| Witches' broom disease is considered a potentially serious disease that affects a large number of bamboo species. Although switches' broom caused malformation of the culms and affects culm production, data on economic losses are not available from any affected districts. A detailed investigation on bamboo switches' broom was conducted at different ecological sites of bamboo growing areas, including Ya'an, Yibin, Leshan and Meishan city. Through the analysis of the historic and present circumstances of disease occurrence, the degree of losses are associated with different species. It was found that bamboo switches' broom occured in Phyllostachys pubescens, Ph. Heteroclada, Ph. Bambusoides and not in Neosinocalamus affinis, Pleioblastus nakai, Dendrocalamus latiflorusoIt is wildly discussed in China what is a causal agent of bamboo witches' broom. It was considered that switches'-broom of bamboo was caused by Balansia take. Some reported that phytoplasma was also observed in the phloem of bamboo under the electron microscope.Axenic culture of Aciculosporium take Miyake is obtained from the tip of the switches'broom, which is different from other fugi. It grows slowly and usually contaminated. The colony is about 6-10mm on diameter after 15 days and seldom has mycelium. We extracted DNA from infected tissues, Nested Polymerase Chain Reaction (PCR) using a combination of two phytoplasma-specific 'universal' primer pairs (R16mF2/R16mR1-R16F2/R16R2) amplified 16S rRNA fragment (about 1.2 kb) from infected tissues.The result indicates the existence of phytoplasma associated with this disease. It is testified further that Aciculosporium take Miyake and phytoplasma are both exist in witches' broom-deformed branches.The phytoplasma was designated as PhBWB. The result comparing homology ofnucleotide sequences of amplified 16S rDNA fragment shows that phytoplasma of phyllostachys bambusoides f. witches'-broom (PhBWB) is closed related to Aster yellows (AY). Therefore, we can estimate that PhBWB is one of the phytoplasma of 16Sr I group.The results of the analysis of metabolic product from Aciculosporium take Miyake by HPLC revealed that gibberellins and cytokinins exist. Peroxidase and Polyphenol oxidase of healthy leaf (A), healthy leaf of infected branches (B) and bamboo witches broom(C) were compared. The results showed that: PODa< PODc, There is significant difference of POD activity between A and C at 0.01 level, whereas, PPOA > PPOC, There is significant at 0.05 level. Each enemzy activity of B is unstable, on the whole, between A and C. At 0.05 level, there is insignificant difference of POD between A and B, and also no difference of PPO between B and C.Since it was observed that endogenous indole-3-acetic acid is reduced in the twigs of the diseased bamboo, the symptoms (bushy appearance) may be induced by reduction in auxin levels. Most research figured out that the unbalance of the ratio of C/A cause the appearance of characteristic witches'broom symptoms. Based on the obtained results, we assumed that the pathogen infection causes increases of peroxidase and corresponding isoenzyme activities of bamboo switches' broom, and decreases of catechol or other kinds of polyphenols compounds, thereby promoting oxidation and decomposition of auxin involved with the peroxidases-IAA oxidase system.. It thus results in a drop of free IAA level. In addition, cytokinins exist in the metabolic product of Aciculosporium take Miyake probably increase the ratio of C/A. The low level of free IAA concentration must eventually causes the plant to develop the short internodes, loss of normal apical dominance, proliferation of axillary buds, which finally brings about the appearance of characteristic witches'broomsymptoms.
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