Authors:
Bakelana Zeyimo, Tata Hangy,Tevo Ndomateso, Mahungu NzolaMeso, Monde Godefroid , Tshilenge
Kanana, Lema Ki Munseki and Kalonji Mbuyi,Congo
|
Abstract:
Cassava brown streak disease (CBSD) is the second most important virus disease after Cassava
mosaic disease (CMD), infecting cassava (ManihotesculetaCrantz) in Africa. The disease is
caused by two distinct viruses, Cassava brown streak virus [2, 3] and Ugandan Cassava brown
streak virus (family, Potyviridae: genus, Ipomovirus). Transmission of CBSV from one plant to
another is reported to occur through grafting CBSV-free with infected cuttings and subsequent
dissemination by infected cuttings. The basic approach to control of CBSD is selecting planting
material from symptomless mother plants. Graft inoculation is the most efficient and effective of
the techniques for CBSD virus transmission and consequently cuttings are the most effective
way of the disease spreading.
In early 2000s, cassava root necrosis similar to those of CBSD were reported in western
provinces of Democratic Republic of Congo (RDC) (Kinshasa and Kongo Central) and up to
date PCR diagnoses did not detect any causal agent related to the observed symptoms and the
disease which was still referred as ‘CBSD-like disease’.
Due to lack of molecular data and the similarity of root symptoms with CBSD, the existence of a
virus has always been suspected to be the cause of CBSD-like propagation. Thus, 2 field
experiments were proposed in order to verify the existence of a systematic transmission of a
possible CBSD related virus, knowing that CBSD viruses are transmitted efficiently by
cuttings.
The first trial focused on the field evaluation of CBSD – like infected and apparently uninfected
planting materials, while the second trial involved the importation of tanzanian CBSD resistant
genotypes for evaluation in INERA Mvuazi research center under CBSD-like infection
conditions.
Results of the first trial did not show a systemic transmission of any CBSD-like pathogen while
CBSD-resistant parents involved in the second trial all succumbed to CBSD-like disease.
These results are the first experimental scientific evidence that the pathogen responsible for
CBSD-like is not a virus and is not even related to CBSD viruses.
These results corroborate currently with recent molecular data obtained by NGS and which
confirm the absence of any virus and suspect a possible transmission of CBSD-like by fungi and
/ or bacteria.
Therefore, CBSD-like has been named Cassava Root Necrosis Disease or CRND. |
