Abstract
In vitro propagation of date palm (Phoenix dactylifera L.) through different methods of tissue culture has resulted in large-scale multiplication and distribution to different regions of the world of some elite cultivars which was otherwise difficult to achieve using traditional propagation from offshoots. Propagation by either offshoots or tissue culture generally results in true-to-type plants but some off-types with abnormal phenotypes have developed in tissue cultured plants which may be due to somaclonal variation. In the present study random amplified polymorphic DNA (RAPD) analysis was performed with the aim to detect genetic variation at plantlet stage in female plants of cultivars, 'Khalas', 'Barhy' and 'Sukkary', along with the males of 'Barhy' and 'Sukkary', propagated from offshoots, seeds and through tissue culture. The cultivars showed unique RAPD banding patterns. To facilitate RAPD analysis the 13 DNA samples were divided into two sets of populations. In the first population amplification profiles of 6 DNA samples belonging to two offshoot-derived and four TC-derived plants of cv. Khalas were compared with each other. Out of 18 primers screened, 13 detected polymorphism. The cluster analysis by unweighted paired group method of arithmetic mean (UPGMA) showed two clusters. The genetic distances ranged from 0.634 to 0.825 in the similarity matrix based on Nei and Li's similarity coefficients. In the second population 7 DNA samples belonging to male and female 'Barhy' and 'Sukkary' derived from seedlings and offshoots and a tissue cultured 'Barhy' were compared. All 7 genotypes revealed a unique banding profile with 14 primers used. The genetic distances ranged from 0.232 to 0.810. In this population two clusters were also detected. Offshoots and tissue cultured plants of 'Khalas' when compared showed low level of polymorphism. However tissue cultured 'Barhy' showed a high level of genetic variation when compared with offshoot-derived and seedling-derived male and female 'Barhy'. A significant level of genetic variation was also observed among the cultivars of 'Sukkary' and 'Barhy'. RAPD appears to be an efficient technique for the early detection of genetic variation in plants propagated by tissue culture and from offshoots.