RESUMEN
Trees require a long maturation period, known as juvenile phase, before they can reproduce, complicating their genetic improvement as compared to annual plants. 'Spadona', one of the most important European pear (Pyrus communis L.) cultivars grown in Israel, has a very long juvenile period, up to 14 years, making breeding programs extremely slow. Progress in understanding the molecular basis of the transition to flowering has revealed genes that accelerate reproductive development when ectopically expressed in transgenic plants. A transgenic line of 'Spadona', named Early Flowering-Spadona (EF-Spa), was produced using a MdTFL1 RNAi cassette targeting the native pear genes PcTFL1-1 and PcTFL1-2. The transgenic line had three T-DNA insertions, one assigned to chromosome 2 and two to chromosome 14 PcTFL1-1 and PcTFL1-2 were completely silenced, and EF-Spa displayed an early flowering phenotype: flowers developed already in tissue culture and on most rooted plants 1-8 months after transfer to the greenhouse. EF-Spa developed solitary flowers from apical or lateral buds, reducing vegetative growth vigor. Pollination of EF-Spa trees generated normal-shaped fruits with viable F1 seeds. The greenhouse-grown transgenic F1 seedlings formed shoots and produced flowers 1-33 months after germination. Sequence analyses, of the non-transgenic F1 seedlings, demonstrated that this approach can be used to recover seedlings that have no trace of the T-DNA. Thus, the early flowering transgenic line EF-Spa obtained by PcTFL1 silencing provides an interesting tool to accelerate pear breeding.
Asunto(s)
Flores/genética , Flores/fisiología , Proteínas de Plantas/genética , Pyrus/genética , Pyrus/fisiología , Interferencia de ARN , Secuencia de Bases , Cruzamientos Genéticos , ADN Bacteriano/genética , ADN de Plantas/genética , ADN de Plantas/aislamiento & purificación , Regulación de la Expresión Génica de las Plantas , Genoma de Planta/genética , Genotipo , Patrón de Herencia/genética , Malus/genética , Datos de Secuencia Molecular , Mutagénesis Insercional/genética , Fenotipo , Fotoperiodo , Proteínas de Plantas/metabolismo , Plantas Modificadas Genéticamente , Pyrus/anatomía & histología , Pyrus/crecimiento & desarrollo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , TemperaturaRESUMEN
An ancient date seed (Phoenix dactylifera L.) excavated from Masada and radiocarbon-dated to the first century Common Era was germinated. Climatic conditions at the Dead Sea may have contributed to the longevity of this oldest, directly dated, viable seed. Growth and development of the seedling over 26 months was compatible with normal date seedlings propagated from modern seeds. Preliminary molecular characterization demonstrated high levels of genetic variation in comparison to modern, elite date cultivars currently growing in Israel. As a representative of an extinct date palm population, this seedling can provide insights into the historic date culture of the Dead Sea region. It also has importance for seed banking and conservation and may be of relevance to modern date palm cultivation.
