Fusarium wilt, caused by the soil-borne fungus Fusarium oxysporum f. sp. cubense (Foc), poses a major threat to banana production globally. A variant of Foc that originated in Southeast Asia, called tropical race 4 (TR4), was detected on a Cavendish banana export plantation (Metocheria) in northern Mozambique in 2013. Foc TR4 was rapidly disseminated on the farm, and affected approximately half a million plants within 3 years. The fungus was also detected on a second commercial property approximately 200 km away (Lurio farm) a year later, and on a small-grower's property near Metocheria farm in 2015. Surveys in Mozambique showed that non-Cavendish banana varieties were only affected by Foc race 1 and race 2 strains. The testing of Cavendish banana somaclones in northern Mozambique revealed that GCTCV-119 was most resistant to Foc TR4, but that GCTCV-218 produced better bunches. The occurrence of Foc TR4 in northern Mozambique poses a potential threat to food security on the African continent, where banana is considered a staple food and source of income to millions of people. Cavendish somaclones can be used, in combination with integrated disease management practices, to replace susceptible Cavendish cultivars in southern Africa. The comprehensive testing of African cooking bananas for resistance to Foc TR4 is required, along with the improvement of biosecurity and preparedness of growers on the African continent. Significance: This paper presents the first official report of the invasive pest Foc TR4 in Africa. The spread of Foc TR4 on Cavendish banana farms in Mozambique was documented. Banana varieties that could replace susceptible Cavendish bananas were identified.

Banana Fusarium wilt is a major production constraint globally and a significant threat to the livelihoods of millions of people in East and Central Africa (ECA). A proper understanding of the diversity and population dynamics of the causal agent, Fusarium oxysporum f. sp. cubense (Foc), could be useful for the development of sustainable disease management strategies for the pathogen. The current study investigated the diversity of Foc in ECA using vegetative compatibility group (VCG) analysis, PCR-RFLPs of the ribosomal DNA's intergenic spacer region, as well as phylogenetic analysis of the elongation factor-1α gene. Six VCGs (0124, 0125, 0128, 01212, 01220, and 01222), which all belong to one lineage (Foc lineage VI), were widely distributed throughout the region. VCGs 0128 and 01220 are reported for the first time in Burundi, the Democratic Republic of Congo (DRC), Rwanda, Tanzania, and Uganda, while VCG 01212 is reported in the DRC and Rwanda. Isolates that did not belong to any of the known VCGs were identified as Foc lineage VI members by phylogenetic analysis and may represent novel VCGs. CAV 2734, a banana pathogen collected in Rwanda, clustered with nonpathogenic F. oxysporum isolates in lineage VIII. Results from this study will contribute significantly toward the implementation of banana Fusarium wilt disease management practices in the region, such as the restricted movement of infected planting material and the selective planting of resistant banana varieties.

Auteurs : VINCENT Quentin, Docteur en écotoxicologie et écologie des sols, Directeur Scientifique et Technique et co-fondateur de Sol & co. Vandoeuvre-Lès-Nancy. AUCLERC Apolline, Maître de Conférences, Université de Lorraine /ENSAIA, Laboratoire Sols et Environnement, Vandoeuvre-Lès-Nancy. LEYVAL Corinne, Directrice de Recherche au CNRS, Laboratoire Interdisciplinaire des Environnements Continentaux (LIEC UMR 7360 CNRS UL), Vandoeuvre-Lès-Nancy.

This chapter explores the potential of Northwest Vietnam to diversify its land use through vegetable production systems. Temperate vegetables such as tomato and common cabbage have a high potential for Northwest Vietnam because of its relatively cool climate and these products offer the opportunity to reduce reliance on imported temperate vegetables. Constraints and opportunities for Northwest Vietnam to expand vegetable production were evaluated by focusing on the representative provinces of Son La and Dien Bien and their potential to supply fresh produce to the urban markets of Hanoi. Data from producers and consumers was analyzed for changing trends. In addition, on-farm trials were conducted to determine the suitability of introducing elite vegetable varieties and integrated pest management options into existing farming systems. The use of integrated pest management is particularly important because Hanoi consumers associate vegetables from the Northwest with low levels of pesticide use.

In 2006 and 2007, 75 strains of Ralstonia solanacearum were collected from wilting tomato, pepper and eggplant in Benin. The distribution and the incidence of tomato bacterial wilt in the field were assessed by counting wilted tomato plants on 3 plots of 50m2 per field. The isolated bacterial strains, including the reference strain, were identified using ELISA, pathogenicity test and carbohydrate oxidation. Bacterial wilt is widely distributed in Benin and was found in five of the eight agro-ecological zones (AEZ) of Benin, which correspond to eight of the 12 districts of Benin. The disease was more severe in ferralitic soil (AEZ V), in valleys and lowlands (AEZ IV) and in highlands (AEZ I). The incidence of tomato bacterial wilt was up to 71%. No R. solanacearum strains were isolated from AEZ II, AEZ VII and AEZ VIII. Strains identified as R. solanacearum were more widely distributed in the south than the center and the north of Benin. Based on biochemical characteristics, Beninese R. solanacearum strains were grouped into biovar I/race1 and biovar III/race 1.

Bananas (Musa spp.) are major staple and cash crops in the Great Lakes region of Africa. Yet, banana yields in this region are among the lowest in the world due to a wide range of abiotic, biotic and socio-economic causes. Cropping systems which could contribute to soil fertility replenishment, pest and disease suppression and climate change mitigation might improve banana yields and contribute to uplifting the livelihoods of millions of people in the region. In this context, a survey was conducted over two seasons in banana-based subsistence farming systems in Rwanda, Burundi, north-western Tanzania (Kagera and Kigoma regions) and eastern Democratic Republic of Congo (South Kivu province), to investigate the distribution and incidence of banana Fusarium wilt as related to cropping systems, edapho-climatic and socio-economic factors. Banana Fusarium wilt incidence was found generally high in the region, 54.1% of all farms had disease incidence higher than 40%, with Tanzania having the highest number of farms with high disease incidence (63.6%). Statistical analysis (chi-squared test of association) and GIS mapping, by layering Fusarium wilt incidence over selected predictor maps, showed that disease incidence was lower in farms growing cultivar mixtures (p < 0.01) and at higher altitudes (>1600masl) (p < 0.05), and a significant association of Fusarium wilt and farm age was observed whereby disease incidence was highest in farms aged between 10 and 30 years (p < 0.05). Additionally, this study reports for the first time the occurrence of Fusarium oxysporum f. sp. cubense race 2 in Rwanda and Burundi, and suggests that strategies for banana Fusarium wilt management in east and central Africa should include raising farmers’ awareness on pathogen spread mechanisms and enhancing their access to disease-free planting materials.

An important challenge threatening agriculture in Africa is the difficulty in collecting timely data on disease spread and effectiveness of on-farm control methods. This study served as a case study for assessing the viability of a participatory GIS (Geographic Information System) to enable a plant diagnostics network with fieldworkers. The use of mobile phone applications and a centralized database were integrated to provide a blueprint for how a range of agriculture-focused field organizations can collect data, explain events, predict outcomes and adapt and refine strategies with more accurate, cost-efficient and timely information. Over the course of 2 months, 38 Community Knowledge Workers (CKWs) using mobile phones, MTN Mobile Internet and GPS devices collected 3018 surveys documenting the presence/absence of three banana diseases: Banana Xanthomonas Wilt (BXW), Fusarium Wilt (FW) and Banana Bunchy Top disease (BBTD) in Bushenyi and Mbale districts in Uganda. Costs were saved by only mobilizing CKWs who then trained the communities on methods of banana disease detection, preventative measures and disease control procedures; only when doubts over identification or control occurred did the IITA and NARO technical team then prioritize visits. Although the CKWs provided an efficient and cost-effective information channel that can be leveraged to integrate the efforts of scientists with the needs of rural communities, there were significant gaps in prior farmer knowledge on the three targeted diseases, including how to identify or control them, despite extensive awareness campaigns preceding this initiative. Factsheets used for reference following training greatly improved CKW prior knowledge of disease recognition and control methods; hence, 90% of the surveys conducted during the second month met the data quality standards based on survey completeness, GPS accuracy and quality of symptomatic plant photos. There was significant and consistent demand by farmers for CKW services throughout the pilot period. In-depth training and continuous support of CKWs is thus essential. The technology infrastructure is scalable, and further integration of technology components promises a customizable web-based tool for data collection, GIS analysis, information dissemination and management of agriculture extension operations.

This study was carried out to investigate the potential role of banana weevils as vectors of Xanthomonas campestris pv. musacearum (Xcm), causal agent of banana wilt. Weevils captured from Xcm-infected plants were tested for presence of Xcm, and further raised on Xcm-infected corms for later use as vectors to transmit the pathogen to healthy tissue-cultured plantlets. Analysis of weevils captured from diseased fields revealed more weevils contained Xcm originating from Mbwazirume' compared with Kayinja' cultivars. Colonies of Xcm were recovered from the weevil external body surface, internal organs (mouth parts and abdomen) and faecal matter. There was significantly higher Xcm presence and cfu mL(-1) on the external weevil body surface than within the internal organs. Bacterial populations declined progressively from the external body surface, internal mouth parts, internal abdominal parts and the faecal matter. Following placement of weevils previously fed on Xcm-exuding corms in close proximity to healthy potted plants, infection occurred, with characteristic disease symptoms observed on all cultivars evaluated except Kayinja' which remained symptomless. Isolation from both symptomatic and asymptomatic plants revealed erratic Xcm incidence and cfu g(-1) that did not correlate to the number of weevils released in all cultivars, except for Kayinja'. This study showed that Xcm can survive on and within the banana weevil and potentially spread the pathogen to neighbouring plants.

Parasitic weeds are major contributors to hunger, malnutrition, and food insecurity across sub-Saharan and northern Africa by reducing crop yields in half. Over 20 million hectares of cereal grains in sub-Saharan Africa are infested with Striga (witchweed). Food production losses due to Striga in African countries range from 20% to 90%, amounting to over 10 million tons of food lost annually. The control options for Striga are currently ineffective and management possibilities for these weeds are urgently needed. The research progress with a specific forma speciales of Fusarium oxysporum as a biological control for Striga in Africa illustrates the potential to positively impact many lives and improve the health and livelihood of rural and urban poor. Can F. oxysporum wild type be the Achilles heel of Striga, or do we need enhanced biocontrol to achieve rapid, safe, cost-effective solutions for this major biotic constraint to food production in Africa?