Comparative study of rbcL gene sequences in Fagopyrum and related taxa

Genetic and genomic research for the development of an efficient breeding system in heterostylous self-incompatible common buckwheat (Fagopyrum esculentum)

Common buckwheat (Fagopyrum esculentum Moench; 2n = 2x = 16) is an annual crop that is cultivated widely around the world and contains an abundance of nutrients and bioactive compounds. However, the yield of buckwheat is low compared to that of other major crops, and it contains proteins that cause allergic reactions in some people. Much research has aimed to improve or eliminate these undesirable traits, and some major advances have recently been made. Here, we review recent advances in buckwheat breeding materials, tools, and methods, including the development of self-compatible lines, genetic maps, a buckwheat genome database, and an efficient breeding strategy. We also describe emerging breeding methods for high-value lines.

Development of SSR markers for studies of diversity in the genus Fagopyrum

The numbers of SSR markers and their utilization have not been determined and investigated as extensively in Fagopyrum species as compared to other crop species. The current report presents 136 new SSR markers in Fagopyrum esculentum ssp. esculentum and their application to related species in the genus Fagopyrum. Of the 136 SSRs, 10 polymorphic SSR markers were utilized in a genetic diversity analysis of a common buckwheat population consisting of 41 accessions of diverse origin. The study showed observed (H(O)) and expected (H(E)) heterozygosities ranging from 0.071 to 0.924 (mean = 0.53) and from 0.073 to 0.902 (mean = 0.412), respectively. Forty-one of the 136 SSRs amplified sequences in other Fagopyrum species, including the cymosum and urophyllum groups. The phylogenetic relationships revealed using the SSRs was consistent with results obtained using other marker systems, with one exception. The sequence and diversity information obtained using these new SSRs and their cross-transferability to related Fagopyrum species will increase our understanding of genetic structures and species relationships within the Fagopyrum genus.

Construction of a BAC library for buckwheat genome research - an application to positional cloning of agriculturally valuable traits

We have constructed a BAC library for common buckwheat Fagopyrum esculentum Moench. The library includes 142,005 clones with an average insert size of approximately 76 kb, equivalent to approximately a 7 to approximately 8-fold coverage of the genome. Polymerase chain reaction based screening of the library with AGAMOUS and FLORICAULA/LEAFY primers, has identified 7 and 9 BACs, respectively, which are consistent with the genome coverage. This library represents the first large insert genomic library for F. esculentum and it can be served as a genetic resource facilitating agricultural, pharmacological, physiological, and evolutionary studies of the species. To demonstrate the utilization of the library for characterizing agriculturally valuable traits, we developed a sequence tagged site marker tightly linked to the dwarf E locus as well as to the self-incompatibility complex locus and screened the library to initiate positional cloning of the causative genes.

Phylogenetic relationships among Fagopyrum species revealed by the nucleotide sequences of the ITS region of the nuclear rRNA gene

The DNA sequences of the internal transcribed spacer (ITS) region of the rRNA gene were determined in 20 taxa of 12 species of Fagopyrum. By comparing the sequence data and constructing phylogenetic trees, the phylogenetic relationships among the Fagopyrum species were established. The sequences of ITS (ITS1 and ITS2) were about 3-7 times more variable than those of the 5.8S subunit of the rRNA gene. The classification of Fagopyrum species based on the DNA sequences of the rRNA gene almost coincides with the classification based on morphology, allozyme variability, and nucleotide sequences of the rbcL-accD region of the chloroplast DNA. A close relationship of F. lineare with the F. statice-F. leptopodum clade was suggested and this was strongly supported by a 68-bp gap in ITS1 found in these three species. A tetraploid F. cymosum from Kathi, India, has two distinct rRNA genes probably on homoeologous chromosomes, and was distinguished from the clade of other diploid/tetraploid F. cymosum with a high bootstrap value. This strengthened the hypothesis of the polyphyletic origin of the tetraploid F. cymosum.