Abstract
Banana, a major staple in East and Central Africa is constrained by banana Xanthomonas wilt (BXW) caused by Xanthomonas campestris pv. musacearum (Xcm). Xcm-infected plants are rapidly destroyed leading to 100% yield loss. Cultural controls are effective but laborious attracting laxity among farmers. This has led to epidemic resurgence in areas where BXW had been contained hence spread to new regions. Reliable control option would be planting Xcm-resistant varieties but extensive germplasm evaluation for their identification has not been conducted. Objective therefore was to determine existence of Xcm-resistance in banana by evaluating major banana cloneset representatives among indigenous cultivars plus introduced foreign Musa accessions. Potted plants were artificially inoculated with 0.5 ml (108CFU) of Xcm suspension. Promising selections from pot trial were later evaluated under natural transmission in field. Field trial plants were infected via insect vectors from spreader plants of highly susceptible cv Kayinja infected by spraying flowers with Xcm. Severity of Xcm-infection was semi-quantified using scales 1-5 and 0-5 for pot and field screening trials respectively. This enabled calculation of disease index as a measure of resistance for each genotype. High index implied highly susceptible banana genotype and low index resistant genotype. Findings 44 days after artificial inoculation showed wild banana M. balbisiana had 0.0 disease index thus highly resistant. All other banana genotypes tested under similar conditions had disease index of 100 thus susceptible. In field (insect vector transmission), disease index varied significantly among various genotypes evaluated, some susceptible while others; M. balbisiana, Mbwazirume, M9 and M. Zebrina resistant throughout 360 days of observation. We recommend that heritable traits that confer resistance in M. balbisiana, Mbwazirume, M9 and M. zebrina to Xcm be identified for utilization in genetic modification of farmer preferred bananas. Varieties Mbwazirume and M9 should be promoted for farmer growing to complement cultural controls against BXW. Key words: Xanthomonas campestris pv. musacearum, banana Xanthomonas wilt, banana.
Highlights
Banana (Musa spp.) is an important staple food crop in Uganda where production is globally ranked second largest after that of India (Biruma et al, 2007; Vurro et al, 2010)
banana Xanthomonas wilt (BXW) that is caused by Xanthomonas campestris pv. musacearum (Xcm) (Yirgou and Bradbury, 1974) which leads to complete yield loss
The strain of Xcm utilized in evaluation of banana resistance (Figure 2a) was found to induce wilt symptoms in all eight inoculated plants (100% incidence) of banana “cv” Kisansa within 14 days of pathogenicity confirmation test trial (Figure 2a)
Summary
Banana (Musa spp.) is an important staple food crop in Uganda where production is globally ranked second largest after that of India (Biruma et al, 2007; Vurro et al, 2010). Since the emergence of Banana Xanthomonas wilt (BXW disease in 2001, it has devastated banana production undermining food and income security for more than 70% of Uganda’s population that depend on banana industry (Tushemereirwe et al, 2004; Biruma et al, 2007). Banana plantations in as far as Burundi, the Democratic Republic of Congo, Kenya, Rwanda, Tanzania and Uganda (Tushemereirwe et al, 2001; Ndungo et al, 2006; Biruma et al, 2007; Reeder et al, 2007; Carter et al, 2010) have been affected
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