Effects Of Collection Culture On The Genetic Diversity Of Acacia Pennata In Xishuangbanna Of Yunnan Province

Acacia pennata (Linn.) Willd is one of the main economic source plants in tropical and subtropical area. In the present study, the genetic diversity and population genetic structure of the natural populations and with geographically related homegarden stands in seven places (DML, MDJ, ML, JH, DDG, PW and ML in Xishuangbanna of Yunnan province, SW China)were investigated using SSR technique. The purpose of this study was to evaluate the genetic diversity level and genetic differentiation of the natural populations and present scientific basis to the conservation and utilization of A. pennata. Furthermore, we could evaluate the possible losses of genetic variation in farm stands of A. pennata by comparing with corresponding natural populations. The results could provide valuable information to evaluate the effects of farmers'collection activities on the genetic diversity of A. pennata and whether on– farm stands were suitable sources of material for further planting activities. The results could guide genetic management strategies which could be benefit for conservation and utilization of A. pennata.A relatively high level of genetic diversity was detected in A. pennata species with six polymorphic microsatellite loci. Based on six primers, 23 alleles were detected. Average (N_a) and effective number (N_e) of alleles were 3.381 and 2.460 respectively. The mean expected heterozygosity (H_e) was 0.573 and Nei's diversity index (h) was 0.567. The highest genetic diversity was found in Jinghong population, and the lowest was found in Manla population. The majority of genetic variation occurred within populations and could have resulted from low genetic differentiation (F_ST=0.113). A. pennata is a perennial species with a wide distribution; these characteristics could account for the relatively high genetic diversity we observed. Furthermore, this species has an outcrossing breeding system and its seeds are widely dispersed, which could be the primary reasons of the higer genetic diversity and low level of genetic variation between populations. These results presented scientific basis to the conservation and utilization of A. pennata. Considering that the genetic diversity of A. pennata mostly distributed within populations, we suggested that sampling abundantly within populations which have the higer genetic diversity and involving different populations were feasible in ex-situ conservation of A.pennata.We compared the assessment with geographically related forest and homegarden stands from seven places (DML, MDJ, ML, JH, DDG, PW and ML), 136 garden samples and 124 natural samples. The results revealed that no planted stands scored higher values than any natural stands. The mean values for planted and natural stands were N_e = 2.326, h = 0.539 and N_e = 2.460, h = 0.567 respectively, which showed that the planted stands contained about 95% of allelic diversity of the natural stands because of effective ex-situ conservation of A. pennata.Their collection method could be regarded as random and reasonable sampling, and thus avoided bottleneck effects, which supported the notion that human interventions had not significant impacts on genetic diversity in A. pennata at population level in Xishuangbanna. This study provided useful information for the effects of collection culture on the genetic diversity of A. pennata, guiding genetic management strategies and could be benefit for conservation and utilization of A. pennata.