Cultivated Bananas Research Articles

Morpho-taxonomical and molecular assessment of Musa genotypes from north-east India by morphological and inter-retrotransposon amplified polymorphism markers

The states of north-eastern region of India are home to several wild and cultivated bananas. There is a dearth of information on the genetic diversity of Musa resources of the region to assist in crop improvement programmes. Twenty-five genotypes of Musaceae accessions including one Ensete species maintained at Institute of Bioresources and Sustainable Development (IBSD), Imphal, were characterized based on 60 morpho-taxonomic characters and seven inter-retrotransposon amplified polymorphism (IRAP) primer combinations. The morphological data were presented in the form of hierarchical clusters and principal components. Hierarchically, the Musa genotypes can be grouped into distinctive clusters, and while the first four principal components could explain 58.66 % of variation of the total morphological traits studied. A total of 337 amplicons were generated using 12 IRAP primer combinations with an average percentage polymorphism of 96.12. The molecular markers used in this study could reveal intra- and inter-group diversity among the genotypes with similarity coefficients ranging from 0.16 to 0.90. It could also differentiate the clusters of all the edible cultivated Musa genotypes from the wild/semi-wild ancestors. Thus, the chosen parameters seem to be especially important in the varietal or genotype identifications.

Origins and domestication of cultivated banana inferred from chloroplast and nuclear genes.

BackgroundCultivated bananas are large, vegetatively-propagated members of the genus Musa. More than 1,000 cultivars are grown worldwide and they are major economic and food resources in numerous developing countries. It has been suggested that cultivated bananas originated from the islands of Southeast Asia (ISEA) and have been developed through complex geodomestication pathways. However, the maternal and parental donors of most cultivars are unknown, and the pattern of nucleotide diversity in domesticated banana has not been fully resolved.Methodology/Principal FindingsWe studied the genetics of 16 cultivated and 18 wild Musa accessions using two single-copy nuclear (granule-bound starch synthase I, GBSS I, also known as Waxy, and alcohol dehydrogenase 1, Adh1) and two chloroplast (maturase K, matK, and the trnL-F gene cluster) genes. The results of phylogenetic analyses showed that all A-genome haplotypes of cultivated bananas were grouped together with those of ISEA subspecies of M. acuminata (A-genome). Similarly, the B- and S-genome haplotypes of cultivated bananas clustered with the wild species M. balbisiana (B-genome) and M. schizocarpa (S-genome), respectively. Notably, it has been shown that distinct haplotypes of each cultivar (A-genome group) were nested together to different ISEA subspecies M. acuminata. Analyses of nucleotide polymorphism in the Waxy and Adh1 genes revealed that, in comparison to the wild relatives, cultivated banana exhibited slightly lower nucleotide diversity both across all sites and specifically at silent sites. However, dramatically reduced nucleotide diversity was found at nonsynonymous sites for cultivated bananas.Conclusions/SignificanceOur study not only confirmed the origin of cultivated banana as arising from multiple intra- and inter-specific hybridization events, but also showed that cultivated banana may have not suffered a severe genetic bottleneck during the domestication process. Importantly, our findings suggested that multiple maternal origins and a reduction in nucleotide diversity at nonsynonymous sites are general attributes of cultivated bananas.

Rheological and chemical predictors of texture and taste in dessert banana (Musa spp.)

To be able to account for sensory qualities earlier in the assessment of a new banana hybrid in a selection scheme, predicting the sensory perception of banana texture and taste by instrumental parameters was investigated. Thirteen cultivated banana and four new triploid hybrids were characterized by sensory profiling, and rheological and chemical analyses. Multilinear regressions were used to calibrate predictions using 13 cultivated bananas, and the quality of predictions was validated using four hybrids. The sensory characteristics sourness and sweetness were predicted by titratable acidity (R2=0.68) and pH (R2=0.66). Malate and citrate were the main contributors to sweetness and sourness. Astringency was predicted by total tannins (R2=0.55). Rheological parameters from texture profile analyses (stress at fracture, fracturability) were more suitable than pulp puncture force to predict the sensory texture properties firmness (R2=0.47) and melting (R2=0.60). These textural properties were predicted by titratable acidity and dry matter content (R2=0.62). Predictions of mealiness, adhesiveness, and heterogeneity were not efficient. Differences of 3.6–3.7meq100g−1 FW in titratable acidity or of 0.30g100g−1 FW in malate or citrate were required to ensure a detectable difference in sourness or sweetness (p=0.9). Pulp puncture force needed to differ by a minimum of 0.9N before a difference in firmness could be perceived by the panelists. In conclusion, while models to predict sourness and sweetness can now be used for high throughput phenotyping, we recommend additional tests for other sensory attributes.

Development and characterisation of microsatellite markers for wild banana (Musa balbisiana)

SummaryThe wild banana species, Musa balbisiana Colla., is one of the progenitors of cultivated banana and belongs to the family Musaceae. M. balbisiana is native to Southeast Asia.The species harbours many useful and important traits such as disease resistance and abiotic stress tolerance, and represents an important genetic resource for banana improvement programmes. Thus, the development of microsatellite markers for this species could be of value for use in germplasm conservation, genetic studies, and gene mapping. We report the development of 63 microsatellite (simple sequence repeat; SSR) markers from a microsatellite-enriched library, and have demonstrated their utility in characterising 30 banana accessions belonging to the AA, BB, or AB genome types. The number of alleles detected per locus ranged from two to 21 (mean = 11). The expected heterozygosity (He) ranged from 0.138 – 0.934 (mean = 0.817), and the polymorphic information content (PIC) ranged from 0.131 – 0.912 (mean = 0.771).The total probability of identity (i.e., the probability of two cultivars sharing the same genetic profile by chance) was 1.06 10–66. Thus, the 63 SSR markers developed here will be useful for genotyping, for genetic diversity studies, and for gene mapping in the genus, Musa.

Analysis of Genetic Variation among Different Banana Cultivars

The banana (Musa spp.) is considered as an important crop plant due to its high economic value as good dietary source. Banana is the rich source of carbohydrates and vitamins, particularly vitamins B; it is also a good source of potassium, phosphorus, calcium and magnesium. Here, we analyzed the genetic relationship of four different banana varieties that are cultivated in south India. Random amplified polymorphic DNAs (RAPDs) fingerprinting of these banana varieties (Grand Naine, Nendran, Poovan and Red Banana) were carried out by five decamer primers (OP-5, OP-6, OP-7, OP-8,OP-11) led to DNA amplification. The distances in the dendrogram constructed by UPGMA (Unweighted pair group method Arithmetical Means) were compared with the genetic distances between genotypes pairs to calculate the cophenetic correlation. The genetic variation between Grand naine and Nendran was found to be 0.89 nucleotide. Similarly the Poovan is getting 0.94 nucleotide variation from the above one and Red is getting 0.97 nucleotide at the highest from all. The results presented here also contribute to narrowing the gaps in our current understanding of the migration path of bananas and the emergence of secondary centers of diversity. Cultivated bananas (Musa spp.) are mostly diploid or triploid cultivars with various combinations of the A and B genomes inherited from their diploid ancestors Musa acuminata Colla. and Musa balbisiana Colla. respectively.

Did backcrossing contribute to the origin of hybrid edible bananas?

BackgroundBananas and plantains (Musa spp.) provide a staple food for many millions of people living in the humid tropics. The cultivated varieties (cultivars) are seedless parthenocarpic clones of which the origin remains unclear. Many are believed to be diploid and polyploid hybrids involving the A genome diploid M. acuminata and the B genome M. balbisiana, with the hybrid genomes consisting of a simple combination of the parental ones. Thus the genomic constitution of the diploids has been classified as AB, and that of the triploids as AAB or ABB. However, the morphology of many accessions is biased towards either the A or B phenotype and does not conform to predictions based on these genomic formulae.ScopeOn the basis of published cytotypes (mitochondrial and chloroplast genomes), we speculate here that the hybrid banana genomes are unbalanced with respect to the parental ones, and/or that inter-genome translocation chromosomes are relatively common. We hypothesize that the evolution under domestication of cultivated banana hybrids is more likely to have passed through an intermediate hybrid, which was then involved in a variety of backcrossing events. We present experimental data supporting our hypothesis and we propose a set of experimental approaches to test it, thereby indicating other possibilities for explaining some of the unbalanced genome expressions. Progress in this area would not only throw more light on the origin of one of the most important crops, but provide data of general relevance for the evolution under domestication of many other important clonal crops. At the same time, a complex origin of the cultivated banana hybrids would imply a reconsideration of current breeding strategies.

A First Assessment of Home Range and Foraging Behaviour of the African Long-Tongued Bat Megaloglossus woermanni (Chiroptera: Pteropodidae) in a Heterogeneous Landscape within the Lama Forest Reserve, Benin

We investigated spatial use and foraging behaviour of the nectarivorous African long-tongued bat, Megaloglossus woermanni (Chiroptera: Pteropodidae), in the Lama Forest Reserve, southern Benin, West Africa. We monitored movement and activity patterns of two males and two females that were fitted with position-sensitive radio transmitters for five to nine nights within a three-month study period. The study site comprised the central patch of relatively undisturbed forest (‘Noyau Central’), and a mosaic of orchards, agroforestry plantations, and degraded forests surrounding the central patch. Spatial use of M. woermanni was characterized by small home ranges and high site-fidelity. Mean home range sizes (minimum convex polygon) were larger in females (139.0 and 146.8 ha) than in males (99.8 and 102.9 ha). Throughout the study period, long-tongued bats were frequently observed visiting flowers of cultivated bananas. The mean foraging areas (95% density kernel) of females (39.0 and 109.4 ha) were much larger than in males (12.3 and 14.1 ha). Difference in core areas (50% density kernel) between the sexes was less marked (both females: 6.8 ha, males: 2.7 and 2.9 hectares). Core areas constituted only a small part of home ranges (2.6–4.9%). Large segments of the home ranges were only used for commuting flights between discrete resource patches. Our study provides, for the first time, information on home ranges and foraging behaviour of the sole obligate nectar-drinking bat in Africa.

Evaluation of genetic diversity between 27 banana cultivars (Musa spp.) in Mauritius using RAPD markers

Cultivated bananas (Musa spp.) are mostly diploid or triploid cultivars with various combinations of the A and B genomes inherited from their diploid ancestors Musa acuminata Colla. and Musa balbisiana Colla. respectively. Random amplified polymorphic DNA (RAPD) markers were used to establish the relatedness of 27 accessions in the Mauritian Musa germplasm. 15 decamer primers produced a total of 115 reproducible amplification products, of which 96 were polymorphic. Computation of the genetic distances shows that similarities ranged from 0.3 to 1.0 with an average of 0.51. With a few exceptions, cluster analysis differentiated pure A containing cultivars from those containing at least one B genome. This paper answers long standing questions on the taxonomic placement of the cultivar ‘Banane Rouge’ by providing the basis for its classification within the homogenomic A cultivars. The results presented here also contribute to narrowing the gaps in our current understanding of the migration path of bananas and the emergence of secondary centers of diversity.

Pacific Bananas: Complex Origins, Multiple Dispersals?

This paper reviews recent genetic evidence for the origins of the traditional cultivated bananas of the Pacific, and shows that they are unexpectedly complex. Current assumption of their prevailing west-to-east spread from Southeast Asia into the Pacific thus needs modification. Although bananas are widely assumed to have been part of the set of crops transported to Polynesia at first settlement, the linguistic evidence on which this is based underestimates the diversity of bananas in the New Guinea region and is suspect. Archaeological evidence of bananas is so far very tenuous. Recent genetic evidence of the parentage of most groups of cultivated bananas shows that the primary step toward edibility occurred in the Philippines– New Guinea region. Early movements westward across Island Southeast Asia must have occurred, and the complexity of hybrids makes regionally dispersed development likely. There is no demonstrable link with Taiwan or the adjacent coast of China. There is no evidence that the genetically distinct lineages of bananas found in Polynesia were brought together in the putatively ancestral Lapita crop assemblage of the northern New Guinea region. The complex phylogeny of the cultivated Pacific bananas may thus suggest multiple prehistoric introductions of bananas to Polynesia. If bananas were part of the founding set of crops of Remote Oceania, the question ''which bananas?'' is currently unanswered.

Diversity and phylogenetic relationships among wild and cultivated bananas (Silk-AAB) revealed by SSR markers

SummaryGenetic diversity and phylogenetic studies were undertaken to identify possible progenitors of Silk banana varieties for use in conventional breeding. Genetic diversity and phylogeographical relationships among 33 accessions of banana belonging to the Silk (AAB) sub-group were studied and compared with their wild progenitors. Seventy-eight alleles were identified among the test accessions, with a mean frequency of 6.5 alleles per locus, and the polymorphism information content (PIC) values varied from 0.28 – 0.55, with an average of 0.41. The co-phenetic correlation coefficient (r) was 0.9, suggesting a good fit between the dendrogram and the similarity matrix. UPGMA cluster analysis based on Sequential Agglomerative Hierarchical and Nested (SAHN) clustering methods exhibited an eccentric lineage of ‘Khungsong wild’ (Musa balbisiana-BB) with Silk accessions, implying its putative ancestry. The microsatellite markers selected for this study clearly distinguished wild M. acuminata, wild M. balbisiana, and bi-specific cultivated Silk accessions. The results suggest that, irrespective of geographical origin, the Silk group of bananas have a narrow genetic base, with > 80% similarity, and could be derived from a single genotype. This situation offers limited opportunities to improve resistance against Fusarium wilt and Sigatoka leaf spot complex through classical breeding, and will necessitate the use of other biotechnological approaches. This study also revealed a grouping of ‘Khungsong wild’ (BB) with Silk group accessions instead of wild M. balbisiana and wild M. acuminata, suggesting its possible involvement in the evolution of the Silk group.

Molecular phylogeny of banana cultivars from Thailand based on HAT-RAPD markers

Musa acuminata Colla (AA genomes) and Musa balbisiana Colla (BB genomes) are the wild progenitors of the cultivated banana, they are highly variable in Thailand. The genetic system is relatively unknown and complicated due to interspecific hybridization, heterozygosity and polyploidy, which are common in most clones. These factors make identification of closely related banana cultivars difficult, especially when sterile. The high annealing temperature-random amplified polymorphic DNA (RAPD) technique was used to estimate the genetic relationship between 22 selected banana cultivars, utilizing 14 random primers. Phylogenetic relationship was determined by unweighted pair group method with arithmetical averages cluster analysis. The dendrogram constructed from the similarity data showed that all the 22 cultivars analysed were closely related with a narrow genetic base. There were sufficient RAPD polymorphisms that were collectively useful in distinguishing the cultivars. The dendrogram grouped all the AA, BB, AAA, AAB and ABB genomes into a major cluster. Several subgroups are recognized within the major clade. As expected, Ensete glauca Roxb. (Musaceae) and Strelitzia reginae Banks (Strelitziaceae) were clearly differentiated from the analysed edible bananas. Our study showed that RAPD markers are sufficiently abundant to classify and readily dissect genetic differences between the closely related Musa germplasm and provide a basis for the selection of parents for improvement of this germplasm.

Genetic diversity of wild banana (Musa balbisiana Colla) in China as revealed by AFLP markers

Wild banana Musa balbisiana Colla is one of the progenitors of cultivated bananas and plantains. It is native to Southeast Asia and the western Pacific. South China represents the northern limit of its distribution range. The genetic diversity of Musa balbisiana was assessed by the amplified fragment length polymorphism (AFLP) fingerprinting in 15 populations of China. Four primer pairs produced 199 discernible loci. High levels of genetic diversity were detected, with P = 78.5%, HE = 0.241, and Hpop = 0.3684 at population level, and P = 100%, HT = 0.3362 and Hsp = 0.5048 at species level. Significant genetic differentiation among populations was detected based on Hickory’s analysis (27.6%), Shannon’s diversity index (27.0%) and AMOVA (27.1%). The AFLP results are discussed and compared with data obtained by microsatellites method. The estimates of genetic diversity and differentiation between each pair of populations computed with microsatellites and AFLP markers were not significantly correlated. Conservation strategies for Musa balbisiana in China are proposed.

Population structure of wild bananas, Musa balbisiana, in China determined by SSR fingerprinting and cpDNA PCR‐RFLP

Both demographic history and dispersal mechanisms influence the apportionment of genetic diversity among plant populations across geographical regions. In this study, phylogeography and population structure of wild banana, Musa balbisiana, one of the progenitors of cultivated bananas and plantains in China were investigated by an analysis of genetic diversity of simple sequence repeat (SSR) fingerprint markers and cpDNA PCR-RFLP. A chloroplast DNA (cpDNA) genealogy of 21 haplotypes identified two major clades, which correspond to two geographical regions separated by the Beijiang and Xijiang rivers, suggesting a history of vicariance. Significant genetic differentiation was detected among populations with cpDNA markers, a result consistent with limited seed dispersal in wild banana mediated by foraging of rodents. Nuclear SSR data also revealed significant geographical structuring in banana populations. In western China, however, there was no detected phylogeograpahical pattern, possibly due to frequent pollen flow via fruit bats. In contrast, populations east of the Beijiang River and the population of Hainan Island, where long-range soaring pollinators are absent, are genetically distinct. Colonization-extinction processes may have influenced the evolution of Musa populations, which have a metapopulation structure and are connected by migrating individuals. Effective gene flow via pollen, estimated from the nuclear SSR data, is 3.65 times greater than gene flow via seed, estimated from cpDNA data. Chloroplast and nuclear DNAs provide different insights into phylogeographical patterns of wild banana populations and, taken together, can inform conservation practices.

Occurrence of blood disease of banana in Sumatra, Indonesia

Since 1991, the sudden death of cultivated banana plants has been widely observed in the southern region of Sumatra Island, Indonesia. Wilting from loss of petiole and midrib turgidity, yellowing, and necrosis of leaves was followed by death of the whole plant. Reddish brown bacterial ooze exuded from the cut surface of infected pseudostems and fruits. The colony appearance of the isolated bacterium was similar to that of Ralstonia solanacearum. The bacterium was pathogenic to banana plants but not to tomato. Its bacteriological properties agreed with those of blood disease bacterium (BDB) of banana described previously. The 16S rDNA sequence of strain Banana E had conserved bases characteristic of BDB. Based on these results, the causal agent was identified as BDB, which is a close relative of Ralstonia. The isolates have resistance against antibiotics, such as chloramphenicol and tetracycline.

Genetic characterization of cultivated bananas and plantains in Kenya by RAPD markers

A polymerase chain reaction (PCR)-based approach, namely, random amplified polymorphic DNA (RAPD) was used to estimate the genetic relationships among 20 selected banana cultivars from different regions of Kenya. Nineteen random primers were used. The polymorphisms in PCR amplification products were subjected to the unweighted pair group method for arithmetic averages (UPGMA) and plotted in a phenogram. The dendogram constructed from the similarity data showed that all the 20 cultivars analysed were related. The highly related cultivars included Ng’ombe, Nusu Ng’ombe, Ntobe, Sialamule, Kimuga, Kibuzi, Sibusi, Bukamba, Mfupi and Gitigi whose genome was AAA. The cultivars Manyatta, Mokoya, Murure and Horn plantain whose genome was AAB were less similar while Pekera, Muraru, Spambia, Matumbo, Nyar Sausett and Mtama formed the least related group.

Sectional relationships in the genus Musa L. inferred from the PCR-RFLP of organelle DNA sequences.

The objective of this study was to construct a molecular phylogeny of the genus Musa using restriction-site polymorphisms of the chloroplast (cpDNA) and mitochondrial DNA (mtDNA). Six cpDNA and two mtDNA sequences were amplified individually in polymerase chain reaction (PCR) experiments in 13 species representing the four sections of Musa. Ensete ventricosum (W.) Ch. was used as the outgroup. The amplified products were digested with ten restriction endonucleases. A total of 79 restriction-site changes were scored in the sample. Wagner parsimony using the branch and bound option defined two lines of evolution in Musa. One lineage comprised species of the sections Australimusa and Callimusa which have a basic number of x = 10 chromosomes, while most species of sections Eumusa and Rhodochlamys ( x = 11) formed the other lineage. Musa laterita Cheesman ( Rhodochlamys) had identical organellar genome patterns as some subspecies of the Musa acuminata Colla complex. The progenitors of the cultivated bananas, M. acuminata and Musa balbisiana Colla, were evolutionarily distinct from each other. Musa balbisiana occupied a basal position in the cladogram indicating an evolutionarily primitive status. The close phylogenetic relationship between M. laterita and M. acuminata suggests that species of the section Rhodochlamys may constitute a secondary genepool for the improvement of cultivated bananas.

Ascertaining maternal and paternal lineage within Musa by chloroplast and mitochondrial DNA RFLP analyses.

In banana, the maternal transmission of chloroplast DNA and paternal transmission of the mitochondrial DNA provides an exceptional opportunity for studying the maternal and paternal lineage of clones. In the present study, RFLP combined with hybridization of heterologous mitochondrial and chloroplastic probes have been used to characterize 71 wild accessions and 131 diploid and 103 triploid cultivated clones. In additon to Musa acuminata and Musa balbisiana, other species from the four Musa sections were studied to investigate their contribution to the origin of cultivated bananas. These molecular analyses enable the classification of the Musa complex to be discussed. Results ascertain relationships among and between the wild accessions and the mono- and interspecific diploid and triploid bananas, particularly for the acuminata genome. Parthenocarpic varieties are shown to be linked to M. acuminata banksii and M. acuminata errans, thus suggesting that the first center of domestication was in the Philippines - New Guinea area.

Analysis of genetic diversity and sectional relationships in Musa using AFLP markers.

The AFLP technique was used to assess the genetic diversity and sectional relationships in 39 accessions representing the four main sections of the genus Musa. Eight AFLP + 3 primer pairs produced 260 polymorphic bands that were used in cluster and PCO analysis. A wide range of variability was observed among the species within the sections of the genus Musa. AFLP data was useful in separating the different sections of the genus as well as differentiating the different genomic groups of section Eumusa. Section Rhodochlamys ( x = 11) appeared as a distinct entity and clustered closely with the Musa acuminata Colla complex of section Eumusa that has the same basic chromosome number. This relationship is congruent with previous studies. However, unlike previous proposals that questioned the identity of Rhodochlamys as a separate taxonomic unit, PCO analysis of the AFLP data showed that it is a distinct entity. Musa laterita Cheesman ( Rhodochlamys) and Musa schizocarpa Simmonds clustered with the M. acuminata complex suggesting that they may be sources of useful genes for the improvement of the cultivated bananas. Callimusa formed a distinct unit and was closer to Australimusa than to the other sections. Although both sections share the same basic chromosome number of x = 10 these sections are genetically distinct

Genetic Diversity of the Wild Banana Musa acuminata Colla in Malaysia as Evidenced by AFLP

Musa acuminata Colla (Musaceae), the wild progenitor of the cultivated banana, is highly variable in Malaysia and presents several unresolved nomenclatural problems. AFLP was employed to distinguish among three subspecies of Musa acuminata(subsp. truncata and subsp. malaccensis from peninsular Malaysia and subsp. microcarpa from Borneo) and to examine whether subsp. truncata is a distinct taxon. Eight primer combinations revealed molecular markers specific for each of the three taxa. UPGMA cluster analysis showed the three taxa were distinct. Subspecies malaccensis which is endemic in peninsular Malaysia and subsp. microcarpa which is endemic in Borneo were found to be more similar to each other in their DNA patterns than they are to subsp. truncata, which is endemic to peninsular Malaysia. Since subsp. truncata is genetically separate from subsp. malaccensis and subsp.microcarpa , it cannot be regarded as synonymous with either of these subspecies. This paper sheds light on the nomenclature of the three subspecies of Musa acuminata.

First archaeological evidence of banana cultivation in central Africa during the third millennium before present

Phytoliths recovered from refuse pits excavated in central Cameroon and dated to ca 2500 B.P. have been positively identified for the first time in Africa as derived from Musa the cultivated banana, after a comparative study of Musa and Ensete phytoliths. This discovery provides archaeologists with unequivocal proof of early agriculture in central Africa. Furthermore, the presence of banana in Cameroon much earlier than previously assumed could explain how agriculture spread through the rain forest. Lastly, as Musa is of Asian origin, this study provides the first concrete evidence of contacts across the Indian Ocean a millennium earlier than currently accepted.