LEAF UNROLLING OF 3 WHEAT GENOTYPES IN RUSSIAN WHEAT APHID EXTRACTS

The Russian wheat aphid (RWA) is an important pest on wheat and barley in several areas of the world. It would be desirable to have an indir ect screening test for resistance when aphids are not available. Three wheat genotypes, one susceptible Carson and two resistant, CORWA1 and PI294994, to the Russian wheat aphid, were used to test their in vitr o responses to aphid extracts. Etiolated seedlings at single leaf stag e about 10 to 15 cm tall were cut into 1.5 to 2 cm long segments. The segments just above the coleptile were incubated in crude RWA extract or buffer. The degree of unrolling of the leaf segments was scored. Si gnificant differences existed in unrolling between the leaf segments i ncubated in buffer only and buffer plus RWA extract. There were also s ignificant differences between the susceptible genotype and the two re sistant ones. No significant difference was detected between the two r esistant genotypes in leaf unrolling. This Laboratory leaf unrolling t est shows promise for genotype selection and needs further testing.