Broad-Spectrum Resistance to Different Geographic Strains ofPapaya ringspot virusin Coat Protein Gene Transgenic Papaya

Abstract

Papaya ringspot virus (PRSV) is a major limiting factor for cultivation of papaya (Carica papaya) in tropical and subtropical areas throughout the world. Although the coat protein (CP) gene of PRSV has been transferred into papaya by particle bombardment and transgenic lines with high resistance to Hawaii strains have been obtained, they are susceptible to PRSV isolates outside of Hawaii. This strain-specific resistance limits the application of the transgenic lines in other areas of the world. In this investigation, the CP gene of a local strain isolated from Taiwan, designated PRSV YK, was transferred into papaya via Agrobacterium-mediated transformation. A total of 45 putative transgenic lines were obtained and the presence of the transgene in papaya was confirmed by polymerase chain reaction amplification. When the plants of transgenic lines were challenged with PRSV YK by mechanical inoculation, they showed different levels of resistance ranging from delay of symptom development to complete immunity. Molecular analysis of nine selected lines that exhibited different levels of resistance revealed that the expression level of the transgene is negatively correlated with the degree of resistance, suggesting that the resistance is manifested by a RNA-mediated mechanism. The segregation analysis showed that the transgene in the immune line 18-0-9 has an inheritance of two dominant loci and the other four highly resistant lines have a single dominant locus. Seven selected lines were tested further for resistance to three PRSV heterologous strains that originated in Hawaii, Thailand, and Mexico. Six of the seven lines showed varying degrees of resistance to the heterologous strains, and one line, 19-0-1, was immune not only to the homologous YK strain but also to the three heterologous strains. Thus, these CP-transgenic papaya lines with broad-spectrum resistance have great potential for use in Taiwan and other geographic areas to control PRSV.

Transformasi Gen Antisens ACC Oksidase pada Pepaya dengan Teknik Penembakan Partikel

“…Di Australia, pengujian pepaya transgenik di lapang untuk program pemuliaan tanaman telah menghasilkan galur yang tahan terhadap isolat lokal PRSV (Lines et al 2002). Taiwan telah berhasil merakit tanaman pepaya transgenik dan memperlihatkan potensi hasil dan ketahanan yang tinggi terhadap penyakit PRSV (Bau et al 2003).…”

Viral inhibitors to control the Papaya ringspot virus on Carica papaya

“…To reinforce the mechanical inoculation, plants were reinoculated using five aphids (Myzus persicae) per plant, previously fed on diseased papaya plants (Bau et al, 2003;Cruz, 2007).…”

Post-transcriptional gene silencing is involved in resistance of transgenic papayas to papaya ringspot virus

“…It is generally considered, that transgene similarity greater than 90 % to the virus is sufficient to induce durable resistance (Moreno et al 1998), although only as 84 % identity was sufficient to induce plum pox resistant plum trees (Guo et al 1998). In the case of transgenic papaya in Taiwan, Bau et al (2003) recorded resistance towards PRSV bearing 89.7 % transgene similarity. According to this work, the crucial CP part for the resistance against PRSV is the 100 bp region in the 3' part including the 3'NTR.…”