Pollen Variations among some Cultivated Citrus Species and its Related Genera in Egypt

The present investigation aims to study the pollen morphology and ultrastructure of pollen grain characteristics for nine Citrus species and three related genera cultivated in Egypt. The pollen grains were photographed by using both Light Microscope (LM) and Scanning Electron Microscope (SEM). Twelve qualitative and quantitative pollen morphological characters were used to differentiate among the studied taxa. Statistical analysis of palynological data indicated that the pollen size, shape, colpi length, apertures number and type, ora size, amb shape, mesocolpium diameter, and the exine ornamentation were the most distinguished characters in the circumscription of the studied taxa and were of taxonomic value. On the contrary, the other studied pollen characters including the ratio between Polar length/Equatorial diameter (P/E), ora shape and exine thickness were not found to be of taxonomic value in the differentiation among the closely related taxa of Citrus, Fortunella margarita, Limequat hybrid and Poncirus trifoliate in the present study.