Bringing improved banana hybrids a step closer to farmers’ fields

In East and Central Africa banana cultivation covers over 50% of the area under permanent crop cover, representing around half of the area under banana cultivation across Africa. This is currently annually equivalent to about 21 million tons of banana, valued at $4.3 billion for East and Central African countries (Burundi, DR Congo, Kenya, Rwanda, Tanzania, and Uganda).

In East and Central Africa banana cultivation covers over 50% of the area under permanent crop cover, representing around half of the area under banana cultivation across Africa. This is currently annually equivalent to about 21 million tons of banana, valued at $4.3 billion for East and Central African countries (Burundi, DR Congo, Kenya, Rwanda, Tanzania, and Uganda).

Consequently, banana constitutes an indispensable part of life in this region and is strongly interwoven into local customs as well as providing an important nutritional component of the diet. Up to one-fifth of total calorie consumption per capita is provided by banana, amounting to an average daily energy consumption of 147 kcal per person or six times the African average.

Unlike many staple crops, banana delivers food throughout the year and quickly recovers from drought stress at the onset of rains. Cultivation of cooking banana in Uganda and Tanzania is dominated by Matooke (East African Highland cooking banana, EAHB) and Mchare types, which represent a unique set of Musa germplasm found only in East and Central Africa. Some Matooke types have a high water content and are used for juice production.

Banana production in the region has stagnated at 9% of the yield potential. Pests and diseases are a key component of this problem and pose a particularly significant threat to the future sustainability of production, with the potential of further destabilizing both food security and household incomes across this region. Diseases, such as Black leaf streak (black Sigatoka) and Fusarium wilt (Panama disease), and pests, such as nematodes and weevils, are especially damaging.

Breeding banana is slow, costly, and fraught with numerous difficulties, largely arising from inherent sterility and the very poor germination of the few seeds that are produced. To optimize efforts and skills, the National Agricultural Research Organization (NARO) of Uganda and IITA joined forces under a combined effort to breed Matooke in Uganda. Over a period of 18 years a series of high-yielding EAHB hybrids were jointly developed and are now referred to as the NARITA hybrids (http://www. promusa.org/NARITA+hybrids), embodying the joint contribution.

Banana breeding involves first the identification of seed-producing Matooke varieties, which are rare and difficult to find. Twelve such triploid Matooke varieties were identified, mass-multiplied in vitro as tissue culture plants, planted in the field, and then carefully hand pollinated using improved diploid banana. This process created tetraploid plants. Although these tetraploid plants had desired attributes, they were not good final products for the end users as they contained residual seed fertility that poses a problem in fruit quality. To circumvent this problem, tetraploids were further crossed with improved diploids to generate secondary triploid NARITA hybrids that are seed-sterile. The resultant NARITAs were then planted in the field and higher yielding hybrids (1–2 plants) were selected once bunches had developed. Planting material from the selected hybrids was then multiplied and the superiority of each hybrid for bunch yield, fruit taste, and reaction to black leaf streak was evaluated from 10 plants of each hybrid.

Over several years of this intensive and laborious breeding process, 27 superior NARITA hybrids were finally selected for delivery to farmers. Their yield ranged from 9.1 t/ha to as high as 37.8 t/ha with bunches weighing up to 30.4 kg, depending on the hybrid. All NARITAs are resistant to black leaf streak (http://www.musalit.org/seeMore.php?id=15482). Seventeen of these NARITA hybrids exhibit high black leaf streak resistance (80– 100%), even after three production cycles, demonstrating durable resistance against this disease and possibly against nematodes and weevils. Although 12 Matooke cultivars were initially used for breeding, the Enzirabahima and Nakawere varieties delivered most of the highyielding and preferred hybrids with minor but significant contributions from Kabucuragye, Entukura, and Nfuuka. Some NARITA hybrids had 16 parents, while others had just four. The noted hybrid vigor is now under investigation. Despite the use of only cooking banana in the breeding program, seven of the hybrids were surprisingly selected as juice banana.

In a next step, yield stability, taste quality, and farmer preference are being evaluated across a range of environments (http://www.iita.org/ Farmers participating in a participatory rural appraisal. Source: Bioversity International. 29 news-item/matoke-east-africa-planned-regional-testing-first-ever-highyielding-hybrids/Farmers participating in a participatory rural appraisal. Source: Bioversity International. 29 news-item/matoke-east-africa-planned-regional-testing-first-ever-highyielding-hybrids/) to scale out their use and expand their potential. NARITAs are currently being evaluated in two locations in Uganda (Kawanda and Mbarara), and three in Tanzania (Bukoba, Kilimanjaro, and Mbeya). Private tissue culture laboratories in each country have been subcontracted to produce the desired quantities of plants.

The yield and pest/disease status are being evaluated in a research collaboration led by Bioversity International together with IITA, NARO, and the Agricultural Research Institute, Tanzania (ARI) and Stellenbosch University, South Africa (http://bananabreeding.iita.org/ index.php/2017/01/24/work-package-4-empowering-end-userevaluation/). A barcode labeling system was developed that allows the scientists to identify unambiguously each plant in the trial and follow its development over time; plant performance data are collected with an electronic form uploaded on a tablet or smart phone. This multilocational evaluation of the hybrids also provides the platform from which to investigate farmers’ criteria for selection and baseline studies for enduser preferences in EAHB value chains. Such a study paves the way for future participatory breeding and feedback to breeders on the important traits that farmers use for selection.

The team, with partners (CIRAD, France; Makerere University, Uganda; and Clark University, USA), have developed participatory rural appraisal (PRA) tools including an intra-household survey, seasonal and daily calendar exercises, a community wealth ranking exercise, and a trait preference exercise to characterize the target population environments in terms of agroecological and socioeconomic conditions and existing production systems.

The NARITA multilocational trials will also serve as demonstration fields for farmers, while results will provide an important step towards selective breeding and distribution of improved banana. Additional production cycles and farmer responses will continue to be collected towards the generation of a Musa database (https://musabase.org/), which will be used to support future breeding activities, among other things. Meanwhile, NARITAs are becoming very popular, with high demand for their testing and distribution elsewhere, such as in Rwanda, Burundi, and DR Congo.

The development of the hybrids to the point of regional testing and generating demand from across the whole of the banana-growing region of ECA demonstrates the success of this collaborative venture between NARO and IITA. The lengthy breeding process is now beginning to bear fruit. However, significant efforts are being undertaken to reduce the length of time, improve the efficiency of the breeding pipeline, and increase the rate of delivery of improved banana within the project “Improvement of banana for smallholder farmers in the Great Lakes Region of Africa” (http://bananabreeding.iita.org/), funded by the Bill & Melinda Gates Foundation. The evaluation of NARITA hybrids in Tanzania and Uganda is a component within the same project.

ORCID: 0000-0002-5258-9043, 0000-0002-2030-6328, 0000-0002-4468-5932, 0000-0002-2022-2159, 0000-0001-7460-9001

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