Abstract Detail

Population Genetics

Ageru, A. A. [1], Snow, Allison [2], Sweeney, P. M. [2].

Outcrossing rates of wild and weedy sorghum (Sorghum bicolor ) in Ethiopia: implications for crop-to-wild gene flow .

Gene flow via pollen allows crop genes, including transgenes, to introgress into sexually compatible wild or weedy populations that occur nearby. Because transgenic sorghum ( Sorghum bicolor L.) is being developed for Africa, our research group is investigating the potential for transgenes to spread to conspecific wild/weedy sorghum populations in Ethiopia, which is considered the center of origin for cultivated sorghum. Our previous studies showed that wild and cultivated sorghum often co-occur and flower synchronously in Ethiopia. Furthermore, crop-wild hybrids from artificial crosses involving accessions are fertile and vigorous. In the current study, we investigated the extent of outcrossing in six wild/weedy sorghum populations collected from a total of five regions in Ethiopia (Ghibe, Hararghe, Pawe, Tigray, and Wello) at elevations ranging from 631-1709 m. Using a Whatman filter paper technique, we collected DNA samples from 20 maternal plants per population and 8 progeny plants grown from each of the twenty maternal genotypes. Data from five polymorphic microsatellite markers were used to estimate outcrossing rates based on Ritland’s multilocus mating system program. The average multilocus outcrossing rate was 0.51, with a range of 0.31-0.65 among populations, which is higher than reported earlier for cultivated sorghum. Previous studies of sorghum landraces in Cameroon, Morocco, and Burkina-Faso also report variable outcrossing rates, ranging from ~0.05-0.40. The highest outcrossing we observed (0.65) was recorded in a weedy population that was intermixed with an improved crop variety in Abuare (Wello region). Outcrossing rates were positively correlated with plant height. Biparental inbreeding was evident in all populations and averaged 0.24 (range = 0.10-0.33). The high outcrossing rates of wild/weedy sorghum populations in Ethiopia indicate a high potential for crop-to-wild gene flow. Effective risk management strategies may be needed if the introgression of transgenes or other crop genes from improved cultivars into wild or weedy populations is deemed to be undesirable.

Broader Impacts:
This research is useful to regulatory agencies that evaluate the biosafety of transgenic crops. It also provides basic information about the wild relatives of sorghum, a staple crop in Africa.

1 - Addis Ababa University, Department of Biology, Addis Ababa, Ethiopia
2 - Ohio State University, Department of Evolution, Ecology and Organismal Biology, 300 Aronoff Laboratory, 318 W. 12th Ave., Columbus, Ohio, 43210-1293, USA

Keywords:
sorghum
gene flow
introgression
outcrossing
Africa
Biotechnology
biosafety
cultivar.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Hall A/Convention Center
Date: Monday, August 2nd, 2010
Time: 5:30 PM
Number: PPG003
Abstract ID:367