| Bananas and plantains (Musa spp.) are tropical giant perennial herbs of the genus Musa within family Musaceae (Order Zingiberales). Southeast Asia is the center of origin of Musa species. The genus Musa is composed of a total of between 30 and 40 species, probably about 37, and is usually divided into five sections: Australimusa, Callimusa, Eumusa, Rhodochlamys and Ingentimusa.Wild Musa species of M. acuminate,M. balbi -siana, M. itinerans, M. paracoccinea, M.coccinea, M. rubra, M. sanguinea,M. nagensium and M. basjoo are present in Southern and West Southern China. Bananas and plantains are one of important food crops, especially in tropical and subtropical areas, cultivated for their parthenocarpic, seedless fruits. Bananas and plantains thrive in a wide range of environments between 30°North and South of the equator. However, they are mostly cultivated in the Latin America, tropical Africa and Southeast Asia. Bananas are mainly cultivated in the provinces of Guangdong, Guangxi, Fujian, Hainan, Yunnan and Taiwan of China. The banana total yield in China is followed from that in India and Brazil in the world. It is the fourth fruit and the first tropical fruit after apple, pear and orange in terms of total yield of production in China.The vast majority of cultivated bananas and plantains have originated from intra- or inter-specific hybridization and evolution of two wild species: M. acuminate Colla (AA genome) and M. balbisiana Colla (BB genome) as well as seldom Fe′i cultivars planted in Pacific area. Bananas are divided into two types generally. One type can be eaten as a dessert fruit, while the other type is unpalatable when raw and must be cooked before consumption as cooking banana type. Based on the morphological and agronomic traits, the varieties of dessert bananas are grouped into four groups: Xiangyajiao(AAA),Dajiao (ABB),Fenjiao(ABB) and Longyajiao (AAB). The most widely cultivated clones of commerce are the triploids. Tetraploid clones are rare while diploids are often cultivated for local consumption and some are valued for their good flavoured fruit. The problems of variety classification and variety identification by morphology arise largely due to the complex of genome and various ploidy levels of chromosome in Musa spp. In this thesis, analyses of genetic diversity were carried out for three groups of banana varieties: varieties with A genome and various ploidy levels, varieties with A genome or B genome or their hybrids and various ploidy levels, and exotic varieties, respectively. In addition, the fingerprints of some varieties were primarily constructed.A total of 40 SSR markers were used to assess the genetic diversity among 32 banana varieties with A genome. The number of alleles per locus ranged from three to fifteen when scoring was restricted to strongly amplified fragments with an average 2.99 polymorphic alleles per locus. The average polymorphism information content (PIC) was 0.62, ranging from 0.00 to 0.88. The average pair-wise genetic distances among varieties were estimated from 0.00% to 34.27% with an average of 12.45%, which revealed a narrow range of variability among varieties with the exception of FHIA 25,Yangambi KM 5,Pisang Jari Buaya,Rose(M01) and Huangdijiao. Based on the genetic distance by SSR data, the cluster analysis with unweighted pair-group method using arithmetic averages produced two majo r clusters that closely corresponded to the degrees of genetic differentiation. Gaojiao -qingyajiao and Gaojiaodundilei were identified as identical variety.The 39 SSR markers were used to assess the genetic diversity among 32 banana varieties with A genome or B genome or A and B genomes. The number of alleles per locus ranged from four to twenty when scoring was restricted to strongly amplified fragments and the means of polymorphic alleles per locus was 2.78. The average polymorphism information content (PIC) was 0.80, ranging from 0.45 to 0.91. The average pair-wise genetic distances among varieties were estimated from 3.06% to 43.61% with an average of 30.73%, which revealed a wide range of variability among them. Based on the genetic distance by SSR data, the cluster analysis with unweighted pair-group method using arithmetic averages produced two major clusters that closely corresponded to the genome composition of the varieties (A genome and their hybrids between A genome and B genome). The China landrace groups of Dajiao bananas and Fenjiao bananas were distinct with those of exotic Dajiao bananas and Fenjiao bananas, which implied that they might originate from various regions or they might originate from the same area with a second differentiation.The SSR markers were used to assess the genetic diversity among 33 exotic varieties and 1 indigenous variety. All microsatellite loci were polymorphic among varieties. The number of alleles per locus ranged from 4 to 17 when scoring was restricted to strongly amplified fragments, and averaged 3.05 polymorphic alleles per locus. The average polymorphism information content (PIC) was 0.78, ranging from 0.21 to 0.91. The average pairwise genetic distances among varieties were estimated from 0.00% to 45.53% with an average of 28.19%, which revealed a wide range of variability among them. Based on the genetic distance by SSR data, the cluster analysis with unweight pair-group method using arithemetic averages produced two major clusters that closely corresponded with the genome composition of the varieties (A genome and their hybrids between A genome and B genome). Many exotic varieties, having significant genetic difference with popular cultivars of Williams and Brazil Jiao, were observed, and will be utilized in banana production as new cultivars and banana breeding as parents. Honduras 3 and M-931, Honduras 1 and Honduras 2 were identified as identical variety, respectively.The fingerprints of 34 banana varieties were primarily constructed using 13 SSR markers, which laid a foundation for the systemic construction of other banana varieties. The banana fingerprints can be utilized for fast identification and property right of banana varieties.The very narrow genetic base among popular cultivars was observed. According to breeding targets, new varieties, having wider adaptation and higher tolerance to some stress, could be developed by cross breeding between various cluster of banana varieties or by biotechnology based on the research results.
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