Submitted to: North American Barley Research Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2014
Publication Date: 6/30/2014
Citation: Mornhinweg, D.W. 2014. Bird cherry-oat aphid: do we have resistance? [abstract]. In: Proceedings of the 21st North American Barley Researchers Workshop, June 29-July 2, 2014, Minneapolis, MN. 1 p. Available: http://www.nabrw.umn.edu.
Technical Abstract: Bird cherry-oat aphid (BCOA), Rhopalosiphum padi (L.), is a highly efficient, non-propagative, persistent vector of the phloem limited leutovirus BYD-PAV. BYD is the most important viral disease of cereal grains in the world and PAV is the most prevalent strain of BYD in North America. Not all BCOA acquire the disease. Aviruliferous BCOA can feed on barley in the spring and winter but injury to shoots and roots is often not recognized because it is asymptomatic in the field. Yet, aviruliferous populations as low as 11 aphids/tiller have been shown to reduce grain yield significantly. Greenhouse seedling screening of barley with aviruliferous BCOA has shown symptomatic damage or desistance resulting in stunting, chlorosis, and necrosis even unto seedling death. A visual rating scale of 1 - 4 has been defined by percent of leaf chlorosis (1=0-25 percent, 2=26-50 percent, 3=51-75 percent, and 4=76-100 percent) and resistant lines have been identified. It is yet to be determined if resistance in these lines will protect grain yield. Eight previously identified BCOA-resistant, spring barley lines plus a susceptible, Morex, were screened with aviruliferous BCOA. Identical flats were planted and kept aphid free with repeated insecticide applications. Seedlings were rated with a 1 - 4 scale when all Morex were dead. Seedling height and leaf number were measured. Resistant seedlings and non-infested controls were transplanted to pots in a RCB design with 9 replications and are currently being evaluated in the greenhouse for plant height, heading date, yield components, and grain yield. Preliminary data will be presented. The type of resistance in these lines has yet to be determined and the type of resistance desired for BCOA is unclear. Antixenosis resistance, involving high levels of allelochemicals usually under single gene control, and historically most often employed by plant breeders, can cause yield drag, damaging side effects on natural enemies and biotype shift. Tolerance resistance has more recently been desired because it has the least effect on biotype shift and natural enemies; however, sustained phloem ingestion by a persistent transmitter of BYDV like BCOA might not be desirable. Although virus transmission can occur quickly, there is a higher transmission frequency with sustained phloem ingestion. Antibiosis resistance negatively effects the multiplication of aphids that have colonized a resistant plant by decreasing survival, growth and fecundity and extending development time of the aphid. Antibiotic resistance in barley to BCOA has been reported but whether this resistance is meaningful (protects grain yield) has yet to be shown. Regardless, we need to develop and employ resistance which will reduce yield loss from aviruliferous BCOA feeding with the potential added benefit of decreased yield loss from BCOA vectored BYDV.