| The resistant mechanisms to the race 3 of soybean cyst nomatode (lie terodera glycines, SCN) were systematically studied in this paper. The number of SCN second stage juvenile (12) was researched in soil with and without host plant, the result showed that the cysts could hatch in soil absenting host plants with optimum condition. On the other hand, the relationships among the soybean cultivars, the SCN number and the SCN development in soybean roots in field were studied. The results showed that males developed three days earlier than females. The sixty-eight resistant soybean cultivars to race 3 of SCN were divided into three groups on the basis of the total SCN number in soybean roots, such as one remarkable peak value of SCN in roots, one peak value of SCN in roots and no peak value of SCN in roots. Furthermore, the resistant mechanismic characteristics of different resistant soybean cultivars were researched and analyzed in detail. The results indicated that some resistant soybean cultivars could make 12 leave roots about 13 6 days after emerging; more resistant soybean cultivars inhibited 12 and J~ development; some resistant soybean cultivars inhibited J4 development; the ratio of males to females in the roots of more resistant soybean cultivars was significantly higher than the roots of susceptible soybean cultivars. The host soybean resistance was seriously influenced by SCN hatching. So the influences of 7-day-old root-exudates, 15-day-old seedling root-exudates, 30-day-old root-exudates, calli exudates and pH value on hatching of SCN were studied. The results showed that the root-exudate of the susceptible cultivar Liaodou 10 more strongly stimulated hatching than the resistant cultivars, and hatching was higher in alkaline condition than in acid condition. It was one of the resistant mechanisms that root-exudates inhibited or not stimulated the hatching, which made the number of the SCN 12 decline near the soybean rhizosphere. The electric charge of SCN 12 was firstly studied by low electric field intensity. The head of 12 was positive charge, the tail was negative charge and the charge of the head was larger than the charge of the tail, and negative electrode more significantly attracted 12 than positive electrode. In addition, the root hair interrupted zone and extension zone more attracted 12 than other root zones. Furthermore, the root of the susceptible soybean cultivar Li.aodou 10 more strongly attracted 12 than most resistant cultivars, and the root of resistant cultivar P1437654 significantly repelled 12. Cal ii di (1 not. suhst i to to roots for chock ng in II uence on hatch ng and taxis of SCN. CaIIi must he induced into tissue to determine expression of SCN resistance in transgenic soybean. In addition, live 12 were used as inoculum in this paper replacing eggs and cysts to study that host resisted the invasion and the colonization of SCN, and SCN in roots was checked on the fifteenth day after inoculation. The results indicated that P190763 and P1437654 strongly resisted invasion and the colonization of SCN. In the experiments of induced resistance, the soybean cultivars were divided into the three groups that were separately treated by different methods. And the three groups were thai group A was by live 12 for the second time in greenhouse and group C was inoculated by live .12 in greenhouse. Moreover, cysts hatched in the root-exudates... |
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