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Pak. J. Bot., 47(6): 2309-2320, 2015.

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INTRA-SPECIFIC GENETIC DIFFERENTIATION SHAPING THREE  PORTULACA OLERACEA L. MICRO-SPECIES

RANYA El-BAKATOUSHI

Biological and Geological Sciences Department, Faculty of Education,

University of Alexandria, 21526 El-Shatby, Egypt

Corresponding e-mail: ranyaelbakatoushi@edu.alexu.edu.eg; Fax: +034865671; Tel: 01002417351

Abstract: Three Portulaca oleracea L. taxa were used as pure and mixed populations. The pure taxa are geographically separated and identified as the micro species P. granulatostellulata, P. oleracea and P. nitida. DNA tetraploids were recorded in all P. nitida, P. granulatostellul at aindividuals and surprisingly for P. oleracea which is known as DNA hexaploid. It was found that the Nei’s gene diversity (h) in all pure taxa were lower than the same taxa at the mixed case. The observed heterozygosity (H_o) of pure populations were significantly different from the mixed populations of the taxa (T = -3.14 p<0.05). Mean inbreeding coefficient (F_IS) was significantly higher in mixed populations than in pure populations. The mean G + C content differed by 1% between the pure and mixed populations of all trnL-F alignments studied here. The mean nucleotide diversity (Pi) value of mixed populations was higher than of pure populations. Hierarchical analyses under AMOVA indicated that the highest value of genetic variation occurred within populations in both maternal (cpDNA) and biparental (isozymes) markers. Gene flow among populations based on cpDNA data (N_m= 5.48) was higher than the one based on isozymes (N_m = 0.302).The phylogentic tree based on the trnL-F sequence comprised all the pure and the mixed populations of P. olereaceas L., in one clade with high bootstrap support (100%), except for one individual of P. oleracea growing sympatrically with P. granulatostellulata population. The study suggested that a higher rate of gene flow occurs between these taxa than expected and P. oleracea taxa are kept distinct in the mixed case by the slight difference in selfingrate, which could be one of the ambient conditions shaping the P. oleracea L. phenotype.

Key words: Portulaca oleracea, Genetic differentiation, Isozyme, cpDNA.