IN VITRO CULTURE AND GENETIC ANALYSIS OF MALE AND FEMALE DATE PALM (PHOENIX DACTYLIFERA L.)

Abstract

Previously for micropropagation of date palm only shoot tip was used as an explant. In an attempt to utilize different explants, shoot tip and base of flower rachis of male and female plants of variety 'Barhy' were used to initiate callus cultures on modified Murashige and Skoog medium containing different concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-isopentenylaminpurine (2-iP), kinetin and α-naphthalene acetic acid (NAA). Male shoot tip cultures produced embryogenic callus at significantly lower frequency as compared to the female cultures. Female rachis cultures produced embryogenic callus while male rachis cultures produced mostly non-embryogenic callus. After two years, only female shoot tip cultures produced plantlets. Liberation of phenolics was significantly higher in male cultures, enabling differentiation between male and female plants and justifying the slow growth of male cultures. For early identification of cultivars and tracing genetic diversity among date palm genotypes of different origin, offshoot-derived, male and female plants of cultivars 'Barhy' and 'Sukkary', seed-derived plants, and two in vitro cultures of both of these cultivars were subjected to Randomly Amplified Polymorphic DNA (RAPD) analysis. Similarity matrixes based on Nei and Li's coefficients show that offshoot-derived male plant of 'Barhy' was 73.6% genetically similar to its female counterpart, while similarity between male and female plants of 'Sukkary' was 43.1%. In the case of seedlings, male and female plants of 'Barhy' were 87.2% similar and those of 'Sukkary' were 62.3% genetically alike. Two in vitro cultures of 'Barhy' and Sukkary were 73.3% and 70% similar to the normal offshoot-derived plant respectively. These affinities were also reflected in cluster analysis by unweighted paired group means (UPGMA). Results of the study suggested that DNA fingerprinting can be utilized for early detection of date palm sex and genotype and that in vitro behavior of male and female plants of date palm cultivars is differential and their DNA profiles are divergent, which can help in selecting preferable males.