Highland Banana Research Articles

Ecological characteristics and cultivar influence optimal plant density of East African highland bananas (Musa spp., AAA-EA) in low input cropping systems

Numerous studies have been conducted on the effects of plant density on growth and yield of dessert bananas in the humid tropics, but effects of plant densities in relations with ecological characteristics in low input East African highland banana (Musa spp., AAA-EA genome) cropping systems have not been reported. On-station field experiments were conducted in three contrasting agro-ecological sites of Rwanda (Kibungo low rainfall with medium soil fertility, Rubona high rainfall with low soil fertility and Ruhengeri high rainfall with high soil fertility) to explore germplasm×environment interactions. Five different plant densities (plantsha−1): 1428, 2500, 3333, 4444 and 5000 and two cooking (“Ingaju”, “Injagi”) and one beer (“Intuntu”) cultivars were investigated. The effect of plant density on plant performance (growth and yield) over two cropping cycles in low input systems was determined. The effects of site×cultivar and site×density interactions on yield traits were significant (p<0.05). Annual yield increased with increasing plant density but strongly depended on agro-ecological site (from 6.1 to 9.2tha−1yr−1 at Kibungo, 9.5 to 21.5tha−1yr−1 at Rubona and 7.0 to 25.0tha−1yr−1 at Ruhengeri). Yields of beer cultivars increased with density, but those of cooking cultivars decreased. Maximum yields were attained at 4444plantsha−1 at Kibungo and Rubona whilst yields increased linearly beyond this level at Ruhengeri. Crop cycle duration was prolonged with increasing plant density. Relationships between bunch yield, the total above ground dry matter yields and soil chemical properties suggest that nutrient deficiencies were larger at Kibungo (e.g. K) and Rubona (e.g. K, P, Ca and Mg) compared with Ruhengeri, where yield correlated significantly with leaf area index (LAI). LAI increases up to 4, where 95% of solar radiation was intercepted by the crop canopy, indicating that increasing the LAI above 4 would have little effect on production. Evaporation was much greater at lower rainfall areas (e.g. Kibungo) and accompanied by negative annual water deficit (−135mmyr−1) than at high rainfall areas (e.g. Ruhengeri) with positive water surplus (382mmyr−1). Growing degree days from planting to bunch harvest were higher at Kibungo (3675°C days) but much less at the Ruhengeri cooler site (1729°C days), implying temperature is not restrictive at Ruhengeri. This study showed that the optimal density for bananas depends on water availability, soil fertility and cultivar, which serves as an entry point to maximize yield potential for the East African smallholder farmers rather than using a uniform blanket recommended density. We suggest that agronomic optimal plant density is lower (<4444plantsha−1) in low rainfall (<1000mmyr−1) and less fertile areas but seem to be higher (>5000plantsha−1) in areas with high fertility which receive high rainfall (>1300mmyr−1).

Content and Retention of Provitamin A Carotenoids Following Ripening and Local Processing of Four Popular Musa Cultivars from Eastern Democratic Republic of Congo

&lt;p&gt;Changes in the concentrations and retention levels of total and individual provitamin A carotenoids (pVACs) during ripening and local processing of the four most popular &lt;em&gt;Musa&lt;/em&gt; cultivars of Eastern Democratic Republic of Congo were established through HPLC analysis. The predominant pVACs were all &lt;em&gt;trans&lt;/em&gt; ?- and ?-carotene, together constituting about 90% of total pVACs content in raw and processed &lt;em&gt;Musa&lt;/em&gt; fruit pulp. The proportion of ?- and ?-carotene was not significantly different in the tested East African Highland Bananas (AAA-EAHB) (‘Nshikazi’ and ‘Vulambya’); in the plantains (‘Musilongo’ and ‘Musheba’), proportion of ?-carotene was almost twice that of ?-carotene. An increase in total pVACs was observed during ripening, with highest levels at ripening stage 3 in all four cultivars. Total pVACs values were as high as 1081µg/100gfw in ‘Vulambya’ and 1819µg/100gfw in ‘Musilongo’. Boiling of the AAA-EAHB and AAB-Plantains resulted to retention of between 40-90% and &amp;gt;95% respectively. Plantains deep-fried in fully-refined palm oil and crude red palm oil for 2 minutes did not seem to lose any pVACs, the levels of total pVACs observed after frying were 100% of what was observed when the fruit was raw. Retinol Activity Equivalents (RAE), in boiled products varied between 22.3 and 173 RAEµg/100gfw, whereas deep fried products had &amp;gt;190 RAEµg/100g edible portion. These results show that the tested AAA-EAHBs and the plantains could meet at least 14% and 30 % of Vitamin A recommended dietary intakes respectively. The findings can therefore guide consumer consumption patterns to maximize vitamin A intake for improved health in these regions and also direct researchers in the selection of &lt;em&gt;Musa&lt;/em&gt; cultivars to be incorporated within existing farming systems in the fight against vitamin A deficiency (VAD).&lt;/p&gt;

A historical overview of the appearance and spread of Musa pests and pathogens on the African continent: highlighting the importance of clean Musa planting materials and quarantine measures

AbstractThe 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.

Differential gene expression in East African highland bananas (Musa spp.): Interactions between non-pathogenic Fusarium oxysporum V5w2 and Radopholus similis

Endophytic non-pathogenic Fusarium oxysporum isolates are known to control Radopholus similis through induced resistance. Using complementary (c)DNA-amplified fragment length polymorphism (cDNA-AFLP), we identified genes induced in nematode-susceptible and -tolerant bananas following colonization by non-pathogenic endophytic F. oxysporum isolate V5w2. Quantitative real-time polymerase chain reactions (qRT-PCR) were then used to analyze expression profiles of selected genes. Accumulated gene transcripts included those involved in signal transduction, cell wall strengthening, Jasmonic acid (JA) pathway and transport of defense molecules. Endophyte colonization primed the expression of β-1,3-glucan synthase and Coronatine insensitive 1 (COI1) in the susceptible cultivar, and that of COI1 and Lipoxygenase (LOX) in the tolerant. We isolate and identify for the first time genes involved in the interaction between endophytic non-pathogenic F. oxysporum and banana.

Ecological characteristics influence farmer selection of on-farm plant density and bunch mass of low input East African highland banana (Musa spp.) cropping systems

East African highland bananas (Musa spp., AAA-EA group) are a primary food and cash crop for smallholders in Rwanda and much of the East African highlands. Their production generally declines over time due to poor farm management and declining soil fertility. Farmers believe that among the bunch mass maintaining factors, plant density management offers some prospect. They often decrease banana mat (i.e. a single mother plant with interconnected suckers) density in an effort to increase bunch size, but the effectiveness and profitability of this practice has not been studied. In addition, not much research has been executed on the influence of climatic and edaphic factors on variations in on-farm plant density. An on-farm survey was conducted in contrasting agro-ecological sites of Rwanda (Ruhengeri, Rusizi, Karongi, Butare, Ruhango, Kibungo and Bugesera) to determine existing densities and their relationship to bunch mass. A plant density assessment method was used that measures the average distance of five mats to their respective nearest four mats to calculate average mat spacing. Plant density positively correlated with surplus/deficit water supply (i.e. difference between rainfall and water demand by bananas) (r2=0.62), with highest plant densities (>1500matsha−1) found in high rainfall areas (>1200mmyr−1) with water surplus (218–508mmyr−1) and lowest plant densities (1000–1400matsha−1) found in lower rainfall areas (1000–1200mmyr−1) with water deficit (from −223 to −119mmyr−1). Heaviest bunches (18.1–20.8kgfreshmassplant−1) were found at lowest plant densities and medium sized bunches (14.7–15.5kg) at highest plant densities. Lower soil and banana leaf nutrient contents (especially N, K, Ca and Mg) were observed on weathered soils (Acrisols) and were associated with smaller bunch mass in comparison to fertile soils (Andosols, Nitisols). Farmers tended to reduce mat densities (i) if they wanted to intercrop bearing in mind site characteristics, and (ii) to increase bunch mass to adapt to market preferences. The plant densities generally recommended by extension bodies (3m×3m or 2m×3m; i.e. 1111 and 1666matsha−1, respectively) are seldom practiced by farmers, nor do they seem to be very appropriate, as higher densities seem productive in areas with high rainfall and relatively good soil fertility.

Isolation and characterisation of a banana CYCD2;1 gene and its over-expression enhances root growth

Stimulation of the cell cycle by over-expression of Arabidopsis CyclinD2;1 enhanced growth in tobacco and rice, but not Arabidopsis. To broaden the range of species and to improve an important crop species for developing countries, a CyclinD2;1 homologue was isolated from an East African highland banana cultivar ‘Nakasabira’ ( Musa spp., AAA group) and designated Musac;CYCD2;1 (Genebank accession no HQ839770). Musac;CYCD2;1 amino-acid sequence exhibited 40, 54, 57 and 57% identity with CYCD2;1 sequences of Arabidopsis, rice, maize and wheat, respectively. Over-expression of Musac;CYCD2;1 driven by the CaMV 35S promoter in cultivar ‘Sukali ndizi’ (AAB) resulted in transformed plants with no significant increase in total banana CYCD2;1 transcripts in the shoot, but up to 66-fold increase of total banana CYCD2;1 transcripts in roots. Correspondingly, transformed plants had no change in above-ground growth but produced longer main roots and more lateral roots under in vitro conditions. A deeper root system was observed in one transgenic line relative to non-transformed plants when grown in soil. Results demonstrate that a banana homologue of Arabidopsis CYCD2;1 can also enhance growth in a homologous background and the potential of enhancing banana root growth. Key words: CyclinD2;1 gene, Musa spp., banana transformation, CyclinD2;1 over-expression, root growth.

Male Fertility in Uganda Banana Germplasm

Identification of fertility levels in banana germplasm collection at Kabanyolo, Uganda, was conducted by dehiscing the anthers using a glass rod. The study involved 151 accessions. The quantity of pollen grains per anther was ranked 0-5; where 0 had no grains and 5 had abundant pollen grains. A correlation between pollen output and inflorescence characters revealed a positive relationship (r = 0.69, P ≤ 0.01) to inflorescence diagnostic characters. A quantitative determination of pollen output per anther and percentage pollen viability based on starch test using the Heamocytometer method revealed that the amount of starch filled grains did not proportionally vary with the total pollen output. Pollen output varied from cultivar to cultivar. Most East African highland banana cultivars were found to have more pollen than the recently introduced banana cultivars. A few highland banana cultivars were non-polleniferous. The results indicate the relative potential of using various cultivars in hybridization and, anther and pollen culture programmes. Keywords: Bananas, Heamocytometer, fertility, pollen

NORMS FOR MULTIVARIATE DIAGNOSIS OF NUTRIENT IMBALANCE IN THE EAST AFRICAN HIGHLAND BANANAS (MUSA SPP. AAA)

Despite low yields and soil fertility problems, fertilizer use in the East African Highland banana (AAA-EA) production is absent. High fertilizer costs increase the need for site-specific fertilizer recommendations that address deficiencies. This study aimed to derive and compare norms for AAA-EA bananas, using Compositional Nutrient Diagnosis (CND), Diagnosis and Recommendation Integrated System (DRIS), and a DRIS that includes a filling value (DRIS-Rd), and study nutrient interactions. Data on foliar nitrogen, phosphorus, potassium, calcium, and magnesium concentrations, and plant performance were obtained from 300 plots in Uganda. CND indices were closely related to DRIS and DRIS-Rd indices (R2 > 0.965). Four nutrient interactions were common in both low and high bunch weight subpopulations. Although the three approaches can be used to determine nutrient imbalances in AAA-EA bananas, we recommend CND for ease of use. Diagnosis of nutrient deficiencies should be based on methods that identify plant nutritional imbalances.

SCREENING MUSA GENOTYPES FOR BANANA BUNCHY TOP DISEASE RESISTANCE IN BURUNDI

The original publication is available at www.actahort.org. Banana bunchy top disease (BBTD), caused by the Banana bunchy top virus (BBTV), is reported as one of the most devastating diseases affecting banana and plantain cultivation worldwide. In order to identify putative sources of resistance, a cultivar screening trial comprising 40 Musa genotypes was established in March 2007 at the ISABU Mparambo research station in northwestern Burundi (893 m a.s.l.). Dessert bananas (AAA group), East African highland bananas (AAA, EAHB), plantains (AAB), cooking bananas (ABB), a tetraploid hybrid and wild diploid bananas (Musa acuminate and Musa balbisiana) were assessed. Ten plants per genotype were planted in a completely randomised design with border rows consisting of BBTV-infected 'Yangambi Km 5' (AAA) plants. Colonies of Pentalonia nigronervosa collected in BBTV-infected fields were released in the plot to enhance disease spread. Twenty-eight months after trial establishment, 32 genotypes have shown typical banana bunchy top symptoms. The first symptoms appeared 80 days after trial establishment on 'Yangambi Km 5'. Twenty-eight months after trial establishment, only eight genotypes [Musa balbisiana type Tani (BB), 'Kayinja' (ABB), 'FHIA-03' (AABB), 'Prata' (AAB), 'Gisandugu' (ABB), 'Pisang Awak' (ABB), 'Saba' (ABB) and 'Highgate' (AAA, Gros Michel subgroup)] have not manifested typical disease symptoms on any of the ten plants per genotype. Plant samples taken from these visibly healthy cultivars and analysed at a molecular level [at the Faculte Universitaire des Sciences Agronomiques de Gembloux (FUSAGx) in Belgium] indicated the presence of the virus in 'Pisang Awak', 'Saba' and 'Highgate'. These genotypes can be considered as BBTD tolerant. They could potentially act as a reservoir for the virus. Further diagnostic tests will be carried out on the five BBTV-free genotypes to confirm the extent of latent infections. Preliminary results indicate that genotypes with one or two B genomes tend to be more tolerant to BBTD.

Drought is a major yield loss factor for rainfed East African highland banana

Abstract Although drought stress has been identified among the production constraints of East African highland bananas (Musa spp., AAA-EA genome), no quantitative data were available to support this assumption. This study uses data from three on-station fertilizer trials (5–6 cycles) in Central and Southwest Uganda to quantify the effect of drought stress on banana production and explore possible interactions with nutrient availability. Production data were collected at individual plant basis from 1996 to 2002 in one trial and from 2004 to 2009 in two trials. Cumulative rainfall in the 12 months before harvest (CRF12) was computed per plant from daily rainfall measurements. Average bunch weight ranged from 8.0 to 21.9 kg between trials and cycles and was 8–28% less in dry (CRF12 ≤ 905 mm) than in normal (905

ROLE OF BIOTECHNOLOGY AND TRANSGENICS IN BANANAS (MUSA SPP.) IN AFRICA

ISHS IV International Symposium on Banana: International Conference on Banana and Plantain in Africa: Harnessing International Partnerships to Increase Research Impact ROLE OF BIOTECHNOLOGY AND TRANSGENICS IN BANANAS (MUSA SPP.) IN AFRICA

SOMATIC MUTATIONS AND THEIR IMPLICATIONS TO THE CONSERVATION STRATEGIES OF THE EAST AFRICAN HIGHLAND BANANAS (MUSA SPP.)

Somatic mutations in bananas (Musa spp.) nave been exploited for selection of favorable traits, both for consumption and commercial purposes, and they have been responsible for the current diversity of the East African highland bananas (EAHB). The role of mutations in the selection and subsequent conservation of banana cultivars by communities is not clearly understood. It is, however, believed that farmers play important roles in initiating and adjusting the proportions of cultivars on-farm, based on different traits. The purpose of this study was to: (a) initially determine the levels of somatic mutations in each clone set of the EAHB ex-situ collections; (b) establish cultivar richness and evenness to understand the conservation potential of each clone set; (c) determine the relationship between mutant traits with richness and evenness; and (d) compare the similarity between cultivar selection criteria and the mutant traits. Correlation and distance coefficients were used to determine accessions that are closely related, but not identical, on the basis of 61 morphological traits of 192 EAHB accessions of ex-situ collections in Uganda. Cultivar richness and evenness of clone sets of the landraces were then determined in three benchmark sites in Uganda and Tanzania. These measures of diversity were correlated with overall mutant traits and comparisons were made between cultivar selection criteria and the traits. Mutations were more frequent in 'Nfuuka' and a positive strong correlation between richness and mutant traits supported this. There was, however, a highly negative correlation between mutant traits and evenness. The traits that were more associated with mutations and selection criteria of farmers were related to bunches and fruits; an indication of the possible role of mutations in the selection and subsequent conservation of banana diversity on-farm.

FACTORS DRIVING FERTILIZER ADOPTION IN BANANA (MUSA SPP.) SYSTEMS IN UGANDA

ISHS IV International Symposium on Banana: International Conference on Banana and Plantain in Africa: Harnessing International Partnerships to Increase Research Impact FACTORS DRIVING FERTILIZER ADOPTION IN BANANA (MUSA SPP.) SYSTEMS IN UGANDA

ON-FARM PARTICIPATORY EVALUATION OF EAST AFRICAN HIGHLAND BANANA 'MATOOKE' HYBRIDS (MUSA SPP.)

ISHS IV International Symposium on Banana: International Conference on Banana and Plantain in Africa: Harnessing International Partnerships to Increase Research Impact ON-FARM PARTICIPATORY EVALUATION OF EAST AFRICAN HIGHLAND BANANA 'MATOOKE' HYBRIDS (MUSA SPP.)

Boiling water treatment: A simple, rapid and effective technique for nematode and banana weevil management in banana and plantain ( Musa spp.) planting material

We studied the effect of treating banana and plantain ( Musa spp.) suckers using boiling water for the generation of healthy planting material. Small, medium and large-sized suckers of two East African highland bananas (cvs. Mbwazirume, Kibuzi, AAA-EA) and one of plantain (cv. Agbagba, AAB) were dipped in boiling water for 10, 20 or 30 s after root removal and corm (sucker) paring. Treatments were compared with a conventional farmer method (control), which was not pared or treated with boiling water, and also with pared only. At three months after treatment, germination, plant height and girth of plants were similar within sucker size and between treatments for each cultivar. Root health was improved by boiling water treatment for all cultivars compared to untreated controls. Boiling water treatment of suckers reduced combined nematode densities of Helicotylenchus multicinctus, Radopholus similis and Meloidogyne spp. to 0.7% of farmer controls. Boiling water-treated suckers had less banana weevil damage than controls. Treatment of pared suckers for at least 20 s and up to 30 s was highly efficient for disinfesting banana and plantain planting material. This modification of the hot water treatment is a practical adaptation, suitable for smallholder growers to improve the quality of banana and plantain planting material in smallholder farms.

&amp;#946-carotene, iron and zinc content in Papua New Guinea and East African highland bananas.

Nutritional disorders due to inadequate intake of vitamin A, iron and zinc in the East African region are unusually high. Interventions to alleviate these deficiencies rely on supplementation and food fortification programs, which are not sustainable and do not reach all the affected. Sustainable solutions to malnutrition can be developed through linking agriculture, nutrition, and health. Promotion of consumption of bananas with enhanced micronutrient content as well as enriching bananas with micronutrients through breeding could go a long way towards preventing micronutrient deficiencies in the region, since bananas are a widely consumed staple. As a starting point in promoting consumption of bananas with enhanced micronutrients and breeding for higher micronutrient content in bananas, banana accessions both local and exotic hybrid Papua New Guinea (PNG) were screened. Pulp color intensity was measured, ß-carotene was measured by high-performance liquid chromatography and iron and zinc were determined by atomic absorption spectrophotometry. ß-carotene concentrations ranged from 92.3 µg/100g to 2594.0 µg/100g, while iron and zinc concentrations ranged from 0.063 mg/100g to 0.608 mg/100g and 0.00003 mg/100g to 0.598 mg/100g, respectively. Banana pulp color intensity had a significant (P

The agronomic and economic benefits of fertilizer and mulch use in highland banana systems in Uganda

Banana is the most important food crop in Uganda. However, there has been a decline in productivity, attributed to declining soil fertility, drought, pests and diseases and crop management factors. This study aimed to explore the possibility of increasing yields through the use of fertilizer and mulch, and to evaluate the benefits of these inputs across the major banana producing regions in Uganda. This study was carried out in 179 smallholder plots in Central, South, Southwest and East Uganda in 2006/7. Half of the plots were ‘demonstration plots’ of an agricultural development project, while the other half were neighboring farmer plots that acted as ‘control’. Demonstration plots received mineral fertilizer (100% of plots), averaging 71 N, 8 P, 32 K kg ha −1 yr −1 and external mulch from grass and crop residues (64% of plots), whereas control plots received no mineral fertilizer and little external mulch (26% of plots). Demonstration plots had significantly ( P ⩽ 0.05) higher yields than control plot in Central, South and Southwest, but average yield increases varied from 4.8 t ha −1 yr −1 (Southwest) to 8.0 (Central), and 10.0 (South). Average weevil corm damage (3%) and nematode-induced root necrosis (7%) was low and similar for both plot types, so yield increases could only be explained by the use of fertilizer and mulch. The highest demonstration plot yield increases were observed where fertilizer addressed key nutrient deficiencies identified using the compositional nutrient diagnosis approach. Farm gate bunch prices declined from 0.17 (Central Uganda) to 0.07 USD kg −1 (Southwest Uganda). Consequently, average marginal rate of return (MRR) of fertilizer and mulch use ranged from 0.1 (Southwest) to 5.8 (Central). The technologies were likely to be acceptable to farmers (MRR ⩾ 1.00) up to 160 km away from the capital. Fertilizer use is likely to be acceptable in all regions (MRR = 0.7–9.4) if local fertilizer prices of 2006/7 (average USD 0.56 kg −1 of fertilizer) declined by 50%. Doubling of fertilizer prices is likely to make fertilizer use unacceptable beyond 100 km away from the capital. The study concludes that there is scope for increased input use in banana systems in Uganda, but that regional variations in crop response, input/output prices, and price fluctuations have to be taken into account.

Expression of sweet pepper Hrap gene in banana enhances resistance to Xanthomonas campestris pv. musacearum

Banana Xanthomonas wilt (BXW), caused by the bacterium Xanthomonas campestris pv. musacearum, is the most devastating disease of banana in the Great Lakes region of Africa. The pathogen's rapid spread has threatened the livelihood of millions of Africans who rely on banana fruit for food security and income. The disease is very destructive, infecting all banana varieties, including both East African Highland bananas and exotic types of banana. In the absence of natural host plant resistance among banana cultivars, the constitutive expression of the hypersensitivity response-assisting protein (Hrap) gene from sweet pepper (Capsicum annuum) was evaluated for its ability to confer resistance to BXW. Transgenic lines expressing the Hrap gene under the regulation of the constitutive CaMV35S promoter were generated using embryogenic cell suspensions of two banana cultivars: 'Sukali Ndiizi' and 'Mpologoma'. These lines were characterized by molecular analysis, and were challenged with Xanthomonas campestris pv. musacearum to analyse the efficacy of the Hrap gene against BXW. The majority of transgenic lines (six of eight) expressing Hrap did not show any symptoms of infection after artificial inoculation of potted plants in the screenhouse, whereas control nontransgenic plants showed severe symptoms resulting in complete wilting. This study demonstrates that the constitutive expression of the sweet pepper Hrap gene in banana results in enhanced resistance to BXW. We describe the development of transgenic banana varieties resistant to BXW, which will boost the arsenal available to fight this epidemic disease and save livelihoods in the Great Lakes region of East and Central Africa.

Testing for a suitable culture medium for micropropagation of East african higland bananas

A study was conducted to find a suitable culture medium for micropropagation of East African highland bananas ( Musa spp.). Modified Eriksson (ER), Gamborg’s B-S (B-S) and Murashige-Skoog (MS) media were tested with a roasting cultivar Gonja-Horn plantain (AAB), a dessert Bogoya-Gros Michel (AAA) and three East African highland cooking (AAA) cultivars Kibuzi, Mbwazirume and Namwezi for in vitro proliferation induction. The media were supplemented with 4.5 mg l -1 Benzylaminopurine (BAP) and with or without 0.186 mg l -1 Naphtalene acetic acid (NAA). Only ER and MS gave proliferation. AAB cultivar proliferated significantly more than AAAs which did not differ among themselves. The AAA cultivars showed precocious rooting in the absence and presence of 0.186 mg l -1 NAA on ER and MS media supplemented with 4.5 mg l -1 BAP. However, the presence of auxin NAA significantly lowered shoot proliferation with concomitant significant induction of precocious rooting. This indicated a high level of endogenous auxin in these cultivars and, therefore, the unnecessity of exogenous auxin for their maximum in vitro proliferation. It was also found that ammonical nitrogen content determined the suitability of a culture medium thus making ER an alternative to the MS salts.

Scientific basis for banana &lt;i&gt;cultivar&lt;/i&gt; proportions on-farm in East Africa

Banana (Musa spp.) production and diversity in the East African region, has been on the decline for the last 20 years due to both a biotic and biotic problems. There has been an ecological and socio-economic imbalance in the East African Highland banana (Musa AAA-EA) growing systems due to this decline. However, farmers have been growing these bananas in cultivar mixtures, a practice which ensures the continuous sustainability of the system. Cultivar mixtures, however, seem to be in specific proportions based on the strength and weakness of each cultivar and so affecting the clone sets to which cultivars belong, as well as providing predictions on the conservation status of each clone set. The primary objective of the study was to account for the farmers’ perceptions behind cultivar proportions and to understand the scientific basis of these proportions in selected sites in East Africa. The study was carried out in Karagwe, Bushenyi and Masaka districts in East Africa, a region considered to be a secondary centre of diversity for bananas. Thirty farms were sampled in one selected parish/ward in the three sites for ecological data. The quadrat method was used to record abundances of identified cultivars in order to determine the cultivar proportions. Ethno-botanical data collected on traditional knowledge was analysed for twenty-three identified traditional cultivar-selection criteria used in the participatory rural appraisal (PRA), as well as interviews from 15 key informants of each study area. A total of 105 cultivars were identified, 76% of which were the East African Highland bananas. Although fourteen cultivars were common to the three sites, Masaka had the highest proportion with Nfuuka cultivar leading the five clone sets. Cultivar diversity indices explained the proportions in terms of richness and evenness and Nfuuka was the richest clone set. Although all clone sets were represented at each site, they were not evenly distributed; a factor which is disadvantageous in the conservation status of the crop. While results indicated that the agro-ecological and traditional utilisation criteria formed the basis for cultivar proportions on farm for both Karagwe and Masaka, farmers were found to do so because of the high traditional values attached to the crop. However, knowing cultivar proportions in terms of richness and evenness can assist in predicting the stability or change in diversity of banana growing sites.