In vitro Induction and Phenotypic Variations of Autotetraploid Garlic (Allium sativum L.) With Dwarfism

Tetraploidization Altered Phenotypic Traits and Metabolite Profile of Java Ginseng (Talinum paniculatum (Jacq.) Gaertn.)

Polyploidization is a beneficial technique for enhancing the biomass of and secondary metabolite concentrations in plants. Java ginseng (Talinum paniculatum (Jacq.) Gaertn.) can be used as an alternative source of nutrition and has both ornamental and medicinal value. To improve the biomass and content of medicinal ingredients, this study established an in vitro system that was used to induce polyploidy of java ginseng. Tetraploids were successfully produced by exposing the axillary buds to colchicine. The most favorable medium for inducing polyploidy was Murashige and Skoog medium devoid of hormonal substances, while immersing stem segments in a solution of 1-3 mg/mL colchicine for 48 h could achieve tetraploidy induction with a maximum rate of 18.03%. Tetraploids were distinguished from diploids by flow cytometry, with the tetraploids exhibiting darker and thicker leaves, bigger fruit and pollen, and larger stomata but lower stomatal density, while the aboveground biomass yield was reduced significantly compared with that of the diploids. Tetraploidization also altered the metabolite profile, with 22 metabolite concentrations being significantly increased (p < 0.05) and 74 metabolite concentrations being significantly decreased (p < 0.05) in the leaves of the tetraploids. The autotetraploid produced in this study could provide novel insights into artificial polyploid breeding and could be utilized as a germplasm to generate new polyploids.

Evaluation of host status of garlic varieties for a plant-parasitic nematode, Ditylenchus destructor, by using in vitro inoculation

Ditylenchus destructor is a plant-parasitic nematode that severely damages garlic (Allium sativum L.) in Japan. D. destructor is detected in roots, bulbs, and outer bulb skins of garlic at harvest; however, the resistance of garlic to D. destructor infection is not well understood. Here, we investigated the propagation of D. destructor in storage organs and roots using in vitro plantlets of six Japanese garlic varieties to exclude the effects of microbes and to uniform growing conditions. In vitro inoculation can proceed simultaneously with vegetative growth, storage organ formation of garlic plantlets, and D. destructor infection. In 'Fukuchi-white', a variety susceptible to D. destructor, nematodes successfully propagated in storage organs and roots. Furthermore, the nematodes invaded and propagated in the newly formed storage organs. By contrast, 'Kirishima', 'Hirado', and 'Shishimaru' substantially suppressed more the propagation of the nematodes in storage organs and roots than 'Fukuchi-white'. Additionally, the propagation of nematodes in newly formed storage organs was inhibited in these three varieties. 'Shishimaru' showed unique responses to D. destructor infection: nematode propagation was the lowest among six varieties in inoculation tests and the nematode-inoculated cloves turned brown. Our results suggest that several garlic varieties have resistance mechanisms that suppress the propagation of D. destructor in storage organs and roots, and that in vitro inoculation methods are useful for selecting resistant garlic varieties. These findings will help developing novel D. destructor-resistant garlic varieties and our further understanding of garlic-nematode interactions.

Turning Garlic into a Modern Crop: State of the Art and Perspectives

Garlic is cultivated worldwide for the value of its bulbs, but its cultivation is challenged by the infertility of commercial cultivars and the accumulation of pathogens over time, which occurs as a consequence of vegetative (clonal) propagation. In this review, we summarize the state of the art of garlic genetics and genomics, highlighting recent developments that will lead to its development as a modern crop, including the restoration of sexual reproduction in some garlic strains. The set of tools available to the breeder currently includes a chromosome-scale assembly of the garlic genome and multiple transcriptome assemblies that are furthering our understanding of the molecular processes underlying important traits like the infertility, the induction of flowering and bulbing, the organoleptic properties and resistance to various pathogens.

The creation of autotetraploid provides insights into critical features of DNA methylome changes after genome doubling in water spinach (Ipomoea aquatica Forsk)

Water spinach (Ipomoea aquatica Forsk) is an essential green leafy vegetable in Asia. In this study, we induced autotetraploid water spinach by colchicine. Furthermore, DNA methylation and transcriptome of tetraploid and diploid were compared using Whole Genome Bisulfite Sequencing (WGBS) and RNA-sequencing techniques. Autotetraploid water spinach was created for the first time. Compared with the diploid parent, autotetraploid water spinach had wider leaves, thicker petioles and stems, thicker and shorter adventitious roots, longer stomas, and larger parenchyma cells. The whole genome methylation level of the autotetraploid was slightly higher than that of the diploid. Compared with the diploid, 12281 Differentially Methylated Regions (DMRs)were found in the autotetraploid, including 2356 hypermethylated and 1310 hypomethylated genes, mainly enriched in 'Arginine and Proline metabolism', 'beta - Alanine metabolism', 'Plant homone signal translation', 'Ribome', and 'Plant - pathgen interaction' pathways. Correlation analysis of transcriptome and DNA methylation data showed that 121 differentially expressed genes undergone differential methylation, related to four pathways 'Other types of O-glycan biosynthesis', 'Terpenoid backbone biosynthesis', 'Biosynthesis of secondary metabolites', and 'Metabolic paths'. This work obtained important autotetraploid resources of water spinach and revealed the genomic DNA methylation changes after genome doubling, being helpful for further studying the molecular mechanism of variations caused by polyploids of the Ipomoea genus.