The Study on Lavender Root Rot caused by Pythium

• Main Authors: Sy-Yeu Chen, 陳思羽
• Other Authors: En-jung Sun
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/86150110179105419060

碩士 === 國立臺灣大學 === 植物病理與微生物學研究所 === 99 === Lavender as an ornamental, culinary and medicinal herb, now is one of the economically important crop in agricultural industry in Taiwan. Since lavender introduced from abroad, it was found to be frequently affected with root rot diseases. The diseased plants showed symptoms of root browing and root rot . The severely infected plants wilted, and died in the long run. In this study, the root rot diseases of lavender plants can be found in all three lavender plantation areas in northern and central parts of Taiwan in 2011. Five root rot isolates, including Pythium irregulare, Pythium “group F”, Pythium spinosum, Pythium myriotylum and Phytophthora nicotianae were isolated from these diseased roots of lavender and sweet marjoram. Results also showed that Pythium spp. are dorminant pathogens as 59% of the diseased roots contained this species. Pathogenicity tests using zoospore suspensions or mycelial pellets to inoculate the healthy lavender cuttings in tubes showed that all five isolates can induce the root browing and root rot symptoms on all three lavender cultivars including dentata lavender, fernleaf lavender ,sweet lavender and sweet marjoram. No symptoms developed on control plants. Five root rot pathogens can be consistently reisolated from symptomatic roots after the pathogenicity tests . These results proved that all of five isolates are root rot pathogens of lavender or sweet marjoram according to the Koch’s postulates. Among these pathogens, three are stronger pathogens as they can cause wilt and death of the test cuttings. They are Pythium spinosum, Pythium myriotylum and Phytophthora nicotianae . On the other hand, Pythium irregulare and Pythium “group F” are weak pathogens to all the four different test cuttings. They can only produced subclinical root rot symptoms. This study also found that among these three lavender cultivars, dentata lavender was the most susceptible host to these root rot pathogens, while fernleaf lavender showed the higher resistence to them. Sweet marjoram was, however, only susceptible to Pythium myriotylum.