Effects of Mikania micrantha wilt virus on endogenous hormones and interspecific competitive ability in Mikania micrantha HBK

We compared the content of endogenous hormones [indole-3-acetic acid (IAA), cytokinin (CTK), gibberellin (GA(3)), abscisic acid (ABA)] and auxin in Mikania micrantha wilt virus (MMWV) infected and healthy plants using enzyme-linked immunosorbent assay (ELISA) 1, 4, 7, 10, 13 and 16 days after infection. The results showed that there was positive correlation between the magnitude of plant disease and the content of IAA, GA(3), CTK and auxin in MMWV-infected plants. The content of ABA in MMWV-infected plants accumulated continuously with the increase in inoculation time and was constantly higher than in healthy plants. The ratios of IAA/ABA and GA(3)/ABA in the MMWV-infected plants were significantly lower than in healthy plants, which indicated that MMWV infection disrupted the balance of endogenous hormones and altered the growth and development of plants. Furthermore, the competition experiment was done to investigate the effects of MMWV on the interspecific competitive ability of M. micrantha with its coexisting plant Bidens pilosa L. The results indicated that MMWV-infected plants were less competitive against B. pilosa than healthy plants. These results suggested that the poor growth of M. micrantha after infection may be closely related to the decrease in IAA, GA(3), CTK and auxin and the increase in ABA, which weakened the competitive ability.