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. 2019 Jan:105:77-87.
doi: 10.1016/j.pmpp.2018.09.002.

A method for generating virus-free cassava plants to combat viral disease epidemics in Africa

M N Maruthi  1 , E Charles Whitfield  1 , Gerald Otti  1 , Silver Tumwegamire  2 , Edward Kanju  2 , James P Legg  2 , Geoffrey Mkamilo  3 , Robert Kawuki  4 , Ibrahim Benesi  5 , Anabela Zacarias  6 , Therezia Munga  7 , Francis Mwatuni  8 , Edward Mbugua  9
Affiliations

A method for generating virus-free cassava plants to combat viral disease epidemics in Africa

M N Maruthi et al. Physiol Mol Plant Pathol. 2019 Jan.

Abstract

Here, we report a method to clean cassava plants from viral infections that cause cassava mosaic and brown streak diseases in Africa. Infected plants of resistant or tolerant varieties from Malawi, Mozambique, Kenya, Tanzania and Uganda were cleaned in the UK using a combination of tissue culture, chemotherapy and thermotherapy. In the first cycle of our virus-indexing procedure, we successfully cleaned 27 of the 31 varieties (87%), and after an additional three cleaning cycles, all plants were virus-free. Virus-free tissue-cultured plants were shipped back to Africa for distribution to farmers. This first cross-boundary effort provides important lessons for mitigating the two-major cassava viral diseases.

Keywords: ACMV, African cassava mosaic virus; CBSD, Cassava brown streak disease; CBSV, Cassava brown streak virus; CMD, Cassava mosaic disease; CTAB, Cetyl trimethylammonium bromide; Cassava brown streak disease; Cassava mosaic disease; EACMV, East African cassava mosaic virus; EACMV-Ug, East African cassava mosaic virus-Uganda; LFC, Laminar flow cabinet; MS, Murashige and Skoog; Manihot esculenta; PPM, Plant Preservation Mixture; RH, Relative humidity; SDW, Sterilised deionised water; UCBSV, Ugandan cassava brown streak virus; UIC, Unique identifying code; Virus diagnosis; Virus indexing.

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Figures

Fig. 1
Fig. 1
Typical symptoms of CMD (left) and CBSD (right) on cassava leaves.
Fig. 2
Fig. 2
Schematic diagram of one cycle of cleaning and indexing to generate virus-free cassava plants. Each cycle is divided into four phases.
Fig. 3
Fig. 3
Duplex RT-PCR results (A) CMBs and CBSIs, (B) and UCBSV and CBSV. The New England Biolab's 1 Kb and 500 bp markers are used in (A) and (B), respectively. Samples amplified were mixed infections with respective viruses identified on the pictures.
Fig. 4
Fig. 4
(A) Sterilisation and seeding the media with cassava nodes. Surface-sterilised cassava explants in the laminar flow ready for rinsing with SDW. (AB) Cassava node buds trimmed and ready for transferring into the culture medium. (C) Transferring nodes into the culture medium. (D). Media tubes with cassava node buds ready for labelling and incubation.
Fig. 5
Fig. 5
Transplanting tissue-cultured cassava plants into soil and their growth. (A) Easing the plantlet from the culture tube and (B) gently removing as much media gel as possible. (C) Rinsing any remaining gel in warm water (∼25 °C). (D) A plant being transplanted and (E) transplanted plants under propagator lid.
Fig. 6
Fig. 6
An example of the plant-labelling system using unique identification codes (UIC) at each stage of the plant multiplication process.
See this image and copyright information in PMC

References

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