Combining Biological Approaches to Shed Light on the Evolution of Edible Bananas

researchDeciphering the diversity of the banana complex needs a joint characterization and analysis of the original wild species and their relatives, primitive diploid forms and triploid derived varieties. Sexuality, the primary source of diversity, is strongly disrupted in the cultivated varieties (sterility, parthenocarpy and vegetative propagation) by human selection of vegetatively maintained punctuated mutations. Many biological tools are available for characterizing this diversity, each one illustrating some peculiar facets, and we show that their joint analysis enables an evolutionary reading of this diversity. We propose various scenarios regarding the structure of wild species, on the domestication of the edible diploids from hybrids between wild forms, on the direct ancestry of triploids from cultivated diploids, and on the ancient migrations dispersing cultivated forms around the world. The comparison with data from archaeology, linguistics and human genetics will enable the validation, refinement and dating of the proposed domestication process

Plant regeneration from long-term callus culture of AAA-group dessert banana

A bananeira é uma das plantas mais cultivadas no mundo. Porém, o melhoramento genético de bananeira tem sido um processo vagaroso, em virtude das baixas taxas de formação e germinação de sementes. São técnicas promissoras a seleção de variações somaclonais úteis e a transformação genética em células e calos, para acelerar o processo de melhoramento. Realizou-se a cultura de calos, com o objetivo de estabelecer um protocolo de regeneração de plantas, para ser usado no programa de melhoramento genético de bananeira. Discos de bainha foliar da banana cv. Nanicão (Musa sp., grupo AAA, subgrupo Cavendish) foram cultivados no meio básico de Murashige e Skoog (MS) suplementado com carvão ativado (0,2%), MES (ácido 2 [N-morfolino] etanesulfônico) (15,3 mM), arginina (300 mM), Picloram (414 mM) e 2ip (2-isopentenil adenina) (492 mM). Calos globulares surgidos nos tecidos foliares foram subcultivados no mesmo meio, e obteve-se uma aparência friável e translúcida após um ano e meio de cultura. Os calos friáveis foram transferidos para meio sem reguladores de crescimento e arginina, e suplementado com caseina hidrolisada (0,05%), onde formaram estruturas semelhantes a embriões após transferência à luz. A partir destas estruturas, foram obtidos brotos com raízes, dos quais se originaram plântulas. O protocolo da regeneração de plantas apresentado aqui poderá ser útil para o melhoramento genético de bananeira via variação somaclonal.The banana plant is one of the most widely cultivated crops in the world. However, banana breeding has been a slow process, due to the low seed set and low germination rates. Selection of useful somaclonal variations and genetic transformation in cells or calluses are promising techniques to accelerate the breeding process. Therefore, callus culture was carried out, aiming the establishment of one protocol for plant regeneration, to be used in banana breeding program. Leaf sheath disks of 'Nanicão' banana (Musa sp., AAA group, Cavendish subgroup) were cultured on a Murashige and Skoog (MS) basal medium supplemented with activated charcoal (0.2 %), MES (2 [N-morpholino] ethanesulfonic acid) (15.3 mM), arginine (300 mM), Picloram (414 mM) and 2iP (2-isopentenyl adenine) (492 mM). Globular calluses developed on the leaf tissue were subcultured in the same medium, acquiring a friable and translucid appearance after one and a half year of culture. The friable calluses were transferred to the medium without growth regulators and arginine, and supplemented with casein hydrolysate (0.05%), where they formed embryo-like structures after transference to light. From these structures, shoots with roots were obtained and plantlets developed. The plant regeneration protocol shown here may be useful to banana breeding via somaclonal variation

Plant regeneration from long-term callus culture of AAA-group dessert banana

A bananeira é uma das plantas mais cultivadas no mundo. Porém, o melhoramento genético de bananeira tem sido um processo vagaroso, em virtude das baixas taxas de formação e germinação de sementes. São técnicas promissoras a seleção de variações somaclonais úteis e a transformação genética em células e calos, para acelerar o processo de melhoramento. Realizou-se a cultura de calos, com o objetivo de estabelecer um protocolo de regeneração de plantas, para ser usado no programa de melhoramento genético de bananeira. Discos de bainha foliar da banana cv. Nanicão (Musa sp., grupo AAA, subgrupo Cavendish) foram cultivados no meio básico de Murashige e Skoog (MS) suplementado com carvão ativado (0,2%), MES (ácido 2 [N-morfolino] etanesulfônico) (15,3 mM), arginina (300 mM), Picloram (414 mM) e 2ip (2-isopentenil adenina) (492 mM). Calos globulares surgidos nos tecidos foliares foram subcultivados no mesmo meio, e obteve-se uma aparência friável e translúcida após um ano e meio de cultura. Os calos friáveis foram transferidos para meio sem reguladores de crescimento e arginina, e suplementado com caseina hidrolisada (0,05%), onde formaram estruturas semelhantes a embriões após transferência à luz. A partir destas estruturas, foram obtidos brotos com raízes, dos quais se originaram plântulas. O protocolo da regeneração de plantas apresentado aqui poderá ser útil para o melhoramento genético de bananeira via variação somaclonal.The banana plant is one of the most widely cultivated crops in the world. However, banana breeding has been a slow process, due to the low seed set and low germination rates. Selection of useful somaclonal variations and genetic transformation in cells or calluses are promising techniques to accelerate the breeding process. Therefore, callus culture was carried out, aiming the establishment of one protocol for plant regeneration, to be used in banana breeding program. Leaf sheath disks of 'Nanicão' banana (Musa sp., AAA group, Cavendish subgroup) were cultured on a Murashige and Skoog (MS) basal medium supplemented with activated charcoal (0.2 %), MES (2 [N-morpholino] ethanesulfonic acid) (15.3 mM), arginine (300 mM), Picloram (414 mM) and 2iP (2-isopentenyl adenine) (492 mM). Globular calluses developed on the leaf tissue were subcultured in the same medium, acquiring a friable and translucid appearance after one and a half year of culture. The friable calluses were transferred to the medium without growth regulators and arginine, and supplemented with casein hydrolysate (0.05%), where they formed embryo-like structures after transference to light. From these structures, shoots with roots were obtained and plantlets developed. The plant regeneration protocol shown here may be useful to banana breeding via somaclonal variation

A saturated SSR/DArT linkage map of Musa acuminata addressing genome rearrangements among bananas

Background: The genus Musa is a large species complex which includes cultivars at diploid and triploid levels. These sterile and vegetatively propagated cultivars are based on the A genome from Musa acuminata, exclusively for sweet bananas such as Cavendish, or associated with the B genome (Musa balbisiana) in cooking bananas such as Plantain varieties. In M. acuminata cultivars, structural heterozygosity is thought to be one of the main causes of sterility, which is essential for obtaining seedless fruits but hampers breeding. Only partial genetic maps are presently available due to chromosomal rearrangements within the parents of the mapping populations. This causes large segregation distortions inducing pseudo-linkages and difficulties in ordering markers in the linkage groups. The present study aims at producing a saturated linkage map of M. acuminata, taking into account hypotheses on the structural heterozygosity of the parents. Results: An F1 progeny of 180 individuals was obtained from a cross between two genetically distant accessions of M. acuminata, 'Borneo' and 'Pisang Lilin' (P. Lilin). Based on the gametic recombination of each parent, two parental maps composed of SSR and DArT markers were established. A significant proportion of the markers (21.7%) deviated (p < 0.05) from the expected Mendelian ratios. These skewed markers were distributed in different linkage groups for each parent. To solve some complex ordering of the markers on linkage groups, we associated tools such as tree-like graphic representations, recombination frequency statistics and cytogenetical studies to identify structural rearrangements and build parsimonious linkage group order. An illustration of such an approach is given for the P. Lilin parent. Conclusions: We propose a synthetic map with 11 linkage groups containing 489 markers (167 SSRs and 322 DArTs) covering 1197 cM. This first saturated map is proposed as a "reference Musa map" for further analyses. We also propose two complete parental maps with interpretations of structural rearrangements localized on the linkage groups. The structural heterozygosity in P. Lilin is hypothesized to result from a duplication likely accompanied by an inversion on another chromosome. This paper also illustrates a methodological approach, transferable to other species, to investigate the mapping of structural rearrangements and determine their consequences on marker segregation. (Résumé d'auteur

Application des techniques de culture in vitro a l'amelioration du bananier (Musa sp.)

SIGLECNRS T 55570 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Breeding for fruits

Working Groupe 2Breeding for fruit