Inducement Of Azoxystrobin-resistance Mutants Of Phytophthora Infestans And Its DNA Fingerprint Analysis

Because of fungicide resistance of Phytophthora infestans, the effect of fungicides was decreasing on potato late blight. In this paper, the sensitivities of P. infestans to azoxystrobin were determined, the azoxystrobin-resistance mutants of P. infestans were induced, and molecular marker of P. infestans to azoxystrobin resistance was detected. The results derived from this study would preliminarily evaluate the risk of P. infestans to azoxystrobin resistance and gain the molecular marker which could be applied to identify the azoxystrobin-resistant and azoxystrobin-sensitive isolates of P. infestans. A theoretical basis was provided for the scientific application of azoxystrobin and the development of managing strategies when isolates of P. infestans to azoxystrobin resistance were occurred.1. The sensitivities to azoxystrobin of 30 P. infestans isolates collected from different geographical regions in different years were determined in vitro. The results showed that all the isolates were sensitive to azoxystrobin. The EC50 value ranged from 0.0351 to 0.1492μg/mL. There was no cross resistance between azoxystrobin and metalaxyl in P. infestans populations tessted.2. The baseline-sensitivity of P. infestans to azoxystrobin was found, with an everage EC₅₀ value 0.0604±0.0226μg/mL.3. One lower level mutant X-DC98-3 of P. infestans with azoxystrobin-resistance was isolated by treating mycelium with azoxystrobin and ultraviolet radiation. The resistance level of mutant X-DC98-3 was 20 times as original isolate. By validating resistance, the result suggested that the resistance to azoxystrobin of other low azoxystrobin-resistant mutants of P. infestans was decreased.4. The fingeprint of azoxystrobin-resistant mutants and wild isolates of P. infestans were amplified using AFLP. The differencial bands between azoxystrobin-resistant mutants and wild isolates of P. infestans were produced with 8 primers combination out of 144. Among them, 1 to 2 specific bands between isolates X-DC98-3 and DC98-3 were amplified by primer combination E4/M5, E4/M8, E7/M5, E15/M6, E16/M9, respectively. One 250bp specific band was amplified from X-DC98-3, one 170bp specific band was amplified from isolates X-DC98-3, X-DK98-1 and DK98-1 with primer combinations of E19/M4. One 280bp specific band was amplified with primer combination E15/M19 between isolates X-DK98-1 and DK98-1. One 200bp specific band was amplified with primer combination E20/M11 from isolates X-DC98-3, A-HH00-2, A-HW00-5 and UV-HD01-4.5. Two SSR primers of Pi4B and Pi4G were charged for amplifing the azoxystrobin-resistant mutants and wild isolates of P. infestans. The result showed that the SSR genotypes of azoxystrobin-resistant mutants were the same with their wild isolates of P. infestans. It mignt be infered that the SSR genotypes was not linked with the sensitivity to azoxystrobin of P. infestans.