Physiological changes and scanning electron microscope observation of Carica papaya L. infected with PLDMV

ObjectiveThe infection mechanism of Papaya leaf-distortion mosaic virus(PLDMV)and the mechanism of Carica papaya L.defense system against virus after infection were elucidated to provide reference for papaya virus di-sease.MethodC.papaya variety Tainong 2 was used as material.The infection situations of C.papaya in treatment group with PLDMV inoculation(T)and healthy blank control group(CK)were confirmed by RT-PCR detection.The influence of PLDMV infection on C.papaya related physiological indexes was determined by spectrophotometry.Scanning electron microscopy was used to observe the difference in microstructure between the two groups.ResultRT-PCR test showed that T group was infected with PLDMV.There were obvious differences in the characterization,microstructure and physiologi-cal indexes between leaves in T and CK.Palisade tissue to cavernous tissue ratio of vertical section leaves and density of back tomentum in T were smaller than those in group CK,and the stomatal density in group T was larger than that in group CK.In physiological indexes,the activities of peroxidase(POD),polyphenol oxidase(PPO)and phenylalanine am-monia lyase(PAL),and contents of proline(Pro),malondialdehyde(MDA)and superoxide anion(O)in T group were significantly higher than those in CK group(P<0.05,the same below).Catalase(CAT)activity and chlorophyll(Chl)con-tent in T group was significantly lower than those in CK group.Superoxide dismutase(SOD)and chitinase were not signi-ficantly different from each other(P>0.05).ConclusionAfter PLDMV infection,C.papaya leaf structure is damaged, the cells are seriously poisoned,metabolic disturbance occurs,multiple metabolic regulation are imbalanced,therefore, the development and growth of papaya is blocked.