Potential Distribution Of Wild Camellia Oleifera And Its Genetic Differentiation Along Latitude Gradient

Camellia oleifera is the dominant woody oil crop in China.The rapid development of C.oleifera industry can help to increase the self-sufficiency rate of vegetable oil in China and ensure the national grain and oil security.Wild C.oleifera is the important genetic resource for C.oleifera breeding.To understand the geographical distribution of wild C.oleifera and analyze the genetic differentiation of different geographical populations are the bases for the conservation and utilization of wild C.oleifera genetic resources.Using distribution data of wild C.oleifera from the Chinese Virtual Herbarium,together with climate and soil data,ecological niche models were constructed with Max Ent and GARP models to predict the potential distribution of wild C.oleifera.The major environmental factors affecting the distribution of wild C.oleifera were analyzed.For reflecting the latitudinal gradient distribution of wild C.oleifera,seven wild C.oleifera populations were chosen and a total of 374 leaf samples were collected.Based on high throughput transcriptome sequencing of 8 wild C.oleifera samples from Lushan Mountain and Jinggangshan Mountain,65 polymorphic microsatellite(SSR)markers were selected.With high-throughput sequencing,35 polymorphic SSR markers were used to genotype wild C.oleifera samples from different latitudes.Given unknown or known allele frequencies at SSR loci,the differences in genetic diversity and genetic structure analyses were compared for hexaploid wild C.oleifera.The genetic structure and genetic diversity of wild C.oleifera were analyzed.The main results and conclusions are as following:1.Both Max Ent and GARP models can well represent the distribution of C.oleifera.Predictions of both MaxEnt and GARP models showed that the potential distribution regions of wild C.oleifera were located mainly in the subtropical evergreen broad-leaved forest areas in the Yangtze River Basin and its south.The predictive results of the MaxEnt model are more conservative,but may be more accurate.The GARP model predicts a wider range of distribution areas reflecting the maximum potential distribution areas,but may have a higher false positive rate.According to the predictions of the Max Ent model,the highly suitable growing regions could be divided into three large regions:(1)northeastern-southwestern trending Wuyi Mountain and adjacent mountain regions;(2)eastern-western trending Nanling Mountain and adjacent mountain regions;(3)northeastern-southwestern trending Wuling Mountain and adjacent mountain regions.The analysis of the MaxEnt model showed that the major environmental factors affecting the distribution of wild C.oleifera were mean monthly diurnal temperature range,precipitation of driest quarter and precipitation of warmest quarter.2.We proposed a new method for the efficient development of polymorphic SSR markers.Of the 153 predicted polymorphic SSR markers,65 were polymorphic(allele number 2-12),and 31 were highly polymorphic(allele number 6-12).The successful rate for developing polymorphic SSR markers is generally higher than other methods.The number of alleles obtained by the experiment is higher than the number of alleles predicted by this method,but there is a significantly positive correlation between them.Therefore the number of alleles predicted by this method can reflect the actual levels of polymorphism.3.This study shows that,genotype the microsatellite multiplex PCR amplification products with high-throughput sequencing could improve the efficiency and accuracy of traditional genotyping methods,and especially it can help to accurately estimate allele frequencies of polyploids.When the allele frequency is known,the estimation of the genetic diversity of wild C.oleifera populations is more accurate,the genetic structure is clearer and the genetic differentiation is more obvious.4、Along the latitudinal gradient,the wild C.oleifera population showed a distinct pattern of genetic differentiation.When the allele frequency is known,the genetic differentiation between the Lushan Mountain population(Jiangxi Province)in the north and the Luofu Mountain(Guangdong Province)and Potang(Hainan Province)populations in the south is the largest,and the populations located between them are in the middle,showing the trend of genetic structure transition from north to south.The genetic diversity of wild C.oleifera populations increased with the decrease of latitude,and the Hainan Potang population has the highest genetic diversity.Compared with Fst,Rho is more suitable for the analysis of genetic differentiation among hexaploid C.oleifera populations.This study can provide technical support and reference for the protection,exploration and utilization of wild C.oleifera genetic resources.