Genetic diversity, population genetic structure and gene flow in the rare and endangered wild plant Cypripedium macranthos revealed by genotyping-by-sequencing.

BACKGROUND: Genetic diversity, genetic structure, and gene flow in plant populations and their influencing factors are important in conservation biology. Cypripedium macranthos is one of the few wild orchids with high ornamental value in northern China. However, over the past decade, excessive collection, trading, tourism development, habitat fragmentation, deceptive pollination, and seed germination difficulties have all caused a sharp decline in the number of C. macranthos individuals and its population. In order to propose a scientific and effective conservation strategy, the genetic diversity, genetic structure and gene flow of the current CM population are urgent scientific issues to be clarified. RESULTS: Here, 99 individuals of C. macranthos from north and northeast China were analyzed to evaluate the genetic diversity, gene flow among populations, and genetic structure by genotyping-by-sequencing. More than 68.44 Gb high-quality clean reads and 41,154 SNPs were obtained. Our data based on bioinformatics methods revealed that C. macranthos has lower genetic diversity, high levels of historical gene flow, and moderate-to-high genetic differentiation between populations. The gene migration model revealed that the direction of gene flow was mainly from northeast populations to north populations in China. The results of genetic structure analysis showed that 11 C. macranthos populations can be considered as two groups, and further divided into four subgroups. Moreover, the Mantel test detected no significant "Isolation by Distance" between populations. CONCLUSIONS: Our study demonstrates that the present genetic diversity and genetic structure of C. macranthos populations were mainly caused by biological characteristics, human interference, habitat fragmentation, and restricted gene flow. Finally, constructive measures, which can provide a basis for the proposal of conservation strategies, have been suggested.

Flexible and robust low-loss selenium-based multimaterial infrared fibers towards CO2 laser ablation.

A small-scale delivery medium for CO2 laser energy with stable performance, flexibility, and high-strength is crucial in extreme laser processing environments, especially for minimally invasive surgery in high-humidity, twisty and narrow channels. Here, flexible and robust multimaterial infrared fibers made of selenium-based chalcogenide glasses and thermoplastic polymer were developed with a low loss of 7.18 dB/m at 10.6 µm. The resulting fibers were capable of stably delivering single-mode CO2 laser with 0.42 W average power. Moreover, to achieve precise control over the fibers in the practical clinical environment, customized co-polymers of polyphenylene sulfone resin and polyvinylidene fluoride were used as the fiber built-in jackets. Consequently, the fibers exhibited hydrophobicity, thermostability, high tensile strength, and low bending stiffness. The results demonstrated that the fibers can be used to deliver CO2 laser energy for fabric cutting and bio-tissues ablation, making them attractive for CO2 laser material processing and minimally invasive laser surgery.