Diversity levels in populations of barley landraces may be influenced by va
rying levels of natural outcrossing caused by environmental conditions, Out
crossing was studied in 10 accessions of the barley landrace Arabi Aswad fr
om different environments in Syria. Electrophoretic variation at two codomi
nant isoenzymes (Est1 and Est2) in six seeds of 50 families per population
were analysed and multilocus outcrossing rates calculated. Results were cor
related with interpolated environmental conditions. Outcrossing was, on ave
rage, 1.7% and not significantly different from the outcrossing rate of wil
d barley. A significant increase of outcrossing was observed with increasin
g inter-annual variation in rainfall and decreasing minimum temperatures of
the coldest month.