Genetic Analysis of Shikimate Dehydrogenase Allozymes,a Genetic Marker Resisting to Chustnut-blight,in Hybrid of Castanea mollissima×C.dentata

In plants,the shikimate pathway is an important metabolism pathway in response to wounding and fungal attack.The genetic analysis of enzymes in the pathway can provide the basic information about their applicability as a genetic marker.In this study,variability and inheritance of shikimate dehydrogenase (SKD;EC 1.1.1.25 ) allozyme,one of the key enzymes in shikimate pathway,was investigated in Castanea mollissima and C.dentata using isoelectric focusing in thin-layer polyacrylamide slad gels.The single-tree progeny method and intra-and interspecific controlled cross families were used for the analyses.The results showed SKD had four activity zones and exhibited species specific banding patterns in Castanea.Two alleles were detected at each four locus and inherited in Mendelian fashion.Locus Skd-1 and Skd-2 unique to C.dentata seemed to be segregated independantly,while a highly significant linkage was observed between two loci Skd-3 and Skd-4 unique to C.mollissima.However,the phenotypic analysis of SKD allozyme banding patterns in F₂ populations of C.mollissima×C.dentate revealed that the linkage group between Skd-3 and Skd-4 maybe have been replicated in C.mollissima.It is speculated that Skd-1 and Skd-2 in C.dentata possibly come from repetition linkage groups during a speciation process.Because of expression of the double SKD loci activity,the shikimate pathway in C.mollissima is considered more efficient and consequently,responses of C.mollissima to Cryphonectria parasitica invasion and other microbial attack may be elevated.So the resistance of C.mollissima to chestnut blight is considered increase.This study suggested that SKD allozyme could be a potential genetic marker for aided selection on blight-resistance and have potential application in the backcross-breeding program of C.dentata.