Ultrastructural study of colonization of resistant Oriental lily clones by Fusarium oxysporum f. sp. lilii
2017
Zhang, Y. P. | Qu, S. P. | Ma, L. L. | Yang, X. M. | Xu, F. | Wang, J. H. | He, Y. Q.
The production of lily bulbs and flowers is under serious threat from basal rot of the bulbs caused by the soil-borne fungus Fusarium oxysporum f. sp. lilii. Clones of Oriental lily hybrid 'Casa Blanca' resistant to F. oxysporum f. sp. lilii were obtained by toxin screening. To explore disease resistance based on cytology, the colonization processes in resistant Oriental lily clones following inoculation with F. oxysporum f. sp. lilii was studied using transmission electron microscopy. Samples of susceptible clones and resistant clones were collected before inoculation and 1-7 days after inoculation. Ultrastructural sections were prepared and processed following conventional procedures. Before inoculation, the ultrastructure of the cells and tissues showed that there were about 40 starch grains per cell in selected resistant somaclones, but only about five starch grains per cell in susceptible somaclones. There were about 8-fold more starch grains in selected resistant clones than in susceptible somaclones. After inoculation, from the ultrastructure of the cells and tissues, we found that selected disease-resistant clones were superior to susceptible somaclones, mainly in terms of resistance to fungal extension. Fewer hyphae were found in disease-resistant clone cells. Cells of resistant clones showed large amounts of degradable material and secretion, making them more able to prevent fungus extension. These results show that the process of further expansion of F. oxysporum after invasion is greatly hindered in disease-resistant clones.
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