BURIAL AND SEED SURVIVAL IN BRASSICA-NAPUS SUBSP OLEIFERA AND SINAPIS-ARVENSIS INCLUDING A COMPARISON OF TRANSGENIC AND NONTRANSGENIC LINESOF THE CROP

The creation of transgenic plants through genetic engineering has focu sed interest on how the fitness of a plant species may be altered by s mall changes in its genome. This study concentrates on a key component of fitness: persistence of seeds overwinter. Seeds of three lines of oilseed rape (Brassica napus subsp. oleifera DC Metzger) and of charlo ck (Sinapis arvensis L.) were buried in nylon mesh bags at two depths in four habitats in each of three geographically separated sites: Corn wall, Berkshire and Sutherland. Seeds were recovered after 12 and 24 m onths. Charlock exhibited much greater seed survival (average 60% surv iving the first year and 32.5%, surviving the second year) than oilsee d rape (1.5% surviving the first year and 0.2%, surviving the second) at all sites. Charlock showed higher survival at 15 cm burial than 2 c m burial at certain sites, but oilseed rape showed no depth effect. Di fferent genetic lines of oilseed rape displayed different rates of see d survival; non-transgenic rape showed greater survival (2%) than the two transgenic lines, one developed for tolerance to the antibiotic ka namycin (0.3%) and one for tolerance to both kanamycin and the herbici de glufosinate (0.25%). The absolute and relative performances of the different genetic lines of oilseed rape were context specific, illustr ating the need to test hypotheses in a wide range of ecological settin gs.