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Fecundity, phenology, and seed dormancy of F 1 wild–crop hybrids in sunflower ( Helianthus annuus, Asteraceae)
Author(s) -
Snow Allison A.,
MoranPalma Pedro,
Rieseberg Loren H.,
Wszelaki Annette,
Seiler Gerald J.
Publication year - 1998
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.2307/2446414
Subject(s) - biology , hybrid , helianthus annuus , introgression , fecundity , sunflower , backcrossing , crop , agronomy , germination , botany , horticulture , population , gene , biochemistry , demography , sociology
Crop‐to‐wild hybridization has the potential to introduce beneficial traits into wild populations. Gene flow from genetically engineered crops, in particular, can transfer genes coding for traits such as resistance to herbicides, insect herbivores, disease, and environmental stress into wild plants. Cultivated sunflower ( Helianthus annuus ) hybridizes spontaneously with wild/weedy populations (also H. annuus ) , but little is known about the relative fitness of F 1 hybrids. In order to assess the ease with which crop‐to‐wild introgression can proceed, we compared characteristics of F 1 wild–crop progeny with those of purely wild genotypes. Two nontransgenic, cultivated varieties were crossed with wild plants from three different regions—Texas, Kansas, and North Dakota. Seed burial experiments in the region of origin showed that wild–crop seeds had somewhat higher germination rates (less dormancy) than wild seeds from Kansas and North Dakota, while no differences were seen in seeds from Texas. Progeny from each type of cross were grown in outdoor pots in Ohio and in a weedy field in Kansas to quantify lifetime fecundity and flowering phenology. Flowering periods of hybrid and wild progeny overlapped considerably, especially in plants from North Dakota and Texas, suggesting that these hybrids are very likely to backcross with wild plants. In general, hybrid plants had fewer branches, flower heads, and seeds than wild plants, but in two crosses the fecundity of hybrids was not significantly different from that of purely wild plants. In Ohio, wild–crop hybrids from North Dakota appeared to be resistant to a rust that infected 53 % of the purely wild progeny, indicating a possible benefit of “traditional” crop genes. In summary, our results suggest that F 1 wild–crop hybrids had lower fitness than wild genotypes, especially when grown under favorable conditions, but the F 1 barrier to the introgression of crop genes is quite permeable.