Sustainable production and distribution of clean banana

Bi Irie Vroh,

Banana (Musa spp.) including the plantain type are among Africa’s most important staple food and cash crops. Nearly 30 million t of banana are produced yearly in Africa, mostly by smallholders and consumed locally.

The major edible types are parthenocarpic (produces fruit without fertilization) and seedless. They are propagated traditionally by planting corms and suckers (daughter plants that grow from the rhizomes at the base of mother plants).

However, propagation material derived from the infected mother stocks results in perpetuation of diseases (e.g., viruses such as banana bunchy top, banana streak) and pests (e.g., nematodes and weevils) leading to low yields and poor quality fruits.
Due to the unavailability of disease- and pest-free or clean planting materials, farmers in sub-Saharan Africa traditionally plant suckers derived from their own plantations, most of which are affected with pests and diseases.

IITA has been using three approaches to generate clean planting material of farmer-favored banana cultivars:

Boiling water treatment of suckers: Suckers are submerged in boiling water for 30 seconds to kill nematodes and weevils. This method is efficient and easy for farmers, but it has low output and is laborious.

IITA’s Emmanuel Njukwe, Paula Bramel, and Bi Irie Vroh visit the Fritz Jakob Foundation. Source: B. Vroh, IITA.
IITA’s Emmanuel Njukwe, Paula Bramel, and Bi Irie Vroh visit the Fritz Jakob Foundation. Source: B. Vroh, IITA.

Macropropagation using the PIF technique: Through the technique known as PIF (plantes Issues de Fragments de tige) tens of good quality plantlets are produced within two months at relatively low costs. In this approach, the primary buds of entire suckers or fragments of corms are destroyed and axillary buds are exposed to high humidity to induce sprouts which are then harvested, hardened, and distributed.

This approach can be implemented in remote rural areas near farmers’ fields or by NGOs in direct contact with farmers for training and the distribution of good planting materials. This procedure is simple to replicate using locally made humidity chambers.

Micropropagation: Also known as in vitro production of tissue culture (TC) material this is the most efficient approach to the production of clean planting material in terms of throughput and germplasm exchanges across international borders. In vitro plantlets are micropropagated in the TC laboratory of IITA in Ibadan, Nigeria, and hardened first in the acclimatizing rooms, then in screenhouses before being distributed to farmers. Planting materials from preferred landraces and improved hybrids are propagated through TC, and hardened for use or maintained in a conservation cold room where each genotype is replicated several times from the initial meristem for future use.

IITA’s Delphine Amah holding racks of TC plants in a growth room. Source: B. Vroh, IITA.
IITA’s Delphine Amah holding racks of TC plants in a growth room. Source: B. Vroh, IITA.

Combining the TC pipeline with the macropropagation through PIF, IITA regularly distributes thousands of seedlings to NARS, NGOs, and farmers in West and Central Africa. Besides the preferred local varieties, the most distributed improved materials include the plantain hybrids PITA 14, PITA 21, and PITA 23 and the cooking banana hybrid BITA 3. These hybrids express a higher level of tolerance for black Sigatoka diseases compared with local varieties.

IITA trains farmers in applying boiling water treatment of suckers and macropropagation by PIF to produce clean planting material. However, IITA primarily uses micropropagation as the method of choice for conservation, propagation, and distribution of germplasm, and also to support its breeding programs. IITA also provides training programs on TC operations for NARS. For IITA’s projects in West Africa, clean planting materials are produced by TC or by PIF, hardened and raised in screenhouses, and then transferred to specific project sites.

Hardening of clean planting materials produced by TC and PIF methods. Source: B. Vroh, IITA.
Hardening of clean planting materials produced by TC and PIF methods. Source: B. Vroh, IITA.

In rural communities, IITA emphasizes training for farmers and rural entrepreneurs so they can produce clean planting materials in their own communities. These various efforts enhance the farmers’ access to clean planting materials and also encourage involvement of commercial operators in distribution of planting materials. The improvement of the capacity of NARS and the involvement of the private sector are needed to scale up the technologies for the sustainable production of clean planting materials of banana and plantain.

Developing clean seed systems for cassava

James Legg,

Cassava stems for future crop. Photo by L. Kumar, IITA.
Cassava stems for future crop. Photo by L. Kumar, IITA.

Cassava is one of those crops that uses part of the plant for propagation. It is very convenient to use vegetative material from a previous crop to plant a new one. This is one of the beauties of vegetatively propagated crops. However, this convenience comes at a price. The use of planting material from a previous generation to establish the next provides an easy way for disease-causing pathogens, particularly viruses, to pass directly from one plant generation to another. So, while they offer convenience, vegetatively-propagated crops are often more widely affected by pathogens than those planted in the form of true seeds.

In Africa, cassava is the most widely cultivated of the vegetatively-propagated crops, being grown on more than 12 million ha across the continent. The exotic pest introductions, cassava mealybug and cassava green mite, caused great damage to Africa’s cassava crop in the 1980s and 1990s, but both have been effectively managed through the implementation of a classical biological control program.

The fungal diseases, cassava bacterial blight (Xanthomonas axonopodis pv. manihotis) and cassava anthracnose (Colletotrichum gloeosporioides f. sp. manihotis) are locally important. The greatest current constraints to cassava production, however, are the virus diseases, cassava mosaic disease (CMD) caused by cassava mosaic geminiviruses (CMGs) and cassava brown streak disease (CBSD) caused by cassava brown streak viruses (CBSVs), which together cause crop losses worth more than US$1 billion annually.

One of the most important approaches to controlling these virus diseases, as well as other pathogens of cassava, is through the avoidance of infection. This can be achieved by starting out with pathogen-tested plants, and then bulking the planting material through a series of quality controlled multiplication steps. Although it sounds very simple, this can be difficult to achieve in practice.

Pathogen testing requires well-equipped laboratories run by adequately trained staff. Quality management in the field requires extensive grassroots knowledge of disease symptoms and the involvement of an appropriately trained and resourced national plant protection organization. In many parts of sub-Saharan Africa, capacity for these functions remains insufficient to meet the demands.

IITA and its partners have made significant progress in developing and implementing new systems to maintain the health of cassava through seed systems. For instance, through the Great Lakes Cassava Initiative (GLCI), a multi-partnered project implemented from 2007 to the present in Burundi, Democratic Republic of Congo, Kenya, Rwanda, Tanzania, and Uganda, a rigorous system has been put in place to assure the health of cassava planting material. This has been particularly important in view of the rapid recent spread of a devastating pandemic of CBSD in East Africa.

Healthy cassava plant. Photo by IITA.
Healthy cassava plant. Photo by IITA.

The key components of the quality and health management system are as follows: Primary (centralized seed production sites) managed by researchers or qualified seed producers, secondary, and tertiary multiplication sites (usually in farmers’ fields) are all assessed, at least once in a year, using the Quality Management Protocol (QMP). This sets out quality levels, primarily in terms of disease and pest incidence and material quality that must be met if the field is to “pass”.

The QMP standards for CMD and CBSD incidences ascertained by diagnostic tests are <10% for primary and secondary sites and <20% for tertiary sites in endemic areas. Planting materials from fields that fail to meet QMP standards are not distributed or used for further multiplication, although the tuberous roots can be used by the growers for consumption. Fields that meet the QMP standard and test negative for CBSVs are approved for more widespread dissemination.

This is the first time that this level of rigor has been applied to maintaining the health of cassava through multiplication programs in sub-Saharan Africa. It has been invaluable in assuring the health of the planting material provided to more than half a million beneficiaries in six countries, and provides an important model for other current and future cassava development programs.

Much remains to be done before such an approach can be used in a more sustainable way. Most importantly, basic capacity needs to be strengthened in most countries. Key elements of this include the laboratory and human capacity for virus indexing, as well as the knowledge of QMP and the capacity of the national plant quarantine organization to monitor cassava seed systems.

In addition, the management of cassava diseases could be greatly enhanced by the establishment of isolated nuclear multiplication sites planted with virus-tested cassava plantlets derived from tissue culture, as well as by raising awareness among growers about the importance of establishing the next crop with healthy planting material.

A long-term goal, as the commercial value of cassava increases, will be to provide a mechanism through which planting material certified through the QMP attracts a price premium. Creating added value is certain to be the key to the future development of clean seed systems for cassava in Africa. IITA and its partners are strongly committed to reaching this goal.

Clean yam tubers from vine cuttings

Hidehiko Kikuno,

Production of yam seed tubers using vine cuttings and in vitro micropropagation is quick, cost-effective, and results in clean planting material. This new propagation system for yam developed by IITA uses vine cuttings grown on carbonized rice husks combined with in vitro micropropagation (tissue culture).

The traditional system uses tubers as seeds, is inefficient and costly. High production costs are attributed to the use of seed yam tubers, which account for about 30% of the total yield and as much as 63% of the total variable cost incurred per season of cultivation. The multiplication rate in the field using the traditional system is also very low (1:5 to 1:10) compared, for instance, with some cereals (1:300). Low quality seed yam containing pests (nematodes) and pathogens (viruses) also result in a poor yield of ware yam tubers.

Clean seed tuber production system using vine propagation in combination with tissue culture techniques. Source: H. Kikuno, IITA.
Clean seed tuber production system using vine propagation in combination with tissue culture techniques. Source: H. Kikuno, IITA.

The use of vine cuttings as a planting material gives a higher multiplication rate that is about 20−50 times more than the traditional system. It also significantly lowers the risk of nematode infestation and promotes faster multiplication and better and more uniform crop quality. Although viruses are difficult to eliminate, planting materials (seedlings or tubers) produced by this approach are relatively clean compared with those from other propagation methods used in the open field.

An experiment conducted from 2009 to 2010 using seed tubers produced by vine propagation and planted at 25 cm × 1 m spacing resulted in the production of tubers both large (200−400 g) and small (<10−30 g). Large tubers are suitable for use as seed yam for planting in the field, whereas small tubers are resown to obtain appropriately sized seed yam (about 200−400 g) (Table 1).

Tubers from vine cuttings. Photo by. H. Kikuno, IITA
Tubers from vine cuttings. Photo by. H. Kikuno, IITA

Attempts are also being made to standardize the procedure for the direct use of vine cuttings as planting material using cv. TDr 95/18544. The success of this approach could change the way in which yam is propagated in the future and eliminate the dependence on seed yam for planting needs. It would also boost the availability of yam by ~30% (Table 1).

Another trial conducted to understand the appropriate time to excise vine cuttings established from tissue culture materials revealed that the best time for vine cutting is before the rapid tuberization stage. Vine cuttings taken after tuberization were poorly established (see figure below; Kikuno et al. 2010).

Correlation between rooting of vine cuttings and dry weight of tubers formed on mother plants. Time course of rooting of wild vine cuttings and growth of tubers of mother plants on yam (D. alata cv. 95/00361). Bars in each figure indicate % of vine cuttings with rooting. Source: H. Kikuno.
Correlation between rooting of vine cuttings and dry weight of tubers formed on mother plants. Time course of rooting of wild vine cuttings and growth of tubers of mother plants on yam (D. alata cv. 95/00361). Bars in each figure indicate % of vine cuttings with rooting. Source: H. Kikuno.

This new technology offers a rapid solution for a high-output production of seed yam or yam planting material. At the same time, it addresses the need for large numbers and the quick distribution of improved varieties to farmers. This knowledge would be useful for NARES, CSOs, and farmers involved in producing and distributing seed yam, and in maintaining and multiplying breeder and foundation seeds. The technologies can also be used as a research tool by scientists.

The project was funded by the Japanese Government (Ministry of Foreign Affairs), Sasakawa Africa Association, Tokyo University of Agriculture, and International Cooperation Center for Agricultural Education at Nagoya University in Japan under the Ministry of Agriculture, Forestry and Fisheries funded the project. Partners include the Tokyo University of Agriculture; National Root Crops Research Institute at Umudike, Nigeria; Crop Research Institute, Ghana; and Institute of Agricultural Research for Development, Cameroon.

Kikuno H, Matsumoto R, Shiwachi H, Toyohara H, and Asiedu R. 2007. Comparative effects of explants sources and age of plant on rooting, shooting and tuber formation of vine cuttings from yams (Dioscorea spp.). Japanese Journal of Tropical Agriculture 51, Extra issue 2.

Maria Ayodele: Invest in people

Maria Ayodele. Photo by IITA

Dr Maria Ayodele is from Cameroon. She set up and has been in charge of IITA’s Germplasm Health Unit (GHU) since 1998. IITA recognizes that germplasm health is a very important concern, and is proactive about ensuring the production of good quality and healthy plants by guarding against the introduction of exotic seed-borne pests, and preventing their spread to collaborating countries and partners. The GHU has thus adopted strict phytosanitary measures and has facilitated the movement of thousands of items of germplasm materials for its mandate crops every year.

Dr Ayodele obtained her first degree in the Netherlands on tropical agriculture, MSc in plant bacteriology from the University of Aberdeen, Scotland, and PhD in plant pathology, University of Ibadan, Nigeria. She also has a Diploma in Bible Studies and a Certificate in Discipleship, and is an Assistant Pastor of the Redeemed Christian Church of God. Dr Ayodele is a mother of six and several other children in the Lord; she specializes in mothering and welfarism.

Please tell R4D Review about yourself.
I am a plant pathologist by training, specializing in bacteriology and mycology (fungi), but also in seed pathology, phytosanitary regulations, and capacity building. I take care of plant health testing and diagnostics, and liaise with breeders and other scientists for test results, and with national partners for phytosanitary requirements and plant quarantine.

Please describe your work. What is your main research interest?
As a research support scientist, I help IITA in testing seeds for import or for sending to partners by making sure that they are disease-free to prevent the spread of exotic pests and diseases. I do plant health testing and grow seeds or other plant parts, such as leaves, stems, or tubers, in a containment facility; I inspect the plants in the field or in the genebank; take care of the bacteriology and mycology screening; send the materials to the Virology Unit for viral testing; compile all the test results and send them to the scientists; and make sure that all the proper documentation in terms of phytosanitary permits or requirements are provided for each crop and for each cooperating country.

I liaise with the plant protection and quarantine service organizations of partner countries where IITA sends or imports seeds or other plant materials for use in research. With FAO, I provide technical backstopping in plant health and phytosanitary regulation, and also capacity building for SSA partner countries, including Nigeria, Bénin, Burkina Faso, Gabon, Gambia, Guinea Bissau, Mali, Togo, Cote’Ivoire, Niger, and Senegal. For example, since some partners do not have the capacity for plant health diagnosis, IITA works with the Plant Quarantine Service (PQS) or the national plant protection organizations in doing the testing, with the PQS doing their own inspection. Otherwise, I travel to where the test plants are and inspect them.

Last year, I was part of a team that conducted training on pest risk analysis and the safe movement of germplasm for partners in the national programs of Tanzania, Zanzibar, Uganda, Kenya, and Zambia, Burundi, Malawi, and DR Congo.

I also do some research, specifically in the areas of classification and characterization of anthracnose for yam, morphological characterization of gray leaf spot in maize, and the establishment of pest-free areas for multiplying germplasm materials.

Maria Ayodele checking yam plants. Photo by IITA

What are some of the highlights of your career at IITA?
I have enjoyed the capacity building part—coordinating training and sharing my knowledge with partner-participants and investing in people. I maintain links with participants who start as students and later become colleagues, and keep communication lines open. They can always come back to me with questions. My relationship with them is based on honesty and mutual respect. This approach has helped such that I have never had any difficulty when asking for plant quarantine documentation.

What is your work philosophy?
I believe that people should be happy with what they are doing, or not do it at all. I like my job, I like what I am doing, and I am happy transferring knowledge and building the capacity of partners in plant health testing and diagnostics.

It is important to me that the type of job that I do motivates me. That way, I get complete satisfaction. I want to see that the client is happy, so it is important to work together with clients—work with people, work with results; in short, be self-motivated. Getting good results makes people happy, and I make sure that I deliver on those results.

I am most happy when I am in the field—I see the challenges there—and they make me think and look for solutions to problems; for example, why are this year’s plants different from those of last year? Was it the climate?

What lessons or insights do you want to share with colleagues?
I work a lot with partners in the national programs and this is very challenging because of differences in capacities. When I work with my “students”, I usually break down information and bring it to their level. This means simplifying language to make science, even common concepts, understandable. I provide hands-on exercises so participants are exposed to the practical side; for example, I bring them to the field to do actual disease diagnosis.

I am now working on a practical manual on field diagnosis for each IITA crop. This is intended for students of agriculture, universities and colleges, extension workers, farmers, and partners. Our scientists should be encouraged to produce simple monographs on their research breakthroughs, documents that are easily affordable and accessible to our clients. At the moment, our scientists write mainly for academic journals. Of course, we know that many of our clients have no capacity to pick up information in those journals.

When I approach work, I do not look only at the problems. Yes, I find out what the weaknesses are, but I focus on the strengths and think of solutions. I use this approach for everything. Not everything can be bad. Negativity is a wrong thing in life, so it is best to find the positive aspects in people or situations. Once you get a working system, look at what needs to be changed. Oh, and do not criticize—be constructive.

Lastly, we should also be resourceful and show our initiative at work.

You would be retiring from IITA soon. What would you want colleagues (or partners) to remember you by?
I want colleagues or partners to remember me as a good teacher and effective communicator—a colleague who is results-oriented, or who works until she gets results. But you should be asking my colleagues about this, not me!

What do you wish for Africa?
My wish is for Africa to have the phytosanitary structures in place where feasible, to prevent the introduction of exotic pests and diseases that are dangerous to African crops, and to assist and sustain agricultural development for food security and the prevention of genetic erosion. We can sustain agriculture in Africa if we protect it by preventing the introduction of pests accompanying plant imports—unintentionally introduced—and avoiding the spread and establishment on alternativee hosts.

Would you like to share some personal details?
Although I am an extrovert, I am a very private person. So, take what you see, and whatever you don’t see, don’t bother to look for it.