NRU :: Browsing by Author "Blomme, G."

Browsing by Author "Blomme, G."

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An analysis of the risk from Xanthomonas campestris pv. musacearum to banana cultivation in Eastern, Central and Southern Africa
(Bioversity International, Montpellier, France, 2008) Smith, J.J.; Jones, D.R.; Karamura, E.; Blomme, G.; Turyagyenda, F.L.
Xanthomonas wilt, which is commonly known in East Africa as banana Xanthomonas wilt (BXW), banana bacterial wilt or enset wilt, is a devastating disease caused by the bacterium Xanthomonas campestris pv. musacearum. It was first reported in 1968 in Ethiopia, where it remained confined until it was observed in Uganda in 2001. The subsequent spread of the bacterium throughout the Great Lakes region, where banana forms a large proportion of the diet, is posing a serious threat to food security. The authors, scientists from the Central Science Laboratory in the UK and Bioversity International in Uganda, discuss the distribution and epidemiology of the causal agent and the measures farmers can use to protect their plants from contracting this deadly disease. They also analyse the impact of the measures deployed to date and make recommendations to reduce the risk of the disease spreading to other countries.
Banana Xanthomonas wilt in Ethiopia: Occurrence and insect vector transmission
(African Crop Science Journal, 2008) Ahimelash, D.; Alemu, T.; Addis, T.; Turyagyenda, L.; Blomme, G.
Bacterial wilt caused by Xanthomonas vasicola pv. musacearum (Xvm) is an important disease of enset and banana in south and south-western Ethiopia where, the diversity of the insect fauna on banana inflorescences was unknown and the role of insects as vectors of the disease had not been studied. The objectives of this study were to assess the occurrence of bacterial wilt and male bud infection, the diversity of insect families in banana plantations and the presence of the bacteria on insects collected from diseased inflorescences in south and southwestern Ethiopia. Surveys were carried out and insects were collected from three different zones in 2005. The diversity and richness of the insect families was assessed across sites and genotypes and comparisons were made using the Shannon Diversity Index and the Jack knife estimator, respectively. Correlations were made between the abundance and incidence of insects with the incidence of male bud infection on ‘Pisang Awak’ plants. A wide range of insect families were recorded and they varied according to banana genotype and altitude. The Drosophilidae and Apinae families were most frequently recorded across sites and genotypes. The ‘Wendo’ variety (AAA Cavendish group) had the highest diversity and richness of insect families within and across sites. In contrast to the Kembata Tembaro and Bench Maji zones, severe and widespread male bud infection of banana was found in Kaffa, where there was a high diversity of insects on the ‘Pisang Awak’ and ‘Abesha muz’ plants. The incidence of male bud infection on ‘Pisang Awak’ plants was highly correlated with the incidence of insects (R2 = 0.964). The incidence of male bud infection however depends on the floral morphology and altitude. Artificial inoculation with Xvm ooze on fresh male bract and flower scars resulted in infections on ‘Pisang Awak’ and ‘Abesha muz’ plants, but the ‘Dwarf Cavendish’ plants with persistent bracts and flowers remained healthy. Few male bud infections were observed at altitudes above 1,700 masl. Xvm was isolated from Apinae, Lonchaeidae, Muscidae, Tephritidae and Vespidae insect families. Lonchaeidae (Silba spp.) were frequently observed on banana bract and flower scars and could thus be an important insect vector of Xvm in Ethiopia.
The Effect of the Prompt Removal of Inflorescence-Infected Plants and Early Debudding of Inflorescences on the Control of Xanthomonas Wilt of Banana
(ISHS Acta Horticulturae, 2007) Blomme, G.; Turyagyenda, L.F.; Mukasa, H.; Ssekiwoko, F.; Mpiira, S.; Eden-Green, S.
Xanthomonas wilt of banana, caused by Xanthomonas campestris pv. musacearum, is an important constraint to banana production in Uganda. Different strategies to control the disease were investigated in an attempt to identify those methods that could be used by small farmers in East Africa. The effect of removing pseudostems showing early and late symptoms of inflorescence infection on the spread of the disease in ‘Kayinja’ (syn. ‘Pisang Awak’, ABB genome) was studied. Suckers of ‘Kayinja’ did not become infected when pseudostems derived from the same mat were removed at an early stage of inflorescence infection. In addition, the results of experiments to determine the effectiveness of bagging and debudding inflorescences at different stages to prevent insect-borne infection are reported. This research was undertaken using ‘Kayinja’, mixed plantings of East African highland cultivars (AAA) and high-yielding exotic/improved cultivars in farmers’ fields. ‘Kayinja’ was the most susceptible cultivar to floral infection, followed by the East African highland cultivars. Exotic/improved cultivars had the lowest number of infections. Lower numbers of floral infections may be attributed to the persistence of male flowers and bracts. No flower infection was observed on plants that were debudded immediately after the formation of the last cluster and on those that were bagged until the formation of the last cluster and debudded right after. However, plants that were bagged until the formation of the last hand, but not debudded, or debudded after 2 weeks or more, showed high levels of inflorescence infection. This indicates that insect-vector transmission occurs only via the male parts of the inflorescence. Prompt removal of the whole pseudostems showing symptoms of early inflorescence infection and early debudding are simple, cheap, easily applicable and highly effective methods for controlling Xanthomonas wilt. Results of a cost-benefit analysis of control options are discussed.
The effectiveness of different herbicides in the destruction of banana Xanthomonas wilt infected plants
(African Crop Science Journal, 2008) Blomme, G.; Turyagyenda, L.F.; Mukasa, H.; Eden-Green, S.
Early detection followed by the destruction of infected mats is one of the recommended and effective methods of controlling banana Xanthomonas wilt. As manual destruction is very tedious and time consuming, herbicide injections in the pseudostem or the stump were evaluated as a suitable alternative. The study was carried out in Luwero district in central Uganda. Herbicide injections were made on ‘Pisang Awak’ plants (Musa ABB group) using different concentrations of Roundup and 2,4-D at a pseudostem height of 30 and 100 cm. In addition, the herbicide was injected in the centre (diameter-wise) and in the peripheral part of the pseudostem (tangentialwise). Herbicide applications into the stump were also evaluated. All plants (100%) injected with 2,4-D had fallen and started rotting by three weeks after application. However, at three weeks, none of the plants treated with Roundup, regardless of the concentration and the height of injection had died. Similarly plants injected with 2,4-D had less re-sprouting compared to plants treated with Roundup. Therefore, 2,4-D is more effective than Roundup in destroying ‘Pisang Awak’ plants and in suppressing the re-sprouting of lateral shoots. Since 2,4-D is also cheaper than Roundup it is recommended for use on small-scale plantations. At least 1.6 ml of the original concentrate of 2,4-D and 2.0 ml of the original concentrate of Roundup needs to be applied per mature plant. The most effective pseudostem injection height was found to be 100 cm. The angle of injection whether peripherally or central and the plant growth stage did not affect the herbicides’ efficiency. The results also showed that pseudostem injections are more effective than stump herbicide applications.
Garden Tool Transmission of Xanthomonas campestris pv. musacearum on Banana (Musa spp.) and Enset in Ethiopia
(Harnessing International, 2008) Addis, T.; Turyagyenda, L.F.; Alemu, T.; Karamura, E.; Blomme, G.
Xanthomonas wilt caused by Xanthomonas campestris pv. musacearum has been an important constraint to enset (Ensete ventricosum) and banana (Musa spp.) in Ethiopia. It was postulated that Xanthomonas wilt has a similar epidemiology as other banana bacterial wilts, which are known to be transmitted by insect vectors and garden tools. A study to determine the role of garden tools in the transmission of Xanthomonas wilt was carried out on enset in a greenhouse at the Southern Agricultural Research Institute, Awassa, Ethiopia and on ‘Pisang Awak’ (AABB genome) in the field at Amaro, Southern Ethiopia. A contaminated knife was used to infect plants. The treatments in the greenhouse trials comprised of cutting: green leaves; broken green leaves; dry leaves; the pseudostem; and roots. Similar treatments were carried out on the field-grown ‘Pisang Awak’ plants with two additional treatments: desuckering and debudding. Debudding was done by cutting off the male bud with a contaminated machete, while a forked stick was used for control samples. In addition, bacterial ooze was smeared on fresh and dry flower and bract scars at the male part of inflorescences. All plants treated with a contaminated machete: enset and banana when cut in the pseudostem; and all banana plants when debudded got infected. Similarly, cutting green leaves and cutting broken green leaves resulted in a high disease transmission of respectively 67 and 62% in banana and 58 and 54% in enset. Similar high transmission rates (90%) were obtained for desuckering on banana. On the other hand, cutting roots with a contaminated machete resulted in low transmission levels, with 20% in bananas and 25% in enset suggesting that tool infections mainly occur above ground. This calls for rigorous tool disinfection, while desuckering and deleafing in highly infected fields should be avoided. Debudding should be carried out with a forked stick.
Rehabilitation of Banana Farms Destroyed by Xanthomonas Wilt in Uganda
(J. Appl. Biosci, 2008) Turyagyenda, L.F.; Blomme, G.; Ssekiwoko, F.; Karamura, E.; Mpiira, S.; Eden-Green, S.
The measures that have been recommended for banana wilt management in Uganda include debudding, disinfection of garden tools and destruction of diseased plants. However, the adoption rate for these options has been low and the disease has reached epidemic levels. Destruction and removal of the infected plants followed by a fallow period or planting of a crop that is not a host of Xcm, and subsequent replanting with healthy banana suckers could restore banana plantations in areas affected by wilt. This study was carried out to determine the most effective method of destroying infected plants and an appropriate fallow period to ensure replanted suckers are not reinfected. Trials were carried out at three field sites with 68-76% of mats infected at the beginning of the experiment. Treatments evaluated were: (1) killing plants by injecting a herbicide (2,4-D) into the pseudo-stems; (2) plants manually cut down and their rhizomes dug out; (3) plants cut down at ground level and re-sprouting suckers continuously mechanically removed. The banana plant debris was piled on ridges between the plots. Replanting with healthy banana suckers started one month after clearing the diseased plants, using tissue culture plantlets of cultivar Pisang Awak and Mpologoma. A portion of the field was replanted each month up to eight months after the onset of the trials. An economic viability analysis of the different options of destroying infected plants was carried out. Banana suckers planted after a one-month fallow period had a 25% survival rate, while all suckers planted after seven and eight months of fallowing survived. Generally, more dead plants were recorded with cv. Mpologoma than cv. Pisang Awak. Incidence of re-infection was highest in the plots where re-sprouting suckers were being continuously removed and lowest in plots where plants had been completely uprooted. A fallow period of at least six months is required to restore health to farms after infection by Xanthomonas wilt. Complete uprooting of infected plants and removing plant debris onto ridges is the best option for managing Xanthomonas wilt. However, the economic viability analysis indicated that farmers preferred to use herbicide to kill the plants rather than uprooting which is more laborious and expensive. The use of herbicide is hence recommended followed by a 6 month fallow or crop rotation period.
Relationship between root and shoot growth traits during the plant crop and first ratoon in banana and plantain (Musa spp.) and its implications for perennial cultivation on degraded Ultisols in south-eastern Nigeria
(Journal of Applied Biosciences, 2008) Blomme, G.; Swennen, R.; Soka, G. E.; Turyagyenda, F. L.; Tenkouano, A.
This study assessed the relationships of root and shoot growth within and across two consecutive crop cycles in 32 widely differing Musa spp. genotypes.A reduction in leaf area, corm weight, root dry weight, cord root number and lengthoccurred during the reproductive stage of both the plant crop and the first ratoon cycle. Most leaves died off during the reproductive stage, while the decay of the outer leaf sheets resulted in a reduction of the pseudostem circumference. The corm fresh weight was reduced by 20 and 13 % during the reproductive stage of the first and the second cycle, respectively. A reduction in cord root number of 8 and 12 % was observed during the reproductive stage in the first and second cycle, respectively. Cord root length was reduced by 40 % during the reproductive phase of both cycles. The effect of crop cycle was significant on the different corm traits and the cord root diameter. The corm of the first ratoon plants was bigger and taller than the corm of the plant crop, resulting in a slight increase in number and diameter of cord roots. In contrast, cord root length of the first ratoon was less than that of the plant crop. Number of suckers decreased from 16 to 12, while height of the tallest sucker was 120 cm and 68 cm at flower emergence of the plant crop and the first ratoon crop, respectively. Significant positive correlations were observed between mother plant (plant crop) and sucker growth characteristics, mostly within but not across genotypes. While fast-growing plants may also have better developed suckers, it is not apparent that breeding for genotypes with a larger root system would lead to better suckering. The observed reduction in sucker vigour during the reproductive phase of the ratoon crop may be attributed to the observed high mat and possible soil degradation. This would affect plant anchorage and stability, and limit possibilities for perennial production of bananas and plantains under mono-cropping conditions on degraded Ultisols
Relative performance of root and shoot development in enset and east African highland bananas
(African Crop Science Journal, 2008) Blomme, G.; Sebuwufu, G.; Addis, T.; Turyagyenda, L.F.
East African highland bananas and enset belong to the genera Musa and Ensete (Ensete ventricosum), respec-tively. The root, corm and shoot growth of field-established enset and East African highland banana cultivars was assessed. Banana and wild enset plants were assessed in Uganda, while domesticated enset plants were assessed in Ethiopia. Growth traits of the enset and banana mats in Uganda were recorded at flower emergence of the banana plant crop, while enset plants in Ethiopia were assessed at 4 and 5 years after planting. The results obtained in Uganda indicate that enset had a significantly (P<0.05) shorter and thicker pseudostem compared to banana. In addition, enset had a larger root system with thicker cord roots. Results further showed that young enset plants had a significantly lower shoot-root ratio compared to the bananas. The shoot-root ratio in enset is, however, clone dependent and increases with an increase in age. The results also showed that root density in enset sharply decreases with increasing soil depth.
Spread of Xanthomonas campestris pv. musacearum in Banana (Musa spp.) Plants Following Infection of the Male Inflorescence
(ISHS Acta Horticulturae, 2008) Ssekiwoko, F.; Turyagyenda, L.F.; Mukasa, H.; Eden-Green, S.; Blomme, G.
Xanthomonas campestris pv. musacearum (Xcm) causes Xanthomonas wilt of banana (Musa spp.) and enset (Ensete ventricosum) in East and Central Africa. The disease is spread by insects that visit the male inflorescence, through the use of infected planting materials and by contaminated garden tools. To evaluate the most appropriate control options, the spread of bacteria within the plant following natural flower infection was studied in Luwero and Mpigi districts of central Uganda. Banana tissue samples were collected from the corm, true stem and leaf sheaths of ‘Pisang Awak’ (ABB genome) and ‘Matooke’ (AAA genome) mother plants, showing four progressive stages of disease development: stage 1 – male bud wilting; stage 2 – decaying rachis; stage 3 – premature fruit ripening; and stage 4 – rotting of fruit bunches. Thirty plants were sampled per stage and per cultivar. Additional samples were taken from attached suckers. Bacteria were isolated from surface-sterilized plant samples and identified by colony characteristics on a semi-selective medium. Following inflorescence infection, Xcm moved along the true stem, into the youngest leaf sheaths inserted on the true stem, down into the corm and into the older leaf sheaths. At early stages of inflorescence infection (stage 1), bacteria were restricted to the upper parts of the true stem in ‘Pisang Awak’, but had moved further down the stem in ‘Matooke’. Therefore, cutting down mother plants at stage 1 could stop Xcm from reaching the corm and eventually crossing to the suckers of ‘Pisang Awak’ but this was less likely to be effective for ‘Matooke’ plants. The bacteria were recovered from suckers of both cultivars showing symptoms at stage 4, but at stage 3 only from ‘Pisang Awak’. It is recommended that whole mats should be completely uprooted or killed by herbicides in case mother plants show symptoms beyond stage 1 for ‘Pisang Awak’ and at all disease symptom stages for ‘Matooke’.

Browsing by Author "Blomme, G."

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