Interspecific somatic hybrids between Solanum bulbocastanum and S. tuberosum and their haploidization for potato breeding.

Protoplast fusion between incongruent Solanum bulbocastanum and S. tuberosum haploids was accomplished to produce hybrids combining elite traits from both parents. We identified 11 somatic hybrids out of 42 regenerants analyzed through ISSR markers. Some hybrids had loss or gain of fragments compared to the parents, likely due to rearrangements and deletions of chromosome segments after fusion, and/or to somaclonal variation during hybrid regeneration. Increased heterotic vigor for some traits as well as high diversity was observed as the effect of both ploidy and fusion combination. Microsporogenesis analysis indicated the occurrence of multivalent configurations and several meiotic abnormalities, such as chromosomes bridges and various spindle orientations. Since all hybrids were sterile, in vitro anther culture was employed for haploidization as a possible strategy to overcome barriers to hybridizations. Haploids were obtained from all the tetraploid S. bulbocastanum (+) S. tuberosum somatic hybrids tested, although with differences in both the number of embryos per 100 anthers cultured and the number of differentiated green plantlets. This is the first report on the successful production of haploid plants from S. bulbocastanum (+) S. tuberosum hybrids

Analysis of 90 Mb of the potato genome reveals conservation of gene structures and order with tomato but divergence in repetitive sequence composition

<p>Abstract</p> <p>Background</p> <p>The Solanaceae family contains a number of important crop species including potato (<it>Solanum tuberosum</it>) which is grown for its underground storage organ known as a tuber. Albeit the 4^thmost important food crop in the world, other than a collection of ~220,000 Expressed Sequence Tags, limited genomic sequence information is currently available for potato and advances in potato yield and nutrition content would be greatly assisted through access to a complete genome sequence. While morphologically diverse, Solanaceae species such as potato, tomato, pepper, and eggplant share not only genes but also gene order thereby permitting highly informative comparative genomic analyses.</p> <p>Results</p> <p>In this study, we report on analysis 89.9 Mb of potato genomic sequence representing 10.2% of the genome generated through end sequencing of a potato bacterial artificial chromosome (BAC) clone library (87 Mb) and sequencing of 22 potato BAC clones (2.9 Mb). The GC content of potato is very similar to <it>Solanum lycopersicon </it>(tomato) and other dicotyledonous species yet distinct from the monocotyledonous grass species, <it>Oryza sativa</it>. Parallel analyses of repetitive sequences in potato and tomato revealed substantial differences in their abundance, 34.2% in potato versus 46.3% in tomato, which is consistent with the increased genome size per haploid genome of these two <it>Solanum </it>species. Specific classes and types of repetitive sequences were also differentially represented between these two species including a telomeric-related repetitive sequence, ribosomal DNA, and a number of unclassified repetitive sequences. Comparative analyses between tomato and potato at the gene level revealed a high level of conservation of gene content, genic feature, and gene order although discordances in synteny were observed.</p> <p>Conclusion</p> <p>Genomic level analyses of potato and tomato confirm that gene sequence and gene order are conserved between these solanaceous species and that this conservation can be leveraged in genomic applications including cross-species annotation and genome sequencing initiatives. While tomato and potato share genic features, they differ in their repetitive sequence content and composition suggesting that repetitive sequences may have a more significant role in shaping speciation than previously reported.</p

DNA-based technologies for grapevine biodiversity exploitation: state of the art and future perspectives

The cultivated grapevine, Vitis vinifera subsp. vinifera L., is represented by an enormous population of varieties and clones. They arise from the accumulation of gametic and somatic mutations during centuries of sexual and asexual propagation. These varieties represent a vast reservoir of traits/alleles that could be useful in improving the berry quality as well as against environmental stresses. However, most of them are still unexploited. For this reason, an efficient characterization system is essential to define the varietal identity, avoid cases of synonymy (identical genotypes but different names) and homonymy (same names but different genotypes) and deepen our understanding of the existing diversity within the grape germplasm. The plethora of DNA-based high-throughput technologies currently available provides promising tools for the analysis of diversity, overcoming many of the limitations of phenotypic-based diversity analyses. However, the analysis of intra-varietal diversity remains challenging. In this scenario, after summarizing the causes and consequences of grapevine genetic inter- and intra-varietal diversity, we review the DNA-based technologies used for varietal genotyping, emphasizing those able to distinguish clones within a variety. This review provides an update on the technologies used to explore grapevine diversity, the knowledge of which is necessary for an efficient exploitation and conservation of the grapevine germplasm

Autopolyploid inheritance and a heterozygous reciprocal translocation shape chromosome genetic behavior in tetraploid blueberry (Vaccinium corymbosum)

Understanding chromosome recombination behavior in polyploidy species is key to advancing genetic discoveries. In blueberry, a tetraploid species, the line of evidences about its genetic behavior still remain poorly understood, owing to the inter-specific, and inter-ploidy admixture of its genome and lack of in depth genome-wide inheritance and comparative structural studies. Here we describe a new high-quality, phased, chromosome-scale genome of a diploid blueberry, clone W85. The genome was integrated with cytogenetics and high-density, genetic maps representing six tetraploid blueberry cultivars, harboring different levels of wild genome admixture, to uncover recombination behavior and structural genome divergence across tetraploid and wild diploid species. Analysis of chromosome inheritance and pairing demonstrated that tetraploid blueberry behaves as an autotetraploid with tetrasomic inheritance. Comparative analysis demonstrated the presence of a reciprocal, heterozygous, translocation spanning one homolog of chr-6 and one of chr-10 in the cultivar Draper. The translocation affects pairing and recombination of chromosomes 6 and 10. Besides the translocation detected in Draper, no other structural genomic divergences were detected across tetraploid cultivars and highly inter-crossable wild diploid species. These findings and resources will facilitate new genetic and comparative genomic studies in Vaccinium and the development of genomic assisted selection strategy for this cro

Selection for aneuploid potato hybrids combining low wild genome content and resistance traits from Solanum commersonii

A breeding scheme based on the production of progenies with odd ploidy was followed to introduce useful genes from the wild Solanum commersonii (cmm) into S. tuberosum (tbr) genome. Hybrids from 5x x 4x crosses were characterized for traits of interest, and selection was assisted by amplified fragment length polymorphism (AFLP) analysis. As expected, most of the hybrids were aneuploids, with a trend towards a low degree of aneuploidy. Despite the fact that aneuploidy has often been associated with a reduction in male and female fertility, most of the hybrids were fertile following crosses with tbr, making it possible to produce viable offspring. A screening for resistance traits deriving from cmm was also carried out. With respect to freezing resistance, the killing temperatures of cold-acclimated genotypes were distributed between the wild and cultivated parental values, with some hybrids displaying an acclimation capacity higher than 3 degreesC. A wide variability was also found for tuber soft rot resistance, and hybrids with high levels of resistance were identified. Selection of hybrids was based on a two-stage scheme that consisted of conventional phenotypic selection followed by an estimation of the wild genome content still present in order to identify hybrids combining noteworthy traits with a low wild genome content. Previously selected cmm-specific AFLPs were used to monitor the degree of wild genome content still present in each hybrid. The percentage of cmm-specific markers ranged from 59% to 91%, with an average value of 75%. AFLP analysis was employed to assist in the selection of valuable hybrids for further breeding efforts