Citrus species are among the most important fruit trees in the world and are considered as a major export product of Egypt. Forty-eight Citrus L. accessions representing six citrus groups (orange, mandarin, lemon, sour orange, grape fruit and pummelo) were collected. Chemical proprieties including pH, total acidity, total soluble solids and ascorbic acid of different fruit juices were determined. Eight accessions representing different citrus groups were screened for their antibacterial activity against five pathogenic bacteria (Escherichia coli, Salmonella typhi, Staphylococcus aureus, Micrococcus spp. and Bacillus pumilus). Lemon and lime accessions exhibited the highest antibacterial activity compared to the standard antibiotics (ampicillin and streptomycin). However, grapefruit and pummelo accessions showed no inhibitory effect. Inter-simple sequence repeats (ISSR) markers were used to study the genetic diversity and phylogenetic relationships among citrus accessions. The highest level of polymorphism (71%) was detected amongst lemon and lime accessions, whereas, the lowest percentage of polymorphism (18%) was identified within the sour orange group. The phylogenetic tree separated the varieties into discrete clusters according to their respective citrus group. Citrus groups were initially divided into two main clusters at 0.18 level of similarity. Lemon, lime, mandarin and sour orange were grouped in the first cluster, while sweet orange, grapefruit and pummelo were nested in the second cluster.
Key words: Citrus, genetic diversity, ISSR markers, chemical analyses, antibacterial.
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