Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/19/2007
Publication Date: 12/10/2007
Citation: Snow, A.A., Sweeney, P.M., Grenier, C., Tesso, T., Kapran, I., Bothma, G., Ejeta, G., Pedersen, J.F. 2007. Lifetime fecundity of F1 crop-wild sorghum hybrids: implications for gene flow from transgenic sorghum in Africa. N.C. Weed Science Society Meetings, December 10-13, 2007, St. Louis, MO. Proceedings of the Gene Flow Symposium of the North Central Weed Science Society Annual Meeting #77. Interpretive Summary:
Technical Abstract: Researchers are developing transgenic crops with enhanced nutrition and higher yields for Africa, but few studies have assessed possible environmental risks of growing these crops. Plans to release transgenic sorghum (Sorghum bicolor) should consider consequences of gene flow to wild relatives, which represent valuable germplasm and sometimes occur as weeds. Our previous studies in Ethiopia and Niger showed that wild and cultivated sorghum often co-occur and flower simultaneously. Here, we tested for spontaneous hybridization between accessions of wild S. bicolor and local cultivars from eastern Africa at times when their flowering periods overlapped. Plants were grown in field plots in Ohio, with a ratio of more than 20 crop plants per wild individual. Microsatellite DNA markers showed that some seeds on wild plants were fertilized by crop pollen, as expected. We also studied the lifetime fecundity of F1 hybrids between a male-sterile cultivar and three wild accessions. Wild and hybrid progeny were grown in common garden experiments in Niger, Ohio, and Indiana. The relative fecundity of hybrids was fairly consistent across locations and differed somewhat among accessions. For two accessions, crop-wild hybrids produced considerably more seeds per plant than the wild parent. For a third accession, hybrids produced similar numbers of seeds per plant as wild plants in the USA and Niger. In all crosses, F1 crop-wild hybrids were vigorous and fertile, indicating the ease with which this generation can contribute pollen and seeds to subsequent generations. This study shows that selectively neutral or advantageous crop alleles are expected to persist in wild sorghum populations following hybridization. Before transgenic sorghum varieties are grown in the vicinity of its wild relatives in Africa, consequences of crop-to-wild gene flow should be examined on a case-by-case basis, taking into account the transgenic traits involved and their ecological effects on other organisms.