Genetic Diversity and Structure Analysis of Masson Pine Clonal Seed Orchard
Abstract
An experiment stand of clonal orchard of masson pine , which included the 123 plus trees of 8 provenances collected from 8 provinces of Southern China, was founded at Jingshan County of Hubei province. Randomly amplified polymorphic DNA (RAPD) technique was applied to assess genetic diversity and structure for this clonal seed orchard . Total genomic DNA was extracted from fresh needle tissue with Plant Genomic DNA Extraction Miniprep System made by Viotechnology Corporation The result s indicate d that the clonal seed orchard of masson pine had higher genetic diversity . The average genetic diversity of the clonal seed orchard was 0.3169, the Shannon ’s information index was 0.4813 respectively, and t he percentage of polymorphic loci was 71.0%. Observed number of alleles (Na), effective number of alleles (Ne), Nei’s gene diversity (H), Shannon’s information index (I) and percentage of polymorphic loci (P) within population of Jiangxi, Hunan and Zhejiang were bigger than those of Guangdong, Guangxi, Anhui and Sichuan. Genetic distances among 8 populations were range from 0.0225 to 0.2175, whereas genetic identities were range from 0.8045 to 0.9777. 8 populations were clustered into 7 clusters, which showed that populations with similar latitude were clustered together and the clustering had nothing to do with geographic distributing. There was not significant correlation between genetic distance and geographic distance, while the correlation between genetic distance and latitude was more signific ant.
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Introduction
Since 1940s, forest tree genetic improvement has been performed principally for the purpose of seed orchard establishment, which is the bridge between breeding and afforestation. At present, seed orchards of more than 80 species of coniferous and broad-leaved trees have been established, including Pinaceae, Taxodiaceae Cupressaceae, Araucariaceae, Myrtaceae, Fagaceae, Verbenaceae, Lauraceae, Juglandaceae, Betulaceae, Rosaceae, Leguminosae, Aceraceae，Chenopodiaceae etc (Lai Huanlin and Wang Zhangrong, 1997). Seed or chards are production populations which produce high quality seeds for afforestation within a certain fixed range, and from which the genetic quality of seeds is transferred to the generation. First generation seed orchards were established after phenotypic selection of plus trees from natural or artificial forests. Their genetic structure relationship among clones in seed orchard was not known It is important to know their genetic structure and genetic diversity for afforestation and forest management . The results could help to make sure the genetic quality of seed, improvement direction of seed orchard. But until now there is very few report about these.
DNA markers are able to reflect the variation degree directly on the DNA level and are more sensitive than protein markers. DNA markers are generally used to study the genetic variation because they could detect much more DNA sites and are not affected by development stages, physiological status and environments, etc (Lin and Sui 2010, Cai and Shao 2014). Under controlled condition, Random Amplified Polymorphic DNA (RAPD) markers can be used to identify taxons (Williams 1990, Wachira 1995) with a close relationship and to clarify the genetic variation of population for its higher sensitivity (Lynch 1994, Gillies 1997, Schierenbeck 1997), genetic diversity within and among populations of shortleaf pine and loblolly pine (Lynch 1994, Gillies 1997; Schierenbeck 1997), Characterization of the genetic diversity of the Tall coconut (Reina & Baudouin 2010). Genetic diversity within and among populations of shortleaf pine and loblolly pine (Shiqin & Tauer 2008), the genetic diversity and introgression of Juglans regia and Juglans sigillata in Tibet (Hua & Gang, 2015), patterns of genetic diversity of Prunus africana in Ethiopia ( Mihreti & Schueler,2015) and genetic diversity and inbreeding in natural and managed populations of Scots pine (Rosario & Valentina, 2015) were also reported recently. To know the genetic diversity and variation within and among populations is very important to tree breeding and forest improvement.
Masson Pine (Pinus massoniana Lamb.), one of the most ecologically and economically important coniferous species for forest products, is widely distributed in 13 provinces of Southern China. It is also provide habitat for wildlife and other environmental amenities, including soil stabilization, clean water and air, and carbon sequestration. Because Masson Pine is widely distributed over most of the central and southern China, it is suggested that it possess a large amount of genetic variation due to adaptation to a variety of environments. In this paper, the genetic diversity and structure of the clonal seed orchard of Masson Pine have been studied by RAPD marker. Although, to date, molecular marker-based studies have been limited to genetic diversity and population structure for Masson Pine, the genetic analysis and structure of its clonal seed orchard has not been studied.
Conclusion
This study show ed that the clonal seed orchard of Masson Pine ha d a high er level of gen etic diversity , which was similar to the results of Lai’s study. As a kind of explanation verified by Wheeler & Jech, natural forests differentiated geographicall y and genetically, from which plus trees were selected, then, the higher genetic diversity was transferred to the seed orchards. Genetic structure between filial and parental generations had a close correlation, which was proved by a lot of studies. Szmidt also had verified that the genetic diversity of the offspring of seed orchard did not decline obviously compared with that of the offspring of the natural forests (Szmidt 1984, Reina 2010, Mihreti 2015, Hua 2015). Lai drew a conclusion that there was no significant change of frequency between seed orchard and its progeny forest.
Genetic diversity among forest population had been revealed in this study, perhaps, which was connected with the different population samples. Providing that raising the number of population samples of Gongdong, Guangxi, Anhui, Sichuan, the genetic diversity of this seed orchard would be much higher. Therefore, quantifying the total number of the seed orchard and the number of each provenance is the most concern in seed orchard establishment, which is related both to the level of genetic diversity and genetic gain obtained from afforestation. As for the next step for seed orchard management, mating ability and inbreeding depression should be estimated via controlled pollination, based on which and the genetic structure clarified above, the seed orchard should be improved, or the second generation seed orchard should be established.
