Control of LSV Virus in Lily by Antiviral Chemicals and Humid Heat Treatment

Gyeongbuk Agricultural Research and
Extension Services, Korea
Tel: (82 53) 321-6634
Fax: (82 53) 320-0221
E-mail: jhwlily@yahoo.co.kr, 2004-09-01

Lily, a vegetatively propagated crop, is susceptible to virus infection during propagation and cultivation. The spread of diseased plants has increased the risk of spreading viruses through cuttings, bulbs, and corms. Twenty species of virus have been reported to infect lily plants worldwide. These viruses significantly affect both the quality and quantity of bulbs, as well as those of cut flowers. Multiple infections were also observed in plants. Therefore, propagation with virus-free bulbs is very important for the production of quality cut flowers and pot plants.

The Technology

Many lily cultivars infected with the lily symptomless virus (LSV) remain undetected. Plants often show reduced growth and smaller flowers, and have a pronounced lower bulb yield and a shorter vase life of cut flowers. Symptoms (Fig. 1) become evident at temperatures lower than 15oC. In this study, lilies were infected with two more viruses along with LSV. Some leaves showed vein-clearing or light-green stripes between the veins. After flowering, small light-brown spots on the lower surface of the leaves developed further into yellow, purple or brown spots on the upper surface which led to premature death of the plants at the end of the growing season.

The LSV in lilies can be eliminated by using thermotherapy and antiviral agents in vitro. As shown in Table 1, a thermotherapy of 2-4 weeks during the tissue culture with a humid warm temperature of 35oC was effective for virus elimination. However, thermotherapy was not able to eliminate viruses in cultured shoot apex, because each plant has a different heat tolerance. Highly effective virus elimination can be achieved when an antiviral agent is used along with the thermotherapy (Fig. 2). As shown in Table 2, three antiviral agents, Virazole, Azauracil and Thiouracil, were tested and were all found effective in viral elimination at various concentrations. From the test results, it was recommended that the optimum concentration for high plant survival is around 20µM in all viral agents.

Effectiveness

High quality cut flowers and potted plants can be produced by using virus-free bulbs. A simple application of antiviral agent and proper humid heat treatment were found to be effective in producing virus-free stocks.

Precaution

This technique may not be applicable to all lily species and varieties as they have different heat tolerance. It was also observed that the method may not be effective for other viruses infecting lilies.

Index of Images

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  Table 1 Plant Survival and LSV Elimination in Lilium Oriental Hybrid `Casa Blanca' When Treated with Thermotherapy during Tissue Culture

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  Figure 1 Various Virus Symptoms of Lilium Oriental Hybrid `Casa Blanca'

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  Figure 2 Confirmation of LSV Elimination by Direct Tissue Blotting Immunoassay (Dtbia). (a: Before Antiviral Agent Treatment, B: After Treatment)

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  Table 2 Plant Survival and LSV Elimination in Lilium Oriental Hybrid `Casa Blanca' When Treated with Antiviral Agents during Tissue Culture

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