Heteromorphism of normal and abnormal flowers of date palm cv. “Barhee” and comparison of green and red Ghanami pollens as dominant pollen

Abstract

A major limitation to the use of tissue culture techniques for propagating date palms cv. "Barhee" is the production of plants with abnormal phenotypes (low fruit set and multi-carple fruits) as a result of somaclonal diversity. In addition, pollination with specific of male date palm pollen results in better fruit set and thus higher fruit production. So, this study was conducted to compare the anatomical and morphological characteristics, investigate the possible abnormalities of off-shoot and tissue culture-derived trees, and compare the pollen grain characteristics of Green Ghanami and Red Ghanami male date palm cultivars as the dominant Pollinator of "Barhee" during the growing season of 2019–2020 at Date palm and Tropical Research Center and Shahid Chamran Univeristy of Ahvaz, Iran. This experiment was laid out as a randomized complete blocks design with nine replications. The results revealed that the pollen grain of Green Ghanami had higher polar and equatorial axis than those of Red Ghanami, while the P/E ratio index and inter-edge distance of pollen grains of Red Ghanami were significantly higher than those of Green Ghanami. On the other hand, off-shoot-derived trees of cv. "Barhee" had larger flowers with lower flower density per strand than the tissue culture-derived trees. The stigma characteristics of the upper and lower flowers strands of the offshoot-derived trees were similar to each other and had three completely intact stigmas capable of receiving pollen grains. In tissue culture-derived trees, the lower flowers of the strand had wrinkled and dried stigmas, whereas the three stigmas of the upper flowers were completely undamaged. In addition, the flower of the tissue culture-derived trees had three carpels, one of which had an ovary with an aborted egg. In contrast, in the flower of off shoot-derived trees, only one carpel had a healthy ovary and the other two carpels were without ovaries and degenerated.Generally, it can be concluded that heteromorphic self-incompatibility and abnormality of the atypical flower stigma of tissue culture-derived trees cause the pollen grain not to germinate and grow inside the style.