Karyotype differentiation in cultivated chickpea revealed by Oligopainting fluorescence in situ hybridization

Chickpea (Cicer arietinum L.) is one of the main sources of plant proteins in the Indian subcontinent and West Asia, where two different morphotypes, desi and kabuli, are grown. Despite the progress in genome mapping and sequencing, the knowledge of the chickpea genome at the chromosomal level, including the long-range molecular chromosome organization, is limited. Earlier cytogenetic studies in chickpea suffered from a limited number of cytogenetic landmarks and did not permit to identify individual chromosomes in the metaphase spreads or to anchor pseudomolecules to chromosomes in situ. In this study, we developed a system for fast molecular karyotyping for both morphotypes of cultivated chickpea. We demonstrate that even draft genome sequences are adequate to develop oligo-fluorescence in situ hybridization (FISH) barcodes for the identification of chromosomes and comparative analysis among closely related chickpea genotypes. Our results show the potential of oligo-FISH barcoding for the identification of structural changes in chromosomes, which accompanied genome diversification among chickpea cultivars. Moreover, oligo-FISH barcoding in chickpea pointed out some problematic, most probably wrongly assembled regions of the pseudomolecules of both kabuli and desi reference genomes. Thus, oligo-FISH appears as a powerful tool not only for comparative karyotyping but also for the validation of genome assemblies

Chromosome painting facilitates anchoring reference genome sequence to chromosomes In Situ and integrated karyotyping in banana (Musa Spp.)

Open Access Journal; Published online: 20 Nov 2019Oligo painting FISH was established to identify all chromosomes in banana (Musa spp.) and to anchor pseudomolecules of reference genome sequence of Musa acuminata spp. malaccensis “DH Pahang” to individual chromosomes in situ. A total of 19 chromosome/chromosome-arm specific oligo painting probes were developed and were shown to be suitable for molecular cytogenetic studies in genus Musa. For the first time, molecular karyotypes of diploid M. acuminata spp. malaccensis (A genome), M. balbisiana (B genome), and M. schizocarpa (S genome) from the Eumusa section of Musa, which contributed to the evolution of edible banana cultivars, were established. This was achieved after a combined use of oligo painting probes and a set of previously developed banana cytogenetic markers. The density of oligo painting probes was sufficient to study chromosomal rearrangements on mitotic as well as on meiotic pachytene chromosomes. This advance will enable comparative FISH mapping and identification of chromosomal translocations which accompanied genome evolution and speciation in the family Musaceae

Filling the gaps in gene banks: Collecting, characterizing, and phenotyping wild banana relatives of Papua New Guinea.

International audienceSince natural habitats are disappearing fast, there is an urgent need to collect, characterize, and phenotype banana (Musa spp.) crop wild relatives to identify unique genotypes with specific traits that fill the gaps in our gene banks. We report on a collection mission in Papua New Guinea carried out in 2019. Seed containing bunches were collected from Musa peekelii ssp. angustigemma (N.W.Simmonds) Argent (3), M. schizocarpa N. W. Simmonds (4), M. balbisiana Colla (3), M. acuminata ssp. banksii (F. Muell.) Simmonds (14), M. boman Argent (3), M. ingens Simmonds (2), M. maclayi ssp. maclayi F.Muell. ex Mikl.-Maclay (1), and M. lolodensis Cheesman (1). This material, together with the seeds collected during a previous mission in 2017, form the basis for the development of a wild banana seed bank. For characterization and phenotyping, we focused on the most ubiquitous indigenous species of Papua New Guinea: M. acuminata ssp. banksii, the ancestor of most edible bananas. We calculated that the median genomic dissimilarity of the M. acuminata ssp. banksii accessions was 4% and that they differed at least 5% from accessions present in the International Transit Centre, the world's largest banana gene bank. High-throughput phenotyping revealed drought avoidance strategies with significant differences in root/shoot ratio, soil water content sensitivity, and response towards vapor pressure deficit (VPD). We deliver a proof of principle that the wild diversity is not yet fully covered in the gene banks and that wild M. acuminata ssp. banksii populations contain individuals with unique traits, useful for drought tolerance breeding programs

Fonio millet genome unlocks African orphan crop diversity for agriculture in a changing climate

International audienceSustainable food production in the context of climate change necessitates diversification of agriculture and a more efficient utilization of plant genetic resources. Fonio millet (Digitaria exilis) is an orphan African cereal crop with a great potential for dryland agriculture. Here, we establish high-quality genomic resources to facilitate fonio improvement through molecular breeding. These include a chromosome-scale reference assembly and deep re-sequencing of 183 cultivated and wild Digitaria accessions, enabling insights into genetic diversity, population structure, and domestication. Fonio diversity is shaped by climatic, geographic, and ethnolinguistic factors. Two genes associated with seed size and shattering showed signatures of selection. Most known domestication genes from other cereal models however have not experienced strong selection in fonio, providing direct targets to rapidly improve this crop for agriculture in hot and dry environments