5.3.13
COAT PROTEIN GENE-MEDIATED RESISTANCE TO BYMOVIRUSES IN TRANSGENIC BARLEY

S KASHIWAZAKI1, KJ LEE1 and T HAGIO2

1National Agriculture Research Center, Tsukuba 305, Japan; 2National Institute of Agrobiological Resources, Tsukuba 305, Japan

Background and objectives
Barley yellow mosaic (BaYMV) and barley mild mosaic (BaMMV) bymoviruses are both transmitted by the soil-inhabiting fungus Polymyxa graminis, and are responsible for economic losses in barley crops in Asia and Europe. Because chemical control of the vector is ineffective, the losses can be prevented only by growing resistant barley cultivars. The objective of this study is to produce resistant barley plants by transformation with viral coat protein (CP) genes.

Materials and methods
Plant expression vectors, containing the BaYMV or BaMMV CP genes downstream of a modified 35S promoter (with seven copies of an enhancer) and intron 1 of the phaseolin gene, were used to transform immature embryos of barley cv. New Golden by particle bombardment [1]. Regenerated plants possessing the CP gene were selected by PCR and Southern hybridization, and self-fertilized. Seedlings of T1 or T2 lines were tested by mechanical inoculation for virus resistance, and examined by PCR and Western blot analysis for CP.

Results and conclusions
Resistance tests of T1 lines transformed with the BaYMV CP gene showed that at least four independent lines had clear resistance to BaYMV (i.e. no visible symptoms), but two other lines were highly susceptible with severe symptoms. T2 progenies derived from the resistant T1 lines also showed resistance. In contrast, only one out of 21 independent T2 lines transformed with the BaMMV CP gene tested showed no symptoms after inoculation with BaMMV, and others were very susceptible. Further analyses of resistance and CP gene expression are in progress.

References
1. Hagio T, Hirabayashi T, Machii H, Tomotsune H, 1995. Plant Cell Reports 14, 329-334.