Use of a chimeric transgene construct to confer broad resistance in zucchini (Cucurbita pepo L.) plants against cucurbit-infecting potyviruses occurring in KwaZulu-Natal, South Africa

Abstract

The frequent identification of cucurbit-infecting viruses across the province of KwaZulu-Natal (KZN) in South Africa necessitates developing effective methods of controlling these diseases. Putative transgenic baby marrow (Cucurbita pepo L.) plants resistant to Zucchini yellow mosaic virus (ZYMV), Moroccan watermelon mosaic virus (MWMV) and Zucchini shoestring virus (ZSSV), three potyviruses occurring in KZN, were developed in this study. A portion of the coat protein coding sequences of each of the selected viruses was amplified by RT-PCR and inserted into the plant expression vector pEPJ86-m/2N. The segment containing the expression cassette was subcloned into the binary vector pGA482G before being introduced into Rhizobium radiobacter (formerly Agrobacterium tumefaciens) strain LBA4404 (pAL4404)(pBI121). Baby marrow cotyledon explants, transformed using Rhizobium-mediated transformation, were regenerated in vitro under kanamycin selection. A total of 94 putative transgenic marrows lines were successfully regenerated from 250 explants. PCR results showed that 84 out of the 94 lines had the transgene. Of these 84 lines, 76 showed resistance after mechanical inoculation with the viruses under study. The preliminary results show the potential of using transgenic cucurbits with resistance to the three potyviruses as an effective strategy to control potyvirus diseases on cucurbits.