1.11.61
PAPAYA LEAF-DISTORTION MOSAIC POTYVIRUS (PLDMV) HAS A NON-PAPAYA INFECTIVE TYPE

T MAOKA1, C NODA1, T USUGI1, S KASHIWAZAKI2, S TSUDA3 and H HIBINO4

1Japan International Research Center for Agricultural Sciences, Okinawa Subtropical Station, Ishigaki, Okinawa 9070002, Japan; 2National Agriculture Research Center, Tsukuba, Ibaraki 305-8666, Japan; 3Plant Biotechnology Institute, lbaraki Agricultural Center, lwaina, Nishi-Ibaraki, lbaraki 319-0206, Japan; 4National Institute of Agro-Environmental Sciences, Tsukuba, lbaraki 305-8604, Japan

Background and objectives
Papaya (Carica papaya) is one of the most important fruits in tropical and subtropical areas. In Japan, papaya leaf-distortion mosaic potyvirus (PLDMV) and papaya ringspot potyvirus (PRSV) were reported as the causal viruses of papaya disease [1]. Out of them, PLDMV is the most destructive factor of papaya production in Japan [1]. They both belong to the genus potyvirus, and have similar properties such as symptoms on papaya plants, host range and aphid transmission.

Materials and methods
PLDMV-C was isolated from Brynopsis laciniosa in Okinawa, Japan in 1995. Three PLDMV-P isolates (leaf-distortion mosaic, yellow mosaic and mosaic isolates) were isolated from papaya plants in Okinawa, Japan during 1990-92. The CP gene of leaf-distortion mosaic isolate was first sequenced [2], and those of other isolates were cloned using RT-PCR and then sequenced [4]. Sequence data were analyzed with the DNASIS program and 'gap', 'pileup', 'distances' and 'growtree' programs of GCG.

Results and conclusions
From the sequence data of PLDMV isolates, their deduced CP amino acids were translated. The number of CP amino acids of three PLDMV-P isolates was 293, while that of PLDMV-C was 291. Deletion of two amino acids was found in the N terminus of PLDMV-C. The amino acid identities between PLDMV isolates and PRSV or other potyvirus were approximately 60%. This results indicates that PLDMV is a distinct virus in the genus potyvirus.

The dendrogram of relationships among PLDMV and PRSV isolates indicates that PLDMV-C was clusterd with the three PLDMV-P isolates, and they were not clustered with PRSV isolates. From these results, it was found that two papaya potyviruses had non-papaya infective types. It may be possible to say that PLDMV-P has also arisen from PLDMV-C, as for PRSV-P from PRSV-W described by Bateson et al. [3]. It is expected that PLDMV-P and PRSV-P may have been adapted to infect papaya.

References
1. Maoka T, Kawano S, Usugi T, 1995. Annals of the Phytopathological Society of Japan 61, 91-94.
2. Maoka T, Kashiwazaki S, Tsuda S et al., 1996. Archives of Virology 141, 197-204.
3. Bateson MF, Henderson J, Chaleeprom W et al., 1994. Journal of General Virology 75, 3547-3553.
4. Maoka T, Usugi T, Noda C et al., 1997. Abstracts of International Symposium on Biotechnology of Tropical and Subtropical Species. p. 132. Brisbane, Australia.