| Oilseed rape, not only one of the main sources of plant edible oil for humankind but also the alternative of the non-renewable energy resource, is widely grown in Europe, North America and Asia. Sclerotinia stem rot, infected by Sclerotinia sclerotiorum, is a devastating threat to oilseed rape production with substantial yield loss and quality decline. The burst of the pathogen decrease the yield by10%-70%and deprive the oil content by1%-5%. S. slcerotiorum is a non-specific plant pathogen, which can infect more than400plant species.As the advocation of cultivation with high plant density and the exacerbation of the climate, the damage of the disease may become more serious. Many approaches have been adopted to control the disease including soil amendment, crop rotation, chemical application and variety breeding. However, the effect of cultural practice is limited because of the persistent nature of sclerotia and the wide host range of this pathogen. And chemical control effect dependes on the match of ascospores release with fungicide application during the grow season. In addition, chemical fungicide possiblly pollutes the environment and increases the cost. Among the measures, variety breeding focusing on high resistance is the most effective and economical choice. Whereas, there is no resistance in current Brassica napus gene pools, which hinders the resistance breeding and the relative basic research.Compared with B. napus, B. oleracea possesses various cultivated and wild genotypes, which can be used to widen the genetic basis of B. napus. A line of wild B. oleracea, B. incana (C01) was identified with high resistance against sclerotinia rot at Chongqing Rapeseed Engineering and Technology Research Center, which is tremendously potential to to improve the resistance againt S. sclerotiorum in B. napus.Using C01and C41(another B.oleracea, susceptible to S. sclerotiorum) as the main experimental materials, in the present study we observed the different influence of them on the growth and invasion of the hyphae; measured the dynamics change of oxalic acid content; detected the relative expression of the genes encoding PGIPs and GLP, as well as the marker genes involved in SA and JA signal transduction pathway; resynthesized RS line using C01as parent and identified the resistance; analysized relationship between the relative expression of PR genes and the resistance in RB165, a newly resynthsized B. napus with high resistance. The results are shown as following,1) C01affected the growth and infection cushions of S. sclerotiorumThe morphological character of the hyphae and the formation of the infection cushions on the infected leaves of C01, C41was observed with light microscope and scanning electronic microscope. Compared with C41, C01inhibited the growth and delayed the formation of infection cushions. In addition, the infection cushions on C01leaves were fluffy and scattered on the infected leaves.2) Immanent content of oxalic acid in C01is higher and the increment is lessly influenced by S. sclerotiorum infection The content of oxalic acid in the leaves of C01and C41infected by S. slcerotiorum was measured with HPLC. The result showed that C01possessed higher oxalaic acid inherently. After the inoculation with S. sclerotiorum, the content of oxalic acid increased but the increase was lower than that in C41. The content of oxalic acid in the lesion is lower than that in the interface part between the lesion and the healthy tissues, but higher than that of the outside of the interface part.3) Expression of several members of PGIPs were induced by S. slcerotiorumThe relative expression of five members of PGIPs was detected in the leaves of C01and C41challenged by S. sclerotiorum. It indicated that PGIP1and PGIP5were induced by the pathogen. On the contrast, PGIP9and PGIP12were inhibited. The expression of PGIP2was induced in B. napus but inhibited in B. oleracea. The expression pattern of PGIP in C01and C41was similar, but the expression level in C01was higher than that in C41.4) Expression of GLPs was induced by S. sclerotiorumTwo members of GLPs, namely GLP3and GLP12, were induced by S. sclerotiorum, but the pattern was different among the members. GLP3was induced in the early inoculation stage and the induced effect in GLP12emerged in the later stage. As far as the expression level was concerned, it was higher in CO1than that in C41.5) Defense response in C01was regulated by the coolaboration of SA and JA signal transductionPartial marker genes involved in SA and JA signal transduction were induced by S. slcerotiorum to some extent. It is implied that the crosstalk between the ways regulated the response, but the induction related to SA was earlier than JA.6) Improvement of resistance against S. sclerotiorum in resynthesized B. napus using C01as resistance donorResynthesized B. napus were obtained using C01as parent hybred with other Brassicas. The resistance in the resynthesized B. napus was identified through detched leaves and stems. The results showed that the resistance in resynthesized B napus was better than that of ZY821and the correlation of the resistance between resynthesized B. napus and the corresponding donor was moderate. RB165is one of the resynthesized B. napus with high resistance. It was more resistant to S. sclerotiorum than natural rapeseed, such ZY821and ZS9(Zhongshuang9). However, the resistance of RB165is not consistent to the expression of some PR genes, i.e., OXO, Cu/Zn SOD, PR2and PR3. |
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