Investigation And Ananalyses Of Genetic Diversity By ISSR On The Wild Banana Germplasm In The Upstream Areas Of Minjiang River

Banana is an important economic crop in tropical and subtropical regions and wild bananas as an important part of banana germplasm resources could provide abundant genetic information for banana new varieties breeding. It has been reported that different wild banana natural population and its ability to resist stress are easily affected by environmental factors such as geographic distribution, water flow and so on. Therefore, it is an important subject of current research on banana to study genetic structure and genetic diversity in natural population of wild banana, in order to reveal its genetic background. Fujian province is one of main producing areas of banana in our country, and there are a lot of wild banana germplasm resources in many rivers and mountains. Therefore, in this article, minjiang river-the largest river in Fujian province-was used as the research scope to invest the distribution of wild banana natural populations and its biological characteristics in the upstream of the river. And ISSR molecular marker technology was used to analyze the genetic polymorphism of these banana populations. At the same time, the relevant softwares such as SPSS, STRUCTURE and NTSYS were used to analyze the genetic similarity coefficient, genetic distance and genetic structure, in order to provide scientific basis for the development and utilization of Fujian wild banana germplasm resources. The results are as follows:1The distribution and biological characteristics of wild banana natural populations in Minjiang River upstream regionSix wild banana natural populations were found in cities of Sanming and Nanping in Minjiang River upstream region by means of field investigation. Wild bananas in Shunchang belong to Futunxi tributaries; Wild bananas in Xiamao, Gongchuangl andGongchuang2belong to Shaxi tributaries; Wild bananas in Daheng belong to Jianxi tributaries; Wild bananas in taqian situate along the upstream Minjiang River, near the intersection of the three major tributaries. The GPS observations showed that these wild banana natural populations distribute in the mountainous areas between26°08.619N,117°29.467E to26°43.124N,118°13.836E, with a altitude between85m and422m. Further investigation into the distribution environment showed that those wild bananas distribute mainly in places with sufficient water and sunlight such as the stream or small ditch water, where there are no other tall vegetation communities nearby. However, because of the land reclamation, housing construction and highway construction, the natural populations in this region are in serious damage. After surveying the biological characteristics of wild bananas in this region, we found that their plants, leaf and stem were morphologically similar to those in other parts of Fujian province, while the color of the fruit and flower varied significantly among different wild banana plant strains or different places because of the differences in light, moisture, nutrients and other environmental conditions or the genetic differences between individuals.2Analysis of genetic polymorphismWe got12ISSR primers whose electrophoretic bands are clear and polymorphic is good from16ISSR primers screened from our laboratory. These12primers were used to do the ISSR-PCR analysis to the205samples from six wild banana natural populations. We totally got119clear bands between200bp to2500bp,9.917bands per sample. The percentage of polymorphism reached95.8%, which indicated there was high genetic polymorphism in wild bananas from the Minjiang River upstream region.3the analysis of genetic similarity coefficientSPSS19.0was used to analyze the genetic similarity coefficient of wild banana natural populations in the Minjiang River upstream region. The results showed that the genetic similarity coefficients between individuals among wild banana natural populations in this region are between0.509and1.0and that the genetic similarity coefficient between populations was higher than that between individuals in the same population. From above, it can be inferred that the genetic diversity of wild bananas in this region may mainly come from the differences between populations.4The NTSYS genetic diversity analysis based on the distance modelNTSYS2.10e was used to cluster the205wild banana individuals. According to the clustering tree, the205wild banana samples could be divided into two big groups with a threshold of0.730. Wild bananas in Xiamao, gonchangl and Gongchuang2were in the first group. Wild bananas in Daheng, taqian and Shunchang were in the second group. The result was consistent to distribution by water flow. When the threshold was set to be0.758, wild bananas in both groups could be divided into two subgroups. The first subgroup of the first group included wild banana natural population in Xiamao and the second subgroup included those in Gongchuangl and Gongchuang2. The first subgroup of the second group included wild banana natural population in Daheng which was in Jianxi tributary and the second subgroup included those in Taqian and Shunchang which were along the Minjiang River and in the Futunxi tributary. No overlapping phenomenon was found among the different geographic population and the classification results was consistent with the geographic distribution. When the threshold was set to be0.814, wild bananas in gonchuanl and gonchang2were divided into two independent groups. And only when the threshold reached0.87would the those in taqian and Shunchang be separated independently. According to the results above, it showed that some part of wild banana nature populations in this region might be affected by water flow and geographic distribution obviously. The further analysis on the principal coordinates scatter diagram showed consistent results with the system tree, but difference did exist. It will be more accurate to combine these two means together to do the analysis.5Analysis of genetic structure based on model in clusteringClustering analysis software STRUCTURE2.2was used to do the genetic structure analysis of205wild banana samples. The205wild banana samples were divided into five groups. They were xiaomao wild banana natural population (Ⅰ), Daheng wild banana natural population (Ⅱ), Shunchang and Taqian wild banana natural population (Ⅲ), Gongchuang2wild banana natural population (IV), and Gongchuang2wild banana natural population (Ⅴ). According to the result, most wild bananas from different natural populations could be independently classified according to their geographic distribution. But Shunchang wild banana natural population and Taqian wild wild banana natural population were classified into the same group mainly because of closer geography distribution. Combined with further analysis of Q value distribution, most wild bananas had high percentage of possibility to be in their respective groups and the classification basis was relatively clear. Therefore, it indicated that the genetic diversity of wild banana in natural population was significantly affected by the geographical distribution and water flow.6The analysis of genetic structure in wild banana natural populationsFurther classification by STRUCTURE2.2was done to the results of first round of it. For example, wild bananas in Xiamao were classified to4subgroups (ⅰ,ⅱ,ⅲand ⅴ). More significant difference in individuals among these four subgroups was found. Based on the results of classification by STRUCTURE2.2and Q value analysis, it can be concluded that genetic diversity within this population is relatively abundant and that gene exchange phenomenon among individuals is obvious.