Study On The Resistance Of Fusarium Oxysporum F.sp. Fragariae To Carbendazim And Tebuconazole

The purpose of this paper is to study the resistance of Fusarium oxysporum f.sp. fragariae to carbendazim and tebuconazole. In this study, the resistance selection of Fusarium oxysporum f.sp. fragariae to carbendazim and tebuconazole and the cross-resistance test of each resistant strain was carried out. The resistance rule of each strain was studied. The differences on some characterization such as the growth rate, carbon sources, nitrogen sources and the capacity of spore production were studied. The effect of different pH values and temperature on sensitive and resistant strain was also studied. After immersed into carbendazim solution and tebuconzaole solution with different concentrations, the conductivity and the activity of phenylalanine ammonia lyase (PAL) and peroxidase (POD) was compared. At last, the resistance mechanism was studied. And the resistance risk of Fusarium oxysporum f. sp. fragariae to carbendazim and tebuconazole was evaluated. The results could be summarized as follows:1. The studies of resistance selection showed that the resistant ratio of ZY-D which is resistant to carbendazim had reached 53.91 fold after 45-time selection, and the ZY-W which is resistant to tebuconazole reached 34.22 fold after 36-time treatment in the laboratory. After 8 successive incubations on the free-fungicide medium, the resistant strains could maintain their resistance.2. The cross-resistance of induced resistant strains to fungicides were as follows: the ZY-D had significant positive resistance to Thiophanatemethy and Thiram, the resistance ratio was 29.98 and 27.58 fold, respectively, while the resistance ratio of triadimefon, difenoconazole, myclobutanil, propiconazole and tebuconazole was 7.15, 5.42, 5.07, 4.78 and 2.73 fold; the ZY-W had significant positive resistance to triadimefon, propiconazole, diniconazole and myclobutanil, the resistance ratio was 22.21, 14.12, 11.91 and 10.52 fold, while the resistance to thiophanatemethy , difenoconazole and carbendazim was still remarkable, the resistance ratio was 6.96, 4.55 and 2.12 fold respectively. 3. By mycelia growth rate tests and counting the number of spore production, the effect of different carbon and nitrogen sources, pH value and temperature on the resistant strains and sensitive strain was determined. The results are as follows: in the different carbon sources, the sensitive strain grew fastest in glycerol and sucrose, while the ZY-D grew fastest in sucrose and maltose, and the ZY-W grew fastest in glycerol and maltose, the number of spore production of the resistant strains and the sensitive strain in sucrose, amylum and glycerol was higher than that in other carbon sources. In the different nitrogen sources, the resistant strains and the sensitive strain grew fastest in KNO3 and NaNO3. For the spore yield of sensitive strain, yeast extract, peptone and carbamide were the best nitrogen source; for the spore yield of ZY-D, yeast extract, carbamide and beef extract were the best nitrogen source; for the ZY-W, yeast extract, beef extract and peptone were the best. There was no significantly difference in the effect on the sensitive and resistant strain of pH value and temperature.4. In the medium with high and low concentration of dextrose, there was difference among ZY-D, ZY-W and sensitive strain. In the high concentration of dextrose, the ZY-D was inhibited more than other strains; while in the middle concentration of dextrose, the ZY-W was inhibited more than other strains. In different concentration of NaCl, the ZY-W was inhibited more than other strains. The colony diameter of the ZY-W had negative relationship with concentration of NaCl.5. After treated with middle and low concentration of carbendazim, the relative leakage of resistant strains is higher than that of sensitive strain. Moreover, the relative leakage had positive relation with treated time. After treated with high concentration of carbendazim, at the beginning, the relative leakage of ZY-D and sensitive strain was decreased, and then the relative leakage of both strains was increased. Furthermore, the sensitive strain could leak more electrolyte than the ZY-D in the short time. However, the relative leakage of ZY-D is higher than sensitive strain finally. After treated with different concentration of tebuconazole, the strain ZY-W could leak more electrolyte than the sensitive strain continuously.6. After treated with carbendazim, the activity of phenylalanine ammonia lyase(PAL) and peroxidase(POD) of the resistant strains was higher than that of the sensitive strain. After treated with carbendazim, the activity of PAL of the ZY-D and sensitive strain firstly increased, and then decreased. After treated with tebuconazole, the activity of PAL of the ZY-W was higher than that of sensitivity. After treated with tebuconzaole, the activity of PAL of the ZY-W and sensitive strain firstly increased, and then decreased.7. The fitness differences between sensitive and two resistant strains are as follows: the ZY-D work best in suiting NaCl and dextrose, and leaking fungicide; followed by the sensitive strain; and the ZY-W is the last one. Both resistant strains have more POD and PAL than the sensitive strain.