Submitted to: Journal of Plant Growth Regulation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/1994
Publication Date: N/A
Citation: Interpretive Summary: The Russian wheat aphid (RWA) is a devastating pest of wheat and barley in the United States. Currently, there are no available cultivars that are resistant to the RWA. Breeding activities are underway to develop RWA-resistant barley cultivars, but more information is needed to help barley researchers understand the way RWA damages the plant. An increased understanding of the physiological mechanisms involved in RWA damage will aid in the development of RWA-resistant barley germplasm. Many symptoms of damage occur when RWA feed on a susceptible barley plant. Foremost among these symptoms are (1) chlorotic streaks on the leaves, (2) failure of new leaves to unroll, and (3) stunting of leaves. In other crop species under attack by aphids, ethylene (a plant hormone) was found to be involved in the damage to plant cells. The objectives of this study were to determine if aphids (RWA and greenbugs) induced ethylene production in barley, and if fethylene is produced, to determine if it has a role in producing the typical RWA damage symptoms (leaf streaking, rolling, and stunting). We found that RWA induced ethylene production in RWA-susceptible barley but not in RWA-resistant barley. Exposure of the barley plants to ethylene (without RWA feeding) did not produce the typical RWA damage symptoms. These results indicate that other factors, besides ethylene, are involved that result in the expression of RWA damage symptoms. More work is needed to identify these factors.
Technical Abstract: The recently arrived Russian wheat aphid (RWA) is a major pest of wheat and barley in the United States. RWA induced ethylene production in Morex, a barley variety susceptible to RWA, but induced little ethylene production in PI 366450, a barley resistant to RWA. Greenbugs, another aphid pest, induced ethylene production in PI 366450 and Morex, both of which are susceptible to greenbugs. RWA infestation results in pronounced symptoms o barley including leaf streaking, stunting of growth, and rolled leaves. Incubation of barley in ethylene (5 and 50 ul/l) or other plant hormones (auxin, gibberellic acid, zeatin, kinetin, and abscisic acid at 10-4 M) failed to produce streaking or rolling in uninfested plants or to alter the production of these symptoms in infested plants. Incubation of Morex and PI 366450 in ethylene caused some stunting of the leaves and internodes that emerged during or soon after ethylene incubation. However, the leaf and internode that emerged 9 days after incubation showed some compensatory, o increased, growth.