Identification of pathogens of root-knot nematode disease of Scutellaria baicalensis in Gansu province
In this study,the species causing root knot nematode disease on Scutellaria baicalensis in Longxi county,Gansu province was isolated and identified and its pathogenicity to S.baicalensis was determined by indoor artificial inoculation.The results showed that the morphological characteristics and measurements of the nematode population fromS.baicalensis were basically consistent with those of Meloidogyne hapla.rDNA-ITS and 28S rDNA D2/D3 sequences showed 99.60%and 99.74%identity with M.hapla in NCBI,respectively(rDNA-ITS:JX024147;28S rDNA D2/D3:MW288147).The Bayesian phylogenetic tree indicated that this nematode population clustered with other M.hapla populations with a confidence level of 95%.A specific fragment of 457 bp in size was obtained by amplification with the M.hapla-specific primers Mh-F/Mh-R and sequencing.Based on morphology,rDNA-ITS,28S rDNA D2/D3 sequences,and the specific sequence,the pathogen of the nematode population on S.baicalensis was identified as M.hapla.After inoculation with this nematode population,S.baicalensis grew slowly with yellowing leaves,and obvious root knots were observed on fibrous roots 40 days after inoculation.In conclusion,the pathogen responsible for the root knot nematode disease of SS.baicalensis in Longxi county,Gansu province is M.hapla,which demonstrates strong pathogenicity to S.baicalensis with a reproductive coefficient of 1.997.