Highland Banana Research Articles

Effect of timing of diseased plant cutting, altitude and banana cultivar on efficacy of singly removing Xanthomonas wilt infected banana plants

The single diseased stem removal (SDSR) technology (i.e. timely cutting of diseased banana plants) is an important Xanthomonas wilt (XW) control method being promoted in XW-endemic zones of east/central Africa. Proper SDSR application leads to quick field recovery. However, its efficacy on farms has been variable. For example, delayed cutting of diseased stems/plants is postulated to increase Xcm inoculum buildup and risk of infection in other physically attached shoots, while larger suckers were thought to be less reliant on the mother plants for nutrients and water thus being less susceptible than small suckers. Previous SDSR evaluations took place at mid-high altitudes dominated by east African highland bananas whereas low-lying altitudes especially dominated by ABB types exist, and this site and type is more prone to insect-mediated XW infections. This study hence determined effects of: i) timing of cutting symptomatic plants on recovery of mats, ii) size of attached suckers at infection on their susceptibility to infection, and iii) the efficacy of SDSR at an ABB banana dominated low altitude site. XW incidence in suckers increased with a delay in cutting of symptomatic mother plants, with lowest incidence (0.27%) observed when symptomatic plants were immediately cut upon symptom expression and highest (1.61%) when plants decayed in situ. The larger maiden (32.1% diseased shoots) and sword suckers (22.2%) were significantly more susceptible than the small peepers (7.4%). XW incubation period was shorter for the maiden suckers (4.5 to 6.2 months) compared to 8.9–11.3 months for sword suckers and 11.3 months for peepers. Immediate cutting of plants after first visible symptoms should be recommended to farmers, while additional studies to understand the low susceptibility of small peepers would be warranted. SDSR was observed to be as effective at the ABB banana dominated low altitude sites as previously reported for highland bananas and environments.

Controlling Xanthomonas wilt of banana: Influence of collective application, frequency of application, and social factors on the effectiveness of the Single Diseased Stem Removal technique in eastern Democratic Republic of Congo

The continuous cutting of single diseased stems at soil level (Single Diseased Stem Removal - SDSR) reduces Xanthomonas wilt incidence from as high as 80% to below 2% within 3–4 months when applied weekly and collectively by all farmers within a village or landscape. However, various constraints (e.g. labour shortage, absentee farmers, perception on the effectiveness of the technology) may hamper frequent and collective SDSR application. The current study explored effects of varying the intensity of SDSR application in space (collective vs individual/isolated farm application) and frequency of application at mid-high elevations (1400–1800 m a.s.l.) dominated by east African highland bananas. In addition, farmer technology adoption or disadoption (i.e., tried out the technology and then [partially] adandoned it) levels, and the bottlenecks to SDSR application were assessed 6 and 12 months after close of study site, through a survey of farms that participated in the SDSR experiments in east Democratic Republic of Congo (DR Congo). Research results suggest that initial application of SDSR preferably needs to be carried out at regular intervals (i.e. at least weekly) during the first 3–4 months of application, to remove most of the Xanthomonas campestris musacearum (Xcm) inoculum from a field or landscape. This is valid for both collective and individual/isolated disease control approaches. After this phase of rigorous removal of inoculum, frequency of application could be reduced (e.g. to bi-weekly applications), in case e.g. labour is a constraint. With the exception of the weekly SDSR application, collective application relative to the isolated/individual application more rapidly reduced the XW infection levels. An isolated SDSR application compared to collective application did not significantly differ for the weekly SDSR application. Specific level/speed of success will hence mainly depend on frequency of SDSR application. For SDSR, the continuous appearance of diseased plants, even when numbers are very low, over an often large time period, is discouraging small-scale farmers who often want quick results. This is calling for continuous support and training of affected farm communities. Tool sterilization, one of the recommended SDSR package technologies was poorly applied across the sites due to damage caused to metal farm tools by fire. Novel approaches of tool sterilization thus need to be explored.

Limits to biofortification: farmer perspectives on a vitamin A enriched Banana in Uganda

ABSTRACTBiofortifying staple crops with enhanced nutritional content has been touted as a means of addressing micronutrient deficiency and has emerged as a key component of the Green Revolution for Africa (GR4A). In Uganda, biofortification efforts have centered on utilizing genetic modification (GM) as a means of enhancing the East African Highland Banana, known locally as matooke. This paper draws on three data sets to evaluate whether this technological fix synchs with existing farming systems. We argue that the positive scenario outlined by proponents rests on a number of assumptions related to the health, social and economic contexts facing producers.

Banana Farming, Cultivars, Uses, and Marketing of Nkore in Southwestern Uganda

Small scale banana cultivation for self-consumption and domestic market use yields almost half of banana production of the world. These bananas are more frequently cooked as staple food and snack, and used for brewing than eaten in the raw form. Each banana farming area has developed a unique set of cultivars°, cropping systems, and uses of bananas. Humid zones in the southern part of Ugandan, as well as Rwanda and western part of Tanzania, are famous areas for fanning unique banana cultivar subgroup called the East African highland bananas' (AAA-EA). As a conventional cropping system, it has extremely high productivity and supports local people in areas with one of the highest population density in Africa. However, in Uganda with population migration, land shortage, and pest and disease prevalence, areas that produced and supplied bananas to urban areas have drastically changed in the last half century. This paper reports the current situation of banana-based livelihood system of Nkore, formerly agro-pastoralists in Southwestern Uganda, presently the main banana producing area in Uganda. We describe their farming system, cultivars, uses, and distribution of bananas.

Molecular and Cytogenetic Study of East African Highland Banana.

East African highland bananas (EAHBs) are staple food crop in Uganda, Tanzania, Burundi, and other countries in the African Great Lakes region. Even though several morphologically different types exist, all EAHBs are triploid and display minimal genetic variation. To provide more insights into the genetic variation within EAHBs, genotyping using simple sequence repeat (SSR) markers, molecular analysis of ITS1-5.8S-ITS2 region of ribosomal DNA locus, and the analysis of chromosomal distribution of ribosomal DNA sequences were done. A total of 38 triploid EAHB accessions available in the Musa germplasm collection (International Transit Centre, Leuven, Belgium) were characterized. Six diploid accessions of Musa acuminata ssp. zebrina, ssp. banksii, and ssp. malaccensis representing putative parents of EAHBs were included in the study. Flow cytometric estimation of 2C nuclear DNA content revealed small differences (max ~6.5%) in genome size among the EAHB clones. While no differences in the number of 45S and 5S rDNA loci were found, genotyping using 19 SSR markers resulted in grouping the EAHB accessions into four clusters. The DNA sequence analysis of the internal transcribed spacer region indicated a relation of EAHB clones with M. acuminata and, surprisingly, also with M. schizocarpa. The results suggest that EAHB cultivars originated from a single hybrid clone with M. acuminata ssp. zebrina and ssp. banksii being its most probable parents. However, M. schizocarpa seems to have contributed to the formation of this group of banana.

English

Globally, interests to increase carbon stocks have gained momentum in both woody and non-woody ecosystems. Despite efforts made to generate appropriate methods to estimate these stocks, most equations developed do not cater for intraspecific variabilities across e.g. species, regions or growth stages; especially in the case of bananas. Therefore, there is need to develop more robust equations to improve on the precision of biomass-carbon prediction especially at local scales to facilitate estimation of specific carbon stocks often lost in global assessments. This study aimed at developing cultivar-specific biomass estimation relationships and determining carbon content of EAHB cultivars at two growth stages. Plant data were collected purposively using destructive sampling techniques on farmers’ plots for 4 cultivars (Kibuzi, Nakitembe, Enyeru and Nakinyika) in two agro-ecological zones: the L. Victoria crescent and the South-western farmlands in the districts of Lwengo and Mbarara respectively. Results show that biomass differed across cultivars (P<0.001); hence four equations (Enyeru, Nakinyika, Kibuzi_Nakitembe and Generic) were developed following an exponential function, y=Aexp(ax), using diameter at breast height (DBH) as the predictor variable with an R2 range of 82-94%. EAHB mean carbon content varied significantly with growth stage (P<0.05) (47.6% for maiden plants before flowering and 48.8% for mature plants with a developed bunch). This study concludes that it is important to develop cultivar-specific equations for biomass-carbon estimation of EAHB cultivars to help assess their contribution to the carbon cycle especially in future studies. Key words: East African Highland Bananas (EAHB) cultivars, allometric equations, total plant biomass, carbon content, growth stage.

Banana21: From Gene Discovery to Deregulated Golden Bananas.

Uganda is a tropical country with a population in excess of 30 million, >80% of whom live in rural areas. Bananas (Musa spp.) are the staple food of Uganda with the East African Highland banana, a cooking banana, the primary starch source. Unfortunately, these bananas are low in pro-vitamin A (PVA) and iron and, as a result, banana-based diets are low in these micronutrients which results in very high levels of inadequate nutrition. This inadequate nutrition manifests as high levels of vitamin A deficiency, iron deficiency anemia, and stunting in children. A project known as Banana21 commenced in 2005 to alleviate micronutrient deficiencies in Uganda and surrounding countries through the generation of farmer- and consumer-acceptable edible bananas with significantly increased fruit levels of PVA and iron. A genetic modification approach was adopted since bananas are recalcitrant to conventional breeding. In this review, we focus on the PVA-biofortification component of the Banana21 project and describe the proof-of-concept studies conducted in Australia, the transfer of the technology to our Ugandan collaborators, and the successful implementation of the strategy into the field in Uganda. The many challenges encountered and the potential future obstacles to the practical exploitation of PVA-enhanced bananas in Uganda are discussed.

Silencing of the Mitogen-Activated Protein Kinases (MAPK) Fus3 and Slt2 in Pseudocercospora fijiensis Reduces Growth and Virulence on Host Plants.

Pseudocercospora fijiensis, causal agent of the black Sigatoka disease (BSD) of Musa spp., has spread globally since its discovery in Fiji 1963 to all the banana and plantain growing areas across the globe. It is becoming the most damaging and economically important disease of this crop. The identification and characterization of genes that regulate infection processes and pathogenicity in P. fijiensis will provide important knowledge for the development of disease-resistant cultivars. In many fungal plant pathogens, the Fus3 and Slt2 are reported to be essential for pathogenicity. Fus3 regulates filamentous-invasion pathways including the formation of infection structures, sporulation, virulence, and invasive and filamentous growth, whereas Slt2 is involved in the cell-wall integrity pathway, virulence, invasive growth, and colonization in host tissues. Here, we used RNAi-mediated gene silencing to investigate the role of the Slt2 and Fus3 homologs in P. fijiensis in pathogen invasiveness, growth and pathogenicity. The PfSlt2 and PfFus3 silenced P. fijiensis transformants showed significantly lower gene expression and reduced virulence, invasive growth, and lower biomass in infected leaf tissues of East African Highland Banana (EAHB). This study suggests that Slt2 and Fus3 MAPK signaling pathways play important roles in plant infection and pathogenic growth of fungal pathogens. The silencing of these vital fungal genes through host-induced gene silencing (HIG) could be an alternative strategy for developing transgenic banana and plantain resistant to BSD.

Ecologically sustainable technologies for management of highland banana pests in East and Central Africa

Ecologically sustainable technologies for management of highland banana pests in East and Central Africa

Germplasm screening of Musa spp. for resistance to Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4)

Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) has seriously threatened global banana production. Recently, identification of Foc TR4 in the Caribbean and Mozambique has aroused widespread concern because it may be directly related to food security for millions of people in Africa and Latin America. To identify a resistant or highly resistant germplasm, 129 accessions were evaluated for Foc TR4 resistance in greenhouses and 100 of them were also assessed in the field. In total, 10 accessions were highly resistant (HR) to Foc TR4; these include four from the AA group, two from the BB group, one of the East African highland bananas (EAHBs), two plantains, and one from wild relatives of banana. Of these, Pahang (AA), Calcutta 4 (AA), and Musa itinerans exhibited the highest degree of resistance with an index of disease (ID2) less than 10, and Foc TR4 could not infect any of them in the field. Furthermore, 31 accessions from AA, AB, AAB, AAAB, and ABB groups and wild relatives were identified as a resistant (R) germplasms. All tested EAHBs and plantains exhibited resistance or high resistance to Foc TR4 infection. Our results provide valuable genetic resources for banana breeding and for studying the mechanisms underlying Fusarium wilt resistance. Furthermore, evaluation of EAHBs and plantains provided a rational for local banana producers and researchers to grow EAHBS and plantains.

Farmers’ knowledge of the banana (Musa sp.) agro-forestry systems in Kiboga district, central Uganda

Banana is a major food and cash crop in Uganda, particularly in the central and southwestern regions. However, production is still below attainable yields and at the same time declining due to a number of reasons, with low soil fertility being paramount. Few farmers use inorganic fertilizers, with majority of them relying mainly on organic supplements including integration of trees/shrubs. However, trees and shrubs exist on banana farms in undefined numbers and composition, with no spacing and canopy management recommendations. Also, there is limited information on farmers’ knowledge on these systems. A survey was, therefore, conducted on 70 randomly selected farms in Kiboga district, central Uganda to assess farmers’ knowledge of, as well as identify trees and shrubs species and banana cultivars in their agro-ecologies. A total of 1,558 trees and shrubs belonging to 40 species and 21 families were recorded in the study area (52 trees/shrubs per banana plantation). These were dominated by Jackfruit, Artocarpus heterophyllus (15%), Natal fig, Ficus natalensis (10%), Albizia, Albizia coriaria (10%) and mango, Mangifera indica (9%). Further, 1,779 banana mats belonging to nine (9) cultivars and three (3) genome groups were observed growing underneath these four commonest tree species (2.6 banana mats per tree). The highest number of banana mats was observed growing underneath F. natalensis (54%) and A. coriaria (42%). Most (87%) observed banana cultivars belonged to the cooking East African Highland Banana ( Musa AAA-EAHB) and dominated by Ndibwabalangira (21%). Farmers reported 25 benefits they derive from banana-trees/shrubs integration; with shade and firewood (38%), as well as income and timber (35%) being the main benefits reported. They also reported that the highest percentage of benefits was derived from F. natalensis (44%) and A. coriaria (32%). Of the four (4) most prevalent tree species, A. coriaria (100%) and F. natalensis (96%) were reported as good companion plant to bananas, whereas, A. heterophyllus (99%) and M. indica (97%) were regarded as bad companion plants. Farmers preferred a tree that allows light penetration (96%), is compatible with bananas and other crops (87%) and has easily decomposable leaves (83%). Therefore, F. natalensis and A. coriaria should be integrated in banana agrosystems for soil fertility improvement whereas; A. heterophyllus and M. indica be planted on farm boundaries. However, the best-bet spacing and pruning regimes for these trees should be determined to minimize the negative attributes as much as possible. Keywords: Albizia coriaria, Artocarpus heterophyllus , banana cultivars, benefits, companions , Ficus natalensis, Mangifera indica , tree-species

English

Eastern Democratic Republic of Congo constitutes an area where the East African Highland bananas (Musa-AAA-EA) and plantains (Musa-AAB) meet. However, Musa diversity in this region has never been characterized nor represented in national or international collections, yet increasing human activities and build-up of pests and diseases, especially Xanthomonas wilt of banana and banana bunchy top disease, could negatively affect this diversity. This study assessed, collected and morphologically characterized on-farm Musa diversity in the North Kivu and Ituri provinces. Musa accessions collected were added to the UCG-Butembo in situ field collection. A total of 90 and 150 farms were assessed, respectively, in the North Kivu and Ituri provinces. High Musa variability was observed in both provinces. Forty-one cultivars (six presumed new) were identified in Ituri Province compared to 38 cultivars (13 presumed new) in North Kivu Province. Nineteen cultivars occurred in both provinces. Beni and Lubero territories in North Kivu and Mambasa territory in Ituri Province had greater Musa diversity, varying between 27 and 38 cultivars, approximately double of the number of cultivars observed in the other territories. Twenty-three of the 34 Musa descriptors contributed more to the discrimination of the cultivars identified across the provinces and were therefore used for grouping the cultivars using principal component analysis (PCA). The Morisita index of similarity between Ituri Province and North Kivu Province territories was less than 0.5, suggesting dissimilarity in diversity between these sites. Six cultivars: &lsquo;Kirisirya&rsquo;, &lsquo;Pakuma&rsquo;, &lsquo;Nziravahima&rsquo;, &lsquo;Vuhindi&rsquo;, &lsquo;Tundu&rsquo; and &lsquo;Kisubi musa&rsquo; were reportedly at risk of genetic erosion. Key words: Banana, conservation, cultivars, ex-situ, genetic erosion, genotypes, plantain.

Suitability of existing Musa morphological descriptors to characterize East African highland \u2018matooke\u2019 bananas

Morphological traits are commonly used for characterizing plant genetic resources. Germplasm characterization should be based on distinctly identifiable, stable and heritable traits that are expressed consistently and are easy to distinguish by the human eye. Characterization and documentation of a representative sample of East African highland bananas (Lujugira–Mutika subgroup) was carried out following an internationally accepted standard protocol for bananas. Eleven cultivars were characterized using an existing set of minimum descriptors (31 qualitative and quantitative traits) with the aim of determining stable descriptors and the ability of these descriptors to distinguish among East African highland banana cultivars. There was variation in stability of these descriptors within cultivars and across the 11 cultivars. Only 10 (32%) out of 31 descriptors studied were stable in the 11 cultivars. However, they had similar scores and therefore are not suitable to distinguish between cultivars within this group. Nonetheless, these 10 descriptors may be useful for distinguishing the East African highland bananas as a group from other groups of bananas. A few descriptors were unique to the cultivar ‘Tereza’ and may be used to distinguish this cultivar from other ‘matooke’ cultivars. None of the quantitative descriptors were stable.

Trait variation and genetic diversity in a banana genomic selection training population.

Banana (Musa spp.) is an important crop in the African Great Lakes region in terms of income and food security, with the highest per capita consumption worldwide. Pests, diseases and climate change hamper sustainable production of bananas. New breeding tools with increased crossbreeding efficiency are being investigated to breed for resistant, high yielding hybrids of East African Highland banana (EAHB). These include genomic selection (GS), which will benefit breeding through increased genetic gain per unit time. Understanding trait variation and the correlation among economically important traits is an essential first step in the development and selection of suitable GS models for banana. In this study, we tested the hypothesis that trait variations in bananas are not affected by cross combination, cycle, field management and their interaction with genotype. A training population created using EAHB breeding material and its progeny was phenotyped in two contrasting conditions. A high level of correlation among vegetative and yield related traits was observed. Therefore, genomic selection models could be developed for traits that are easily measured. It is likely that the predictive ability of traits that are difficult to phenotype will be similar to less difficult traits they are highly correlated with. Genotype response to cycle and field management practices varied greatly with respect to traits. Yield related traits accounted for 31–35% of principal component variation under low and high input field management conditions. Resistance to Black Sigatoka was stable across cycles but varied under different field management depending on the genotype. The best cross combination was 1201K-1xSH3217 based on selection response (R) of hybrids. Genotyping using simple sequence repeat (SSR) markers revealed that the training population was genetically diverse, reflecting a complex pedigree background, which was mostly influenced by the male parents.

English

Despite the global interest to increase the world&#39;s carbon stocks, most carbon sequestration strategies have largely depended on woody ecosystems whose production is threatened by the continuous shortage of land, hence the need to explore viable alternatives. The potential of bananas to sequester carbon has been reported but there is limited knowledge on the performance of various cultivars as specific carbon stocks are often lost in global assessments. Therefore, this study aimed at exploring the potential of and variability in carbon stocks of selected East African Highland Banana (EAHB) cultivars. Plant and soil data were collected using destructive and non-destructive techniques in 30&times;30m2 sampling plots for 4 cultivars Kibuzi, Nakitembe, Enyeru and Nakinyika growing in two agro-ecological zones of Uganda being the L.Victoria Crescent and the South-western region. Total carbon and Soil Organic Carbon (SOC) stocks did not differ considerably across cultivars (P&gt;0.05). However, there was significant variation (P&lt;0.05) in plant carbon stock being lowest in two cultivars: Nakinyika at 0.37&plusmn;0.19 Mgha-1 and Nakitembe at 0.40&plusmn;0.19Mgha-1; and highest in Enyeru at 1.64&plusmn;0.18 Mgha-1. The SOC stock variation difference across depth was 2.9-8.5 Mgha-1 being higher in top soil than sub-soil. Despite the small plant carbon stock amounts, the system enables much more carbon to be stored in the soil considering the proportion of what is contained in the plant to that in the soil across all cultivars (0.4-2%). The study therefore recommends revision of existing carbon frameworks to incorporate the contribution of non-woody perennials like bananas in the carbon cycle so that the poor small scale farmers who cannot afford large acreages to establish tree plantations can also benefit from such initiatives.&nbsp; Key words: Agro-ecological zone, growth stage, carbon stock, cultivars, SOC

Azadirachta indica Reduces Black Sigatoka in East African Highland Banana by Direct Antimicrobial Effects against Mycosphaerella fijiensis without Inducing Resistance

Black Sigatoka is a major disease of East African highland cooking bananas in Uganda. Aqueous extracts of Azadirachta indica, Cinnamomum zeylanicum and Capsicum annuum have shown the potential to reduce Black Sigatoka in banana plantlets. The mechanisms by which plant extracts confer protection against plant pathogens has previously been reported to involve activation of defence and direct antimicrobial activity. In the current study, both antimicrobial activities of selected extracts were studied as well as expression of three defence-related genes using quantitative real-time PCR. Gene expression was compared in susceptible (cv. Musakala, genomic group AAA-EA) and resistant (cv. Kayinja, genomic group ABB) banana cultivars. Additionally, Musakala treated with A indica extract at 1 day before inoculation (DBI) was tested for induction of defence-related genes at 0, 10 and 20 days after inoculation (DAI). Pathogenesis-related genes (PR-1 and PR-3) and non-expressor of PR-genes (NPR1B) were up-regulated in the resistant cultivar. The genes analysed responded at late time points to M. fijiensis inoculation in both extract-treated and control plants in the susceptible cv. Musakala. On the other hand, A. indica and C. annuum completely inhibited mycelial growth of M. fijiensis at 30% (w/v). These findings suggest that the effect of plant extracts on Black Sigatoka is strongly associated with the direct antimicrobial effects.

EVALUATION OF NATURAL ENEMIES IN CONTROLLING OF THE BANANA WEEVIL BORER Cosmopolites sordidus Germar IN WEST SUMATRA

&lt;br /&gt;The banana weevil, Cosmopolites sordidus Germar, is an important pest of highland banana and plantain in Africa, but it exists in low densities in presumed area of origin in Southeast Asia such as in Indonesia. This suggests a possible existence of effective co-evolved natural enemies in the origin area of Indonesia, especially West Sumatra. The objectives of this study were: (1) to evaluate banana weevil pest status at selected sites in West Sumatra, (2) to survey parasitoids and predators, and (3) to determine the control potential of the most important natural enemies. Surveys were undertaken in March 2002-August 2003 in five locations in West Sumatra, i.e., Bukittinggi, Sitiung, Pariaman, Pasaman, and Batusangkar. Five farms per site were selected randomly among all farms that contained banana stands of &amp;gt; 0.5 ha. Sampling for banana weevil adults and damage, and for predators was done throughout small banana stands and within a 20 m x 40 m (0.08 ha) subplot on larger farms. Field-collected larvae were taken to the laboratory and reared on corm pieces (3 cm x 3 cm x 3 cm) until pupation. Larvae were collected from pseudostem as well as corm residues. To estimate the abundance of non-social predators, i.e., those other than ants, 10 residues each on each farm were examined from plants that had been harvested 1-4 weeks, 5-8 weeks or 9 or more weeks before our visit to the site. Samples of the different morphospecies were saved in alcohol for later identification. The result showed that the banana weevil incidence was found to be low, 0.6-1.7 adults per trap. Plant damage indices were below 2.2%. We collected and reared 24,360 eggs and 3118 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid beetles, &lt;em&gt;Plaesius javanus &lt;/em&gt;Erichson. In laboratory tests, adults and larvae of P. &lt;em&gt;javanus&lt;/em&gt; attacked 75-88% and 38-53% of banana weevil larvae and pupae, respectively. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found to be associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues. The adult banana weevil mortalities caused by the entomopathogen fungi of Beauveria bassiana from Baso, Sungaitarab, Sei Sariek, and Sikabau at highest density (3.2 x 108 spores ml-1) after two weeks were 96.67%, 90.00%, 60.00% and 83.33%, respectively. The high diversity of habitat conditions in which crop-pest-natural enemies systems exist, support the idea that banana weevil population and damage intensity in the study area is low due to active role of natural enemies.

EVALUATION OF NATURAL ENEMIES IN CONTROLLING OF THE BANANA WEEVIL BORER Cosmopolites sordidus Germar IN WEST SUMATRA

&lt;br /&gt;The banana weevil, Cosmopolites sordidus Germar, is an important pest of highland banana and plantain in Africa, but it exists in low densities in presumed area of origin in Southeast Asia such as in Indonesia. This suggests a possible existence of effective co-evolved natural enemies in the origin area of Indonesia, especially West Sumatra. The objectives of this study were: (1) to evaluate banana weevil pest status at selected sites in West Sumatra, (2) to survey parasitoids and predators, and (3) to determine the control potential of the most important natural enemies. Surveys were undertaken in March 2002-August 2003 in five locations in West Sumatra, i.e., Bukittinggi, Sitiung, Pariaman, Pasaman, and Batusangkar. Five farms per site were selected randomly among all farms that contained banana stands of &amp;gt; 0.5 ha. Sampling for banana weevil adults and damage, and for predators was done throughout small banana stands and within a 20 m x 40 m (0.08 ha) subplot on larger farms. Field-collected larvae were taken to the laboratory and reared on corm pieces (3 cm x 3 cm x 3 cm) until pupation. Larvae were collected from pseudostem as well as corm residues. To estimate the abundance of non-social predators, i.e., those other than ants, 10 residues each on each farm were examined from plants that had been harvested 1-4 weeks, 5-8 weeks or 9 or more weeks before our visit to the site. Samples of the different morphospecies were saved in alcohol for later identification. The result showed that the banana weevil incidence was found to be low, 0.6-1.7 adults per trap. Plant damage indices were below 2.2%. We collected and reared 24,360 eggs and 3118 larvae, but no parasitism was detected. Phorids (Megaselia sp.) and drosophilids were recovered from larval rearings, but most likely were scavengers. A complex of predators was detected, the most important of which was the histerid beetles, &lt;em&gt;Plaesius javanus &lt;/em&gt;Erichson. In laboratory tests, adults and larvae of P. &lt;em&gt;javanus&lt;/em&gt; attacked 75-88% and 38-53% of banana weevil larvae and pupae, respectively. Predatory ants, including species of Myrmicinae, Ponerinae, Formicinae, and Dolichoderinae, were found to be associated with banana plants and residues. Adults of Myopopone castanea Smith (Ponerinae) were directly observed attacking banana weevil larvae in crop residues. The adult banana weevil mortalities caused by the entomopathogen fungi of Beauveria bassiana from Baso, Sungaitarab, Sei Sariek, and Sikabau at highest density (3.2 x 108 spores ml-1) after two weeks were 96.67%, 90.00%, 60.00% and 83.33%, respectively. The high diversity of habitat conditions in which crop-pest-natural enemies systems exist, support the idea that banana weevil population and damage intensity in the study area is low due to active role of natural enemies.

English

Banana Xanthomonas wilt (BXW) is a devastating bacterial disease caused by Xanthomonas campestris pv. musacearum. The disease was simultaneously reported in Cankuzo and Bubanza provinces, Burundi, in November 2010. However, the extent to which the disease has spread to other banana growing regions in the country is unknown. Therefore, to ascertain the distribution and incidence of the disease and farmers’ knowledge on measures to control the disease, a survey was conducted in all 16 banana growing provinces of Burundi in August 2011. A total of 208 farms were sampled, selecting six farms per surveyed commune, three affected and three non-affected. The survey was conducted using a structured questionnaire. The disease was present in 10 out of 16 provinces constituting all agricultural lands in Burundi. The highest incidence was recorded in Ruyigi province (34%), where the Kayinja system is dominant and the lowest in Muyinga (3%), where the East African Highland bananas (EAHB) dominate. Awareness of BXW symptoms, modes of spread and control measures was generally low, ranging from 8 to 30% of households surveyed. The limited knowledge of the disease among farmers was thought to be largely responsible for driving the epidemic in Burundi. Key words: Debudding, disease incidence, Musa species, Xanthomonas campestris pv. Musacearum.

English

The production of the East African highland cooking banana is constrained by pests, diseases and narrow genetic base amongst others. Research to develop resistant / tolerant genotypes has been on going at Kawanda. 18 promising banana hybrids have been identified. The hybrids were planted on farmers’ fields in Kasangombe Sub-county in central Uganda for evaluation against black Sigatoka and yield. Data were collected on some of the agronomic traits, banana weevil damage and response to black Sigatoka disease on the plant and first ratoon crops. The data were analysed using mixed model procedures on SAS software. Means within each crop cycle were separated by comparing hem to Mbwazirume using adjustment to Dunnett’s Test at 5% level of significance. The hybrids had more functional leaves (at least 9) compared to Mbwazirume (approximately 8 leaves). Youngest leaf spotted was significantly higher in the hybrids. All the hybrids except 2734K-1 retained significantly higher number of leaves at harvest (approximately 3 leaves). Most of the hybrids produced bigger bunches (at least 16 kg and 19 in the plant crop and first ratoon respectively) and the yield (t/ha/yr) of the banana hybrids was also higher compared to Mbwazirume. A Bi-plot of principal component analysis 1 against principal component analysis 2 showed that banana hybrids 12419S-13, 2625K-1 and 7798S-2 displayed very good agronomic traits in terms of plant height, girth and bunch weights. They also appeared to be tolerant to black Sigatoka disease as compared to Mbwazirume. These could be recommended for further evaluation with farmers to establish their culinary qualities and acceptability. Key words: East African highland banana hybrids, black Sigatoka disease.