Banana (Musa spp.), a perennial and vegetatively-propagated plant, is an important crop in the tropical and subtropical regions of the world [1]. It is a source of food and income for millions of smallholder farmers, especially in Asia, South and Central America, and sub-Saharan Africa (SSA) [2] [3]. Majority of the banana production in SSA is done on small plots and backyard gardens [3].

Every part of the banana plant is useful although the fruit is the most used plant part. The mature fruit of banana can be utilized in many forms, such as dessert when fully ripe, food when cooked and mashed or eaten directly after boiling or steaming [4] [5]. When cooked or steamed, banana, especially the cooking East African Highland Bananas (EAHBs) “Matooke”, are characterized by a unique flat taste and aroma, golden yellow colour and a soft texture [6]. Fruits, especially those of beer type of bananas “Embire” also the EAHBs can be squeezed when fully ripe to produce a natural sweet juice “Eshande” which upon fermentation can be processed into wine and/or “Waragi”; a tradition drink enjoyed in most east African countries.

The highest per capita consumption of banana in the world is in the East African region, where one-third of the people depend on this crop as a staple food—the crop occupies between 20% and 30% of the acreage under cultivation [7]. Annual production of bananas in the region is worth US$ 4.3 billion, accounting for about 5% of the region’s gross domestic product [8]. The predominant type of bananas grown in East Africa is the EAHBs. These are a subgroup of triploid banana cultivars, with genome code AAA [9].

In Uganda, millions of people rely on banana for income and daily food, with approximately 75% of farmers cultivating the crop [10]. Banana occupies the third largest cultivated area amongst staple food crops in Uganda [1]. Despite the benefits of growing bananas in the country, the yield gap between the actual and potential is high. For example, over the last 30 years, banana yields have been declining with low yields of 5 to 10 t/ha/year compared to potential yield of 70 t/ha/year and bunch mass dropping from 60 to 10 kg/plant or less [1] [11]. The number of years that banana plantations continue to be productive in some parts of Uganda, especially the central region, has been reduced to only five years compared to 50 years of plantation productivity in the past. The leading factors responsible for the decline in yield and productivity life are largely due to susceptibility of local cultivars to pests [11], especially banana weevils and nematodes; and diseases, particularly black Sigatoka [12] [13] [14].

Black Sigatoka, also known as black leaf streak disease, caused by the fungus Mycosphaerella fijiensis (Morelet), is the most serious disease threat to banana production worldwide, causing yield losses of up to 50% [14] [15]. Heavy infestation of black Sigatoka to banana can lead to a considerable reduction in the photosynthetic leaf area of the plant [15]. Consequently, bunches and fruits of infected plants produce lower bunch yield in comparison to those of healthy banana plants. Severe Sigatoka disease infection has also been reported to cause a marked effect on banana ripening after harvest [16].

There are several potential technology-based interventions to address the problem of black Sigatoka disease [17] [18] [19], however, developing resistant cultivars is the most fundamental intervention. Resistant cultivars offer enormous spill over benefits for human health and positive environmental impacts [19] [20].

The National Agricultural Research Organization (NARO) of Uganda initiated a banana breeding program in the early-1990s, which has over the years developed hybrid genotypes, some of which have been officially released to farmers for production [21] [22]. Several other hybrid genotypes are under evaluation for eventual release to farmers. In this study, we present and discuss the results of six new hybrid banana genotypes, which were selected from advanced yield trials of NARO and evaluated together with two control cultivars for traits of relevance for three crop cycles at three locations in the major banana growing areas of Uganda. Adoption of new banana cultivars in Uganda has been reported to be largely dependent on a combination of sensory, yield and disease resistance traits [23]. The objective of this study therefore was to determine the performance of new banana genotypes for bunch mass (BMS) and BMS-related traits, resistance to black Sigatoka and food sensory attributes.

Understanding the performance of new cropgenotypes for traits of relevance is important in cultivar selection to satisfy end-users. This ultimately facilitates faster adoption of new cultivars when right cultivars are selected. The objective of this study was to determine the performance of new hybrid cooking banana genotypes for agronomic, sensory and black Sigatoka resistance traits to inform their selection process. To meet the stated objective, we evaluated eight cooking banana genotypes for bunch mass (BMS) and BMS-related traits, resistance to black Sigatoka and sensory attributes at three diverse locations for three crop cycles in Uganda.

Genotypes, locations and crop cycles and their two-way interaction effects were significantly different for most traits. Significant genotypic effects for the traits assessed revealed that the genotypes evaluated were significantly different and that phenotypic selection would be possible among them. Significant location effects on the other hand revealed that the locations from where the experiments were conducted were different from each other and therefore affected the performance of genotypes for traits evaluated. Certainly, the three sites (Mbarara, Jinja and Kawanda) during the experimental period registered different amounts of rain fall received. Mbarara received a total annual rainfall of 1214 mm while Kawanda and Jinja received total annual rains of 1390 mm and 1400 mm, respectively. Besides, the sites differ by altitude and pressure for black Sigatoka disease. Of the three sites, Mbarara is at the highest altitude characterized by low pressure for black Sigatoka disease due to cooler environments. The three sites are indeed found in three distinct agro-ecological zones that receive different amounts of rain and temperatures and many other conditions [29]. Significant crop cycle effects for BMS, NCL and NFT revealed differences in crop cycles for these traits.

Plant-crop cycle in banana is usually associated with smaller bunches [30] as the initial mother plants are not yet acclimatized to the environmental conditions. With the progression of the cycles (first ratoon crop and subsequently second ratoon crop), bunches grow bigger because the ratoon plants are already acclimatized to the environmental conditions. The implication thereof is that, selection for BMS and its related traits should be appropriately performed on ratoon plants. There were no significant crop cycle effects on NSL and INSL, implying that the crop cycles were not any different for these traits, thus their selection can be conducted at any crop cycle of banana growth and development without losing any valuable information. It may also be important to note that NSL and resistance to black sigatoka are high heritable traits.

Significant genotype × location interaction effects for the traits assessed revealed that some of the genotypes had specific adaptation to one or more of the locations, while the significant genotype × crop cycle interaction effects for BMS and other traits were indicative of differences in patterns of yield performance among genotypes as previously reported [19].

Compared to other sites, Mbarara recorded the best performance for all the agronomic traits. This was due to favourable conditions and low pressure for black Sigatoka. Higher altitude areas in Uganda such as those in Mbarara are characterized by low pressure for black Sigatoka disease due to cooler temperatures [31]. Besides, the hybrids that were studied are derivatives of the local East African highland banana cultivars that are endemic to East Africa and highly adapted to high altitude areas of ≥1400 masl in the East African region.

Performance of the genotypes for BMS and BMS-related traits (NCL and NFT) was generally lowest when bananas were harvested at plant crop cycle and highest when harvested at ratoon crop cycles, a trend that in part reflects the dynamics in banana growth and development [30]. Banana established from suckers or tissue culture plants grow through phases: the vegetative phase characterized by rapid growth of pseudostem and foliage; the flowering phase characterized by rapid shooting out of inflorescence from the heart of the pseudostem; and the fruiting phase, where the ovaries contained in the first (female) flowers grow rapidly, developing parthenocarpically into clusters of fruits, called hands. The numbers of fruits and clusters are cultivar-dependent.

At every phase of banana growth and development, dry mass production and partitioning between plant organs occur, although the rate differs during the growth stages of the plant and is also cultivar-dependent. During the growth of the plant crop, new suckers (ratoons) that would later develop into new mother plants emerge. The ratoon suckers from the initial mother plant are acclimatized to environmental conditions, and therefore produce much higher yields than the plant crop. This occurs usually in the absence of pests and diseases which would otherwise reduce yields of the sucker-plants (ratoon crop). Because the hybrid genotypes were resistant to black Sigatoka, they produced progressive yields from pant crop to ratoon crops (first and second). Mbwazirume a local cultivar susceptible to black Sigatoka, however, had reduced performance for BMS and other traits from the pant crop to ratoon crop. Resistance of hybrids to black Sigatoka was shown by the INSL of over 70% compared to that of a susceptible cultivar “Mbwazirume” of less than 55%. Carlier et al. [26] and Orjeda [32] revealed that bananas require more than 70% of active leaf foliage at flowering for proper development of the banana fruit. Resistance to black Sigatoka of over 70% of INSL is one of the key banana breeding targets of most banana breeding programmes in Africa. Severe infestation of bananas with black Sigatoka, can lead to a considerable reduction in the photosynthetic leaf area of the plant. Consequently, bunches and fruits of infected plants produce lower bunch weight in comparison to those of healthy banana plants [14] [15]. Vuylsteke et al. [33] revealed that resistance to black Sigatoka results from the interaction between a major recessive gene and two modifiers with additive effects.

The sensory attributes (taste, aroma, soft mouth feel, and colour) of “9058K-2” and “8099K-16” were consistently ranked high and closest to those of “Mbwazirume”. “Mbwazirume” is one of the most consumer-preferred landrace cooking banana cultivars due to high quality attributes of its cooked food. It dominates the banana markets in Uganda and is therefore highly marketable. Adoption rates of improved banana cultivars are often low regardless of their economic importance in terms of higher yield and resistance to diseases [3]. Reasons given by farmers for low uptake include inferior taste, poor marketability compared to local cultivars, and risks associated with growing new cultivars [34]. Farmers indicate preference for local cultivars because of their superior sensory attributes (good taste, aromatic, good mouth feel, golden yellow colour), even if new cultivars have better agronomic traits and better response to biotic and abiotic stresses [3] [23]. It is therefore important that new banana cultivars in addition to high yield and resistance to pests and diseases should possess good sensory attributes to meet farmer needs and preferences for higher adoption. In the present study we selected and recommended two banana hybrid genotypes “9058K-2” and “8099K-16” because of their high BMS, resistance to black Sigatoka and good sensory attributes.

Banana genotypes evaluated in this study showed high degree of variation for all the traits assessed, implying high potential for selection among them. Significant differences among crop cycles for BMS, NCL and NFT, with higher mean performance for these traits observed at the second ratoon crop revealed that the selection for BMS and BMS-related traits can be perfectly done at the second ratoon crop for optimal results. Non-significant crop cycle effects for NSL and INSL showed that selection for these traits can be done at any crop cycle of banana without losing any valuable information. The top two banana genotypes that combined high BMS, resistance to black Sigatoka and acceptable sensory attributes were “9058K-2” and “8099K-16” (Table 2). These two genotypes are recommended as potential commercial cultivars in Uganda and/or other East African countries with similar environmental conditions to those where the genotypes were tested.

The authors thank Bioversity International and Government of Uganda for funding the study. They also thank the technicians, farmers and everyone who contributed to the study, especially in data collection and provision of necessary information or otherwise.

The authors declare no conflict of interest.

Tumuhimbise, R., Barekye, A., Talengera, D., Akankwasa, K., Nowakunda, K., Asasira, M., Karamura, D. and Karamura, E. (2020) Assessing New Banana Genotypes for Relevant Traits: Implication for Variety Selection. Agricultural Sciences, 11, 1017-1032. https://doi.org/10.4236/as.2020.1111066