leakage from maize and rice leaves, and cucumber hypocotyls, but not from their radicles. The SA treatments that induced chilling tolerance in the aerial portion of the seedlings did not induce chilling tolerance in the radicles, even though the SA treatments were applied to the radicles. A comparison of activity among five antioxidant enzymes showed that SA did not alter enzyme activities in the radicles, but that chilling tolerance induced by SA in the aerial portions of maize and cucumber plants was associated with an increase in the activity of glutathione reductase and guaiacol peroxidase. [source]

Induction of systemic resistance in Arabidopsis thaliana in response to a culture filtrate from a plant growth-promoting fungus, Phoma sp.

PLANT BIOLOGY, Issue 1 2009
Abstract The plant growth-promoting fungus (PGPF), Phoma sp. GS8-3, isolated from a zoysia grass rhizosphere, is capable of protecting cucumber plants against virulent pathogens. This fungus was investigated in terms of the underlying mechanisms and ability to elicit systemic resistance in Arabidopsis thaliana. Root treatment of Arabidopsis plants with a culture filtrate (CF) from Phoma sp. GS8-3 elicited systemic resistance against the bacterial speck pathogen Pseudomonas syringae pv. tomato DC3000 (Pst), with restricted disease development and inhibited pathogen proliferation. Pathway-specific mutant plants, such as jar1 (jasmonic acid insensitive) and ein2 (ethylene insensitive), and transgenic NahG plants (impaired in salicylate signalling) were protected after application of the CF, demonstrating that these pathways are dispensable (at least individually) in CF-mediated resistance. Similarly, NPR1 interference in npr1 mutants had no effect on CF-induced resistance. Gene expression studies revealed that CF treatment stimulated the systemic expression of both the SA-inducible PR-1 and JA/ET-inducible PDF1.2 genes. However, pathogenic challenge to CF-treated plants was associated with potentiated expression of the PR-1 gene and down-regulated expression of the PDF1.2 gene. The observed down-regulation of the PDF1.2 gene in CF-treated plants indicates that there may be cross-talk between SA- and JA/ET-dependent signalling pathways during the pathogenic infection process. In conclusion, our data suggest that CF of Phoma sp. GS8-3 induces resistance in Arabidopsis in a manner where SA and JA/ET may play a role in defence signalling. [source]

Induction of root-mat symptoms on cucumber plants by Rhizobium, but not by Ochrobactrum or Sinorhizobium, harbouring a cucumopine Ri plasmid

S. A. Weller
Ochrobactrum CSL 2573, Rhizobium CSL 2411 and Sinorhizobium CSL 2611 strains harbouring the Agrobacterium cucumopine Ri plasmid (pRi), previously were shown to induce root-mat symptoms in an in vitro cucumber cotyledon assay. In whole-plant, rockwool-grown cucumber host tests Rhizobium CSL 2411 was shown to be as efficient an inducer of root-mat symptoms as the virulent Agrobacterium radiobacter strain NCPPB 4042, which also harbours a cucumopine pRi. Conjugal transfer of pRi to ingressing, avirulent Agrobacterium isolates was observed within root tissues with symptoms. Ochrobactrum CSL 2573 and Sinorhizobium CSL 2611 were not able to induce root-mat symptoms on plants. Rhizobium CSL 2411 and Ochrobactrum CSL 2573 were reisolated from inoculated plants, but Sinorhizobium CSL 2611 was not detected or isolated from inoculated plants 68 days after inoculation. It was postulated that the differences in pathogenicity observed between the in vitro and in situ host tests were caused by a lack of proper attachment to inoculated root tissues by pRi-harbouring Ochrobactrum and Sinorhizobium in the whole-plant host tests. [source]

Proteome, salicylic acid, and jasmonic acid changes in cucumber plants inoculated with Trichoderma asperellum strain T34

Guillem Segarra
Abstract Trichoderma spp. is one of the most commonly used biological control agents against plant pathogens. This fungus produces changes in plant metabolism, thus increasing growth and enhancing resistance to biotic and abiotic stresses. However, its modes of action remain to be defined. In the first hours of interaction between cucumber plant roots and Trichoderma asperellum strain T34, salicylic and jasmonic acid levels and typical antipathogenic peroxidase activity increase in the cotyledons to different degrees depending on the applied concentration of the fungi. The use of 2-DE protein profiling and MS analysis allowed us to identify 28 proteins whose expression was affected in cotyledons after cucumber root colonization by Trichoderma applied at high concentrations: 17 were found to be up-regulated while 11 were down-regulated. Proteins involved in ROS scavenging, stress response, isoprenoid and ethylene biosynthesis, and in photosynthesis, photorespiration, and carbohydrate metabolism were differentially regulated by Trichoderma. The proteome changes found in this study help to give an understanding of how Trichoderma -treated plants become more resistant to pathogen attacks through the changes in expression of a set of defence-oriented proteins which can directly protect the plant or switch the metabolism to a defensive, nonassimilatory state. [source]

Relationship between potassium fertilisation and nitrate assimilation in leaves and fruits of cucumber (Cucumis sativus) plants

Summary The effect of application of different potassium rates on some parameters of nitrate metabolism and yield in cucumber plants (Cucumis sativus) was studied. All plants were grown under controlled conditions in an experimental greenhouse. The treatments consisted of applications of K+ at three rates in the form of K2SO4 (Kl: 0.075 mg ml,1, K2: 0.15 mg ml,1, and K3: 0.30 mg ml,1). The results showed a positive effect of higher K+ fertilisation (0.30 mg ml,1) on uptake, translocation and reduction of NO3, in leaves compared with the lowest K+ rate. In addition, the higher K+ rates strengthened the translocation of organic nitrogenous compounds (amino acids) towards the fruit, thereby perhaps also enhancing the maximal commercial yield. In conclusion, for improved cucumber cultivation under greenhouse conditions, 0.15 mg ml,1 of K+ gave maximal yield, while the application of 0.30 mg ml,1 increased the metabolism and efficient utilisation of NO3,. [source]