Strategies for Improvement of Succession Cropping Obstacle of Celery
Date Issued
2015
Date
2015
Author(s)
Liu, Yao-Te
Abstract
In Taiwan, the cultivation area and yield of celery are about 970 hectare and 20,289 tonne, respectively, and Changhua and Yunlin are main region for production of celery. For many years, succession cropping obstacle of celery is a serious problem in Taiwan. So far, finding the virgin lands for cultivating celery is the major improvement strategy to avoid the succession cropping obstacle problem of celery, but this improvement strategy has resulted in increased rental costs and difficulties to find suitable places for planting celery. Previous studies concluded that, succession cropping obstacle of celery could be due to (1) Fusarium oxysporum f. sp. apii (Foa) and (2) allelopathy of celery. The objectives of this study were to find out the causing agent(s) of succession cropping obstacle of celery in Taiwan, and then to develop the improvement strategies using soil beneficial microbes. The results showed that Fusarium spp. could be isolated from diseased celery plants, which were collected from the major celery production areas of Changhua and Yunlin. The pathogen was identified as Fusarium oxysporum f. sp. apii by Koch''s postulates, molecular identification, morphological characteristics and a host range assay. On the other hand, aqueous extract of celery and gallic acid not only inhibited seed germination of celery, but also promoted spore germination and the germ-tube growth of Foa. These data indicated that the growth of celery may be inhibited by a synergistic effect of Foa and allelopathy in the field. We have successfully isolated the antagonistic bacteria AB2 and AB78 and the phenol-degrading bacterium PdB5-1. PdB5-1 can significantly degrade gallic acid with a degradation rate more than 99 % in less than 20 hours, and improve the growth inhibition phenomenon of seeds caused by root aqueous extract of celery. AB2 and AB78 could inhibit the growth of Foa mycelium with an inhibitory rate more than 40%, and had good control efficiency on Fusarium yellows of celery at different control timing in a greenhouse assay. In a greenhouse condition simulating the environment of succession cropping obstacle of celery in the field, mixed strains significantly reduced disease incidence and suppressed the population of Foa although the root aqueous extract of celery could increase disease incidence of Fusarium yellows. In the future, we expect to provide a new improvement strategy to reduce the loss caused by succession cropping obstacle of celery in the field using the mixed bacterial strains.
Subjects
Succession cropping obstacle
Fusarium yellows
Fusarium oxysporum f. sp. apii
Allelopathy
Antagonistic bacteria
Phenol-degrading bacterium
Type
thesis
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