Genetic Transformation of Flowering Bulb Crops for Virus Resistance

Abstract

Objectives. The major aim of the proposed research was to establish an efficient and reproducible genetic transformation system for Easter lily and gladiolus using either biolistics or Agrobacterium. Transgenic plants containing pathogen-derived genes for virus resistance were to be developed and then tested for virus resistance. The proposal was originally aimed at studying cucumber mosaic virus (CMV) resistance in plants, but studies later included bean yellow mosaic virus (BYMV). Monoclonal antibodies were to be tested to determine their effectiveness in interning with virus infection and vector (aphid) transmission. Those antibodies that effectively interfered with virus infection and transmission were to be cloned as single chain fragments and used for developing transgenic plants with the potential to resist virus infection. Background to the topic. Many flower crops, as lily and gladiolus are propagated vegetatively through bulbs and corms, resulting in virus transmission to the next planting generation. Molecular genetics offers the opportunity of conferring transgene-mediated disease resistance to flower crops that cannot be achieved through classical breeding. CMV infects numerous plant species worldwide including both lilies and gladioli. Major conclusions, solutions and achievements. Results from these for future development of collaborative studies have demonstrated the potential transgenic floral bulb crops for virus resistance. In Israel, an efficient and reproducible genetic transformation system for Easter lily using biolistics was developed. Transient as well as solid expression of GUS reporter gene was demonstrated. Putative transgenic lily plantlets containing the disabled CMV replicase transgene have been developed. The in vitro ability of monoclonal antibodies (mAbs) against CMV to neutralize virus infectivity and block virus transmission by M. persicae were demonstrated. In the US, transgenic Gladiolus plants containing either the BYMV coat protein or antisense coat protein genes have been developed and some lines were found to be virus resistant. Long-term expression of the GUS reporter gene demonstrated that transgene silencing did not occur after three seasons of dormancy in the 28 transgenic Gladiolus plants tested. Selected monoclonal antibody lines have been isolated, cloned as single chain fragments and are being used in developing transgenic plants with CMV resistance. Ornamental crops are multi-million dollar industries in both Israel and the US. The increasing economic value of these floral crops and the increasing ban numerous pesticides makes it more important than ever that alternatives to chemical control of pathogens be studied to determine their possible role in the future. The cooperation resulted in the objectives being promoted at national and international meetings. The cooperation also enabled the technology transfer between the two labs, as well as access to instrumentation and specialization particular to the two labs.