Study On The Control Of Root-knot Nematode By Brassica Rapa And ITCs

The annual global losses caused by root-knot nematodes are very serious.The cruciferous plants and their production of isothiocyanates?ITCs?are an important resource for controlling disease caused by Meloidogyne spp.As a cruciferae plant,Brassica rapa and its ITCs in the control of plant parasitic nematodes have not been reported.This study was carried out to evaluate the nematicidal activities of different tissues of B.rapa,analyze the volatile components of B.rapa seed oil,compare the nematicidal activities of ITCs,improve the stability of the synthetic ITC compound?NBITC?by embedding technology,and evaluate the control efficiencies of B.rapa seed oil and NBITC clathrate aganist the disease caused by root-knot nematode by greenhouse experiment.The main results were concluded as the follow.1.The nematicidal activities of different tissues of B.rapaLeave of B.rapa not showed nematicidal activity towards J₂ and egg of M.incognita.B.rapa tuber generated its LC90 to J₂ at 0.4153 g.ml^-11 and 0.357 g.ml^-1,respectively by the nematicidal models of fumigation and contact,and showed a LC90value of 0.74 g.ml^-11 to egg by contact.B.rapa seed had its LC90 to J₂ at 0.3934 g.ml^-1and 0.00153 g.ml^-1,respectively by fumigation and contact,and showed a LC90 value of 0.4856 g.ml^-11 to egg by contact.When mixed the seed into soil at the concerntration of 20-25 g.Kg^-1,more than 80%of nematicidal rate was obtained during the depth of10-20 cm.2.The antifungal activity of B.rapa seedVolaties of B.rapa seed showed strong antifungal effects against phytopathogens Fusarium oxysporum and Pestalotiopsis sp.,and showed 100%antifungal activities to the two pathogens at concentration of 0.2 g.ml^-1and 0.4 g.ml^-1,respectively.3.The nematicidal activity and volatiles of seed essential oilAt the concentration of 10?g.ml^-1,seed essential oil showed 88%,90%,89%of nematicidal activities against nematodes of C.elegans?P.redivivus?M.incognita,respectively.The seed essential oil contained 19 volatile components when analysized by GC-MS,in which,two nematicidal ITCs?allyl isothiocyanate andphenethyl isothiocyanate?were identified.4.Nematicidal characteristics and stability of the synthesized ITC compound NBITCThe nematicidal activitiy of NBITC was better than the common ITCs,which show the LC90 of 1.194?g.l^-1and 2.746?g.l^-1,respectively to M.incognita J₂ and egg.The NBITC was stable at high temperature,but volatile and hydrolytic easily.Xylene and twin-20 were the suitable solvent and emulsifier for the preparation of 10%NBITC agent.5.The embedding technology and effect of NBITCThe optimum conditions for embedding NBITC with the?-cyclodextrin were determined.Under the conditions of 500:3 material liquid ratio,1000 rpm speed,0.06ml.s^-11 titration,50?temperature,the highest yield of clathrate was obtained.At a concentration of 5?g.ml^-1,the period of hydrolytic stability and volatile stability of this clathrate respectively increased from 6 d to 10 d,and 2 d to 20 d,when keeping its nematicidal activity at 100%.6.The contrl efficiencies of B.rapa seed and NBITC clathrate towards root-knot nematode diseaseAccording to the results greenhouse experiment,the efficiencies of B.rapa seed towards nematode disease were 86.79%and 87.92%,respectively at the concentration of 10 and15 g.Kg^-1.The protective effects of 10%NBITC clathrate against nematode disease respectively were 76.92%and 82.05%,when diluting the agent of 5000 and10,000 times and applying 3 times.