Coat protein-mediated resistance to isolates of barley yellow dwarf in oats and barley.

Abstract

Tissue cultures of GAF30/Park oats were biolistically co-transformed with constructs containing the coat protein (CP) genes of the P-PAV, MAV-PS1 or NY-RPV isolates of barley yellow dwarf virus (BYDV), together with a construct containing the bar gene for herbicide resistance and the uidA reporter gene. Transformed, herbicide-resistant tissue cultures were screened by PCR for the presence of the CP genes. Fertile regenerated plants were recovered from some CP-transformed tissue cultures. T1 progeny of these plants were screened for resistance to the BYDV isolate corresponding to the introduced gene by inoculation with viruliferous aphids followed by ELISA tests. Variation in ELISA values for GAF30/Park control plants made interpretation of the data difficult, but oat plants resistant to each of the three isolates of BYDV (ELISA values less than 0.3; virus titers equivalent to less than 25% of infected controls) were identified in T1 generations. Further testing of MAV-PS1 CP-transformed lines to the T2 generation, NY-RPV CP-transformed lines to the T3 generation and P-PAV CP-transformed lines to the T4 generation identified further resistant plants. Similarly, immature embryos and calli of the barley cultivar Golden Promise were biolistically bombarded with constructs containing the CP gene of the P-PAV isolate of BYDV and the bar and uidA reporter genes, lines of self-fertile P-PAV CP-transformed barley plants were developed, and T1plants were screened for resistance to P-PAV. Eight plants from six lines showed moderate to high levels of resistance to P-PAV that correlated with the presence of the CP gene. Plants giving low ELISA values were also found in other lines, even though the CP gene was not detected in these plants. Some T2 plants derived from resistant parents that contained the CP gene were themselves highly resistant.