Anatomical Changes in Leaf Midrib of Huanglongbing-Affected Citrus by Staining Technique
Keywords:
huanglongbing, HLB, midrib, citrus, staining techniqueAbstract
Huanglongbing (HLB), also knows as Citrus greening disease is an extremely destructive disease of citrus worldwide, caused by Candidatus Liberibacter asiaticus (Las) which is a phloem-limited bacterium. HLB leads to decreased productivity and chlorosis of leaves which results in the collapse of phloem tissue. In this study, the Las infection status of all diseased leaf samples was verified by PCR. Tangerine, lime and pomelo were the representative citrus tested. The results showed that 13 samples were positive with Las from 28 samples. The basic structure of vascular and surrounding tissue from HLB-free and HLB-affected trees were examined under a compound microscope. The study of histological sections used a freezing microtome for sectioning. The tissue was stained with 0.1% Toluidine blue as a background stain and 3% Iodine to detect starch accumulation in midrib structures. The results showed that HLB affected the vascular tissue system, caused phloem fiber disorganization, hypertrophy of phloem parenchyma cells and thickening in phloem and massive starch accumulation
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