Aspectos bioquímicos da resistência do algodoeiro à ramulose potencializada pelo silício

Abstract

ResumoObjetivou-se avaliar o efeito do silício (Si) sobre a ramulose e aspectos bioquímicos da resistência do algodoeiro a essa doença. Os cultivares BRS Araçá e FM 993 foram desenvolvidos em solução nutritiva contendo (+Si) ou não (-Si) silício. Avaliou-se o período de incubação (PI), incidência (I), área abaixo da curva do índice da ramulose (AACIR) e concentração foliar de Si (CFSi).A CFSi e o PI aumentaram em 76% e 19,5%, respectivamente, nas plantas +Si em relação às -Si, e a I e a AACIR diminuíram em 64% e 18%, respectivamente. A concentração dos compostos fenólicos solúveis totais (CFST) e dos derivados da lignina-ácido tioglicólico (DLATG) dos dois cultivares supridos com Si aumentou durante o progresso da ramulose, porém essa concentração foi inferior à daquelas que não receberam Si. No cultivar BRS Araçá +Si a atividade das enzimas quitinase (QUI) e glicanase (GLI) aumentou até os 10 dai em relação às plantas -Si. A atividade das enzimas peroxidase (POX) e polifenoloxidase (PPO) no cultivar BRS Araçá +Si aumentou entre 20 e 30 dai em relação às plantas -Si, enquanto na FM 993 +Si o aumento foi de até 10 dai. No cultivar FM 993 +Si, a atividade da fenilalanina amônia-liase (FAL) aumentou. O fornecimento de Si às plantas de algodoeiro aumentou a resistência à ramulose mediante incremento na concentração CFST e de DLATG nos dois cultivares e na atividade das POX, PPO, QUI e GLI na BRS Araçá, e de POX e FAL na FM 993.Palavras-chave: bioquímica, compostos de defesa, enzimas, Colletotrichum gossypii var. cephalosporioides, resistência. Biochemical aspects of resistance to cotton ramulosis powered by silicon AbstractThe aim of this study was to evaluate the effect of using silicon (Si) on the control and biochemical aspects of cotton resistance to ramulosis. Cotton plants of BRS Araçá and FM 993 were grown in nutrient solution containing (+Si) or not (-Si) silicon. We evaluated the incubation period (PI), the incidence (I), the area under the curve of index ramulosis (AACIR) and leaf concentration of Si (CESi). The CESi and PI increased by 76% and 19.5% in plants supplied with Si relative to the -Si and the AACIR decreased by 64% and 18%, respectively. The concentration of total soluble phenolics (CFST) and derivatives of lignin-thioglycolic acid (DLATG) in plants of both cultivars supplied with Si increased during the progress of ramulosis, but were lower as compared to plants that did not receive Si. In BRS Araçá supplied with Si, the activity of the enzymes chitinase (QUI) and glucanase (GLI) increased until 10 days after inoculation (dai) compared to -Si plants. The activity of peroxidase (POX) and polyphenol oxidase (PPO) in BRS Araçá supplied with Si increased between 20 and 30 dai with regard to plants -Si, while FM 993 supplied with Si presented increases in the activity of PPO and POX up to 10 dai. In FM 993 supplied with Si there was no increase in the activity of phenylalanine ammonia-lyase (FAL). The supply of Si to cotton plants increased resistance to ramulose by increasing the concentration CFS...

Silicon, acibenzolar-S-methyl and potassium phosphite in the control of brown spot in rice

“…The PPO participates in the oxidation of phenolics leading to the production of quinones, which are extremely toxic to many pathogens (Campbell and Sederoff 1996). Guerra et al (2013) and Liang et al (2005) reported that Si potentiated the resistance to ramulosis and powdery mildew in cotton and cucumber, respectively, through an increase in the activities of POX and PPO that stimulated the accumulation of phenolic compounds. Tatagiba et al (2014) reported that high concentrations of soluble phenolics (SP) (hbi) with X. oryzae pv.…”

“…The Si-mediated plant resistance to pathogens has been attributed to an increase in the density of the long and short silicate cells in the leaf epidermis or the existence of a thick silica layer below the cuticle that forms a physical barrier which prevents or slows fungal penetration (Hayasaka et al 2008;Kim et al 2002). Furthermore, increases in the concentrations of soluble phenolics, lignin, and phytoalexins, an enhanced activity of defense-related enzymes, and the fast and strong transcription of genes that are related to host defense against pathogens are the reported biochemical mechanisms that are potentiated by Si in plants infected by pathogens (Guerra et al 2013;Liang et al 2005;Rodrigues et al 2003Rodrigues et al , 2004Rodrigues et al , 2005Tatagiba et al 2014).…”

“…The induced synthesis of PR-proteins and secondary metabolites in plants supplied with Si or when exposed to exogenous spray of ASM and Phi has been investigated for many host-parasite interactions (Araujo et al 2015(Araujo et al , 2016Babu et al 2003;Guerra et al 2013;Liang et al 2005;Rios et al 2014;Rodrigues et al 2003Rodrigues et al , 2004Rodrigues et al , 2005Rohilla et al 2001;Tatagiba et al 2014). The increase in the activities of peroxidases (POX), polyphenoloxidases (PPO), phenylalanine ammonialyases (PAL), chitinases (CHI), β-1,3-glucanases (GLU), and lypoxigenases (LOX) is one of the most common and efficient defense mechanism activated after the recognition of a pathogen by its host (Van Loon et al 2006).…”

“…High PR-proteins synthesis in plants with induced resistance has often been associated with reduction of diseases symptoms on infected plants (Babu et al 2003;Rodrigues et al 2005;Rohilla et al 2001;Rios et al 2014;Tatagiba et al 2014). The synthesis of secondary metabolites in plants also play a pivotal role in the host defense against pathogenic infection because these compounds show antimicrobial activity against various pathogens (Araujo et al 2015(Araujo et al , 2016Guerra et al 2013;Liang et al 2005;Nicholson and Hammerschmidt 1992;Rodrigues et al 2003).…”

Componentes bioquímicos e epidemiológicos associados à resistência do arroz à mancha parda

“…A atividade da QUI (EC 3.2.1.14) foi determinada por meio da quantificação colorimétrica da liberação de "pnitrophenyl" clivado do substrato análogo da quitina "p-nitrophenyl-β-D-N,N'diacetylchitobiose"(PNP) (Sigma-Aldrich, São Paulo, Brasil) e expressa em mM de "p-nitrophenyl" produzido por min -1 mg -1 de proteína. A atividade da enzima fenilalanina amônia-liase (FAL, EC 4.3.1.5) foi quantificada conforme descrito em Guerra et al (12), baseado na quantificação calorimétrica do ácido trans-cinâmico liberado do substrato fenilalanina (Sigma-Aldrich, São Paulo, Brasil) e expressa em μmol de ácido trans cinâmico min -1 mg -1 de proteína. A concentração de proteínas utilizada para o cálculo da atividade das enzimas foi obtida pelo método de Bradford, usando albumina sérica bovina como padrão.…”