Genetic Engineering for Resistance to Phytopathogens

摘要

Plants are immobile and as such are incapable of escaping attack by insect and microbial pests. Crop losses due to pests can be devastating to the point of creating a famine. Fungal and bacterial pathogens account for the greatest overall losses associated with plant diseases. Well documented examples associated with plant diseases. Well documented examples include the infamous Irish potato famine of 1845 due to Potato include the infamous Irish potato famine of 1845 due to Potato Late Blight caused by the fungus Phytophthora infestans, coffee rust caused by the fungus Hemileia vastatrix in Ceylon (Sri Lanka) in the late 1800s and bacterial rice blight disease caused by Xanthomonas oryzae in India in 1979(1). Not long ago (in the 1970s) corn production in the USA was threatened by a highly aggressive new race of Cochliobolus heterostrophus (race T) and wheat production is currently under threat from Karnal bunt caused by Telletia indica. In addition to yield losses, some fungal pathogens (e.g. Aspergillus spp., Fusarium spp.) caused food and feed safety concerns because of their ability to produce the potent mycotoxins, aflatoxin and fumonisin, respectively (2). One of the primary objectives of conventional plant breeding was to develop resistance to plant diseases (3). Results, however, were limited due to the length of time needed to developed varieties through conventional breeding, the lack of suitable donor varieties, and the ability of microbes to adapt by neutralizing plant defense mechanisms. Agrochemicals have been used but their application is limited by several factors including short durability, occurrence of resistance among phytopathogens, toxicity to humans, animals and the fragile environment (3).