title: Reduced generation time of apple seedlings to within a year by means of a plant virus vector: a new plant-breeding technique with no transmission of genetic modification to the next generation.
abstract: Fruit trees have a long juvenile phase. For example, the juvenile phase of apple (Malus × domestica) generally lasts for 5-12 years and is a serious constraint for genetic analysis and for creating new apple cultivars through cross-breeding. If modification of the genes involved in the transition from the juvenile phase to the adult phase can enable apple to complete its life cycle within 1 year, as seen in herbaceous plants, a significant enhancement in apple breeding will be realized. Here, we report a novel technology that simultaneously promotes expression of Arabidopsis FLOWERING LOCUS T gene (AtFT) and silencing of apple TERMINAL FLOWER 1 gene (MdTFL1-1) using an Apple latent spherical virus (ALSV) vector (ALSV-AtFT/MdTFL1) to accelerate flowering time and life cycle in apple seedlings. When apple cotyledons were inoculated with ALSV-AtFT/MdTFL1 immediately after germination, more than 90% of infected seedlings started flowering within 1.5-3 months, and almost all early-flowering seedlings continuously produced flower buds on the lateral and axillary shoots. Cross-pollination between early-flowering apple plants produced fruits with seeds, indicating that ALSV-AtFT/MdTFL1 inoculation successfully reduced the time required for completion of the apple life cycle to 1 year or less. Apple latent spherical virus was not transmitted via seeds to successive progenies in most cases, and thus, this method will serve as a new breeding technique that does not pass genetic modification to the next generation.
authors.affiliation: Faculty of Agriculture, Iwate University, Morioka, Japan.
authors.forename: Noriko
authors.initials: N
authors.lastname: Yamagishi
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Kishigami
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yoshikawa
mesh_terms: D035264:Flowers / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D027845:Malus / Q000235:genetics* / Q000502:physiology*; D010942:Plant Viruses / Q000235:genetics; D030821:Plants, Genetically Modified / Q000235:genetics / Q000502:physiology; D036226:Seedlings / Q000235:genetics* / Q000502:physiology*
keywords: Apple latent spherical virus vector; apple seedling; early flowering; new breeding technique; reduction in generation time