Biochemical characterization of citrus bent leaf viroid infecting citrus cultivars

Abstract

Citrus bent leaf viroid (CBLVd) is an emerging and widely distributed viroid along with its variants in citrus growing areas of world. Activation of defense mechanism is associated with different enzymes and inhibitors, accumulated in the infected host. Limited studies were found on biochemical characterization of citrus viroids. Therefore, study was focused on the biochemical activities such as determination of chlorophyll contents, total soluble phenolics (TSP), phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) activity in three citrus cultivars kinnow (C. reticulate), feutrell’s early (C. reticulate) and mosambi (C. sinensis) infected with CBLVd from Sargodha, Pakistan. The results showed that chlorophyll contents were significantly lower in the diseased leaves samples of all the citrus cultivars as compared to healthy ones. Whereas, TSP was found in higher concentration in the CBLVd infected samples of citrus cultivars. Similarly, activities of PPO and PAL was increased significantly in leaves of citrus cultivars infected with CBLVd as compared to healthy. These findings were in confirmation that chlorophyll contents, enzymes and inhibitors were associated to response of plants towards pathogen infection. To the best of our knowledge, these biochemical alterations in host plants against CBLVd were studied for the first time not only in the Asian region but also in Pakistan. The results will lead to investigate the biochemical alterations in other citrus viroids infection.