Epidemiological Aspects of the Japanese Tobamovirus Strain, Pepper Mild Motte Virus(PMMoV) Infecting the L2 resistance Genotype of Green Pepper(Capsicum annuum L.)

To understand the epidemiological aspects of tobamovirus infecting the L resistance genotypes of green pepper, fifteen isolates were collected from geographically different fields and were chracterized by their biological properties. All isolates infected L1 and L2 plants systemically, but were localized in L3 and L4 plants. The symptomatology on several test plants and the reactivity to an antiserum showed that they were identical to that of a Japanese strain of pepper mild mottle virus (PMMoV-J). The viral infection was also confirmed by a reverse transcription and polymerase chain reaction (RT-PCR) with oligonucleotide primers that amplity the coat protein gene of PMMoV-RNA. On the other hand, the RT-PCR allowed us to detect PMMoV in seeds of some commercial cultivars of green pepper. Viruses isolated from the seeds could infect L2 plants systemically. Further analysis of the nucleotide sequence of the predicted coat protein gene revealed that the isolates from the commercial seeds were identical to that of PMMoV-J. These results indicated that the L2 resistance-breaking tobamovirus has prevailed in fields of green pepper in Japan. and that infected seeds may be one of the initial sources of the viral infection.