Study Of The Effect Of Aromatic Glucosinolate On Sclerotinia Sclerotiorum In Brassica Napus L

Brassica napus L., or canola, is an important economic crop, and it is widely planted in China. Sclerotinia sclerotiorum causes the most serious diseases in B. napus L., and leads to significant economic losses. Glucosinolate, a kind of plant secondary metabolite, distributes in Cruciferous, Capparaceae and Papaya, and it can be hydrolyzed by endogenous myrosinase, producing a series of products with biological activities. These hydrolysis products can improve the plants’ resistance to diseases. In this paper, leaves from a resistant line Xiangyou 15 and a susceptible near-isogenic lines XYNL were chosen to analyzed the resistant effects of the aromatic glucosinolate in the B. napus L. against S. sclerotiorum. The key genes involved in disease defence were found and further analyses.were adopted to confirm their resistaant function.To compare the resistance of the two varieties, volume of H2O2, O2-, dead cells, and the invaded mycelium in the leaves of the two varieties of canola were detected by utilizing DAB, NBT, Trypan blue, and Coomassie blue stainings respectively.Isothiocyanates are the main functional substance in the hydrolysis products of glucosinolates.Phenethyl glucosinolate is the only one aromatic glucosinolate in B. napus L. leaves. To verify the effect of rapeseed aromatic glucosinolates on S. sclerotiorum, we investigated the inhibition of chemical synthetic 2-phenethyl isothiocyanate (PEITC) on S. sclerotiorum in vitro, and analysed endogenous PEITC content of two varieties by gas chromatography. The results showed that the chemical synthetic PEITC could significantly inhibit mycelial growth of S. sclerotiorum in vitro. The inhibition of mycelial growth of S. sclerotiorum increased with of PEITC concentration. When the concentration of PEITC was higher than 14μg/mL, the inhibition rate on S. sclerotiorum reached 100%; Endogenous PEITC concentration in the resistant line leaves increased from 0.125μg/g to 0.202μg/g, which had an amplification of 61.6% at 72h after inoculation. However, endogenous PEITC concentration in the susceptible line leaves only rose from 0.192μg/g to 0.204μg/g, which just increased by 6.3% at the same time point. Thus this indicated that PEITC was related to the resistance of canola against S. sclerotiorum. We supposed that the aromatic glucosinolate in B. napus L. might affect on the growth of S. sclerotiorum.In order to find the key genes related to resistance, the expression level changes of enzymes in the aromatic glucosinolate synthesis and hydrolysis pathway after inculation were analysed by using real-time quantitative PCR. The results showed that gene expression levels of all the enzymes in the pathway had a significant increase in canola leaves after inoculation except for Myrosinase (MYR). Gene expression levels of CYP83B1 (cytochrome P450, family 83, subfamily B, polypeptide 1) and ST5a (Sulfotransferase) in resistant line leaves showed more significant increse than that in the susceptible one, rising by 219%and 375% respectively compared to the susceptible canola. MYR gene had a reduction in gene expression level, and showed a tendency to increase after the first decrease, which probably owing to the feedback regulation of hydrolysis products of glucosinolates. This inclined that myrosinase might be the key regulation enzyme in the given pathway and the MYR gene had an important role in the pathway. Our results indicated that CYP83B1 gene, ST5a gene and MYR gene might be the key genes in aromatic glucosinolate synthesis and hydrolysis pathway and associated with the defence against S. sclerotiorum.The results in this study showed that the aromatic glucosinolate of B. napus L. played an important role on resistance against S. sclerotiorum in B. napus L. It was also verified that some important genes involved in the aromatic glucosinolate synthesis and hydrolysis pathway, i. e. CYP83B1 gene, ST5a gene and MYR gene, contributed to defence against S. sclerotiorum. Therefore, our research results might provide a new idea for the biological control of S. sclerotiorum and laid a theoretical fundation for the breeding of resistant canola. It could also improve the production of B. napus L.and increase economic benefits by regulating the expression of these genes.