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Subject: Biotechnology and Molecular Biology × Author: Demrew, Zerihun × End date: 2009 × Start date: 2004 ×
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    ThesisItemOpen Access
    Molecular characterization of some citrus cultivars using DNA markers
    (CCSHAU, 2008) Demrew, Zerihun; Boora, K.S.
    The genus citrus, most important fruit crop belongs to the family Rutaceae and sub-family Aurantioideae. It is widely grown in most parts of the world. The genetic diversity and the phylogenetic relationships between different citrus cultivars were studied. Twenty five SSR primers were used to assess polymorphism in twelve genotypes which belong to four species and one hybrid of citrus. A total of 116 clear and reproducible amplified bands were obtained, out of which 103 were polymorphic. The numbers of amplified DNA bands per primer were ranged from 2 to 9 (Molecular size from 100-1200 bp) with an average of 5.27. Percentage polymorphisms ranged from 75- 100 with an average of 89.78% across the genotypes and the PIC values from 0.25 to 0.68 with an average of 0.41. The level of polymorphism among Sweet oranges, Mandarins and Lemons were determined and it was 70.81%, 55.04% and 62.28% with an average PIC value of 0.34, 0.30 and 0.26, respectively. The primers clustered the citrus genotypes into two major groups, and further into many sub groups. The similarity matrices ranged from 0.439 (Cleopatra and Blood Red, most diverse) to 0.801 (Baramasi and Badri lemon, the most closest), with an average of 0.582 across all the genotypes. The cultivars within Sweet oranges were more divergent than cultivars within Lemon. The genetic similarity values ranged from 0.474 to 0.724 (average 0.623) within Sweet oranges and from 0.594 to 0. 801 (average 0.689) within the Lemons. Some markers produced unique alleles in specific genotypes which could be used to distinguish them. The alleles which were unique to one species were also scored to determine how much one species is close to the other: Sweet oranges were more close to Lemons and Mandarins than the other species under investigations, while Mandarin and Citrange hybrid were the most distant in phylogenetic hierarchy. In the current investigations, a huge diversity was observed and relationships among the genotypes determined. The result so obtained can be further used to manipulate genetic determinants of horticulturally important traits to be utilized in citrus breeding programs.