Oviposition deterrence to Sitodiplosis mosellana (Diptera : Cecidomyiidae): a source of resistance for durum wheat (Gramineae)

Over 250 durum wheats, Triticum durum Desf., and close relatives were scree ned for resistance to the wheat midge, Sitodiplosis mosellana (Gehin). Less than 2% showed consistently reduced egg and larval densities in field and laboratory trials. Two related accessions named 'Kahla' had stable, low lar val infestation levels, which were about 30% of those in commercial durum w heat cultivars. No antibiosis was detected in durum wheats. The reduction i n infestation by larvae was associated with a similar reduction in oviposit ion. The resistance reduced egg densities by 80% or more in choice and no-c hoice laboratory tests and by about 70% in the field. Egg group size was no t affected, and therefore reduced oviposition must have resulted from the n umber of egg groups deposited by females. The resistance was not associated with any of 12 morphological traits that were quantified for spikes,'Kahla ' is the first durum wheat identified to have resistance against the wheat midge.