Genetic Diversity Of Bombax Malabaricum In Dry-hot Valleys Of Yunnan

Dry-hot valleys lie in Hengduan mountains in southwest China and their eastern neighbouring regions. Their original vegetation has been destroyed in recent years, and many places have become bald. Breakage and degradation of the vegetation seriously destroys ecological conditions and biodiversity. Moreover, dry-hot valley areas in southwest China will spread and the climate is growing drier and hotter, according to the global climate change. So it's urgent to carry on ecological restoration in dry-hot valleys. Bombax malabaricum is a dominant species in dry-hot valleys, and it's very important for the ecological restoration of dry-hot valley areas to study the genetic diversity of Bombax malabaricum. In order to put forward some constructively genetic information for the ecological restoration of dry-hot valley areas, and choosing, breeding appropriate plant varieties, we investigated the level of genetic diversity and genetic differentiation of Bombax malabaricum. Furthermore, we also surveyed the associations among dry-hot adaptability and genetic diversity. We surveyed the genetic diversity of 4 populations (YJ, YM, QJ, DJ) from dry-hot valleys of Yunnan province, 2 populations (GX, HN) from dry-hot regions and 1 population (BN) from wet-hot region of Yunnan using ISSR molecular markers.Based on 10 selected primers, 138 clear and reproducible DNA fragments were generated. The percentage of polymorphic loci PPB was 89.86%, Nei's(1973) gene diversity H was 0.2552 and Shannon's Information index I was 0.3905. The coefficient of genetic differentiation (GST) was 0.1173 and theФst was 0.111 estimated by AMOVA. The results showed high level of genetic diversity within populations and low level of genetic differentiation among populations. Furthermore, there were no significant associations between genetic and geographic distance among B. malabaricum populations(r=0.3191, P=0.1760>0.05). We tested the associations between the five ecological factors (Annual relative humidity, Annual average temperature, Annual≥10℃accumulated temperature, Annual precipitation, Altitude) and the genetic diversity(observed number of alleles Na, effective number of alleles Ne, PPB, Nei's gene diversity H and Shannon's information index I)of B. malabaricum. The results revealed that there were no significant correlations between the five ecological factors and genetic diversity. We inferred that the high level of genetic diversity and effective gene flow of B. malabaricum may play an important role in its adaptability to dry-hot adversity, and dry-hot environment had neutral or near-neutral effect on its genetic diversity.Considering that the genetic diversity of B. malabaricum mostly distributed within populations, we suggested that sampling abundantly within populations and involving different populations is feasible in introduction of dry-hot regions.