Genetic Structure Of Hexaploid Wild Camellia Oleifera In Mount Jinggang And Lu Based On Microsatellite Markers

Oil-tea camellia(Camellia oleifera) is the first main woody oil crops in China. Development of highly polymorphic microsatellite(also known as simple sequence repeat, SSR) markers can facilitate the marker assisted breeding of oil-tea camellia. Wild oil-tea camellia is a valuable gene pool for the breeding of cultivated oil-tea camellia. Understanding the genetic variation of wild oil-tea camellia along latitude and altitude gradients can help to protect and utilize wild oil-tea camellia resources.In this study, wild oil-tea camellia leaf samples were collected from Mount Jinggang and Lu. The ploidy level of wild oil-tea camellia was determined by flow cytometry. SSR markers were developed based on the leaf transcriptome data from wild oil-tea camellia. Eight highly polymorphic SSR markers were used to study the genetic diversity and genetic structure of wild oil-tea camellia in Mount Jinggang and Lu. The main results and conclusions are as follows:1. The ploidy level of wild oil-tea camellia is 6 in Mount Jinggang and Lu. No variation was observed in the ploidy level of wild oil-tea camellia among different latitudes and altitudes.2. The technical system of SSR marker development and analysis in hexaploid wild oil-tea camellia was established. Seventeen highly polymorphic SSR markers were obtained.3. Similarly high levels of genetic diversity were detected in the wild oil-tea camellia populations from Mount Jinggang and Lu, locating at two different latitudes. The observed heterozygosity is higher than the expected heterozygosity in Mount Lu population. The results implied that wild oil-tea camellia might be an allopolyploid. The genetic diversity detected in our study was also obviously higher than those detected in previous studies on cultivated oil-tea camellia, suggesting that wild oil-tea camellia might contain higher genetic diversity than cultivated oil-tea camellia.4. Clear genetic differentiation was found between the two wild oil-tea camellia populations in Mount Jinggang and Lu, locating at two different latitudes. The geographic distance between the two populations is about 380 km. Isolation by geographic distance and difference in climate conditions between the two sites may be the main reasons leading to the genetic differentiation.5. No obvious genetic differentiation was observed in wild oil-tea camellia at different altitudes from either Mount Jinggang or Mount Lu. The spatial autocorrelation analysis of wild oil-tea camellia at different altitudes in Mount Lu suggested that gene flow distance could be up to 117 m within a wild oil-tea camellia population. This means that a high level of gene flow may occur among wild oil-tea camellia at different altitudes, and therefore prevent obvious genetic differentiation among different altitudes.6. The genetic diversity of wild oil-tea camellia from different sampling sites in Mount Jinggang increased with the increase in altitude, but the inbreeding coefficient decreased accordingly. This may be due to the decrease in the intensity of the human disturbances with the increase in altitude.This study can provide references for the conservation and utilization of wild oiltea camellia genetic resources.