Abstract
The increase in oxidative enzyme activities is related to diminished mite infestation. Some biological aspects of Raoiella indica Hirst reared on the coconut cultivars (‘Jamaican Tall’ (JT), ‘Malayan Yellow Dwarf’ (MYD), Niu Leka (NL) and a hybrid JT x MYD) were studied under laboratory conditions. Aditionally, changes in oxidative enzyme activities (peroxidase and polyphenol oxidase) as response to R. indica feeding were studied in the cultivars where red palm mites showed highest and lowest biological parameters values. Longer time spans and lower oviposition rates observed on the JT suggest this cultivar to be more resistant to R. indica feeding. Cultivar JT showed the highest value in PPO/POX ratio, being about twice the value shown by MYD in the infested plants. The observed enzyme activity ratios in both genotypes showed a slight increase 24 h after mite infestation, suggesting these enzymes could be related to plant resistance to R. indica. However, this relationship is still unclear. The biological parameters of R. indica together with higher enzyme activity, particularly on JT suggest this cultivar could be considered as a more resistant cultivar as compared to MYD. More detailed studies are required to determine the effect of these enzymes on coconut resistance to red palm mites. Key words: Coconut, peroxidase, polyphenol oxidase, red palm mite.
Highlights
Some biological aspects of Raoiella indica Hirst reared on the coconut cultivars (‘Jamaican Tall’ (JT), ‘Malayan Yellow Dwarf’ (MYD), Niu Leka (NL) and a hybrid JT x MYD) were studied under laboratory conditions
The cellular damage by reactive oxygen species (ROS) appears to be due to their conversion into more reactive species such as the formation of OH, which is dependent on both H2O2 and O2− and, its formation is subject to inhibition by both superoxide dismutase (SOD) and catalase (CAT) (Sharma et al, 2012)
Besides SOD and CAT, there is a complex of enzymatic components of the antioxidative defense system that comprise several antioxidant enzymes such as guaiacol peroxidase (GPX), enzymes of ascorbateglutathione (AsA-GSH) cycle ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) (Noctor and Foyer, 1998)
Summary
Changes in oxidative enzyme activities (peroxidase and polyphenol oxidase) as response to R. indica feeding were studied in the cultivars where red palm mites showed highest and lowest biological parameters values. The observed enzyme activity ratios in both genotypes showed a slight increase 24 h after mite infestation, suggesting these enzymes could be related to plant resistance to R. indica. The biological parameters of R. indica together with higher enzyme activity, on JT suggest this cultivar could be considered as a more resistant cultivar as compared to MYD.
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