Cell wall reinforcement in watermelon shoot base related to its resistance to Fusarium wilt caused by Fusarium oxysporum f. sp. niveum

Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum, is one of the limiting factors for watermelon production in Taiwan. In recent research, the phenylalanine ammonia lyase (PAL) gene expressed in the shoot base of the Fusarium wilt resistant line JSB was related to Fusarium wilt...

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Published in:The Journal of agricultural science 2015-03, Vol.153 (2), p.296-305
Main Authors: CHANG, T.-H., LIN, Y.-H., CHEN, K.-S., HUANG, J.-W., HSIAO, S.-C., CHANG, P.-F. L.
Format: Article
Language:English
Subjects:
Agricultural production
Agronomy
biochemical pathways
cell walls
Citrullus lanatus
Citrullus lanatus var. lanatus
Crops and Soils Research Papers
cultivars
defense mechanisms
disease resistance
enzyme activity
Enzymes
Fusarium oxysporum
Fusarium oxysporum f. sp. niveum
Fusarium wilt
gene expression
lignin
pathogens
peroxidase
phenolic compounds
phenylalanine ammonia-lyase
Plant diseases
roots
seedlings
strength (mechanics)
vascular bundles
Vegetables
watermelons
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Summary:Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum, is one of the limiting factors for watermelon production in Taiwan. In recent research, the phenylalanine ammonia lyase (PAL) gene expressed in the shoot base of the Fusarium wilt resistant line JSB was related to Fusarium wilt resistance. Phenylalanine ammonia lyase is the key regulatory enzyme in the phenylpropanoid metabolic pathway. The downstream products of phenolic compounds are considered to be involved in the complicated plant defence mechanisms. They could act as signal molecules, antimicrobial substances and/or structural barriers. To study the resistant mechanisms of Fusarium wilt, the resistant JSB line was examined for comparison of F. oxysporum-watermelon interactions with the susceptible Grand Baby (GB) cultivar. Unlike infected GB, which was seriously colonized by F. oxysporum in the whole plant, the pathogen was limited below the shoot base of inoculated JSB, suggesting that the shoot base of JSB may contribute to Fusarium resistance. The data indicated that a significant increase in PAL activity was found in shoot bases of the resistant JSB line at 3, 9, 12 and 15 days after inoculation (DAI). Shoot bases of resistant watermelons accumulated higher amounts of soluble and cell wall-bound phenolics at 3–9 DAI; the susceptible GB cultivar, however, only increased the cell wall-bound phenolics in shoot bases at 3 DAI. High lignin deposition in the cell walls of vascular bundles was observed in the shoot bases of JSB but not of GB seedlings at 6 and 9 DAI. In the roots and shoot bases of JSB seedlings at 6 DAI, peroxidase enzyme activity increased significantly. In summary, the results suggest that accumulation of cell wall-bound phenolics and increase of peroxidase activity in shoot bases of JSB seedlings during F. oxysporum inoculation, together with the rapid deposition of lignin in the cell walls of vascular bundles, may have provided structural barriers in resistant JSB line to defend against F. oxysporum invasion.
ISSN:0021-8596
1469-5146
1469-5146
DOI:10.1017/S0021859614000057