|Mornhinweg, Dolores - Do|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2009
Publication Date: 11/1/2009
Citation: Mittal, S., Dahleen, L.S., Mornhinweg, D.W. 2009. Barley Germplasm STARS-9577B lacks a Russian Wheat Aphid Resistance Quantitative Trait Locus Present in STARS-9301B. Crop Science. 49:1999-2004
Interpretive Summary: Russian wheat aphids (RWA) feed on plants like barley and have caused substantial losses in the Western United States since they were first identified in Texas in 1986. Russian wheat aphid infestations reduce grain yield and quality of barley and some producers have ceased to grow barley due to RWA damage. While insecticides can be used to control RWA, they are expensive and can leave chemical residues in barley products. We examined RWA resistance from the barley line STARS-9577B by crossing it to a susceptible line Morex to determine the locations of genes for resistance. Progeny from the cross were evaluated twice in the greenhouse for RWA resistance and were screened for differences in DNA markers. Results indicated that STARS-9577B contains two RWA resistance genes, one each on chromosomes 1H and 3H. These appear to be the same loci present in a previously characterized germplasm, STARS-9301B although the alleles on chromosome 1H may be different. Further work is needed to identify lines with different resistance loci to expand the choices for breeding RWA resistance.
Technical Abstract: Russian wheat aphid (RWA, Diuraphis noxia Kurdjumov) infestations of barley (Hordeum vulgare L.) in the western U.S.A. have reduced yield and quality of barley since its introduction in 1986. Resistant germplasm lines have been released and used for cultivar development, including ‘STARS-9577B’, a selection from RWA-resistant Afghanistan introduction CIho 4165. The objective of this study was to map quantitative trait loci (QTL) for RWA resistance in STARS-9577B and compare them to previously mapped loci. A random set of 185 F2:3 families derived from ‘Morex’/STARS-9577B was tested for RWA reaction in replicated trials in the greenhouse based on a 1 to 9 visual rating of chlorosis. Morex is a susceptible 6-rowed malting barley. A B-hordein marker and simple sequence repeat (SSR) markers polymorphic between STARS-9577B and Morex were tested on the population to create a 146 marker linkage map covering the barley genome. QTL analysis located two loci for resistance, on the short arm of chromosome 1H and the long arm of chromosome 3H. The 1H locus was associated with the B-hordein marker, showed additive gene action, and explained 19% of the RWA phenotypic variation. The locus on chromosome 3H was associated with SSR marker EBmac0541, showed partial dominance and explained 47% of the variation for RWA reaction. Combined analysis indicates that the two loci explain 55% of the phenotypic variation for RWA reaction. Results indicate that STARS-9577B lacks one of the QTL found in STARS-9301B, which may explain the consistently higher RWA scores (3 versus 2) in STARS-9577B indicative of lower resistance.