Systemicity of banana bunchy top viral infection in the Kisangani region of the Democratic Republic of Congo

In order to evaluate the systemicity of BBTV from one plant of the mat to the physically attached shoots, 60 mats both of “Yangambi Km5”, Musa AAA and those of the false horn plantain “Libanga Likale”, Musa AAB showing severity levels from 0 to 5 were selected in backyards in Kisangani. In addition, 30 sucker corms per genotype were put under macro-propagation and leaf samples of lateral shoots that had emerged were tested using triple antibody sandwich-enzyme linked immuno sorbent assay (TAS-ELISA). In the backyards, for mats with no visible banana bunchy top disease (BBTD) symptoms, none of the analyzed mats with a total of 29 plants of “Yangambi Km5” and of 35 plants of “Libanga Likale” tested ELISA positive, indicating the absence of the BBTV infection. However, for the severity levels of one to five, 32 to 63.5% of plants in the mats were ELISA positive for “Yangambi Km5”, while 34.9 to 73.2% of plants from “Libanga Likale” tested positive for BBTV. After macro-propagation, 100% of lateral shoots of both cultivars at BBTD severity levels 4 and 5 tested positive. On the other hand, none of the lateral shoots at level 0 tested ELISA positive. However, for levels 1 to 3 some ELISA negative plantlets (40 to 23% for “Yangambi Km5” and 53 to 15% for “Libanga Likale”) were observed. This study indicates the need for the complete destruction of all mats harbouring plants with BBTD severity levels of 3, 4 and 5. Macro-propagation of suckers with severity level 1 symptoms could produce virus-free plantlets but ELISA testing of the lateral shoots is essential to pinpoint the virus-free plantlets

The complex distribution of plantain cultivars (Musa sp., AAB subgroup) in the Bas-Uele province of the Democratic Republic of Congo

Open Access Journal; Published online: 28 June 2018Plantain is one of the most important sources of food in the African lowlands stretching from the lowlands of Guinea and Liberia to the central basin of the Democratic Republic of Congo (DR Congo). Because plantain cultivars do not produce seeds, plantain cultivation is based on vegetatively transplanted lateral shoots/suckers. The way by which plantain reached the African continent is still under speculation. The aim of this study was to shed light on the history of plantain cultivars through a linguistic/synonymy study in northern Democratic Republic of Congo. We report the diversity of plantains in 18 villages across the Bas-Uele province based on a survey. Three villages in which plantain production systems dominated were selected in each territory, and ten households were consulted in each village. In each selected village, a focus group discussion was conducted with a group of at least 30 men, and with a separate group of 30 women to establish a list of plantain cultivars grown and known. A total of 46 cultivars were identified and 294 synonyms detected. The cultivar names are mostly related to animal features and agronomic traits, although there is a need to revisit the list for more specific traditional names. The local differences in cultivar identity, density and distribution are explained partly due to the influence of humid forest versus savanna landscapes, but the main part seems to be due to previous movements of Benza, Boa, Ngbandi, Rambo and Zande ethnic groups with their own set of cultivars. We demonstrate that the recorded synonymy data are useful for a tentative partial reconstruction of the history of some cultivars. This is useful for the genetic improvement of plantain cultivars, which most probably will have to rely for a great deal on the unraveling and management of epigenetic mechanisms

The effectiveness of consistent roguing in managing banana bunchy top disease in smallholder production in Africa

The removal of infected individuals is a common practice in the management of plant disease outbreaks. It minimizes the contact between healthy individuals and inoculum sources by reducing the infectious window of contaminated individuals. This requires early detection and consistent removal at landscape scale. Roguing of mats with symptoms of banana bunchy top disease (BBTD) in Cavendish banana production systems has been tested in Australia, using trained personnel, but has never been tested in smallholder systems. We studied the effectiveness of long-term consistent roguing in prolonging the productivity of banana orchards under smallholder farming systems in highland banana and plantain dominated production systems in Africa. We assessed the possibility of low-risk seed sourcing from the managed plots. Roguing reduced BBTD incidence to 2% in managed farmer fields and to 10% in experimental field plots, while a nonmanaged field eventually collapsed in the same period. With roguing, new infections decreased monthly compared to an exponential increase in a non managed field. The emergence of new infections in both managed and non managed farms followed a seasonal cycle. BBTD managed plots were a source of low-risk seed for replacing the rogued mats in the same fields, but perhaps not safe for use in nonendemic areas. We conclude that it is possible for smallholder farmers to recover and maintain banana productivity with rigorous roguing, which would entail early identification of symptoms and early removal of diseased mats. Studies are needed on the intensity of roguing under different disease and production conditions