Scientists at the International Institute of Tropical Agriculture (IITA) have successfully transferred genes from green pepper to bananas, conferring on the popular fruit resistance to a devastating disease.
Banana xanthomonas wilt (BXW) costs banana farmers about half a billion dollars in damage every year across East and Central Africa. The leaves of affected plants turn yellow and then wilt, and the fruit ripens unevenly and before its time. Eventually the entire plant withers and rots.
BXW affects all banana varieties, including the East African Highland bananas that are a staple food in East and Central Africa. At present there are no commercial chemicals, biocontrol agents, or resistant varieties that can control the spread of the disease. BXW can be managed by de-budding, or removing the male bud as soon as the last hand of the female bunch is revealed, but the tools used to do this must be rigorously sterilized to make sure that they do not spread the disease themselves.
However, the adoption of these practices has been inconsistent at best as farmers believe that de-budding affects the quality of the fruit and sterilizing farm tools is a tedious task.
“Even if a source of resistance were identified today,” said Leena Tripathi, a molecular geneticist at IITA, “developing a truly resistant banana through conventional breeding would be extremely difficult and would take years, even decades, given the crop’s sterility and its long gestation period.” However, two proteins – plant ferredoxin-like amphipathic protein (pflp) and hypersensitive response-assisting protein (hrap) – isolated from sweet green pepper have been shown to prevent the spread of the Xanthomonas bacterium in banana.
“The hrap and pflp genes work by rapidly killing the cells that come into contact with the disease-spreading bacteria, essentially blocking the disease from spreading any further,” Tripathi says. “Hopefully, this will boost the arsenal available to fight BXW and help save the livelihoods of millions of farmers in the Great Lakes region.” This mechanism, known as hypersensitivity response, also activates the defenses of surrounding and even distant uninfected banana plants, leading to a systemic acquired resistance. These proteins can also provide effective control against other BXW-like bacterial diseases in other parts of the world.
In 2010, scientists from IITA successfully transferred genes coding for these proteins into East African Highland bananas. The transformed bananas have shown strong resistance to BXW in laboratory and screen house trials. The IITA team, together with scientists from the National Agricultural Research Organisation (NARO) of Uganda and in partnership with the African Agricultural Technology Foundation (AATF), has begun evaluating the new banana lines in confined field trials at NARO in Kawanda. The trials were authorized by the Ugandan National Biosafety Committee.
The genes used in this research were acquired under an agreement with the Academia Sinica in Taiwan.
Photo courtesy: IITA
This post is part of our series celebrating “40 years of CGIAR”