HortScience (2005) 40, 2083-2087

Manoel T. Souza Jr., Paula F. Tennant and Dennis Gonsalves (2005)
Influence of coat protein transgene copy number on resistance in transgenic line 63-1 against Papaya ringspot virus isolates
HortScience 40 (7), 2083-2087
Abstract: Line 63-1 is a 'Sunset'-derived transgenic papaya expressing the coat protein (CP) gene from a mild mutant of a Hawaiian isolate of Papaya ringspot virus (PRSV). Previous work showed that line 63-1 R₁ plants exhibited a range of resistance to severe PRSV isolates from Hawaii (HA), Jamaica (JA), Thailand (TH), and Brazil (BR). Genetic and molecular data obtained in this study confirm that line 63-1 has two CP transgene insertion sites; segregation analysis shows that the CP and the npt II genes are present at both loci. To study the potential effect of gene dosage on resistance, various populations of R₁, R₂, and R₃ seedlings were challenged by PRSV HA, BR, and TH. A R₁ population obtained by self-pollination of line 63-1 hermaphrodite R₀ plant exhibited resistance to all three isolates. The percentage of plants resistant to all three PRSV isolates increased in 63-1-derived populations as a result of recurrent selection. Additional genetic studies demonstrate that the number of resistant plants in a 63-1-derived population is directly correlated with the number of plants with multiple transgene copies. We conclude that transgene dosage plays a major role in affecting the resistance of 63-1 to PRSV isolates from various geographical locations.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)

Research topic(s) for pests/diseases/weeds:
resistance/tolerance/defence of host

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Papaya ringspot virus	Papaya (Carica papaya)	Thailand
	Papaya ringspot virus	Papaya (Carica papaya)	Jamaica
	Papaya ringspot virus	Papaya (Carica papaya)	U.S.A. (Hawaii)