Identification Of Pathogen And Preliminary Study On Pathogenicity Mechanism Of Mango Malformation

Mango malformation is one of the most important diseases of mango which was reported in mango growing regions of the world. In China, the disease was first found in Yunnan and Sichuan provinces. However, the pathogen was still unknown. Therefore, the paper was designed to conduct the identification of the pathogen based on the morphological characteristics and molecular analysis in Panzhihua. Besides, endohormone content was measured and anatomical morphology between malformed and health tissues were detected for revealing pathogenesis.Isolate of MG6 was confirmed as the pathogen through the Koch's rule. On PSA media, it has white aerial hypha and no pigment. On SNA and CLA, conidiophore was simple braches, polyphialides, slenderly flask-shaped and 9.9～33.1×1.3-1.5μm. Microconidia were ovate to elongated ovoid,3.1～10.2×1.5-2.2μm, formed in false heads and never in chain. Macroconidia were falcate,3-5 septate,18～38×1.8-2.4μm, apical cell slender conical and basal cell unclear. Based on the homologous analysis of ITS,β-tubulin and EF-la sequences, F.mangiferae was the highest. As the result, MG6 was indentified as F.mangiferae Britz, Wingfield & Marasas.An ELISA method was used to detect the endohormone change between malformed buds and healthy. The results showed that IAA, ZR, GA and ABA were 1734.32 ng/mL,987.31 ng/mL,36.25 ng/mL and 22951.20 ng/mL respectively in malformed buds and in health ones, which were 571.99 ng/mL,556.40 ng/mL,7.05 ng/mL and 13151.99 ng/mL. Obviously, difference of GA was the most significant.Anatomical morphology of the stem was observation by paraffin section. The results showed that there were difference between malformed stem and health. There was 9-13 layers of parenchyma cells in malformed cortex, where the health was 4-7.Vascular bundles were flat and long in malformed stem and phloem fiber were more and closer. In cambium layer, there was pigment deposition. Proportion of xylem was larger, less differentiation of vessel cells and shorter in aperture. The parenchyma cells in marrow of the malformed stem were obviously closer and smaller to about 3 times.