Browsing by Author "Turyagyenda, L.F."
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Item 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.Item 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.Item 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.Item Genetic diversity among farmer-preferred cassava landraces in Uganda(African Crop Science Journal, 2012) Turyagyenda, L.F.; Kizito, E.B.; Baguma, Y.; Wanjala, B.W.; Osiru, D.S.O.Understanding of genetic diversity among a breeding population is an important requirement for crop improvement as it allows for the selection of diverse parental combinations and formation of heterotic pools for genetic gain. This study was carried out to determine genetic diversity within and among 51 farmer-preferred cassava (Manihot esculenta) landraces and 15 elite accessions grown in Uganda. Twenty six simple sequence repeat (SSR) markers used for genetic diversity assessment in this study revealed a total of 154 alleles, of which 24% were unique alleles present only in landraces. The genetic diversity and observed herozygosity in landraces were slightly higher than in elite accessions. Elite accessions clustered with some of the landraces indicating that there were some alleles in common. However, 58.8% of the landraces fell into 3 different clusters independent of the elite accessions. Including these landraces with unique alleles in cassava breeding schemes will increase the chances of producing farmer preferred adapted elite cultivars. The study also revealed genetic differentiation among accessions from different regions providing an opportunity for establishment of heterotic pools within a breeding programme.Item 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.Item 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.Item 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’.