FRUIT SET FAILURE IN TISSUE CULTURE-DERIVED DATE PALM TREES (PHOENIX DACTYLIFERA L.) CV. 'NABT SAIF' AS AFFECTED BY POLLINATOR TYPE AND POLLINATION DENSITY

Abstract

There is a special interest in date palm plants regenerated by tissue culture. However, one of the major weaknesses of mass tissue culture propagation is the appearance of undesired off-type plants, such as poor fertility and delayed flowering. During the 2004 and 2005 seasons, the effect of five date palm pollinators, namely ‘Ahmar’, ‘Akhdar’, ‘Fard’, ‘Khenizy’ and ‘Maghool’ as well as sugar palm (Phoenix sylvestris), each with five different pollination densities (10, 20, 30, 40 or 50 strands/female spathe), was studied on fruit set, multi-carpel fruit formation, fruit drop, and fruit quality of eight-year tissue culture derived ‘Nabt Saif’ palm trees growing at Al-Ain oasis, United Arab Emirates, The results showed different degrees of compatibility among the pollinators on ‘Nabt Saif’. The pollinator ‘Khenizy’ resulted in the highest (34.3% and 28.7%, for 2004 and 2005, respectively) and ‘Fard’ the lowest (11. 7% and 20 % for 2004 and 2005, respectively) fruit set level. The pollinator ‘Sugar palm’ (Phoenix sylvestris) was as effective as or better than the other pollinators that belong to the species Phoenix dactlifera. There were no significant differences between the different pollination densities on fruit set and fruit quality during both seasons. Generally, neither the pollinators nor the pollination density resulted in a satisfactory level of fruit set. These results may suggest that other endogenous factors are responsible for such abnormality in the tissue culture derived ‘Nabt Saif’ palms. Some metaxenia effects of the different pollinators on fruit quality characteristics were recorded both at Bisir and Tamr stages. In this respect, the ‘Sugar palm’ pollinator significantly increased fruit and flesh weight, fruit length and diameter and seed weight percentages at Bisir stage, but decreased the concentration of total soluble solids, acidity and vitamin C at both Bisir and Tamr stages compared to other pollinators. More research work is needed on tissue culture derived date palms to understand more clearly the nature of abnormalities that appear in some cultivars.