| Melia Azedarach L. is the model plant of Melia, Meliaceae. It is a fast-growing tree species with high-quality timber and multi-purpose uses. Its distribution is widely in the natural world. Aiming to study the regularity of geographic variation and genetic diversity of distribution of M.azedarach germplasm resources, we carried out the observation of the geographic variation regularity of different provenances on the traits of stone and seed morphologiacal character and germination, and the growth of multi-site comparative trials of provenances. The analysis of genetic diversity of different provenances based on SSR and SRAP molecular marker techniques were applied in this study as well. In addition, we also analyzed the genetic variation of growth traits among or within provenances. Through the analysis, the major conclusions were obtained as follows.1. The traits of nutlet size, seed numbers in each nutlet, endocarp thickness, stone quality, seed size, seed quality, seed germination rate, and seed germination are potential significantly different among the different provenances. With the change of location from south to north where the seeds collected, while the seed size is bigger, seed quality increase gradually, the germination rate becomes higher, stone endocarp is thinner while the average seed numbers in each nutlet decrease from south to north. Moreover, the provenances’ nutlet and seed from high altitude are thicker and bigger, and the nutlet weight is heavier than the provenances from lower altitude area. On the latitude and longitude, the width of nutlet and seed shows a trend of southwest-northeast clinal variation, while the seed and stone mass shows a trend of orthwest-southeast clinal variation. And the endocarp thickness 1, germination rate and germination pentation indicate a trend of south-north clinal variation. With the increasing of altitude, nutlet and seed become more bulky, and seed is heavier. And the higher the altitude, the greater the variation is. However, the germination rate and germination potential have a tendency of decreasing when the altitude going up, and the variation amplitude of germination potential changes faster. When the extreme maximum temperature, air pressure and humidity, and amount of precipitation of the location decrease, the width of the nutlet and seed become bigger, endocarp become thicker, nutlet has more edge numbers, and nutlet weight increases. However, when the extreme minimum, air humidity, amount of precipitation and average air temperature increase, the size of the seed and nutlet are small, endocarp is thin, seed numbers of stone increase and seed mass is smaller. In addition, seeds from the location with lower air humidity, extreme minimum temperature, and higher air pressure, the germination rate and germination potential are higher. According to the traits of nutlet and seeds, the cluster analysis of provenances show thatseedlots from Guangdong, Guangxi, Hainan and parts of Fujian, Jiangxi, Guizhou and Hunan were clustered in group I; provenances from Jiangxi, Hunan, Sichuan, Anhui, Jiangsu, Hubei, Shanxi, and single provenance of Guizhou and Zhejiang were clustered in group II; seedlots from Yunnan, Henan and Hebei were clustered in group III, and provenances from Yunnan, Gansu and parts of Guizhou were clustered in group IV. From group I to group IV, the size of seeds and nutlet were bigger, the number of stone edges and the weight of seed and nutlet increased, the nutlets were rounder.2. The growth comparison trials in Guangdong province showed that the observed traits of chinaberry provenances in three sites were significantly different, and they were greater than the difference between provenances. The analysis of provenances within sites should be more reasonable for geographic variation analysis. In the three trials in Guangdong province, seedlings of the seedlot from Guangdong, Hainan, Guizhou, Guangxi, Fujian province showed excellent performance in growth potential and adaptation ability in Guangdong trials, and the provenances from Jiangxi, Hunan and Yunnan provinces indicated a second place in growth performance. The chinaberry provenance’s geographic variation was controlled by latitude and longitude, mainly for the latitudinal variation. Meanwhile survival rate, seeding height, ground diameter and crown breadth were affected by elevation. It was found that from south to north and from west to east, the seedling grew slowly, and seedings from high altitude grew faster than those from the low altitude region. And the survival rate of seedlings which were from low altitude area were much higher than those from high altitude area. Seven observed traits in these trials presented a geographic trend with south-north clinal variation, and seeding height showed westsouth-eastnorth clinal variation trend, ground diameter and east-west crown showed south-north clinal variation trend, and south-north crown, number of branch and trunk shape presented a trend of eastsouth-westnorth clinal variation. The seedlings from areas with higher average temperature, rainfall, air pressure, extreme maximum temperature, and richer sunshine had greater biomass and straighter stem. Adaptability study of traits in Guandong trials showed that the southern provenances from Fujian, Hainan, Guangdong, and Guangxi were clustered into one group, the northern provenances from Hubei, Anhui, Henan, Shanxi, Gansu, Hebei, and Shandong were clustered in another group, and the provenances from Guizhou, Yunnan, and Jiangxi were scattered in different groups in the analysis.3. The variation of traits of M.azedarach was significant among and within provenances. Based on the adaptation selection according to the survival situation, other traits should be paid more attention to the selection within provenance. The provenance repeatability of survival, ground diameter, and branch number were larger than that of other traits, and the family heritability of branch number, crown breadth and seedling height were higher than that of other traits. The characters were significantly affected by blocks, plots, spatial autocorrelation error of rows and columns between provenances and families. The spatial model improved the acuracy of breeding value and other genetic parameters. The narrow sense heritability per plant of lateral branch number was the largest(0.498±0.054), south-north crown breadth was the second(0.379±0.049), while the stem form was the smallest(0.100±0.022). Among the provenances of chinaberry from Guangdong coastal areas and nearby areas, the adaptability of provenances from Guangdong, Hainan and nearby areas was the best, and part of provenances from Guangxi, Guizhou and Yunnan were also well. The possibility of selecting superior individuals from the provenances with good adaptability was larger. Besides the correlation coefficients among diameter, crown breadth and lateral branch number were above 0.7 between east-west crown breadth and south-north crown breadth, and that the correlation coefficient between height and ground diameter was 0.647, while that between the height and stem form was the smallest(0.299).4.Genetic diversity study of chinaberry provenance by SSR and SRAP showed that 20 pairs of SRAP primers amplified 145 polymorphic bands effectively, the total genetic diversity(Ht) was 0.37, the genetic diversity among provenances(Hs) was 0.20, the average percentage of polymorphic loci(Pp) was 58.24%, Nei ’s average genetic diversity index was 0.20, and Shannon’s average information index was 0.30;15 SSR loci detected 254 alleles in 461 DNA samples of M.azedarach, Nei ’s average genetic diversity index was 0.865, allele abundance ranged from 5.61(SSR123) to 11.81(SSR120), the average inbreeding coefficient in group level(Fit) was 0.120, the average inbreeding coefficient within population(Fis) was 0.017, Coefficient of gene differentiation(Fst) was 0.132, the average gene flow among groups was 1.830, the mean of observed heterozygosity and mean of average expected heterozygosity were 0.74 and 0.75 respectively, AMOVA showed that most variation of M.azedarach mainly came from within the provenance and less from among provenances. The neighbour-joining clustering analysis and the principal component analysis based on genetic distance among provenances by SRAP indicated that thirty-one provenances were divided into four groups, the provenances from Hainan was group I; the seedlots from Guangdong, Guangxi, Fujian, Jiangxi, Hunan and part of Yunnan, Guizhou which were close to Guangxi constituted group II; the provenances from Yunnan, Guizhou, Sichuan, and Gansu clustered into group III; the provenances from Zhejiang, Hubei, Henan, Anhui, Shandong, Shanxi and Hebei formed group IV. The results of SSR UPGMA cluster showed consistency with the results of SRAP cluster. And the genetic distance was significantly correlated with the geographical distance between populations. Genetic structure analysis based on SSR markers showed that thirty-one provenances were grouped into three different homologous gene pools: west population, south population and north population. 5.Based on the genetic distances and genetic structure analysis, combining with geographic variation of the stone of the fruit, seed phenotype and adaptability of provenance in the young forest, it is recommend that the provenances of chinese M.azedarach could be divided into three kinds preliminary. |
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