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Development of novel virus eradication methods for pitaya

Chen Chen: Department of Plant Pathology and Microbiology, National Taiwan University

<div>Pitaya (<em>Hylocereus</em> spp.) in the family <em>Cactaceae</em> is an important fruit crop in Taiwan. Three potexviruses, <em>Cactus virus X</em>, <em>Pitaya virus X</em>, and<em> Zygocactus virus X</em>, have been reported to infect pitaya, and our field surveys showed that almost all pitaya plants in Taiwan are infected by these viruses. In order to obtain virus-free seedlings, we tried to develop new virus eradication methods for pitaya by means of cryotherapy and 24.5 GHz high-frequency microwaves. To achieve our goal, virus-infected pitaya stems were first cultured on MS medium containing plant growth regulators to produce aseptic new shoots which were used for virus elimination experiments. After several tests, vitrification cryotherapy for pitaya was successfully developed, and there were about 60~83% survival rate and 40~70% regrowth rate of the treated pitaya shoot tips. This result indicates that cryotherapy can be applied to a tropical pitaya plant. In addition, exposure to high-frequency microwaves for 1.5 seconds resulted in a temperature increase to 80~90<sup>o</sup>C in aseptic pitaya shoots and 30~40% of the treated shoot tips remained viable. Because plant tissues irradiated by high-frequency microwaves can reach above thermal inactivation point of viruses within seconds, we expect it may become a novel plant virus eradication method. The successful rates of virus elimination by cryotherapy and high-frequency microwaves will be investigated by multiplex RT-PCR.</div>