GENETIC ANALYSIS OF ABNORMAL FRUITING IN TISSUE CULTURE-DERIVED TREES OF DATE PALM 'BARHY' GROWN IN SAUDI ARABIA

Tissue culture via embryogenesis has been extensively applied for the large-scale micropropagation of some elite cultivars of date palm, such as 'Barhy'. Since this method requires high levels of growth regulators (auxins 2,4-D) that are known to cause mutations, and several subcultures to multiply embryogenic callus, cultures are prone to somaclonal variations. Considering the economic loss, Random Amplified Polymorphic DNA (RAPD) analysis was performed on 30 abnormal and normal fruit bearing tissue cultured (TC) 'Barhy' trees and 5 offshoot-derived 'Barhy' trees to resolve genetic variation between the two phenotypes and to tag markers for the early selection of true-to-type plants. Clear amplified DNA products were detected with 25 RAPD primers, but only four of them produced a few reproducible and distinguishable polymorphic bands that indicated some genetic variation. Most of the offshoot and TC-derived plants showed low levels of genetic variation. Only 3 out of 30 TC-derived plants showed a significant level of genetic variation with both offshoot-derived and TC-derived plants. Due to the low levels of genetic variation among the abnormal and normal fruit bearing TC-plants, no marker was identified that could differentiate between the normal and abnormal fruit bearing phenotypes. The results indicated that abnormal fruit development in TC-derived 'Barhy' may be attributed to epigenetic changes occurring during tissue culture stages and not to any major changes in the genome.