The International Institute of Tropical Agriculture (IITA) and Uganda’s National Agricultural Research Organization (NARO) started a breeding program for the East Africa Highland Bananas (EAHB) in the mid 1990s that has delivered exciting results including the first-ever hybrids, dubbed NARITAs.
A team of scientists at IITA, NARO and SLU reviewed the progress and efficiency of this breeding program in the past 21 years at its IITA station in Uganda and outlines progress made to overcome unique botanical challenges encountered in the breeding system of bananas.
The East African Highland cooking banana, known as Matooke, are an important staple food and cash crop for millions of people in the Great Lakes region of Eastern Africa. Banana covers over 50% of the permanent cropped area in the region which produces more than half of the total bananas produced in Africa. Burundi, DR Congo, Kenya, Rwanda, Tanzania, and Uganda produce annually 21 million tons of bananas with a value of US$4.3 billion.
The production of bananas has declined in the last three decades due to attack by a myriad of pests and diseases, declining soil fertility and drought resulting in a high yield gap – with farmers’ harvests averaging between 5-30 t/ha against a potential of 80 t/ha. Some of the contributing pests include banana weevil and burrowing nematode and diseases include black Sigatoka or black leaf streak disease and banana bacterial wilt.
While breeding for improved varieties with resistance to these pests and disease was identified as the most sustainable method for addressing these production challenges, these bananas were for many years regarded as sterile with 0 and 1.5 seeds produced per bunch. The breeding program was initiated when the team identified 37 female fertile EAHB during screening for seed set after artificial pollination. These bananas produced up to a maximum of 25 seeds per pollinated bunch.
In addition to the low seed sets produced by the bananas, another challenge was low seed germination –estimates show that only 1% of hybrid seed germinates when planted in the soil. The seeds were therefore germinated in the tissue culture lab which increased rates of seed germination by a factor of 3 to 10%.
Twenty-five of the EAHB hybrids produced up to 305 seeds per pollinated bunch, and were therefore deemed fertile. The percentage of seed germination varied among crosses between 7.4% and 26% depending on the type of cross performed. In total, twenty-seven NARITA hybrids were selected for further evaluation in the East African region.
Despite all this progress, banana breeding is a slow process and the team is exploring ways to accelerate this process. Through genomic prediction banana hybrids can now be faster selected. Simultaneously efforts are under way to increase the number of hybrids.
The study recommends further research on pollination conditions and optimisation of embryo culture protocols to boost seed set and embryo germination, respectively. DNA marker-aided selection is needed in addition to more research in floral biology and seed germination to increase the efficiency of the EAHB breeding program.
The results of this study were published in Frontiers in Plant Science.