PARENT SESSION
Oral Session # 60: Invasive Species V: Genetics; Chemical Cycling Effects.
Presiding: S Miao
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 204.
Potential for gene flow from cultivated sorghum to shattercane (both Sorghum bicolor ssp. bicolor) in the midwestern U.S.
Johnston, Jill*,1, 2, Reagon, Michael1, Snow, Allison1, 1 Department of Evolution, Ecology and Organismal Biology, Columbus, OH, USA2 Department of Plant Biology, St. Paul, MN, USA
ABSTRACT- Close taxonomic relationships between some crops and agricultural weeds create the potential for beneficial crop genes to introgress into weed populations. Cultivated sorghum has two close relatives that are pests throughout many areas of the U.S. Johnsongrass (S. halepense) is the best-known Sorghum weed, but shattercane shares subspecific status with the crop and therefore has greater potential for rapid crop to weed gene flow. To evaluate the potential for crop-to-weed gene flow, we surveyed six microsatellite loci in eight populations of shattercane and three types of cultivated sorghum from Kansas and Ohio. Four shattercane populations were collected from sorghum fields (contact) and four were collected from other crop fields (non-contact). Based on the shared proportion of 60 alleles, crops are most genetically similar to each other together and to one shattercane population growing in contact with crops. Only one of the shattercane populations that is relatively isolated from cultivated sorghum clusters away from the crops and other shattercane populations. The remaining shattercane populations are very similar genetically. Geographic distance and contact with crop plants does little to explain patterns of genetic similarity among populations. Migration estimates based on Fst statistics are fairly low (Nm = 0.5), and overall there seems to be a large amount of genetic diversity partitioned among populations (Fst 0.3-0.4). While this could suggest a fair degree of isolation among populations, we believe it is more likely the result of recent founding events in these weed populations. Our data show that the most closely related populations are separated by hundreds of miles. This seems most likely due to similar founders or recurring input of similar alleles from nearby crops.
Key words: agricultural weed, gene flow,