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Two Amino Acid Substitutions in the Coat Protein of Pepper mild mottle virus Are Responsible for Overcoming the L4 Gene-Mediated Resistance in Capsicum spp.

July 2007 , Volume 97 , Number  7
Pages  787 - 793

Yoshikatsu Genda , Ayami Kanda , Hiroyuki Hamada , Kyoko Sato , Jun Ohnishi , and Shinya Tsuda

First and fourth authors: Japan Horticultural Production and Research Institute, Matsudo, Chiba 270-2221, Japan; and second, third, fifth, and sixth authors: National Agricultural Research Center, Tsukuba, Ibaraki 305-8666, Japan.

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Accepted for publication 24 January 2007.

The Capsicum spp. L genes (L1 to L4) confer resistance to tobamoviruses. Currently, the L4 gene from Capsicum chacoense is the most effective resistance gene and has been used widely in breeding programs in Japan which have developed new resistant cultivars against Pepper mild mottle virus (PMMoV). However, in 2004, mild mosaic symptoms began appearing on the leaves of commercial pepper plants in the field which possessed the L4 resistance gene. Serological and biological assays on Capsicum spp. identified the causal virus strain as a previously unreported pathotype, P1,2,3,4. PMMoV sequence analysis of the virus and site-directed mutagenesis using a PMMoV-J of the P1,2 pathotype revealed that two amino acid substitutions in the coat protein, Gln to Arg at position 46 and Gly to Lys at position 85, were responsible for overcoming the L4 resistance gene.

Additional keywords: elicitor, methyl bromide, particle assembly.

© 2007 The American Phytopathological Society