The breakthrough debunks the notion that all banana varieties are susceptible to the disease and opens the possibility of breeding resistant varieties, according to Dr Valentine Nakato, plant pathologist at IITA in Uganda.
“This discovery is very important for the millions of smallholder banana farmers in the eastern and central African region as one of the most effective ways to control any disease is developing resistant varieties,” Nakato said.
The IITA research team was led by Prof Rony Swennen (head of banana breeding at the institute), Dr George Mahuku and Dr Nakato, and their findings reported in the Plant Pathology journal.
Bananas are an important staple food in many parts of Tanzania and considered an indispensable part of life across the ECA region, providing up to one-fifth of the total calorie consumption per capita.
As such, the disease - which causes premature ripening and rotting of the fruit, wilting and eventually death of the plant - has drastically affected highland cooking banana plantations across the region and the food and income of millions of farmers.
Until now, the scientific world believed that all banana varieties in the region, except for a wild-seeded banana called Musa balbisiana, were susceptible to the disease which originated from Ethiopia and has now invaded all banana growing areas in the highlands of eastern and central Africa.
The disease is caused by Xanthomonas campestris pv. musacearum bacteria and its symptoms include yellowing and wilting of leaves, a cream to pale yellow bacteria-laded oozing when the plant is cut, shrivelling of the male bud, premature ripening, internal discoloration of fruits, and finally death of infected plants.
Transmission is fast and mainly through contaminated tools, insect vectors, and planting material.
The average daily per capita energy from banana consumption in the ECA region is estimated at 15 times the global average and six times the overall African average.
The region has over 50% of its permanent cropped area under banana; around half of the total area under banana cultivation across Africa. ECA countries (Tanzania, Uganda, Rwanda, Burundi, DR Congo, and Kenya) produce annually 21 million tons of banana with a value of $4.3 billion.
The researchers systematically screened the entire banana collection at IITA in Uganda, identifying 13 other sources of resistance next to M. Balbisiana, plus several diploids derived from Musa acuminate - another wild banana - which are already part of the existing highland breeding program of IITA and Uganda’s National Agricultural Research Organisation (NARO).
“The findings of this study are very significant for the banana breeding community and we will redouble our efforts to develop banana varieties with resistance to the disease,” said Prof Swennen.
IITA and NARO have developed superior high-yielding matoke hybrids dubbed NARITA which will now be screened for bacterial wilt resistance and become part of future breeding schemes to develop bacterial wilt-resistant matoke varieties.
IITA is a not-for-profit institution that generates agricultural innovations to meet Africa’s most pressing challenges of hunger, malnutrition, poverty, and natural resource degradation.
Working with various partners across sub-Saharan Africa, it strives to improve livelihoods, enhance food and nutrition security, increase employment, and preserve natural resource integrity.