Screening Of Heterodeta Glycines-resistsint Germplasms From Wild And Semi-wild Soybean In Eastern Of Hebei Province And Its Resistant Mechnisms

The soybean cyst nematode (SCN), Heterodera glycines, is one of mostseriously devastating crop pests worldwide. Planting of resistant soybean (Glycinesmax) cultivars is the most wiledly used method for limiting yield losses caused bythis nematode, however, the soybean commercial cultivars existing the issue withrelative narrow genetic bases. It is proved that wild soybean (G. soja), the ancestor ofsoybean, retains useful genetic variation for SCN-resistant breeding, and therefore isextremely important germplasm to enrich the soybean resistant gene pool againstSCN. Screening of SCN-resiatant germplasms from wild soybeans is a basis ofresistance breeding, and a better understanding of its mechnisms may provid atheoretical basis for the selection and utilization of wild germplasms.1. In this thesis, a total of202wild and semi-wild soybean (G. gracilis)germplasms from the eastern of Hebei province were identified for their reaction toRace3of SCN based on natural infected and artificial inoculation methods during2012and2013. The results showed the female index of all the germplasms rangedfrom0%~83.2%, indicated that the resistant reaction to SCN among wild soybeangermplasms was totally different. Almost96.4%of wild soybean germplasm showedmiddle susceptible and susceptible reaction to SCN, and wild germplasm ‘188’showed high SCN resistant reaction.2. The SCN life cycle in soybean susceptible variety ‘Lee’ grown undercontrolled greenhouse conditions was indetified with root systerms staining by acidfuchsin-NaClO. Based on this, the SCN-developmential stage in the root systerms of4wild soybean germplasms with different SCN-resistant reaction was compared,respectively. The juveniles were capable to penetrate into wild soybean rootsregardless of their resistance, however, significantly samller number of nematodes inthe roots of resistant germplasm ‘188’ and middle resistant germplasm ‘173’ wereobserved compared to those of other germplasms. The results demonstraed that wildsoybean had no effect on the penetration of second juveniles (J2), but had an effent onthe developmental stage beyond SCN-J2. 3. The defensive enzyme avtivities such as POD, PPO, SOD and PAL of wildsoybean resistant and susceptible germplasms were analyzed in differentdevelopmental stages of SCN. All the defensive enzymes showed high activities onthe peak time of J2penetration. There was significant positive correlation betweenthe resistance to SCN and three enzyme activities including PAL, POD and SOD, butno significant correlation between resistant reaction and PPO acvity. The resultssuggested that PAL, POD and SOD activities could be used as the candidatephysiological index for SCN-resistance identification.4. The endophytic bacterial diversity in the wild soybean root tissues ofSCN-resistant and susceptible germplasms grown under greenhouse condition wasinvestigated by16S rDNA cloning, amplified ribosomal DNA restriction analysis(ARDRA), and sequence homology comparison, respectively. The results showedthat the dominant phyla of wild soybean germplasms were Proteobacteria andFimicutes and endophytic bacterial diversity was higher in the H. glycines-resistantgermplasm than that in susceptible germplasm, indicated that endophytic bacteria inthe wild soybean root might involve in the H. glycines resistance.