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    Defence responses in leaves of resistant and susceptible pepper (Capsicum annuum L.) cultivars infected with different inoculum concentrations of Phytophthora capsici Leon
    (ELSEVIER SCIENCE BV, 2011) Koc, Esra; Ustun, Aysen Sulun; Islek, Cemil; Arici, Yeliz Kasko
    Three pepper cultivars (PM-702: resistant, Demre-8 and KM-hot: susceptible) with different resistances to Phytophthora capsici-22 (P. capsici-22) were inoculated with different concentrations of zoospores to analyze the time course of phenylalanine ammonia lyase (PAL) activity, malondialdehyde (MDA), hydrogen peroxide (H(2)O(2)), praline and total protein. Samples were collected from the leaves of three pepper cultivars on the 2nd, 4th. and 6th days after infection; important differences were observed in PAL activity, MDA amount, H(2)O(2), proline, and total protein with respect to zoospore concentration, infection time, and type of pepper cultivars. Activity of phenylalanine ammonia-lyase (PAL), the first enzyme in the phenylpropanoid biosynthetic pathway, was increased in inoculated leaves of all three cultivars. The increase in production of PAL upon challenge was higher in the infected plants compared to the non-infected (control) plants. An early induction of PAL was observed in the leaves of all peppers infected with P. capsici within two days, making it one of the detected earlier responses to infection. Moreover, pathogen stress increased the rate of lipid peroxidation (which is indicated by increasing MDA content). Production of reactive oxygen species, H(2)O(2), and lipid peroxidation increased in pepper leaves by increasing time of infection and inoculum concentration. The findings suggested that PM-702 pepper cultivar was inherently better protected against lipid peroxidation under P. capsici stress than KM-hot and Demre-8. In addition, it was observed that proline content in the leaves of infected susceptible cultivars increased with time, but highest proline and total protein in non-infected (control) leaves were recorded in resistant cultivar. (C) 2011 Elsevier B.V. All rights reserved.
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    Pretreatment with spermidine and proline reverses inhibitory effects of Phytophthora capsici stress in pepper
    (LITHUANIAN RESEARCH CENTRE AGRICULTURE & FORESTRY, 2016) Koc, Esra; Arici, Yeliz Kasko; Islek, Cemil
    Phytophthora blight (Phytophthora capsici Leon.), which is one of the most important disease factors incurring great economic losses, causes root crown rot. When pepper seedlings were pretreated with 0.1 mM spermidine (spd), 1 mM spd, 0.1 mM spd + 1 mM proline, 0.1 mM spd + 10 mM proline, 1 mM spd + 1 mM proline and 1 mM spd + 10 mM proline and then exposed to P. capsici, they improved their tolerance to subsequent P. capsici-induced oxidative damage. It was detected that cultivar 'Sirena RZ F1' was resistant to P. capsici and it was determined that cultivar 'Sera Demre-8' exhibited sensitive reaction. P. capsici stress caused an increase in total phenolic, malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels, as well as peroxidase (POX) and polyphenol oxidase (PPO) activities in leaves of pepper seedlings. Application of exogenous spermidine and spermidine + proline further increased PPO and POX activity, total phenolic amount. On the other hand, these applications in two cultivars and all days decreased the disease severity, necrosis length and MDA and H2O2 amounts. These data show that antioxidants, especially polyphenol oxidase, peroxidase and total phenolic appear to protect pepper seedlings against stress-related damage. Moreover, spermidine and spermidine + proline have the potential to scavenge directly free radicals and promote the activity of antioxidant enzymes in pepper seedlings under P. capsici stress. In addition, it was also identified that especially 0.1 mM spd, 1 mM spd and 0.1 mM spd + 1 mM proline applications decreased the colony growth of P. capsici and the amount of zoospores. Therefore, we suggest that spermidine and spermidine + proline could play a protective role in protecting the pepper seedlings from P. capsici stress.
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    Spermine and its interaction with proline induce resistance to the root rot pathogen Phytophthora capsici in pepper (Capsicum annuum)
    (Korean Soc Horticultural Science, 2017) Koc, Esra; Islek, Cemil; Kasko Arici, Yeliz
    The root rot pathogen Phytophthora capsici can severely damage production of peppers (Capsicum annuum). This study examined the effect of exogenous spermine and spermine in combination with proline on disease severity in pepper inoculated with P. capsici, as well as the effect of the treatments on P. capsici growth and zoospore development. Peroxidase, catalase, and polyphenol oxidase activity, the levels of phenolic compounds, malondialdehyde (MDA), and hydrogen peroxide (H2O2), and fresh and dry weight were measured on the 3(rd), 5(th), and 7(th) days after P. capsici infection. Disease severity and size of the necrotic lesions increased with the degree of injury caused by the pathogen and decreased in resistant varieties. The cultivar CM-334 exhibited the highest resistance to P. capsici followed by Amazon F1 whereas other genotypes were susceptible to the disease. Treatments with spermine and spermine + proline prior to inoculation decreased the severity of disease, the length of the necrotic lesions, and the MDA and H2O2 levels in all genotypes, and increased peroxidase, catalase, and polyphenol oxidase activity, the total level of phenolics, and fresh and dry weight, when compared to the untreated, inoculated plants. In addition, 1 mM spermine, 1 mM spermine + 1 mM proline, and 1 mM spermine + 10 mM proline decreased colony growth of P. capsici and zoospore production. This study showed that spermine and spermine + proline induced defense responses and increased resistance to P. capsici infection in pepper.
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    Using high hydrostatic pressure as an abiotic elicitor strategy for improving capsaicin production in free and immobilized cell suspension cultures of Capsicum annuum L.
    (Taylor & Francis Ltd, 2021) Islek, Cemil; Koc, Esra; Altuner, Ergin Murat; Alpas, Hami
    In this study, the effects of immobilization and high hydrostatic pressure (HHP) on capsaicin production in cell suspension culture of pepper seeds at different application times were investigated. Callus cultures were obtained from in vitro germinated hypocotyl explants of pepper seedlings and cell suspensions were prepared from calluses. Immobilized cell suspension cultures with calcium alginate and free cell suspension cultures were obtained by using these cell suspensions. 50, 100, 200, 300 and 400 MPa were applied to both free and immobilized cell suspensions as an elicitor. When all the results were compared, the highest amount of capsaicin was achieved in immobilized cell suspensions on the tenth day as 293.187 mu g/g f.w at 400 MPa pressure. As a result, it can be concluded that the combined application of immobilization and elicitor (HHP) caused significant increases (p < .05) in the amount of capsaicin.