Comparison of pathogenicity and reproduction of Bursaphelenchus xylophilus in pine families with different disease resistance
[Objective]To explore whether the interaction of pine families with varying levels of disease resistance in the same plot with pine wood nematode(Bursaphelenchus xylophilus)under natural conditions affects the pathogenicity and reproduction of B.xylophilus,and to determine if the expression level of cytochrome P450 i.e.CYP family-related genes of B.xylophilus strains with noticeable differences in pathogenicity different after interaction with pine trees,the following study was conducted.[Method]This study monitored the gene pools of several families of Pinus densiflora and P.thunbergii,which were introduced from Japan previously in the lab.Field monitoring was conducted over several years,revealing significant differences in disease resistance among different pine families.Dead wood samples from each family in the pine tree gene pool were collected,and automated molecular detection was used to identify B.xylophilus.Nematode samples from five P.densiflora families and five P.thunbergii families,confirmed to have died from B.xylophilus,were isolated.A total of 10 B.xylophilus strains were obtained through monoheterotic in vivo culture,and their pathogenicity and reproduction were tested.The relative expression of two cytochrome P450 genes in four B.xylophilus strains with significantly different pathogenicity was detected by RT-qPCR.[Result]The results indicated that in the same tree species within the same plot,the stronger the disease resistance of the pine families,the lower the reproduction rate of B.xylophilus strains obtained under monoheterotic living culture.Conversely,weaker disease resistance in pine families corresponded with higher reproduction rates of B.xylophilus strains.Inoculating each strain with 2-year-old P.thunbergii revealed that the pathogenicity test results of nematode strains obtained from diseased and dead trees of five P.thunbergii families were positively correlated with the resistance of pine families.The B.xylophilus strain JYK-34,isolated from the most resistant family(34),showed the highest pathogenicity.However,for P.densiflora families,there was no positive correlation between resistance and the pathogenicity of B.xylophilus.The B.xylophilus JYK-18,isolated from a highly resistant family(18),exhibited weak pathogenicity.Compared with the control B.xylophilus,the increased expression of two cytochrome P450 genes,BxCYP33 C4 and BxCYP33 C9,was positively correlated with the pathogenicity of the four B.xylophilus strains,namely JYK-34＞JYK-17＞JYK-18＞JYK-31,after interacting with the P.thunbergii seedlings for 30 days.[Conclusion]The differentiation in the reproduction of B.xylophilus was consistent among different disease-resistant families of P.densiflora and P.thunbergii.The pathogenicity of B.xylophilus isolated from pine trees with different resistance levels within the same plot in the resistant pine tree gene pool was not uniform,with different strains exhibiting varying pathogenicity.The cytochrome P450 genes BxCYP33 C4 and BxCYP33 C9 in B.xylophilus are involved in the interaction between B.xylophilus and pines and are also important genes related to the pathogenicity of B.xylophilus.
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