Abstract
Taxodium is a deciduous conifer belong to family Cupressaceae, commonly known as cypresses. In the present study, two species of Taxodium trees from four locations in Egypt were investigated. Bald cypress and pond cypress as plant genetic resources were surveyed and tested for horticultural and morphological traits using biochemical and molecular genetic techniques. Leaf essential oils (EOs) were analyzed by gas chromatography coupled with mass spectrometry (GC/MS), subjected to bioassay for insecticidal activity against the rice weevil (Sitophilus oryzae L.) and the red flour beetle (Tribolium castaneum (Herbst)), and compared with three monoterpenes (D-limonene, camphor, and carvone). T. distichum var. distichum (bald cypress) growing in the drylands in the Alexandria, El-Beheira, Giza 1, and Qalyubia governorates had lower root hydrogen peroxide (H2O2), proline content, and leaf peroxidase activity than T. distichum var. imbricarium (pond cypress, Giza 2), growing in swamplands of the Giza governorate. Forty random amplified polymorphic DNA (RAPD-DNA) primers and 20 simple sequence repeats (SSRs) indicated 57.41% and 64.50% polymorphism, respectively, between the Taxodium species. The main constituents of leaf EOs from trees growing in Alexandria were germacrene D (14.71%), bomeol acetate (6.81%), ledene oxide-(II) (6.13%), and trans(beta)-caryophyllene (6.13%); thujopsene (18.27%), 3-carene (14.49%), and cedrol (8.02%) were found in trees from Qalyubia; thujopsene (19.93%), acaryophyllene oxide (17.32%), and cedrol (10.87%) from trees in Giza 1, alpha-pinene (63.80%) and thujopsene (10.15%) from trees in Giza 2, and El-Beheira a-pinene (26.66%), thujopsene (22.42%), and cedrol (11.30%) in trees from El-Beheira. S. oryzae was more susceptible than T. castaneum to the EOs from leaves of Taxodium trees from the four localities. Taxodium oil from El-Beheira followed by carvone and EOs from trees grown in Alexandria showed the lowest LC50 against S. oryzae with values of < 50, 28.52, and > 50 mu L/L, respectively. Carvone, Taxodium EOs from El-Beheira and Qalyubia exhibited the lowest LC50 against T. castaneum with values of 53.37, 66.40, and 72.54 mu L/L, respectively.