Studies on melanin biosynthesis inhibitors (MBIs) and strobilurins (QoIs) sensitivity and population diversity of Pyricularia oryzae in Taiwan

• Main Authors: Chien-Hsiang Hsieh, 謝千祥
• Other Authors: Wen-Hsin Chung
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/33568807357880838000

碩士 === 中興大學 === 植物病理學系所 === 99 === A total of 103 isolates of Pyricularia oryzae from different rice production area in Taiwan were examined their sensitivities to tricyclazole, carpropamid, azoxystrobin and kresoxim-methyl. Results showed that the EC50 of tricyclazole to all isolates are 14.63 ± 14.40 ~ 179.34 ± 16.08 μg/ml and EC50 of carpropamid to all isolates are 52.47 ± 5.33 ~ 463.71 ± 202.72 μg/ml or > 500 μg/ml. Moreover, the EC50 of azoxystrobin to all isolates are <1 μg/ml, 1.60 ± 4.49 ~ 483.39 ± 7.18 μg/ml or > 500 μg/ml, and the EC50 of kresoxim-methyl to all isolates are 1.65 ± 0.49 ~ 483.39 ± 7.18 μg/ml or > 500 μg/ml. According the examinations, low sensitive isolates of P. oryzae to carpropamid, azoxystrobin and kresoxim-methyl were identified. For analyzing the mechanism of resistance to different fungicides, two genes of scytalone dehydratase (SDH) and cytochrome b (cyt b) gene were sequenced and analyzed. The previous reported demonstrated that the point mutation in SDH gene can produce resistance to carpropamid and point mutation in cyt b gene can produce resistance to strobilurins. The SDH gene of P. oryzae isolates showed low sensitivity to carpropamid were amplified and sequenced, and the results indicated that low sensitive isolates did not have point mutation at codon 75 in SDH gene. Meanwhile, the isolates of P. oryzae showed low sensitivity to azoxystrobin and kresoxim-methyl also did not have mutation in codon 129 or 143 in cyt b gene. The results revealed that resistant mechanism of isolates showed low sensitivity to carpropamid or showed low sensitivity to azoxystrobin and kresoxim-methyl did not correspond with mutation in SDH or cyt b genes, respectively. For realizing the genetic diversity of population, 103 isolates of P. oryzae were analyzed by PCR-base method. The rDNA of intergenic spacer (IGS) and simple sequence repeat (SSR) were amplified by CNS1 and (CAG)5, and the PCR results were analyzed by iv FreeTree, MEGA 4 and VisionWorks LS software. According to the results, 103 isolates of P. oryzae from different area could be separated into 9 groups, A~I. Among these groups, group A included 72 isolates, group B included 15 isolates and groups C~I included 8, 2, 2, 1, 1, 1, 1 isolates, respectively. Thus, isolates of groups A and B are most dominant population among P. oryzae in Taiwan and have highly molecular relationship with each group. However, these groups did not correspond with collected area or rice cultivar in Taiwan. The other side, the isolates showed low sensitivity to carpropamid and azoxystrobin are located into group A and the isolates showed low sensitivity to kresoxim-methyl are scattered into each group. In this study, several methods were tested for increasing the sporulation of P. oryzae in article media, including hydrogen peroxide (H2O2) added, blue light incubated, colony wounded etc. However, there no significant sporulation on P. oryzae colony after treated with different methods. It is necessary to improve the sporulation of P. oryzae in future.