JIA-2018-09

2029 Tamaki Masahiko et al. Journal of Integrative Agriculture 2018, 17(9): 2024–2030 penetrate the conidia because of the high permeability. The reduction of the width, the void space and the absent lipid granules in the conidia were caused by treatment with BF solution containing both CO 2 MBs (Fig. 3-D and E). This may be due to the expansion of the vacuole by increasing the permeability of BF into the conidia by CO 2 MB, because Fthalide and Ferimzone, the active ingredients in BF, affect the metabolism of P . oryzae Cavara conidium (Chida 1989; Okuno et al . 1989). However, the length of the conidia was unchanged because they are composed of three cells and two septa. 5. Conclusion In the present study, the concentration of BF solution required to inhibit germination and appressorium formation of P . oryzae Cavara conidia could be reduced by using CO 2 MB. Such a reduction in pesticide use is highly beneficial for the sustainable management of agricultural fields and reduces the amount of residual pesticides in the environment. Based on electron microscopic observation, it could be confirmed that physical alterations of the conidia, such as wrinkles, dents and decrease of the width, were caused by the use of BF solution containing CO 2 MB. This infers that the significant inhibition of germination and appressorium formation by BF solution containing CO 2 MB was due to the synergistic effect of CO 2 MB and the high concentration of BF. However, further investigations are needed to understand the underlying mechanisms. References Bourett T M, Howard R J. 1990. In vitro development of penetration structures in the rice blast fungus Magnaporthe grisea . Canadian Journal of Botany , 68 , 329–342. Chida T. 1989. Studies on mechanism of controlling action of Fthalide against rice blast disease. Japanese Journal of Pesticide Science , 14 , 363–371. (in Japanese) A D B C E CW, CM Nu N SEP Na G M L 2 μm 2 μm 2 μm 2 μm 2 μm Fig. 3 Transmission electron microscopy (TEM) images of Pyricularia oryzae Cavara conidia treated with Blasin ® Flowable (BF) solution containing carbon dioxide millibubbles (CO 2 MMB) and both CO 2 microbubbles (CO 2 MBs). A, nontreatment. B, BF solution only. C, BF solution containing CO 2 MMB. D, BF solution containing the gas-water circulating-type CO 2 MB. E, BF solution containing the decompression-type CO 2 MB. CW, cell wall; CM, cell membrane; SEP, septum; N, nuclear; Nu, nucleolinus; M, mitochondria; G, Golgi; L, lipid granule; Na, umbilicum. BF solution diluted to 5 000-fold was used for 5 min.