| Mulberry (Morns, L.) is a perennially and economically important plant, as it is the sole food for the domesticated silkworm, Bombyx mori. Mulberry is widely distributed geographically in China, easily adapted to different ecological conditions, and easily hybridized both naturally and artificially.which formed abundant mulberry germplasm resources. Evaluating the genetic diversity and molecular phylogeny in mulberry (genus Morus) by DNA molecular markers in this paper, it would be valuable for germplasm identification, conservation, using the mulberry germplasms, construction of core collection, and mulberry genetic breeding. The main results were summarized as the following:1. Comparative analysis of genetic diversity among mulberry wild and cultivated species as revealed by ISSR and SSR markersA (CA)15 enriched microsatellite library was constructed for mulberry and screened ten SSR primers with polymorphism. SSR, including 10 novel primers and five primers previously reported, and ISSR markers were used firstly to investigate genetic diversity of 27 mulberry accessions including 19 cultivated accessions and 8 wild accessions. Using 15 ISSR primers, 138 discernible DNA fragments were generated with 126 (91.3%) being polymorphic, the mean PIC (polymorphism information content) values of each ISSR primer was 0.2006. The 15 SSR primers produced an average of 5.13 alleles/locus, and an average PIC value of 0.5210. The mean genetic similarity coefficients among all mulberry accessions ascribed by ISSR and SSR matrices were 0.7677 and 0.6131, respectively. All index values of genetic diversity revealed by both markers indicated that within wild species had higher genetic diversity than within cultivated species. It suggeats that cultivation may cause the loss of genetic diversity of mulberry. Cluster analysis of ISSR and SSR using UPGMA method revealed that the wild species are genetically distant from the domesticated species studied here. Principal coordinates analysis (PCA) for ISSR and SSR data also supports their UPGMA clustering. ISSRs and SSRs were compared in terms of their informativeness and efficiency in a study of genetic diversity and relationships among 27 mulberry accessions, the result showed that SSRs presented a higher level of polymorphism and greater information content, and the correlation coefficients of similarity were performed for both marker systems used. According to the results, the conservation strategy was put forward.2. Construction of fingerprinting and genetic diversity of mulberry cultivars in China by ISSR markersThe ISSR fingerprintings of 24 mulberry cultivars were constructed, and proved that ISSRs were a very effective tool and robust method in the mulberry varieties discrimination. There were 3 independent ways to identify the mulberry varieties, a) unique ISSR markers, b) unique band patterns and c) a combination of the band patterns provided by different primers. 17 ISSR primers amplified 80bands, 40 of them (50.00%) were polymorphic. The mean genetic similarity coefficient, the mean Nei's gene diversity (/?) and the mean Shannon's Information index (/) of mulberry cultivars were 0.8731. 0.1210 and 0.1942, respectively,suggesting that genetic diversity of mulberry cultivars was lower and the genetic base was rather narrow. Both UPGMA cluster and PCA analysis showed clear genetic relationships between the 24 mulberry cultivars.The major clusters were related to known pedigree relationships.3. Genetic diversity of mulberry varieties from different ecotypes as revealed by ISSR analysis in ChinaPopulation structure and genetic diversity of 8 mulberry populations from different ecotypes in China were analyzed by ISSR markers. 12 SSR primers generated a total of 83 amplification products, of which 50 were polymorphic, revealing 60.24% polymorphism among 66 mulberry local varieties, the mean PIC value was 0.1469. The total heterozygosity (Hy), heterozygosity within population (H s), diversity between populations (D St) were 0.1600,0.0851 and 0.0749,respectively.The coefficient of population differentiation (G st) was 0.5678, indicating that the genetic variation between populations was higher than that of within populations. The gene flow (Nm). was 0.4683, suggesting that genetic drift between populations caused local genetic differentiation and therefore, population divergence. The mean genetic similarity coefficient was 0.8456, genetic similarity coefficient among 8 mulberry populations ranged from 0.8441 to 0.9640, indicating that genetic diversity of different populations existed variation. A dendrogram of all 66 local varieties of mulberry based on the genetic similarity using ISSR markers was generated by UPGMA cluster method. In the dendrogram, most varieties from the same ecotype clustered together.4. The ISSR analysis of genetic variation between diploid and artificially induced homologous tetraploid of mulberryISSR markers were used to analyze the genetic variation between 6 diploid mulberry varieties and homological tetraploid chemically induced by colchicines. There were no different bands between Nongsang 8, Husang 197 and Yu 2 and their homologous tetraploid while the polymorphic rate between Husang 32 and its homologous tetraploid was the highest (23.53%). The results showed that genetic variation between diploid and homological tetraploid of mulberry induced by colchicines varied with different mulberry varieties.5. A preliminary analysis of genetic variation in mulberry clones as revealed by ISSR markersGenetic variations of mulberry clones were analyzed by ISSR markers. The results showed that only one variation was tested in the clones within field and tissue culture.suggesting that this result highlighted the genetic stability in the clonally propagated.6. Genetic variation between Fengweisang and its spourts as revealed by ISSR markersThe genetic variation between Fengweisang and its spourts was analyzed at the molecular lever by ISSR primers. From the results of amplification, 3 from 8 ISSR primers showed no different bands between Fengweisang and its spourts while Fengweiyabian showed the highest variation among spourts. The study provided molecular evidence for the genetic variation of the spourts.
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