Rwanda’s cassava sector has faced significant challenges over the years, primarily due to the devastating effects of cassava viral diseases, mainly the Cassava Mosaïc Disease (CMD) and Cassava Brown Streak Disease (CBSD). These two diseases have severely threatened food security and the livelihoods of many cassava farmers nationwide. In 2014/2015, the Kinazi cassava plant, a franchise business established to address market overproduction, nearly shut down due to a shortage of adequate roots for processing. In a desperate bid to alleviate the crisis, the Government of Rwanda (GoR) imported millions of clean stem cuttings from Uganda, providing temporary relief but not a sustainable solution.
In response to this crisis, IITA, in collaboration with the Rwanda Agriculture and Animal Resources Development Board (RAB) and other partners, launched efforts in 2017 to counter the negative impact of cassava viral diseases. The efforts include the IFAD-funded CBSD Control Project, the Dutch government-funded Cassava Agribusiness Seed Systems (CASS) Project, and the recent Bill and Melinda Gates Foundation-funded ViRCA Deployment Project. All these initiatives focused on developing and deploying improved resistant varieties and establishing a sustainable clean seed delivery system. These measures have been crucial in halting disease spread and improving farm cassava productivity.
IITA Cassava Breeder and Seed Systems Expert Silver Tumwegamire said, “Recognizing the severe impact of cassava viral diseases on food security, we initiated and implemented several projects to develop and deploy disease-resistant varieties and establish a robust seed system.”
Initially, IITA and RAB established a pre-basic seed multiplication unit, utilizing optimized protocols for micro-propagating virus-indexed tissue culture plants and acclimatization and macro-propagation techniques under screenhouse conditions. However, the hardening of tissue culture (TC) plantlets under cold Rubona station conditions faced low survival rates, complicating efforts to produce adequate numbers swiftly.
Introducing Semi-autotrophic hydroponics (SAH) technology in 2019 offered a cost-effective and efficient solution. SAH technology significantly improved the survival rates of the hardening plants, making it easier to produce large quantities of clean pre-basic seeds. This technology was introduced through the collaborative support of three projects: the Technologies for African Agricultural Transformation (TAAT), the CBSD Control Project, and the Cassava Agribusiness Seed Systems (CASS) project.
Since its introduction, SAH has revolutionized the production and availability of clean pre-basic seeds in Rwanda. The SAH laboratory, the TC lab, and four large screenhouses collectively comprise a functional pre-basic seed unit under RAB and can produce over 200,000 plantlets or pencil stems per year under a moderate-throughput system.
Athanase Nduwumuremyi, RAB Cassava Breeder and Root Crops Coordinator, explained: “SAH technology has been a game-changer for cassava seed multiplication in Rwanda. It has enabled us to produce high-quality plantlets much faster, ensuring a steady supply of clean seeds for farmers.”
This has tremendously improved multiplication ratios, ensuring an adequate supply of clean plantlets for the next level of early-generation seed multiplication and delivery. From January to April 2024, RAB produced 55,569 pre-basic seeds or plantlets, with a target of reaching 200,000 plantlets by the end of the year. From these plantlets, at least 10 ha of clean essential seeds can be produced annually, yielding at least 2 million stem cuttings for certified one-seed production in the country.
Moreover, RAB supplies plantlets to additional private basic seed multipliers with screenhouses. It is estimated that each establishes at least one hectare of clean basic seed and generates an extra minimum of 0.8 million stem cuttings.
The SAH technology boasts a 90% survival rate for plantlets. In three weeks, 25 plantlets planted in one box can produce 62, which can multiply to 156 after another three weeks, demonstrating a higher multiplication ratio than the two node-cutting multiplication system. SAH’s cost-effective nature, ease of acclimatization, and high survival rates make it a superior alternative to traditional tissue culture and SH micropropagation methods, where only 20% of plantlets may survive.
RAB, supported by IITA, has recently optimized a locally made substrate based on peat moss for micro-propagation under SAH facilities, reducing reliance on the expensive Klansman substrate for macro-propagation. Additionally, RAB is optimizing the one-node cutting macro-propagation technique to enhance the multiplication ratios of pre-basic seeds.
Contributed by Ritha Bumwe
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