Overexpression of Three Glucosinolate Biosynthesis Genes in <i>Brassica napus</i> Identifies Enhanced Resistance to <i>Sclerotinia sclerotiorum</i> and <i>Botrytis cinerea</i>

<div><p><i>Sclerotinia sclerotiorum</i> and <i>Botrytis cinerea</i> are notorious plant pathogenic fungi with an extensive host range including Brassica crops. Glucosinolates (GSLs) are an important group of secondary metabolites characteristic of the Brassicales order, whose degradation products are proving to be increasingly important in plant protection. Enhancing the defense effect of GSL and their associated degradation products is an attractive strategy to strengthen the resistance of plants by transgenic approaches. We generated the lines of <i>Brassica napus</i> with three biosynthesis genes involved in GSL metabolic pathway (<i>BnMAM1</i>, <i>BnCYP83A1</i> and <i>BnUGT74B1</i>), respectively. We then measured the foliar GSLs of each transgenic lines and inoculated them with <i>S</i>. <i>sclerotiorum</i> and <i>B</i>. <i>cinerea</i>. Compared with the wild type control, over-expressing <i>BnUGT74B1</i> in <i>B</i>. <i>napus</i> increased the aliphatic and indolic GSL levels by 1.7 and 1.5 folds in leaves respectively; while over-expressing <i>BnMAM1</i> or <i>BnCYP83A1</i> resulted in an approximate 1.5-fold higher only in the aliphatic GSL level in leaves. The results of plant inoculation demonstrated that <i>BnUGT74B1</i>-overexpressing lines showed less severe disease symptoms and tissue damage compared with the wild type control, but <i>BnMAM1</i> or <i>BnCYP83A1</i>-overexpressing lines showed no significant difference in comparison to the controls. These results suggest that the resistance to <i>S</i>. <i>sclerotiorum</i> and <i>B</i>. <i>cinerea</i> in <i>B</i>. <i>napus</i> could be enhanced through tailoring the GSL profiles by transgenic approaches or molecular breeding, which provides useful information to assist plant breeders to design improved breeding strategies.</p>