| Dry rot of potato is one of the most important postharvest diseases of potato tubers. There is a number of Fusarium species that are involved with the disease. Among them, F. sulphureum,F. sambucinum and F. solani play the most predominant role in casuing dry rot of potato in Northwese of China. In addition to the economic losses, they can also produce mycotoxins, trichothecenes are the main detected mycotoxins. In this study, tubers of the susceptible cultivar(cv. Longshu No.3) and resistant cultivar(cv. Longshu No.6) were chosen as materials,with the help of the UPLC-MS/MS, the accumulation and distribution of trichothecenes in the dry rot of potato tubes were analyzed, and the influence of cultivars, Fusarium strains and storage temperature on trichothecenes production was evaluated, and the treatment effects of three elicitors on controlling the trichothecenes penetrating and diffusing were investigated. Then, T-2, as elicitor, was used to treat slices of potato tuber. The mechanism of induced resistance against dry rot of potato was studied with the help of proteomics technology. The Main results were following:1. The method of UHPLC-MS/MS was developed and proved to be suitable for simultaneous determination four trichothecenes of two type-A of T-2 and DAS, and two type-B of 3ADON and Fus-X in potato tubers inoculated with F. sulphureum. The established method was further evaluated by determining the linearity(R≥0.9995), recovery(113.28-77.97%), precision(RSD≤5.89), and sensitivity(LOD, 0.002-0.005 μg/g; LOQ, 0.005-0.015 μg/g. In addition, it was found that T-2, DAS, 3ADON and Fus-X could be predominantly detected in the lesion, and the toxin could also be identified in tubers without any disease symptoms.2. The concentration of trichothecenecs was much higher in susceptible cultivar(cv. Longshu No.3) than in resistant one(cv. Longshu No.6). The susceptible cultivar infected with F. sulphureum had the maximum concentration of Fus-X, 3ADON and DAS. Among the three Fusarium strains, F. solani had the strongest ability to produce T-2 in both susceptible and resistant cultivars. Room temperature storage was more likely to accumulate trichothecenes than low temperature storage. Meanwhile, the trichothecenes were found not only in the lesion, but also in the adjacent asymptomatic tissue. Trichothecenes concentration showed a strong trend of decline with increase in distance from the infection point. 3. The lesion development in potato tubers inoculated with F. sulphureum were significantly supressed after treated with BABA at 100 m M and chitosan at 0.50% for 3d and sodium silicate at 100 m M for 2d. Meanwhile, the accumulation level of trichothecenes showed a single-apex model with incubation time extended, the highest concentrations for Fus-X and 3ADON appeared in the lesion at 21 d after inoculated, and for DAS and T-2 were at 14 d. In addition, three elicitors of BABA, chitosan and sodium silicate markedly prevented Fus-X, 3ADON, DAS and T-2 penetrating and diffusing in intercellular space of tuber tissue. These findings suggested that the elicitors effectively reduced trichothecenes accumulation in inoculated tubers.4. The results of a comparative proteomic analysis using isobaric tags for relative and absolute quantitation(i TRAQ) technology coupled with 2D LC-MS/MS(Two-dimensional liquid chromatography-tandem mass spectrometry) showed that: A total of 86 proteins were identified as significantly up- or down-regulated in response to T-2 induction in slices of tuber. After functional categorization, these proteins were attributed to metabolism, defense response, protein synthesis, energy pathway, transcription, signal transcription and other. Among them, defence response protein including ROS metabolism related proteins(monodehydroascorbate reductase-like, peroxidase 72-like, peroxidase 12-like), phenylpropanoid pathway related proteins(cinnamic acid 4-hydroxylase,suberization-associated anionic peroxidase, wound-induced basic protein-like) and pathogenesis-related protein(pathogenesis-related protein STH-2-like,pathogenesis-related protein P2-like precursor) were up-regulated in response to T-2 treatment, which suggested that they were involved in induced resistance directly or indirectly. Meanwhile, the energy metabolism related proteins were also involved in induce resistance of against dry rot of potato.In conclusion, UHPLC-MS/MS was a rapid, simple and sensitive method for simultaneous determination four trichothecenes of two type-A of T-2 and DAS, and two type-B of 3ADON and Fus-X in potato tubers inoculated with F. sulphureum. The acculmulation of trichothecenes clearly correlated with potato cultivars, Fusarium strains and storage temperature. BABA, chitosan and sodium silicate have the ability of suppressing the accumulation of trichothecenes in inoculated tubers. In addition, the induced resistance of potato tubers in response to T-2 treatment clearly was correlated with the metabolism of reactive oxygen species, phenylpropanoid pathway and energy. These findings not only have an important significance of theoretical guidance for potato tuber storage and protect the consumer from the risk of exposure to these trichothecenes, but also provide theoretical basis for the mechanism of induced resistance against dry rot in potato tubers by T-2 toxin treatment. |
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