Genetic Diversity Of Germplasm Resources Of Chukrasia Tabularis A. Juss.

Chukrasia tabularis A. Juss (Meliaceae) is a valuable fast-growing tree species native tothe tropical and subtropical regions of southern China. However, genetic diversity andprovenance variation of C. tabularis is not well understood. In this study, provenances andindividual families within provenances of C. tabularis from the species’ distribution rangewere used test material. Evaluation of genetic diversity based on phenotypic, physiological,biochemical, and molecular aspects was carried out to investigate the genetic variation and toprovide the basis for selection of superior provenances for genetic improvement. The mainresults are summarized as follows:1. Seeds of C. tabularis from26provenances in8countries (Australia, China, Laos,Malaysia, Myanmar, Sri Lanka, Thailand, Vietnam) were used to study the variation inmorphological characteristics and nutrient content. Seeds of6provenances were subjected todifferent concentrations of polyethylene glycol (PEG) solution to simulate drought stress. Theresults showed marhed differences in morphological characteristics and nutrient componentsamong different provenances. Principal components analysis and cluster analysis involving the26provenances revealed that the seed sources could be divided into two main groups. The firstgroup included two seed sources from Australia and Malaysia; their seeds were larger andheavier, and higher in nutrient content. The second groups consisted of the remaining24provenances. Cluster analysis and correlation analysis further showed that the seeds fromsouthern latitudes was larger than those from northern latitudes.Different water stress treatments reduced seed germination of C. tabularis and-0.86MPawas the critical potential of seed germination. The study also found that appropriate droughtstress could increase the ratio of root and other plant parts of C. tabularis seedlings.2. There were siginificant differences between provenances in height, ground diameterand biomass growth of1-year-old C. tabularis seedlings. The Logistic curve fitting of seedling growth process showed that seedling height and ground diameter had a "slow-fast-slow"pattern of the "S" type growth rhythm. Seedling height growth model wasH=54.08/(1+e2.149-0.0113t) and diameter growth model was D=6.03/(1+e2.298-0.0132t) which couldbe classified into peak, the end of the peak and later growth period. Cluster analysis of C.tabularis provenances divided the seed sources into3groups. The first group was thefast-growing provenances from Thailand (TH3) and Laos (LA1). The second group wasmoderate growing provenances from China (CN1, CN2and CN3). The third group consisted ofslow growing provenances.3. Comparative study of13phenotypic traits in one-year-old seedlings of C. tabularisshowed significant differences and marked genetic diversity. The genetic variation coefficientof the phenotypic traits was0.63~44.2%. The genetic variation coefficient of leaf area was thegreatest (44.2%) and that of the stoma width was smallest (0.63%). The broad-senseheritability was0.06~0.39, highest in the seedling height (0.39) and lowest in the stomatalwidth tal(0.06).4. Variation in growth and photosynthesis was assessed in2.5-year-old C. tabularisseedlings from22provenances from7countries (China, Laos, Malaysia, Myanmar, Sri Lanka,Thailand, Vietnam). The results showed that the light saturation point was1000μmol·m-2·s-1.There were significantly differencesin growth and photosynthetic indicators of C.tabularisunder the same growth environment. According to the principal components analysis andcluster analysis, the22provenances were divided into3clusters. The first cluster consisted ofthree fast-growing Chinese provenances (CN1, CN2and CN); their net photosynthetic rate andtranspiration rate were higher. The second cluster included10provenances from Laos (LA3),Malaysia (MY), Myanmar (MM3), Thailand (TH8, TH1, TH2, TH3, TH5, TH6) and Vietnam(VN2). The third cluster Laos (LA1,LA2), Myanmar (MM1,MM4), Sri Lanka(LK1, LK2,LK3), Thailand (TH4), and Vietnam (VN3) was characterized by slow growth, and low netphotosynthetic rate and transpiration rates. 5. An experiment was conducted to study the genetic variation in leaf volatile oil of C.tabularis provenances. The results showed that C. tabularis provenances differed in bladechromatographic peak number. CN3had96chromatographic peaks while VN3had54.Provenances differed in composition and percentage content of the volatile oil. In another study,specific volatile oils were detected in some provenancess. The main components of volatile oilfrom leaves were2-Hexenal, gamma-Elemene, alpha-Cubebene, Caryophyllene, GermacreneD, and Eucalyptol.6. Template DNA, primer, dNTPs, Mg2+, concentration of Taq DNA polymerase andannealing temperature were primary factors in ISSR-PCR. Using the genomic DNA of C.tabularis leaves, the above six factors were systematically analyzed. The result showed that theoptimal reaction system of ISSR was20μl containing30ng template DNA,1.0μmol·L-1random primers,0.15mmol·L-1dNTPs,2.5mmol·L-1Mg2+and2.5U Taq DNA polymerase,and that the optimized annealing temperature was56℃, the PCR procedure waspre-denaturizing at94℃for5min, denaturizing at94℃for45s, annealing at56℃for45s,extension at72℃for1.5min, reaction of40cycles and re-extension at72℃for7min, Theproducts were stored at4℃.Selected eight highly reproducibility, specificity primer on DNA of C. tabularis wereamplified by ISSR-PCR from95random primers. A total of137bands was amplified and129bands (94.16%) were polymorphic POPGene analysis results showed that the index Shannonphenotype diversity (I) averaged0.1172, Nei’s gene diversity (H) was0.0784, and genedifferentiation coefficient (Gst) was0.4696. Analysis of molecular variance (AMOVA)indicated that the variation within provenance (54.32%) was greater than the variation betweenprovenances (45.68%), suggesting a higher degree of genetic variation within provenances of C.tabularis. Cluster analysis was performed on23provenances by UPGMA and all provenancescould be divided into two clusters. The frist cluster included14provenances from China (CN1,CN2and CN3), Laos (LA1, LA2and LA3), Sri Lanka(LK1, LK2and LK3), Thailand (TH3, TH6), Vietnam (VN2, VN3and VN4). The second cluster included9provenances fromMyanmar (MM1, MM2, MM3, MM4), Thailand (TH1, TH2, TH4, TH5, TH7).7. Based on multiple criteria decision analysis of one-dimensional optimization methodand1-year phenotypic traits and2.5-year growth and photosynthetic indexes, CN1, CN2, CN3,LA1and TH3were regarded as superior provenances. The growth photosynthetic indicators ofC. tabularis saplings were the main selection traits. In order to further improve the selectionaccuracy, seedling ground diameter, root surface area and stomaal density should be combined.