Effects of seed maturation and temperature in germination of squash accessions: implications for gene flow

摘要

Seed dormancy and germination characteristics are fitness-related traits that effect gene flow from transgenic to either cross-compatible horticultural varieties or wild, free-living populations. Such factors are directly related to the formation of persistent soil-seed-banks and are intrinsic to the dynamics associated with such biological systems. Germination of three Cucurbita pepo accessions were examined and include the ornamental gourd 'Orange Ball', the transgenic cultivar 'Destiny 111', and the wild free-living species form, subsp. ovifera var. ozarkana. Germination rate and percentage was recorded for radical emergence of seeds extracted from open-field-grown fruit at different times (Storage Period) and temperatures (15, 20, and 25 C). Significant differences were recorded in germination rate and percentages among the accessions examined when seed were germinated at different temperature, and different seed extraction dates (Storage Period). The rate and percentage of seed germination of'Orange Ball' and 'Destiny III' was significantly greater than subsp. ovifera var. ozarkana at any temperature, and storage period had no effect on 'Orange Ball' germination. Time- and temperature-related seed dormancy was observed in subsp. ovifera var.ozarkana, but competitive advantage (fitness) could not be implied from these experiments. Nevertheless, hybrids produced by intermatings between wild 'free-living' populations and transgenic plants could result in escaped hybrid populations that possess a wide array of seed germination/dormancy characteristics that possess increased fitness. The determination of the inheritance of seed dormancy in subsp. ovifera var. ozarkana and the fitness of cross progeny derived from matings with transgenic cultivars in such populations would provide supportive information for the estimation of socio-ecological risk.