Distribution patterns of Candidatus Liberibacter asiaticus in Newhall navel orange trees and their impact on the leaves tissue structural changes and lignin synthesis
To ascertain the infection of huanglongbing pathogen (Candidatus Liberibacter asiaticus,C. Las) in different parts of Newhall navel orange trees across various seasons,this study conducted quan-titative real-time PCR (qPCR) testing for the C. Las in leaves samples collected from different parts of trees and in different seasons. Further research was conducted on leaves of the same age but with vary-ing content of C. Las,which were collected in the autumn. This includes paraffin sections to observe the microstructure of leaf veins,determination of lignin content,and analysis of the expression pattern of genes related to lignin synthesis. The results showed that out of the 122 samples collected in the summer,the positive rate of C. Las was 16.02％;while for the 486 samples collected in the autumn,the positive rate was 33.02％,which was significantly higher than in the summer. Among these,178 leaf samples taken from the apical leaves of branches in the autumn had the highest positive rate of 36.88％ . Additionally,308 samples from the basal leaves of autumn branches had a positive rate of 26.84％,both of which were significantly higher than the positive rate for the 60 apical leaves samples (22.98％ ) and 62 basal leaves samples (8.96％ ) from branches collected in the summer. Observations of vascular bundle structures in leaves with varying content of C. Las also revealed a significant increase in the thickness of the phloem in leaves with higher content of C. Las compared with the controls. A comparison of autumn leaves with varying content of C. Las revealed that the lignin content in the leaves increased with the content of C. Las. The expression of three lignin synthesis-related genes Cs4g17860,orange1.1t02755,and orange1.1t04489 was found to be significantly upregulated in the leaves. This study indicates that Newhall navel orange trees infected with C. Las exhibit a higher posi-tive rate in the apical leaves compared with the basal leaves of the same autumn branches,as well as in comparison to leaves from the summer season. The phloem thickness,lignin content and expression of some synthesis-related genes of leaves in response to the invasion of C. Las increased with the leaf bac-terial content.
万方数据
维普
