Abstract:

In this study，a new type of disease-resistant activator named BDO-1，（E）-N-[2-fluoro-4-（trifluoromethyl）styryl]-1-met-hyl-1H-pyrazolo[3,4-d]pyrimidin-4-amine，which belongs to pyrazolium pyrimidine derivative was reported and studied. To reveal the resistance mechanism of BDO-1，the induced resistance effect of the activator to cucumber against Fusarium oxysporum f. sp. cucumerinum was investigated. The antifungal activity of BDO-1 was detected by using plate growth rate method，and the result showed that BDO-1 had no antagonistic effect against F. oxysporum. The leaves were treated with 10 mg · L-1 BOD-1 by foliar spraying method at two-leaf and one-hearted cucumber stage. A total of five times were induced in 25 days and the pathogen F. oxysporum was inoculated after 24 h of last induction.The induced assay results indicated that the induced resistance effect of BDO-1 to cucumber against F. oxysporum was 53.28%. In addition，laser confocal microscopy confirmed that the infection rates of F. oxysporum on cucumber were inhibited by induction of BDO-1. Meanwhile，fluorescence microscopy showed that the secondary metabolite callose accumulated in cucumber plants on the 3rd day post-inoculation，and the highest content of anti-oxidant H2O2 appeared in cucumber plants on the 1st day post-inoculation. Besides，qRT-PCR revealed that BDO-1 could induce expression of six disease-resistant defense genes. After BDO-1 induction，the expression levels of CAT，PAL，LOX and EIN2 in the defense genes of root defense tissues increased significantly from 1st day to 7th day post-inoculation，and the expression levels of PR1 and SOD were higher at 1st day post-inoculation，significantly reduced in 3rd day and 7th day post-inoculation. This study provides an insight and basis for the development and application of BDO-1 as a new type of disease-resistant activator.

Key words: cucumber, pyrazolopyrimidine derivative, cucumber wilt disease, induced disease resistance