Segregation at Microsatellite Loci in Haploid and Diploid Gametes of Musa

Abstract

The triploid genome of plantain (Musa spp., AA group) has been considered intractable to genetic improvement because of the production of putatively homogeneous 2n (= 3x) gametes. Plantain breeding schemes have been based on the hybridization of 2n megaspores from the triploid plantain and haploid microspores from a wild diploid banana. The resultant fuli-sib populations of tetrapioid hybrids exhibited extreme variation in phenotypic characteristics. This study was conducted to analyze the genetic constitution of tetraploid hybrids in order to characterize the nature of the gametes from which they were derived. Parental genotypes were screened with 31 primer pairs specific to different Musa microsatcllite loci. Primers which detected polymorphisms between the parental genotypes were used to screen a population of 14 full-sib tetraploid hybrids. A subset of primers was also used to screen a population generated by self-pollination of the parental diploid banana. During analysis of the tetraploid hybrid population, 75% of the alleles donated by the maternal genotype (Obino I'Ewai) were observed to segregate. These data demonstrate the occurrence of recombination during the formation of 2n megaspores in triploid plantain. Analysis of the paternal diploid banana accession (Calcutta 4) and its selfed progeny suggests that this accession is highly heterozygous. These data demonstrate the importance of genetic characterization to Musa breeding, and also indicate that microsatellite markers are well suited for marker-assisted selection systems in Musa. p ILar~TA~N, a cultivated triploid (2n=3x=33) giant perennial herb, is a natural interspecific hybrid between the two wild species, M. acuminata Colla. and M. balbisiana Colla., which provided the A and B genomes, respectively (Simmonds and Shepherd, 1955). The crop is now among the most important staple food crops in the tropical humid forest regions of Africa and South America (FAO, 1994). Plantain has been considered intractable to genetic improvement (DeLanghe, 1976; Rowe, 1984). However, this hypothesis has recently been challenged by the identification of several hundred hybrids from crosses between fertile triploid plantain (AAB) landraces and wild diploid accessions of M. acuminata (AA). The generation of tetraploid Musa hybrids at IITA followed a breeding scheme based on ploidy manipulation. Haploid gametes were donated by the wild banana M. acuminata ssp. burmannica clone Calcutta 4, and 2n (=3x) gametes were donated by a triploid plantain landrace. Crosses between maternal triploid and paternal diploid

Molecular and cytological characterization of the global Musa germplasm collection provides insights into the treasure of banana diversity

“…2. Briefly, 19 SSR loci (Lagoda et al 1998;Crouch et al 1998;Hippolyte et al 2010) that are well distributed across ten of the eleven Musa genetic linkage groups (Hippolyte et al 2010) were amplified using a set of M13-tailed specific primers to allow universal labelling with fluorescent dyes. Although new SSR markers are accessible thanks to the Musa genome sequence assembly completion (D'Hont et al 2012;Martin et al 2016), the hitherto used marker set was not enlarged, as the reproducibility and comparability of results gathered until now would then not be assured and a re-start of the whole genotyping effort would be inefficient.…”

“…In, Christelová et al (2011) established a standardized procedure for genotyping Musa accessions with 19 SSR markers, which were selected from a larger set of SSR markers developed by Crouch et al (1998), Lagoda et al (1998) and Hippolyte et al (2010). This resulted in the establishment of the Musa Genotyping Centre (MGC) in Olomouc, Czech Republic, under the auspices of Bioversity International.…”

SCAR Marker for the A Genome of Bananas (Musa spp. L.) Supports Lack of Differentiation between the A and B Genomes

“…The plants were selected to represent a wide range of genomic groups that include landraces and synthetic hybrids of known genomic compositions. Genomic DNA was extracted from the samples according to the CTAB procedure (Crouch, Crouch, Jarret, Cregan, & Ortiz, 1998). The DNA samples were quantified according to the protocol using NanoDrop 2000cUV-Vis spectrophotometer (ThermoScientific, Miami, FL) and diluted to 40 ng/µl using TE buffer.…”

Genetic diversity study of some banana genotypes collected from various parts of India through RAPD analysis

“…In view of developing efficient breeding schemes, additional data needs to be generated on the complex genome structure of hybrids and cultivars. To this end, the characterization of indigenous germplasms will offer a precise means of formulating taxonomic, phylogenetic and heterotic groupings within the family Musaceae (Crouch et al, 1998). Cheesman (1948) first suggested that cultivated bananas originated from intra and interspecific hybridization between the two wild diploid species Musa acuminata Colla and Musa balbisiana Colla, each contributing the A and B genomes, respectively.…”