Evaluation of cross-protection with an attenuated isolate of Bean yellow mosaic virus by differential detection of virus isolates using RT-PCR

Abstract

Cross-protection by an attenuated severe isolate of Bean yellow mosaic virus (BYMV), a member of genus Potyvirus, was evaluated. The attenuated isolate, M11, produced no or extremely mild symptoms on broad bean and Nicotiana benthamiana. To differentiate between M11 and severe isolates, we prepared specific primers for analysis by the reverse transcription-polymerase chain reaction (RT-PCR) based on a difference in the nucleotide sequence at the 1676th position in the HC-Pro (helper component proteinase) gene. M11 had a strong ability to cross-protect plants from infection by a severe isolate as shown by RT-PCR. Plants that were first inoculated with a severe isolate and then challenge-inoculated with M11 were dually infected by these viruses, and the symptoms on upper leaves were significantly milder than those on plants infected only with the severe isolate.