Báo cáo khoa học: "llozyme variation in six native oak species in Korea"

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article Original in six native oak in Korea Allozyme variation species ZS Kim SW Lee JO Hyun 1 Department of Forest Resources, Korea University, Seoul 136-701; 2 Department of Forest Resources, Seoul National University, Suwon 440-100, South Korea variation at 6 loci was studied in 28 populations of the 6 oak species native Summary — Allozyme Carruth, Q aliena BI, Q dentata Thunb, Q mongolica Fisch, Q serrata to Korea: Quercus acutissima Thunb, and Q variabilis BI. The proportion of polymorphic loci per population (P) averaged over the 6 species was 74.6%. The average number of alleles/locus (A/L) was 2.26. The average observed and expected heterozygosities (H He) were 0.302 and 0.298, respectively. Only a small amount (7%) of , o the observed genetic variation appeared to be interpopulational. Among the 6 species, Q serrata and Q dentata were genetically less variable than the others. Three loci could be used as markers for distinguishing Q acutissima and Q variabilis from the other 4 species. Based on genetic identity, the 6 oaks were also clustered into 2 groups. This approach yields results similar to the current taxo- nomic treatment by morphological characteristics. allozyme / genetic variation / Quercus species Résumé — Variabilité allozymique chez 6 espèces de chênes indigènes de Corée. La variabili- té allozymique a été étudiée dans 28 populations appartenant à 6 espèces de chênes indigènes de Corée à partir de données issues de 6 loci :Quercus acutissima Carruth, Q aliena BI, Q dentata Thunb, Q mongolica Fisch, Q serrata Thunb et Q variabilis BI. Le nombre moyen d’allèles (A/L) était de 2,26. Les hétérozygoties observées et théoriques (H H étaient de 0,302 et 0,298 respective- ,) oe ment. La variabilité entre populations ne représentait que 7% de la variabilité totale. Parmi les 6 es- pèces, Q serrata et Q dentata étaient les moins variables. Trois loci permettaient de distinguer Q acutissima et Q variabilis des 4 autres espèces. Le calcul des identités génétiques a permis de sé- parer les 6 espèces en 2 groupes. allozyme / variabilité génétique /Quercus
be used to distinguish between the species INTRODUCTION and clarification of the systematic relation- ships among them were also points of in- Quercus acutissima Carruth, Q aliena BI, terest. Q dentata Thunb, Q mongolica Fisch, Q serrata Thunb, and Q variabilis BI are the 6 native deciduous oaks which are dis- MATERIALS AND METHODS tributed throughout Korea (Lee CB, 1987; Yim, 1991).They grow abundantly as dominant trees both in pure stands and A total of 533 mature individuals from 28 popula- tions of the 6 species were examined. From 5 to mixed with other species. This abundance 30 individuals per population were assayed. Lo- is attributed mainly to vigorous sprouting cations and the sample sizes are presented in ability and viability on poor sites. In addi- table I. tion to the important role in forest ecosys- For isozyme analysis, young leaves forced tems, they are economically valuable es- out of dormant twigs were homogenized in a pecially for fuel and structural wood (Lee drop of extraction buffer (50 ml of Tris-HCl buf- CB, 1987; Yim, 1991). fer, pH 7.3, + 0.06 g of ethylenediaminetetra- acetic acid (EDTA) + 0.05 ml of merceptoetha- Due to indiscriminate exploitation of the nol + 5 g polyvinylpyrrolidone (PVP, mol wt wood and poor silvicultural treatments, 40 000)) and extracts were subjected to horizon- most oak stands in Korea exhibit very poor tal starch-gel (12.5%) electrophoresis using 2 growth and quality. In regard to their eco- buffer systems. System I was that reported by nomic and ecological potential, it is likely Poulik (1957) with slight modifications; an elec- trode buffer of 0.063 M sodium hydroxide titrat- that the importance of oak species will in- ed to pH 8.20 with 0.299 M boric acid and a gel crease in the future. For these reasons, buffer of 0.076 M Tris titrated to pH 8.7 with systematic genetic studies on oaks are 0.0068 M citric acid. System II consisted of an now being carried out, but they are still at electrode buffer of 0.07 M Tris titrated to pH 7.0 an early stage (Kim and Hyun, 1990; Lee, with 0.021 M citric acid and a gel buffer obtained 1990; Park, 1991). from a 1:9 aqueous dilution of the electrode buf- fer. System I was used to resolve catalase The objective of this study was to com- (CAT), leucine aminopeptidase (LAP), menadi- pare the genetic variation among the 6 oak one reductase (MNR) and phosphoglucoisomer- species and also among populations in ase (PGI). System II was used to resolve aconi- each species by means of isozyme analy- tase (ACON). The Enzyme Commission numbers sis. Identification of marker genes that can of analyzed enzymes and the number of loci
listed in table II. scored Enzyme activity 1 was present in Q acutissi- CAT-A, allele are of Conkle et al staining protocols were those ma, allele 2 in Q acutissima and Q variabi- (1982) with slight modification. lis and allele 4 was observed in the other 4 The inheritance pattern of observed enzymes species. Among the 4 alleles at MNR-A, al- has already been reported by Kim and Hyun lele 4 was found only in Q acutissima and (1990). The genotypes were scored in the fol- Q variabilis, but allele 1 was observed in lowing manner: the fastest migrating locus was the other species, while alleles 2 and 3 assigned A and the next locus B and so on; the were displayed in all 6 species. Among the fastest allozyme at a given locus was designat- 5 alleles at PGI-B, allele 5 was observed in ed ’1’ and the slower forms were ’2’, ’3’ etc. Q acutissima and Q variabilis, but alleles 1 frequencies, percent of polymorphic Allele and 2 were found in the other 4 species, observed and expected heterozy- loci, the mean gosities, genetic identities (Nei, 1978), and the whereas alleles 3 and 4 were in all 6 spe- phenogram drawn by the UPGMA clustering cies. technique (Sneath and Sokal, 1973) were calcu- Measurements of the genetic variability lated and produced using the BIOSYS-1 pro- of the 6 Quercus species are presented in gram of Swofford and Selander (1989). table IV. The percent of polymorphic loci The amount of interpopulational genetic vari- ranged from 66.7 (Q serrata) to 84.5% ation within Quercus species and populations was determined by analyzing genetic diversity (Q acutissima). The amount of polymor- measures (H H D and G (Nei, 1973, ,, T S ST ) ST phic loci averaged over the 6 oak species 1975). was 74.6%. The mean number of alleles/ locus (A/L) averaged over all loci ranged from 2.03 (Q serrata) to 2.65 (Q mongoli- RESULTS AND DISCUSSION ca) and the mean number averaged over the 6 species was 2.26. The mean ob- Allele frequencies for the 6 loci studied are served heterozygosities within species presented in table III. Five loci (ACON-A, ranged from 0.293 (Q mongolica) to 0.307 LAP-A, MNR-A, PGI-A, PGI-B) were poly- (Q aliena and Q serrata). The mean ex- morphic in all 6 taxa, although not in every pected heterozygosities ranged from 0.276 population. Three loci, CAT-A, MNR-A and (Q dentata) to 0.325 (Q acutissima). The PGI-B, served as allozyme markers for dis- overall means of the observed and expect- criminating Quercus acutissima and Q vari- ed heterozygosities for the 6 species were abilis from the other 4 oak species. At 0.302 and 0.298, respectively.
species and agree with the general rule The mean values of 74.6% polymorphic loci, 2.26 alleles/locus and 0.298 that the wider the range of species, the mean ex- greater the expected genetic polymor- pected heterozygosity (table IV) larger are phism. Q acutissima is the most abundant than those for red oaks in northeastern 29.7%, A/L America (P species with the widest ecological range. 1.37, H e = = = 0.081; Manos and Fairbrothers, 1987). These values are also somewhat larger than those obtained over long-lived peren- nial woody plants (P = 64.7%, A/L = 2.19, He 0.177; Hamrick and Godt, 1989). = Although the enzymes investigated tend to be biased towards the polymorphic en- zymes, these results show that Korean oaks have a great deal of genetic varia- tion. By increasing the number of iso- zymes to be investigated, more reliable data will be obtained. The mean values for the differentiation between populations (G of the 6 oak ) ST species (table V) were from 0.040 (Q den- tata) to 0.115 (Q serrata), and the overall value for the 6 oak species was 0.073. In other words, about 7% of the observed genic diversity appears to be interpopula- tional. This result is similar to that for American red oaks (G ST 0.086; Manos = and Fairbrothers, 1987). Mean identities among the 6 genetic species (table VI) ranged from 0.295 to 0.956. This wide range seems to be due to the presence of different alleles at 3 mark- er genes in the 6 species. The genetic identity between Q acutissima and Q vari- abilis was 0.956, and those among the other 4 species ranged from 0.885 to 0.933. But the genetic identities between the species from each group were very low, ranging from 0.295 to 0.434. Mean identities among populations within spe- cies ranged from 0.937 to 0.995. Two species, Q dentata and Q serrata displayed less genetic variation (P, A/L and H than the other oaks and Q acutis- ) o sima had the most genetic variation. It ap- pears that these results are related to the different ecological characteristics of the
This species is distributed throughout the The 6 oaks were clustered into at least 2 Korean peninsula and also in China and groups: groupI is composed of Q acutissi- Japan (Krüssmann, 1986; Lee CB, 1987; ma and Q variabilis and the other species Yim, 1991). constitute group II. These results are simi- lar to those provided by morphological The dendrogram produced by the characteristics (Ma, 1974; Kim and Kim, UPGMA clustering technique based on 1987). According to Krüssmann (1986), Nei’s identity (1978) is depicted in figure 1.
Krüssmann G (1986) Manual of Cultivated Q acutissima and Q variabilis are classi- Broad-Leaved Trees and Shrubs. Timber fied into the section Cerris of the subgenus Press, Portland, OR, vol 3, 79-111 (English Lepidobalanus, Q aliena, Q mongolica and translation) Q serrata into the section Alba of the sub- (1987) Dendrology. Hyangmoon Publ, Lee CB genus Lepidobalanus. Q dentata is classi- Seoul, Korea (in Korean) fied into the section Dentatae of the sub- Lee DK (1990) Ecological studies on oak spe- Lepidobalanus. genus cies. In: Studies on the Development and Utili- zation of Korean Oak Resources. Ministry of Science and Technology, 41-98 (in Korean) ACKNOWLEDGMENTS Ma SK (1974) Similarity relationship between basic species of oak by the numerical meth- od. J Korean For Soc 21, 47-51 (in Korean) We thank JW Hwang and KW Kwon for the col- Manos PS, Fairbrothers DE (1987) Allozyme lection of plant materials. This work was finan- variation in populations of six northeastern cially supported by the Ministry of Science and American red oaks (Fagaceae: Quercus Technology, Korea. subg Erythrobalanus). Syst Bot 12, 365-373 Nei M (1973) Analysis of gene diversity in sub- divided populations. Proc Natl Acad Sci USA REFERENCES 70, 3321-3323 Nei M (1975) Molecular Population Genetics Conkle MT, Hodgskiss PD, Nunally LB, Hunter and Evolution. North Holland, Amsterdam SC (1982) Starch-Gel Electrophoresis of (1978) Estimation of average heterozy- Nei M Conifer Seeds: A Laboratory Manual. Pacific gosity and genetic distance from a small Southwest Forest and Range Experiment number of individuals. Genetics 89, 583-590 Station, Berkeley, CA Park SY (1991) A systematic classification of Hamrick JL, Godt MJ (1990) Allozyme diversity Korean Fagaceae by the pollen. J Korean in plant species. In: Plant Population Genet- For Soc 80, 151-161 (in Korean) ics, Breeding and Genetic Resources Poulik MD (1957) Starch-gel electrophoresis in (Brown AHD, Clegg MT, Kahler AL, Weir a discontinuous system of buffers. Nature BS, eds) Sinauer Associates, Sunderland, 180, 1477-1479 MA, 43-63 Sneath PHA, Sokal RR (1973) Numerical Tax- Kim ZS, Kim JS (1987) Quantitative taxonomic onomy. WH Freeman, San Francisco, CA studies on the genus Quercus by pollen mor- Swofford DL, Selander RB (1989) BIOSYS-1: A phology. Res Rep Coll Agric, Korea Univ 27, computer program for the analysis of allelic 23-29 (in Korean) variation in population genetics and biochem- Kim ZS, Hyun JO (1990) Genetic variation of ical systematics. Release 1.7. Illinois Natural oak species. In: Studies on the Development History Survey, IL and Utilization of Korean Oak Resources. (1991) Silviculture. Hyangmoon Publ, Yim KB Ministry of Science and Technology, 99-180 Seoul, Korea (in Korean) (in Korean)