Generation of transgenic watermelon resistant to Zucchini yellow mosaic virus and Papaya ringspot virus type W

Abstract

Zucchini yellow mosaic virus (ZYMV) and Papaya ringspot virus type W (PRSV W) are major limiting factors for production of watermelon worldwide. For the effective control of these two viruses by transgenic resistance, an untranslatable chimeric construct containing truncated ZYMV coat protein (CP) and PRSV W CP genes was transferred to commercial watermelon cultivars by Agrobacterium-mediated transformation. Using our protocol, a total of 27 putative transgenic lines were obtained from three cultivars of 'Feeling' (23 lines), 'China baby' (3 lines), and 'Quality' (1 line). PCR and Southern blot analyses confirmed that the chimeric construct was incorporated into the genomic DNA of the transformants. Greenhouse evaluation of the selected ten transgenic lines of 'Feeling' cultivar revealed that two immune lines conferred complete resistance to ZYMV and PRSV W, from which virus accumulation were not detected by Western blotting 4 weeks after inoculation. The transgenic transcript was not detected, but small interfering RNA (siRNA) was readily detected from the two immune lines and T(1) progeny of line ZW 10 before inoculation, indicating that RNA-mediated post-transcriptional gene silencing (PTGS) is the underlying mechanism for the double-virus resistance. The segregation ratio of T(1) progeny of the immune line ZW10 indicated that the single inserted transgene is nuclearly inherited and associated with the phenotype of double-virus resistance as a dominant trait. The transgenic lines derived from the commercial watermelon cultivars have great potential for control of the two important viruses and can be implemented directly without further breeding.

Isolation, identification and molecular characterisation of an isolate ofZucchini yellow mosaic virusoccurring in KwaZulu-Natal, South Africa

“…Tolerant and/or resistant cultivars have been (Beachy 1997, Gonsalves 1998, Ferreira et al 2002. To this end, transgenic cucurbits with resistance to multiple virus infections under field conditions have been developed and have performed well under field conditions (Fuchs and Gonsalves 1995, Tricoli et al 1995, Fuchs et al 1997, Yu et al 2011). The information generated in this study can be a first step in a programme to develop transgenic cucurbits with resistance to multiple virus infections for KZN and South African farmers.…”

Exogenously applied dsRNA molecules deriving from the Zucchini yellow mosaic virus (ZYMV) genome move systemically and protect cucurbits against ZYMV

“…In addition, a translatable CP transgene in transgenic melons provides resistance against ZYMV (Wu et al, 2009). Moreover, an untranslatable chimeric construct containing truncated CP genes from ZYMV and Papaya ringspot virus (PRSV) type W has been transferred to commercial watermelon and melon plants, with the developed transgenic lines exhibiting high resistance against both ZYMV and PRSV Yu et al, 2011).…”

Transgenic Resistance

“…Transgenic N. benthamiana expressing nontranslatable sequences of Prune dwarf virus (PDV) capsid protein gene showed only a recovery form of resistance in one line (Raquel et al, 2008). Similarly, two of 10 transgenic watermelon lines expressing RNA from the same construct were completely resistant to infection by the corresponding viruses with no detectable virus accumulation (Yu et al, 2011). Transgenic papaya of various cultivars were generated expressing nontranslatable RNAs of either the capsid protein encoding sequences of Papaya leaf-distortion mosaic virus (PLDMV) or a fusion of parts of the capsid protein coding sequences of PRSV and PLDMV.…”