Silicon and manganese on the activity of enzymes involved in rice resistance against brown spot

Abstract

This study investigated the role of silicon (Si) and manganese (Mn) rates on the activity of peroxidases (POX), polyphenoloxidases (PPO) and phenylalanine ammonia-lyases (PAL) on rice plants non-inoculated and inoculated with Bipolaris orzyae. Rice plants (cultivar Metica 1) were grown in nutrient solution with 0 (-Si) or 2 mmol Si L -1 (+Si) and with 0.5, 2.5 and 10 µmol Mn L -1 . Plants were inoculated with B. oryzae and leaf samples were collected at 6, 12, 18, 24, 36 and 48 h after inoculation (hai). Leaf samples were also collected from non-inoculated plants at these same time-points. POX activity increased for -Si plants inoculated with B. oryzae at both rates of 0.5 and 2.5 µmol Mn L -1 with one peak at 48 hai at 10 µmol Mn L -1 . For plants supplied with Si, POX activity also increased, but seemed to be low at the rates of 2.5 and 10 µmol Mn L -1 . POX activity did not show to be greatly influenced by the Mn rates in the presence of Si. However, in the absence of Si, POX activity increased. PPO activity on -Si plants increased at the rate of 0.5 µmol Mn L -1 and was not affected by the other two Mn rates, except a peak at 18 hai at the rate of 10 µmol Mn L -1 . In the presence of Si, PPO activity increased on plants supplied with 2.5 µmol Mn L -1 in contrast to the other two Mn rates for which the PPO activity decreased. By comparing the -Si and +Si treatments at the rate of 2.5 µmol Mn L -1 , PPO activity increased from 18 to 36 hai in the presence of Si than on its absence. PAL activity on -Si plants decreased regardless of the Mn rates. On plants supplied with Si and inoculated with B. oryzae, PAL showed low activity at the highest Mn rate and also at the rate of 0.5 µmol Mn L -1 , besides its activity been very low compared to the non-inoculated plants. PAL did not increase in activity in the presence of Si, but on its absence, high levels of activity were achieved. Results from this study showed that the activities of POX, PPO and PAL were not boosted by Si at any Mn rate. Key words: Bipolaris oryzae, Oryza sativa, foliar disease, mineral nutrition. RESUMO Silício e manganês na atividade de enzimas envolvidas na resistência do arroz à mancha pardaO estudo investigou o efeito do silício (Si) e de doses de manganês (Mn) na atividade das enzimas peroxidases (POX), polifenoloxidases (PFO) e fenilalanina amônia-liases (FAL) em plantas não inoculadas e inoculadas com Bipolaris oryzae. Plantas de arroz (cultivar Metica 1) foram cultivadas em solução nutritiva com 0 (-Si) e 2 mmol Si L -1 (+Si) e com as doses de 0,5; 2,5 e 10 µmol Mn L -1 . As plantas foram inoculadas com B. oryzae e amostras de folhas foram coletadas às 6, 12, 18, 24, 36 e 48 h após inoculação (hai). Amostras de folhas de plantas não-inoculadas, nestes mesmos tempos, também foram coletadas. Para as doses de 0,5 e 2,5 µmol Mn L -1 , a atividade da POX aumentou para as plantas -Si com um pico às 48 hai na dose de 10 mmol Mn L -1 . Para as plantas +Si, a atividade da POX também aumentou, mas foi baixa para as doses de 2,5 e 10 mmol Mn...

Primary metabolism plays a central role in moulding silicon‐inducible brown spot resistance in rice

“…Consistent with previous results (Dallagnol et al ., , , b; Rezende et al ., ; Silva et al ., ), the application of Si resulted in a substantial reduction in brown spot disease severity in both intact plant and detached leaf assays (Fig. A–D).…”

O papel do silício nas plantas

“…Diversos estudos comprovam que as plantas respondem de forma positiva a adubação silicatada para supressão de doenças (Tabela 3), essas respostas podem ser a nível físico, químico e molecular. Silva et al (2012) destacam que o Si promove uma barreira física pré-infecção, esse efeito acontece através da deposição deste elemento na parede celular das plantas, pela formação de uma dupla camada de sílica amorfa e salificação das células, efeito que ocasiona dificuldade a penetração de microrganismos fitopatogênicos (Rodrigues et al, 2003). Além disso, barreiras pós-infecção também podem ser formadas no local de entrada destes organismos através de papilas (Pereira et al, 2009).…”

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

“…Whereas, Silva et al (2012) reported that the reduction on brown spot severity was not associated with the increase in POX, PPO, and PAL activities, although it was linked with higher concentrations of SP and LTGA on rice plants supplied with Si (Dallagnol et al 2011). Araujo et al (2016 showed that in the leaf cells of rice plants supplied with Si, the plant cell walls and the hyphae of Microdochium oryzae were protected and surrounded, respectively, by phenolic-like compounds.…”