Study On Genetic Diversity Of Mentha L.in China

The genus Mentha (Labiatae) comprises approximately30species distributed in the temperate zone of northern hemisphere. In China,12species have already been recorded. M haplocalyx Briq., M. spicata L. and M piperita L. are important economic plants, and they are widely used in the Pharmaceuticals, food, cosmetics and perfume industries. The morphological characters, pollen morphology, molecular markers and essential oil of Mentha L. were reported in this study. It will provide an important scientific basis for development and utilization of Mentha germplasm resource in China.There main results are as follows:1. Morphological diversity of Mentha L.The9morphological characters(plant height, leaf length, leaf width, petiole length, leaf pairs, stem thickness, branch number, branch length, node number) of34population of Mentha L. including7species were studied by variance analysis, correlation analysis, principal component analysis and clustering analysis. The results showed that the morphological characters vary greatly among the populations of Mentha L., and the coefficient of variation (CV) was from13.31%to76.29%. There are some correlations between morphological characters. According to PCA, the9morphological characters were summed up to4main characters. The7species were divided into3groups by clustering analysis.2. Pollen diversity of Mentha L.The pollen morphology of9species of Mentha genus, including M. haplocalyx Briq., M. dahurica Fisch., M. spicata Linn., M. crispata Schrad., M. asiatica Briss., M. vagans Briss., M. longifolia Huds., M. rotundifolia Huds. and M. pulegium Linn., were studied through the scanning electron microscope (SEM). The results showed that pollen grains are oblate or subspheroidal in shape and12.73-26.14μm×19.18-26.53μm in size. They have6-8colpi with different length, and exine ornamentation is reticulate. The pollen morphology of Mentha is stenopalynous, and it is evolutional type in Lamiaceae.3. Molecular marker of Mentha L. 3.1ISSR analysis of Mentha L.The genetic diversity of34population of Mentha L. including7species were analyzed using Inter Simple Sequence Repeat(ISSR) markers. A total of68bands were amplified by10ISSR primers, in which59bands were polymorphic(86.7%). Nei’s genetic diversity index, Shannon’s information index and gene flow were0.3457,0.5166and0.7564, respectively.75.64%of genetic variation existed among populations, and24.36%of genetic variation existed within populations. The34populations were divided into3groups by clustering analysis. The study reveals that there is a high level of genetic diversity in Mentha L.3.2SRAP analysis of M. haplocalyx Briq.The genetic diversity of15populations of M. haplocalyx Briq. in China were analyzed using Sequence-related Amplified Polymorphism(SRAP) markers. A total of124bands were amplified by11pairs of SRAP primers, in which115bands were polymorphic(92.7%). Nei’s genetic diversity index, Shannon’s information index and gene flow were0.2948,0.4512and0.6598, respectively.65.98%of genetic variation existed among populations, and34.02%of genetic variation existed within populations. Nei’s genetic distance between populations ranged from0.0287to0.5577. The least genetic distance was observed between Hangzhou and Taihe population, and the highest genetic distance was observed between Mangkuang and Xishangbanna population. The15populations were divided into3groups by clustering analysis. The study reveals that there is a high level of genetic diversity among the populations of M. haplocalyx Briq.,4. Chemical components of essential oil in Mentha L.The essential oils obtained from15population of M. haplocalyx Briq. and8species of Mentha L., including M. haplocalyx Briq., M. piperita L., M. spicata L., M. vagans Boriss., M. dahurica Fisch., M. crispata Schrad., M. rotundifolia Huds. and M. asiatica Briss. by hydrodistillation were analyzed. The results showed that the oil yields and content of menthol vary greatly among15population of M. haplocalyx Briq.. The oil yields ranged from0.31%to1.43%, and the content of menthol ranged from31.25%to83.61%. Fifty-one compounds were identified which represented98.8%,99.3%,94.9%,97.1%,94.2%,98.4%,95.4%and95.4%of the total oil, respectively.4principal components which accumulation contribution rate amount to86.0%were extracted to reflect most of the information by principal components analysis. The eight Mentha species were divided into 3types by clustering analysis, and they belong to menthol chemotype, carvone chemotype and piperitenone oxide chemotype, respectively.