Sebastião de Oliveira e Silva

Genetic diversity and population structure of Musa accessions in ex situ conservation

BackgroundBanana cultivars are mostly derived from hybridization between wild diploid subspecies of Musa acuminata (A genome) and M. balbisiana (B genome), and they exhibit various levels of ploidy and genomic constitution. The Embrapa ex situ Musa collection contains over 220 accessions, of which only a few have been genetically characterized. Knowledge regarding the genetic relationships and diversity between modern cultivars and wild relatives would assist in conservation and breeding strategies. Our objectives were to determine the genomic constitution based on Internal Transcribed Spacer (ITS) regions polymorphism and the ploidy of all accessions by flow cytometry and to investigate the population structure of the collection using Simple Sequence Repeat (SSR) loci as co-dominant markers based on Structure software, not previously performed in Musa.ResultsFrom the 221 accessions analyzed by flow cytometry, the correct ploidy was confirmed or established for 212 (95.9%), whereas digestion of the ITS region confirmed the genomic constitution of 209 (94.6%). Neighbor-joining clustering analysis derived from SSR binary data allowed the detection of two major groups, essentially distinguished by the presence or absence of the B genome, while subgroups were formed according to the genomic composition and commercial classification. The co-dominant nature of SSR was explored to analyze the structure of the population based on a Bayesian approach, detecting 21 subpopulations. Most of the subpopulations were in agreement with the clustering analysis.ConclusionsThe data generated by flow cytometry, ITS and SSR supported the hypothesis about the occurrence of homeologue recombination between A and B genomes, leading to discrepancies in the number of sets or portions from each parental genome. These phenomenons have been largely disregarded in the evolution of banana, as the “single-step domestication” hypothesis had long predominated. These findings will have an impact in future breeding approaches. Structure analysis enabled the efficient detection of ancestry of recently developed tetraploid hybrids by breeding programs, and for some triploids. However, for the main commercial subgroups, Structure appeared to be less efficient to detect the ancestry in diploid groups, possibly due to sampling restrictions. The possibility of inferring the membership among accessions to correct the effects of genetic structure opens possibilities for its use in marker-assisted selection by association mapping.

Comportamento de variedades e híbridos de bananeira (Musa spp.), em dois ciclos de produção no sudoeste da Bahia

The objective of this work was to characterize and evaluate the behavior of 13 banana genotypes (varieties and hybrids) AAA, AAAA, AAB and AAAB genomic groups, in two production cycles in southwest Bahia, using relevant phenotypic descriptors for the identification and selection of superior individuals. The Prata Ana and Pacovan (AAB), Grande Naine and Nanicao (AAA) varieties and the hybrids PA42-44, Pacovan Ken, Japira, Preciosa and ST12-31 (AAAB) and Ambrosia, Calipso, Bucaneiro and FHIA02 (AAAA), selected at Embrapa Cassava and Fruit Crops, were evaluated. The experimental design was in random blocks, with 13 treatments, five repetitions, 20 plants per plot, six useful and 3.00 m x 2.00 m spacing. The following characteristics were considered: Plant height, pseudostem perimeter, number of live leaves during flowering and harvest, number of days from planting to flowering and until harvest, bunch and hand weight, number of fruits, weight, length and diameter of fruit. Grande Naine, and Nanicao stood out for the characteristics of bunch and hand weight, number of fruits, fruit weight and length; the FHIA-02 hybrid presented greater fruit diameter in both production cycles and the earliest flowering and harvest in the second cycle; Calipso was the latest for harvest; ST12-31 was the tallest in height; the Prata Ana variety stood out for number of live leaves during flowering and harvest; the Prata type hybrids, PA42-44, Pacovan Ken, Preciosa and Japira, stood out for the parameters related to fruit quality when compared to its genitors Prata Ana and Pacovan, respectively; there was an increment of the parameters that reflected vegetative growth and yield from the first to the second production cycle for all genotypes evaluated.

Características agronômicas de genótipos de bananeira em três ciclos de produção em Rio Branco, AC

O objetivo deste trabalho foi avaliar caracteristicas agronomicas de genotipos de bananeira, em tres ciclos de producao. O experimento foi realizado em blocos ao acaso, com parcelas subdivididas e cinco repeticoes, em Rio Branco, AC. Os genotipos Preciosa, Japira, Pacovan Ken, Pacovan, PA42-44, Prata-ana, ST12-31, FHIA 02, Nanicao, Grande Naine, Calipso, Ambrosia e Bucaneiro foram avaliados quanto aos caracteres: altura da planta; diâmetro do pseudocaule; numero de folhas vivas na floracao e na colheita; ciclo de formacao do cacho da floracao a colheita; numero de pencas por cacho; massa do fruto e do cacho; e produtividade. As cultivares Preciosa e Pacovan Ken apresentaram as maiores alturas, e os hibridos PA42-44 e FHIA 02, e as cultivares Prata-ana, Nanicao e Grande Naine, o porte mais baixo. As cultivares Nanicao, Ambrosia, Bucaneiro, Pacovan, Prata-ana e Grande Naine e o hibrido ST12-31 apresentaram os menores numeros de folhas vivas na colheita. A cultivar Preciosa e o hibrido FHIA 02 foram os mais produtivos. Os hibridos PA42-44 e FHIA 02 apresentam caracteristicas agronomicas promissoras e podem ser incorporados ao sistema produtivo, assim como os hibridos de Pacovan, ja adaptados e recomendados para o cultivo no Estado do Acre.

Agronomic and molecular characterization of diploid improved banana genotypes.

An investigation about the genetical diversity among eleven banana diploid genotypes using nine agronomical characteristics and sixteen microsatellite markers was implanted at Embrapa Cassava and Tropical Fruits, Cruz das Almas (BA), Brazil. The generalized distance of Mahalanobis indicated the presence of genetic diversity. The genotypes were grouped into tree clusters. Among the investigated characteristics, the plant height, number of bunchs, number of fruits per bunch and pseudostem exhibited high contribution towards genetic divergence. The average number of alleles per primer was 7.51, with a total of 120 alleles identified. The average similarity among the all diploid was 0.44, range from 0.29 up to 0.60. New parental combinations can be identified with base of the divergence between these diploids, contributing for development of new improved diploids preventing the narrow genetic base and creating new genetic variability for selection.

Agronomic and molecular characterization of gamma ray induced banana (Musa sp.) mutants using a multivariate statistical algorithm

Bananas are tropical fruits grown worldwide playing a key role in market trade and especially used as main food source for low income populations. In Brazil, bananas are mainly consumed in natura, occupying the second largest internal market. Nevertheless, this crop presents low availability of productive commercial varieties with good agronomic characteristics. A strategy undertaken to solve this problem is the development of new cultivars through conventional genetic breeding methods. However, this strategy presents some obstacles such as female sterility and low number of seeds. In order to overcome these shortcomings, use of mutation induction aiming the selection of mutants with desirable agronomic characteristics seems to have great potential for developing new cultivars. The objective of the present work was to evaluate the genetic variability in putative banana ‘Pacovan’ (AAB genome, subgroup Prata Type) mutants submitted to gamma ray irradiation, using a set of agronomical and molecular data (ISSR markers). The distance between the putative ‘Pacovan’ mutants varied from 0.26 to 0.64 with cophenetic correlation coefficient of 0.7669. Four mutants were selected based on best agronomical characteristics and height. This data also shows that there is variability that can be explored after the irradiation of ‘Pacovan’ banana mutants, which can be used in the genetic breeding program of banana aiming to develop short new varieties that also present good agronomic characteristics. This is the first attempt to use combined data in order to evaluate the genetic variability in putative banana mutants.

Bap concentration and tetraploid banana micropropagation efficiency (AAAB group)

The objective of the present work was to establish an efficient procedure for the in vitro production of tetraploid banana plantlets (Musa sp. cv. FHIA-01, AAAB group). The cloning effect on the in vitro development of the explants, the rates of contamination and multiplication, and the level of oxidation in culture media with five benzylaminopurine (BAP) concentrations were studied. In the phase of in vitro introduction of explants, a high level of contamination (22.32%), caused mainly by bacteria, was observed. However, the degree of contamination decreased along the subcultures, reaching 1.07% in the eighth subculture. Higher multiplication rates were obtained, averaging 2.65 per subculture, on the MS media supplemented with 4.0 mg L-1 BAP, leading to an estimated production of 584 and 3451 plantlets/initial explant after the 6th and 8th subculture, respectively. A pronounced effect of the cloning on multiplication was observed. Acclimatization efficiency of plantlets was 94%. Somaclonal variations were not observed among in vitro micropropagated plantlets under greenhouse conditions.

Genótipos de bananeira em três ciclos na Zona da Mata Mineira

The objective of this work was to evaluate during three cycles the main vegetative characteristics of the genotypes Prata Ana, Grande Naine, Caipira, Nam, Pioneira, FHIA-01, FHIA-18, PV03-44 and SH3640, aiming to incorporate new genotypes to commercial production systems. An experiment was carried out at Zona da Mata Mineira region during three crop cycles, in randomized block design, with nine treatments (genotypes) and three replications (cycles). Height, precocity, number of leaves, resistance to Yellow Sigatoka and plant suckers were evaluated. The variety Grande Naine had the lower height, while Prata Ana, FHIA-01 and SH3640, the larger diameter. The genotypes that presented higher precocity were Pioneira and FHIA-18. The varieties Nam and Caipira presented the highest numbers and precocity of suckers. The genotypes FHIA-01, FHIA-18 and SH3640 were superiors in relation to the characteristics evaluated.

Suscetibilidade à queda natural e caracterização dos frutos de diversos genótipos de bananeiras

Natural fruit dropping of ripe bananas in result of individual separation of fruits from the hand crown, is called finger drop, this characteristic is undesirable and would limit the marketing of new cultivars. Fruits that stand out in the hand have a reduced shelf life, and do not present a pleasant appearance for customers. This study was carried out in order to quantify the susceptibility to natural fruit dropping in fruits from different genomic groups and ploidies, and to identify correlations between natural dropping and various physical fruit characteristics. Diploid, triploid e tetraploid banana plants from several genomic groups were used, altogether 37 genotypes. The physical characteristics were used in a variance analysis and the results compared with the Scott-Knott test. Results proved the high resistance against dropping among genotypes that belong to the genomic group BB (Butuhan, Pirai and BB Franca), Terra (AAB), Poteau Nain (fig type) (ABB) and Thap Maeo (AAB), while Prata-Ana (AAB), Grande Naine (AAA), Ambrosia (AAAA), Ouro (AA) and FHIA 18 (AAAB) presented intermediate values of dropping resistance. Among banana plants with low resistence, the improved hybrids Pioneira (AAAB), YB42-21 (AAAB), Buccaneer (AAAA) and Calypso (AAAA) and the cultivar Ouro da Mata (AAAB) were outstanding. A higher positive correlation between fruit firmness and resistance toward finger drop could be verified. The study of genotype and ploid groups indicated a greater resistance against dropping among banana plants belonging to the BB group and ABB and AAB triploid genotypes.

Avaliação das cultivares de bananeira Prata-Anã, Thap Maeo e Caipira em diferentes sistemas de plantio no norte de Minas Gerais

Banana is one of the tropical fruits more consumed in the world, answering for approximately 10% of the world trade of fruits. The purpose of this work was to evaluate the growth and production of three banana cultivars under three planting systems, in two production cycles, in the period from March 2004 to October 2006, in Janauba, Minas Gerais. The experimental design was in randomized blocks and two statistical analyses: first: Prata Ana in six different planting systems; second: factorial 2 x 2 + 1, with four repetitions and six useful plants per parcel. The evaluated characteristics were: plant height, pseudostem circumference, total number of leaves, number of green leaves in the crop, number of days from planting to harvest, bunch weight, productivity, number of hands and fingers per bunch. The appraised characteristics were submitted to the variance analysis, being the treatments effects compared by the test of Tukey to 5% of probability. The cultivar mixture and the usage of borders did not influence most of the growth characteristics on the three studied cultivars. The cultivar Thap Maeo was superior to the Caipira in most of the appraised characteristics in the first and second cycles. The planting system with one border was superior. The analysis of the cultivar Prata Ana presented significant difference for the characteristics of green leaves number in the crop in the second cycle, number of hands/ bunch and number of fingers/bunch inside of the six planting systems.

Estimativas de tamanho de parcelas para avaliação de descritores fenotípicos em bananeira

The aim of this work was to estimate the adequate size of experimental plots, for the evaluation of phenotypic descriptors in banana, from a trial of uniformity with the cultivar Tropical, in the spacing of 3x2 m, in a useful area with nine rows of 40 plants. The following variables were evaluated: plant height; pseudostem perimeter; number of emitted suckers and number live leaves, during flowering and at harvest; weight of the bunch and the hands; number of hands and fruits; weight of the second hand; weight, length and diameter of the fruit, in two cycles of production. The plants, considered the basic units, were combined to form various sizes of plots. The data were submitted to the analysis of variance in the hierarchical model. Plot size was estimated by the methods of maximum curvature, modified maximum curvature and comparison of variances. Heterogeneity index of the soil and the detectable difference among treatments mean were determined. The variability increased between cycles with reflexes in the estimates of the plot sizes, which varied with the method used, the variable evaluated and the production cycle. The modified maximum curvature method presents more adjusted estimates. Plots with six basic units (36 m2) are appropriate to evaluate with precision the phenotypic descriptors in the bananas.