Karyotype,genome size,and in vitro chromosome doubling of Pfaffia glomerata (Spreng.) Pedersen

Pfaffia glomerata (Spreng.) Pedersen, known worldwide as Brazilian ginseng, has an important commercial value due to its pharmaceutical properties. In addition to the newly described karyological traits and the first estimation of DNA content, this study reports a protocol for the successful induction of tetraploidy. Natural diploid individuals (2n = 34) showed a symmetric karyotype, centromeric DAPI⁺ bands, one chromosome pair with a CMA⁺ band and 45S rDNA site and another with one 5S rDNA site. To induce chromosome duplication, small nodal buds were cultured in semi-solid MS-based medium with 2.22 μM BA, 2.69 μM NAA, and colchicine or oryzalin at 10, 15, 20, 25, and 30 μM for 1 or 2 weeks before being transferred to MS basal medium. The results showed that colchicine induced tetraploid plants, mainly after 1 week of exposure, whereas oryzalin treatment induced only mixoploid plants. The tetraploid plants exhibited twice the chromosome number and DNA content and twice the number of chromosome markers observed for the diploids. Chromosome duplication reduced the dry mass of the stems and roots of the polyploid plants compared to the diploids, and the stomatal density was also reduced on the abaxial and adaxial leaf surfaces of the polyploids. Additionally, the production of β-ecdysone was 50 % higher in the tetraploids than in the diploids. Thus, chromosome doubling showed that is possible to increase the content of β-ecdysone, highlighting the considerable potential of this technique to produce new cultivars with high commercial value.     

Inheritance of seed phytate and phosphorus levels in common bean (Phaseolus vulgaris L.) and association with newly-mapped candidate genes

Common bean (Phaseolus vulgaris L.) is an important, high-quality staple food that provides large amounts of protein and mineral micronutrients to the diets of people in many countries. Phytates are a storage form of organic phosphorus which is used by the plant in various stages of growth and development but can have certain anti-nutrient properties due to chelation of minerals such as iron and zinc. At the same time, phytates provide certain health benefits and therefore are the subject of both mutagenesis and breeding programs for functional foods. The objective of this study was to evaluate the quantitative trait loci (QTL) associated with seed phytate and seed phosphorus concentration and content on a per-seed basis and to develop functional molecular markers for genes from the phytic acid synthesis pathway. We used a well-characterized mapping population, DOR364?×?G19833, in three field experiments with three repetitions each and two levels of soil phosphorus fertilization, as well as a large set of previously and newly developed primer pairs for the genes myo-inositol (3)P₁ synthase, myo-inositol kinase and various inositol kinases. We identified an association of phytate concentration QTL with one of two paralogs of the myo-inositol (3)P₁ synthase gene family, located on linkage group b01 and expressed in common bean seed rather than in vegetative tissues. We also identified QTL for phytate concentration on linkage group b06 and phytate content on linkage groups b03, b04 and b10. We provide a synteny analysis based on common bean versus soybean genome comparisons of all the phytic acid pathway genes that were genetically mapped and indicate flanking markers that can be used for marker-assisted selection when the genes themselves are not polymorphic as PCR amplicons. We can conclude that natural variability in phytate levels is controlled by the seed-expressed myo-inositol (3)P₁ synthase gene (MIPS) as well as other loci in the common bean genome. This means that breeding of phytate levels in common bean must take into account allele variability at certain candidate genes, such as this seed MIPS gene, a recently cloned ABC trasnporter and additional QTL for the trait, which underlie the oligogenic inheritance for phytate concentration in common bean.