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Poster: Plant-pathogen interactions

Abs # P16064: Resistance mechanism of watermelon to Fusarium wilt: a case study of resistant JSB line in Taiwan

Presenter: Chang, Pi-Fang Linda       Contact Presenter
AuthorsChang, Pi-Fang Linda  (A)   Hsu, Ching-Chi  (A)   Lin, Ying-Hong  (A)   Huang, Jenn-Wen  (A)   Chen, Kan-Shu  (B)   Liou, Tsung-Dao  (B)  
Affiliations: (A): Department of Plant Pathology, National Chung Hsing University
(B): Fengshan Tropical Horticultural Experiment Branch, Agricultural Research Institute, Council of Agriculture

Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum (FON), is one of the limiting factors on watermelon production. In this study, a Fusarium wilt resistant line (JSB), which was derived from mutation of susceptible Sugar Baby population in the watermelon fields, was used to investigate the resistance mechanism of watermelon to FON. The values of xylem vessel number and diameter in resistant plants were significantly different from those in susceptible plants. At 9 days post inoculation (dpi), FON could be recovered from 88% of the roots in the symptomless plants of both watermelon lines, and from 54% and 65% of the stem segments in resistant and susceptible plants, respectively. According to the tissue sections, at 8, 13 and 35 dpi, the xylems of roots and lower stems (close to soil surface) in resistant watermelon plants were also colonized by FON, but to a much lower ratio, as in the susceptible ones; nevertheless, no colonization within higher stems (close to cotyledons, 35 dpi) was observed in the resistant plants. Even though the susceptible plants grown in infested soil were all dead by 35 dpi, the remaining resistant plants still survived thereafter. The survived resistant plants grown in infested soil (81 dpi) showed that pathogens could be isolated from roots and shoot bases but not from the stems and tissue parts above cotyledons. These phenomena suggest that the resistance in JSB may result in reducing FON colonization in the vascular systems of the host. The RT-PCR results showed that the expression of phenylalanine ammonia lyase (PAL) gene induced by FON may also involve in resistance of watermelon to Fusarium wilt pathogen. (This research was supported by grants: NSC 91-2313-B-005-094; NSC 92-2313-B-005-054; NSC 93-2313-B-005-080.)

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