A system for propagating and virus-screening imported pome fruit and stone fruit cultivars under cross-hemisphere conditions

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Abstract A system was developed in New Zealand for the propagation and virus-screening of pome fruit and stone fruit cultivars imported from the northern hemisphere. By using imported scion material received in the mid to late southern hemisphere summer for both propagation and virus indexing, and using controlled environment conditions, it was possible to simulate two growing seasons and release material from plant quarantine within one year of importation, providing no infection by virus or viruslike diseases was found. Propagation plants were forced into growth using artificial heat and light until autumn, when winter dormancy was induced by placing the container-grown plants in a unit with a glass roof and fine mesh walls. Normal spring growth developed on the plants in the following season and continued through the summer. The technique of double budding was used in budding seedlings with buds from the import, and with indicator buds. These were given a winter dormancy, and in the following season the growth from the indicator buds was examined for virus symptoms. Some of the soft shoot growth made on the propagation plants in the spring was used as inoculum to mechanically inoculate herbaceous virus indicator plants. Virus and viruslike disease indicators are listed, and the use or non use of some important indicators is discussed.