Interspecific chromosomal rearrangements in monosomic addition lines of Allium.

Monosomic alien addition lines (MAALs) are useful for assigning linkage groups to chromosomes. We examined whether the chromosomal rearrangements following the introduction of a single onion (Allium cepa) chromosome into the Allium fistulosum genome were produced by homeologous crossing over or by a nonreciprocal conversion event. Among the monosomic lines available, 17 were studied by fluorescent genomic in situ hybridisation, using total A. cepa genomic DNA as the probe and total A. fistulosum genomic DNA as the competitor. In this way, rearrangements such as chromosomal translocations between A. cepa and A. fistulosum were identified as terminal regions consisting of tandem DNA repeats. Homeologous crossing over between the two closely related genomes occurred in 4 of the 17 lines, suggesting that such events are not rare. On the basis of a detailed molecular cytogenetic characterisation, we identified true monosomic alien addition lines for A. cepa chromosomes 3, 4, 5, 7, and 8 that can reliably be used in genetic studies.     

Chromosomal location of rDNA in Allium: in situ hybridization using biotin- and fluorescein-labelled probe

Summary A biotin- and fluorescein-labelled probe of Helianthus argophyllus has been used to map specific repeated rDNA sequences by in situ hybridization on mitotic chromosomes of Alliwn cepa, Allium fistulosum, a diploid interspecific (Allium fistulosum x Allium cepa) F₁ hybrid, and a triploid interspecific (2 x = A. cepa, 1 x = A. fistulosum) shallot. Hybridization sites were restricted to satellited and smallest pairs of chromosomes in both A. cepa and A. fistulosum. The number, size, and position of the hybridization sites distinguish homologous chromosomes and identify the individual chromosomes carrying the nucleolus organizing region (NOR) at the secondary constriction, as well as the individual chromosomes carrying an additional NOR. This in situ hybridization technique is the first reported in a plant species and offers new cytogenetic markers in Allium.     

Challenges facing European agriculture and possible biotechnological solutions

Agriculture faces many challenges to maximize yields while it is required to operate in an environmentally sustainable manner. In the present study, we analyze the major agricultural challenges identified by European farmers (primarily related to biotic stresses) in 13 countries, namely Belgium, Bulgaria, the Czech Republic, France, Germany, Hungary, Italy, Portugal, Romania, Spain, Sweden, UK and Turkey, for nine major crops (barley, beet, grapevine, maize, oilseed rape, olive, potato, sunflower and wheat). Most biotic stresses (BSs) are related to fungi or insects, but viral diseases, bacterial diseases and even parasitic plants have an important impact on yield and harvest quality. We examine how these challenges have been addressed by public and private research sectors, using either conventional breeding, marker-assisted selection, transgenesis, cisgenesis, RNAi technology or mutagenesis. Both national surveys and scientific literature analysis followed by text mining were employed to evaluate genetic engineering (GE) and non-GE approaches. This is the first report of text mining of the scientific literature on plant breeding and agricultural biotechnology research. For the nine major crops in Europe, 128 BS challenges were identified with 40% of these addressed neither in the scientific literature nor in recent European public research programs. We found evidence that the private sector was addressing only a few of these “neglected” challenges. Consequently, there are considerable gaps between farmer’s needs and current breeding and biotechnology research. We also provide evidence that the current political situation in certain European countries is an impediment to GE research in order to address these agricultural challenges in the future. This study should also contribute to the decision-making process on future pertinent international consortia to fill the identified research gaps.     

Global developments of genome editing in agriculture

Genome editing, particularly using of site-directed nucleases such as the CRISPR system, has spread rapidly through the biological sciences. Genome editing in crops could significantly speed up the progress of breeding programs. It could drive the development of traits in new crops and allow improvements in yield and pest resistance, adaptation to climate change, and industrial and pharmaceutical applications. However biofortification is a key challenge to satisfy nutritional needs in vitamins for developing countries and new consumer’s needs for developed countries. China and the USA lead scientific research in crop editing. Nigeria, being headquarters to numerous research consortia, is the most involved country in Africa. Genome editing in animals including pig, cattle, sheep, and carp, has not merely accelerated research but has made possible research that was previously unfeasible. It has been used to increase disease resistance, to make livestock better adapted to farming or environmental conditions, to increase fertility and growth, and to improve animal welfare. The USA, the UK and China are the most involved countries in animal genome editing. Global food production needs to increase as much as 70 per cent to support the growing population. Genome editing could contribute improving the efficiency of food distribution and reducing waste. Depending on the regulatory conditions, genome editing could open up the field to smaller companies and public labs.

     

Allozyme variation within and among populations of onion (Allium cepa L.) from West Africa

Local germplasm of onion (Allium cepa L.) in West Africa is threatened by extinction. Sixteen populations of onion collected in five countries in West Africa were investigated for isozyme polymorphism using four polymorphic enzyme systems (ADH, MDH, 6-PGDH and PGI) among nine enzyme systems assayed. This is the first report on the genetic diversity of local landraces of onion. The inheritance of two dimeric enzyme systems PGI and MDH was demonstrated using F₂ progeny arrays. The PGI system revealed a single locus with three alleles, and the MDH system revealed three loci with four alleles. Four polymorphic systems revealed nine alleles (adh-a1 and a2, mdh-c1 and c2, 6-pgdh-a1 and a2, and pgi-a1, a2 and a3) in the 16 local populations observed. The mean number of alleles per polymorphic locus was 2.25, and 67% of the alleles were present in all populations. Allele 6-pgdh-a2 was present in only two landraces (from Niger and Nigeria); it is considered to be a rare allele (frequency approximately 2%). Among the 16 populations, within-population diversity was greater (90%) than between-population diversity (10%). Genetic distance analyses showed an aggregate of all populations except for two, which originated from Nigeria, an English-speaking country. Received: 24 August 1995 / Accepted: 26 February 2001     

Evolution of genome size across some cultivated Allium species.

Allium L. (Alliaceae), a genus of major economic importance, exhibits a great diversity in various morphological characters and particularly in life form, with bulbs and rhizomes. Allium species show variation in several cytogenetic characters such as basic chromosome number, ploidy level, and genome size. The purpose of the present investigation was to study the evolution of nuclear DNA amount, GC content, and life form. A phylogenetic approach was used on a sample of 30 Allium species, including major vegetable crops and their wild allies, belonging to the 3 major subgenera Allium, Amerallium, and Rhizirideum and 14 sections. A phylogeny was constructed using internal transcribed spacer (ITS) sequences of 43 accessions representing 30 species, and the nuclear DNA amount and the GC content of 24 Allium species were investigated by flow cytometry. For the first time, the nuclear DNA content of Allium cyaneum and Allium vavilovii was measured, and the GC content of 16 species was measured. We addressed the following questions: (i) Is the variation in nuclear DNA amount and GC content linked to the evolutionary history of these edible Allium species and their wild relatives? (ii) How did life form (rhizome or bulb) evolve in edible Allium? Our results revealed significant interspecific variation in the nuclear DNA amount as well as in the GC content. No correlation was found between the GC content and the nuclear DNA amount. The reconstruction of nuclear DNA amount on the phylogeny showed a tendency towards a decrease in genome size within the genus. The reconstruction of life form history showed that rhizomes evolved in the subgenus Rhizirideum from an ancestral bulbous life form and were subsequently lost at least twice independently in this subgenus.     

A preliminary germplasm evaluation of onion landraces from West Africa.

Genetic erosion is observed in traditional populations of onion in West Africa. The present study aimed to assess the agronomical potential for six important traits of 14 landraces collected in West Africa. A multivariate procedure was used to establish a classification within this germplasm on the basis of these traits. The phenotypic variability both within and between landraces is considerable but could be due to traditional agricultural practices still occurring in this area. Three statistically coherent clusters have been identified despite the great phenotypic variation between landraces and could be a basis for building a core collection of West African onion germplasm. This first analysis of traditional onion landraces provides convincing information regarding their agronomic potential. Key words : Allium cepa L., onion, genetic resources, diversity.