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Nakato G.V.,International Institute Of Tropical Agriculture | Ocimati W.,Commodity Systems and Genetic Resources Programme | Blomme G.,Commodity Systems and Genetic Resources Programme | Fiaboe K.K.M.,ICIPE African Insect Science for Food and Health | Beed F.,International Institute Of Tropical Agriculture
Canadian Journal of Plant Pathology | Year: 2014

Banana Xanthomonas wilt (XW), caused by Xanthomonas campestris pv. musacearum (Xcm), results in up to 100% yield loss. The efficiency of XW infection through the corm, pseudostem inoculation at bunch harvest, leaf, female and male bud bracts was evaluated in banana plants. The male and female bud bract inoculations caused the highest incidence (81% and 93%) compared with 0-44% for harvest and corm inoculations. Naturally mediated insect transmission in Pisang Awak resulted in up to 99% disease incidence. Floral inoculations and natural insect-mediated infections only resulted in floral symptoms. Symptom development in insect-transmitted infections simulated artificial male bud inoculations, confirming the male bud bract wounds as the main entry points for insect vector-mediated infections, thus reaffirming the importance of continuous and timely debudding to limit insect spread. Leaf and harvest inoculations resulted only in leaf symptoms, while corm inoculations resulted in late floral symptoms. Floral inoculations were the main mode of infection. Single leaf inoculations resulted in 30% plant mortality despite 100% incidence, with 70% of plants recovering and bearing visibly healthy bunches and suckers. Thus, detection of a diseased plant in a mat shouldnt warrant the destruction of the whole mat. A significant difference in Xcm cfu g-1 was observed between symptomatic and symptomless leaves, suggesting that practices that keep the bacterial load below the disease-causing threshold could benefit the plant. This could explain the observed success of XW control through removal of single diseased stems in farms. © 2014 The Canadian Phytopathological Society.


Were E.,International Institute Of Tropical Agriculture | Were E.,Kyambogo University | Nakato G.V.,International Institute Of Tropical Agriculture | Ocimati W.,Commodity Systems and Genetic Resources Programme | And 4 more authors.
Canadian Journal of Plant Pathology | Year: 2015

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. © 2015 The Canadian Phytopathological Society.


Blomme G.,Commodity Systems and Genetic Resources Programme | Ploetz R.,University of Florida | Jones D.,Droitwich Spa | De Langhe E.,Catholic University of Leuven | And 9 more authors.
Annals of Applied Biology | Year: 2013

The genus Musa is not native to Africa. It evolved in tropical Asia, from southwest India eastward to the island of New Guinea. There is a growing circumstantial evidence which suggests that the East African Highland banana and the tropical lowland plantain were cultivated on the African continent since before 1 AD. It is also probable that ABB cooking and AB and AAB dessert cultivars were brought to the continent from India by Arabian traders from 600 AD, and that these were disseminated throughout East Africa. During the colonial era, the main centres of distribution for banana cultivars were botanical gardens, such as Zomba in Malawi, Entebbe in Uganda and Amani in Tanzania. It appears that the very early introductions of Highland banana and plantain arrived in Africa as a relatively clean material without the conspicuous pests and diseases that affect them in Asia. In contrast, several devastating problems now impact the crop in Africa, including nematodes, the borer weevil and diseases, most notably banana bunchy top, banana streak, Sigatoka leaf spots, Xanthomonas wilt and Fusarium wilt. We (a) provide chronological overviews of the first reports/observations of different Musa pests and pathogens/diseases in Africa, (b) highlight specific examples of when a pest or pathogen/disease was introduced via planting materials and (c) give recent examples of how the pests and pathogens spread to new regions via planting materials. In total, these production constraints threaten banana and plantain production throughout the continent and impact those who can ill afford lost production, the small-holder producer. Our intent in this review is to highlight the significance of these problems and the great importance that infested planting materials have played in their development. © 2012 Association of Applied Biologists.

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