길항근권세균에 의한 감자 역병에 대한 저항성 유도 및 감자수량 증가

Abstract

Efficacy of resistance induction by the bacterial strains Pseudomonas putida (TRL2-3), Micrococcus luteus (TRK2-2) and Flexibacteraceae bacterium (MRL412), which were isolated from the rhizosphere of plants growing in Jeju mountain, were tested in a green house. The disease severity caused by Phytophthora infestans was effectively reduced in the potato plants pre-inoculated with the three bacterial strains compared with those of the untreated control plants. In order to estimate the level of protection by the three bacterial strains, Mancozeb WP (Diesen M^(TM), Kyong nong) and DL-3-amino butyric acid (BABA) were treated before the challenge inoculation with the pathogen, whereas Dimethomorph WP (Forum^(TM), Kyong nong) and potassium phosphonate (KH₂PO₃ or K₂HPO₃) were treated after the challenge inoculation. Disease severities of chemical pre-treated as well as post-treated plants were reduced compare to those of the untreated. The disease reduction in the plants pre-treated with Mancozeb WP was the highest, whereas that of post-treated with Dimethomorph WP was the lowest. The yields of plants pre-inoculated with three bacterial isolates were greatly increased than those of control plants. To clarify the cause of the disease severity reduction, the infection structure were observed at the penetration sites on the leaves of plant inoculated with P. infestans using a fluorescence microscope. In this study the rates of germination and appressorium formation of the cysts of P. infestans were observed on the leaf surfaces of the potato plants expressing systemic resistance mediated by the three bacterial strains as well as by BABA. Furthermore, the frequencies of callose formation of the epidermal cells at the penetration sites were observed after the fungal inoculation. There were no differences on the germination rates among the untreated, the three bacterial strains pre-inoculated and BABA pre-treated plants. However decrease of appressorium formation was observed in BABA pre-treated but not in the bacterial strains pre-inoculated compared to untreated plants. Also, the frequencies of callose formation of the three bacterial strains pre-inoculated were higher than that of untreated plants, indicating an active defense reaction of the pre-inoculated host cells against fungal attack. However, the frequency of callose formation on BABA pre-treated plants were not high as those of bacterial strains pre-inoculated plants. Contrastively, the stronger fluorescent of epidermal cells were observed at the penetration sites compared to those of bacterial strains. Based on these results it is suggested that the defense reduction were differently expressed by the pre-inoculation with the bacterial strains or by the pre-treatment with BABA.