Induction and biological characterization of mutants of Alternaria alternata resistant to azoxystrobin
Received:March 12, 2019    Download the full
DOI：10.16801/j.issn.1008-7303.2019.0076
Key Words:tobacco brown spot  Alternaria alternata  azoxystrobin  resistance  mutant  UV-induced  biological characterization
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Author NameAffiliationE-mail
HUANG Yanfei Subcollege of Gardening and Horticulture, Chengdu Agricultural College, Chengdu 611130, China
Guizhou Academy of Tobacco Science, Guiyang 550081, China 		 
WANG Hancheng Guizhou Academy of Tobacco Science, Guiyang 550081, China xiaobaiyang126@hotmail.com 
WU Qingli Subcollege of Gardening and Horticulture, Chengdu Agricultural College, Chengdu 611130, China  
CHEN Xingjiang Guizhou Academy of Tobacco Science, Guiyang 550081, China  
CAI Liuti Guizhou Academy of Tobacco Science, Guiyang 550081, China  
ZHANG Changqing College of Agriculture, Yangtze University, Jingzhou 434025, Hubei Province, China qingchangzhang@tom.com 
YANG Shu Subcollege of Gardening and Horticulture, Chengdu Agricultural College, Chengdu 611130, China  
HE Yongfu Institute of Plant Protection, Guizhou Academy of Agricultural Sciences, Guiyang 550006, China 3258800369@qq.com 
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Abstract:
      The resistance risk of Alternaria alternata to azoxystrobin was evaluated. Mycelial plugs of the sensitive parent isolate J6 was inoculated onto agar plates amended with azoxystrobin and the conidia of J6 was induced with UV irradiation. The biological characterization of resistant mutants was studied, and the resistance mechanism of mutants was also investigated by the full-length cDNA of target gene cyt b sequence analysis. Seven mutants of A. alternata resistant to azoxystrobin were acquired by UV-induced mutation of conidia, which exhibited a mutation frequency of around 0.007%. The resistance ratios for seven mutants were 5.27, 8.28, 25.28, 12.82, 6.14, 9.28 and 52.91, respectively. However, no mutants were obtained by mycelial plug transferring on the agar plates amended with azoxystrobin. Studies on biological characters of the wild-type and mutant strains of A. alternata showed that all resistant mutants and the parent isolate J6 had equal abilities in the conidia germination and pathogenicity, while resistant mutants had higher conidia production ability and stronger mycelial growth ability (except mutant 6-1) than those of J6. Sequence analysis of the full-length cDNA sequence of cyt b gene showed that there were different point mutations on four mutations of A. alternata. Mutant 6-7 showed mutations at 249 and 871 positions (T mutated to C), while no amino acids mutated. Mutant 6-8 had a point mutation at 734 position (T mutated to C), which resulted in alanine mutated to valine (V245A). Mutant 6-9 had a point mutation at 510 position (T mutated to A), which resulted in arginine mutated to serine (S170R). And mutant 6-11 had a mutation at 732 position (T mutated to A), which resulted in leucine mutated to phenylalanine (L244F); had a mutation at 776 position (T mutated to C), which resulted in valine mutated to alanine (V259A); and had a mutation at 1 156 position (A mutated to G), while no amino acids mutated. These studies suggested that A. alternata has the potential resistant risk to azoxystrobin, and the mutation of cyt b gene in A. alternata was related to the resistance to azoxystrobin.
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