Adaptation Of Ditylenchus Destructor To Low-dose Of Nematicides

Potato rot stem nematode(Ditylenchus destructor) is one of important pathogens of sweet potato in China, and the enormous yield losses to agriculture is very great annually. There were a lot of research espointed out that low dose of pesticides can improve the fitness of pests to environment, which could induce the rampant of pests again and increase the damage. This research was studied on the effect of abamectin, profenofos and aldicarb the infect activity of Ditylenchus destructor Throne in the low dose condition. The inducible expression and biochemical mechanism of heat shock protein70in the stress of chemical pesticides, explore its biochemical mechanism for the further understanding of suitability in the low-dose nematicide stress habitat, and provide basic data and scientific basis for rational use of nematicides.In this study, Pluronic (?) F-127gel as the culture medium, two methods were employed to assess activity of abamectin, profenofos and aldicarb to D.destructor. The first way were that D. destructor inoculated to the medium containing series concentration of substrate with carrot seedling cultivation; another were that D. destructor treated with series concentration solution then inoculated to substrate cultivation with carrot seedling. After14days, The results showed that the effect of two different treatments for activity of pesticide was consistent, the inhibition of aldicarb on infestation of D. destructor was highest, followed by profenofos and lower was abermectin.In order to understand the effect of low does of nematicides on Hsp70s mRNA expression, three Hsp70genes, Dd-Hsp70-A (GenBank accession No. KF792307)、 Dd-Hsp70-C (GenBank accession No. JQ422276) and Dd-Hsp70-F (GenBank accession No. JQ422277), were cloned from Ditylenchus destructor using RT-PCR and RACE techniques, and the mRNA expression levels of D.destructor treated by low dose (10、1、0.1、0.01、0.001μg/mL) of abamectin, profenofos and aldicarb were analyzed using Real-time PCR after24h.The full-length cDNA of Dd-Hsp70-A was2081bp which with anopen reading frame (ORF) of1938bp and encoding645amino acids residues; the full-length cDNA of Dd-Hsp70-C was2436bp with an open reading frame (ORF) of2019bp encoding672amino acids residues; the full-length cDNA of Dd-Hsp70-F was2092bp, which with an open reading frame (ORF) of1959bp encoding652amino acids residues. Homology analysis indicated that those three genes all contained a highly conserved sequence of Hsp70family and were highly homologous to Hsp70genes in other nematodes. The structure of Dd-Hsp70-A,Dd-Hsp70-C and Dd-Hsp70-F genomic include11extonsand10introns,13extonsand12introns,11extonsand10introns,respectively. The predicted protein structure showed that the three genes all had ATPase fragment at the N-terminal and developed substrate peptide and C-terminal domains near the C-terminal.After treated by heat shock and low dose emanectin benzoate, profenofos and aldicarb, the expression levels of Dd-Hsp70-A increased significantly compared with control, while Dd-Hsp70-C and Dd-Hsp70-F showed no significant difference (P<0.05). It is speculated that Dd-Hsp70-A is inducible, Dd-Hsp70-C and Dd-Hsp70-F are constitutive. The results provided useful information for further research mechanisms of nematodes response to low dose of nematicides.