Biochemical Characterization of Compatible Plant Virus Interaction: A Case Study with Bunchy Top Virus-Banana Host-Pathosystem

Abstract

Environmental stresses of both biotic and abiotic nature produce characteristic changes in physiology and metabolic processes of higher plants (Miteva et al., 2005). Among these stresses, infection by the pathogens causes substantial alterations of biochemical changes leading to harmful effects on plant health. Banana cultivation is subjected to many natural calamities including pest and pathogen attacks which constitute the major production problem. Among plant diseases, viral diseases may cause considerable loss on production by retarding plant growth and reducing yield. Four viral diseases viz., Banana Bunchy Top Disease (BBTD) caused by Banana bunchy top virus (BBTV), Bract Mosaic Disease (BBrMD) caused by Banana bract mosaic virus (BBrMV), Banana Streak Disease (BSD) caused by different species of Banana streak virus (BSV) and banana mosaic or infectious chlorosis caused by Cucumber mosaic virus (CMV) occur in most of the banana growing regions of the world. Among banana viral diseases, Banana Bunchy Top Disease (BBTD) is one of the most destructive viral diseases in Tropical Asia, Pacific Indian Oceania (PIO) regions and Africa. Grand Nain, Virupakshi (Hill banana), Robusta, Nendran, Rasthali, Poovan, Ney Poovan, Monthan and Red Banana are severely affected by BBTD. There is no resistance gene source available in germplasm of bananas and plantains (Shekhawat et al., 2012). The BBTV affected plants show intermittent dark green dots, dash, streaks of variable length on leaf sheath, midrib, leaf veins and petioles of infected plants. Leaves produced are progressively shorter, brittle in texture, narrow and gives the appearance of bunchyness at the top leading to 100% yield loss (FAO., 2009). Plants have evolved various pre-existing physical and chemical barriers, as well as inducible defense responses that interfere with pathogen colonization (Jones and Dangl, 2006; Zhao et al., 2008; Vanitha et al., 2009). However, this requires comprehensive studies and understanding of the adaptive mechanisms and responses to BBTV infection in banana. Because viruses cannot be cultured in vitro, our knowledge about their interactions with host and changes on physiology, biochemistry and molecular biology of the host is limited. Moreover, a comprehensive report regarding biochemical alterations in banana plants infected by BBTV is still not clear. Therefore, the present investigation was conducted to find the quantitative estimations of physiological and biochemical parameters such as protein, pigment and carbohydrate contents, phenolic compounds, polyphenol oxidase (PPO), peroxidase (POX), catalase (CAT), ascorbate peroxidise (APX), guaiacol peroxidise (GPX) and superoxide dismutase (SOD) activities, indicating their role in BBTV inoculated and non-inoculated plants of Virupakshi (hill banana), a unique flavoured elite dessert banana cultivar and Grand Nain, which belongs to a Cavendish sub group occupying approximately 50% of area in the world.