RESUMO
A combination of phenotypic characterization and molecular markers may provide reliable information on new plant varieties and elucidate the conservation status of rare species. Five newly developed Magnolia wufengensis cultivars, an endangered plant species endemic to Hubei Province, China, possess more distinctive phenotypes than common Magnolia cultivars. With reference to a wild species population of M. wufengensis and a population of Magnolia denudata, morphological traits of flower organs, simple sequence repeat (SSR), and sequence-related amplified polymorphism (SRAP) markers were used. In the morphological study, six traits of floral organs were investigated and their relationships were analyzed between cultivars. In the genetic study, 9 SSR primer pairs and 10 SRAP primer combinations were screened. The five cultivars maintained a high level of genetic diversity. Genetic diversity of each M. wufengensis cultivar was much lower than that of the wild population, but was slightly higher than that of the M. denudata population. Analysis of molecular variance (AMOVA) revealed that genetic variation among populations was 20% (SRAP) and 30% (SSR), which showed a high degree of genetic differentiation among populations of the five cultivars. The dendrograms illustrated a clear separation between M. wufengensis populations and outer species, and identified two major groups among cultivars. Correlation analysis indicated a good fit between the two marker systems, but a relatively low fit between morphological and genetic traits (SRAP: r = 0.60, SSR: r = 0.52). These findings provide reliable references for the application of these molecular markers in the breeding and conservation of M. wufengensis.
Assuntos
Conservação dos Recursos Naturais/métodos , Marcadores Genéticos/genética , Variação Genética , Magnolia/genética , Repetições de Microssatélites/genética , Melhoramento Vegetal/métodos , Análise de Variância , Antocianinas/análise , Antocianinas/metabolismo , China , Cromatografia Líquida de Alta Pressão , Análise por Conglomerados , Cor , Espécies em Perigo de Extinção , Flores/genética , Flores/metabolismo , Magnolia/classificação , Magnolia/metabolismo , Fenótipo , Filogenia , Pigmentação/genética , Especificidade da EspécieRESUMO
An efficient protocol for the in vitro propagation of Magnolia dealbata Zucc., an important medicinal plant that is the source of the anxiolytic and anticancer compounds honokiol and magnolol, was established. This plant is wild-crafted, and conservationists have expressed concerns with regard to the sustainability of production. In the present work, two factors were found to be of importance for the regeneration of M. dealbata and the production of honokiol and magnolol. These factors were the type of explants and the combination and concentration of plant-growth regulators. Green, compact, nodular organogenic callus was obtained from leaf explants in a medium fortified with Murashige and Skoog salts and supplemented with 1.5 mg/L 2,4-dicholorophenoxyacetic acid and 1.5 mg/L kinetin. Shoots multiplication from callus cultures was achieved in the Murashige and Skoog (MS) medium with 1.5 mg/L thidiazuron (TDZ). Phenol secretion was controlled by the addition of 250 mg/L of activated charcoal. For rooting, shoots were transferred to MS medium supplemented with several auxins. After root induction, the plants were hardened in earthen pots containing sand, soil, and vermiculite. The contents of honokiol (HK) and magnolol (MG) were determined in different plant materials by high-performance liquid chromatography-diode-array detection techniques. This analysis revealed that the honokiol and magnolol content in aerial and underground parts of micropropagated M. dealbata were higher than that observed in wild plants (both 6 months old). Our results suggest that conservation of M. dealbata is possible by means of in vitro multiplication of leaf-derived callus. The usefulness of M. dealbata regeneration and production of HK and MG may be attributed to the proper selection of explant sourcing and identification of the correct growth medium to support adequate growth. This careful selection of explants and growth medium leads to a very useful source of plant material for pharmacological and phytomedicinal screening applications and, above all, would safeguard this plant species from the threat of extinction.