Effects of alfalfa mosaic virus and white clover mosaic virus co-infection on the contents of five endogenous hormones in Nicotiana benthamiana

This study aimed to explore the synergism pathogenic mechanism of alfalfa mosaic virus (AMV) and white clover mosaic virus (WCMV) in co-infected host. To achieve this, Nicotiana benthamiana was co-inoculated with AMV+WCMV as treatment, and N. benthamiana was noculated with AMV, WCMV alone and phosphate buffer solution (pH 7.0, PBS) as controls respectively, the viral content present in the host plant leaves when different inoculated with viruses for 72 h and the content and changes of salicylic acid (SA), jasmonic acid (JA), strigolactones (SLs), brassinolide (BR), and ethylene (ETH) within 72～720 h, were detected using the double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) method under laboratory conditions. The results showed that the symptoms of leaves inoculated with AMV + WCMV (3 ꞉ 1) were more serious than those inoculated with a single virus (AMV or WCMV), the main symptoms were light mosaic, mottled mosaic, heavy mosaic, clear veins and shrinkage. The virus concentration detection results showed that the concentration of AMV virus in leaves inoculated with AMV + WCMV (3 ꞉ 1) was higher than that in leaves inoculated with single virus and AMV + WCMV (1 ꞉ 1, 1 ꞉ 3); the concentration of WCMV was slightly lower than that of its single infection, and higher than that of AMV + WCMV (1 ꞉ 1, 1 ꞉ 3) co-infection at 72 hours after inoculation. Simultaneously, it was found the content of SA, JA, SLs, BR, and ETH differed significantly in the Nicotiana benthamiana leaves co-infected with AMV and WCMV and those infected with AMV or WCMV alone from that in the control treatment (P < 0.05). Among the conditions treatedt, co-infection of AMV and WCMV (3 ꞉ 1) could increase the content of SA, SLs, BR, and ETH in N. benthamiana leaves, and reduce the content of JA. The content of SA, SLs, BR, and ETH in the leaves co-infected with AMV and WCMV (3 ꞉ 1) was higher than that in those infected with AMV or WCMV alone and in healthy plants (CK), which was an increase of more than 36.27%. The JA content in the co-infected leaves was reduced by 59.09% or more compared to those infected with AMV and WCMV alone, and healthy plants (CK) from 72 to 720 h, respectively.