Investigation of the effects of the endophytic microorgamisms on biohardening of micropropagated strawberry seedlings

• Main Authors: Ming-Chu Huang, 黃明珠
• Other Authors: Nai-Chun Lin
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/2d8p6r

碩士 === 國立臺灣大學 === 植物醫學碩士學位學程 === 106 === Strawberry (Fragaria x ananassa Duchesne) is an economically important herbaceous plant belonging to family Rosaceae. Although strawberry is a perennial plant, replacement of mother plants for breeding healthy seedlings is required annually due to severe pest problems and difficulties of strawberry plants to survive over summer. Farmers are still preserving the mother plants by selecting healthy and symptomless plants from fields as the mother plants for next season. Due to latent infection of Colletotrichum gloeosporioides and infection of daughter plants by Fusarium oxysporum. f. sp. fragariae through runners, to ensure whether the mother plants are specific-pathogens-free (SPF) becomes an important issue in the strawberry nurseries. The purpose of this study was to screen beneficial endophytic bacteria from strawberry roots for biohardening of the micropropagated strawberry seedlings, making them capable of growing fast and resistant to anthracnose, and shortening acclimatization time. Hopefully, these endophytic bacteria can be introduced into the three-tier seedling production system in the near future. Endophytic bacteria isolated from the healthy strawberry roots were firstly tested for their potential in promoting plant growth activities, including phosphate solubilization, siderophore production, and nitrogen-fixation, through plate assay methods. The micropropagated strawberry seedlings after biohardening for 30 days with five endophytic bacteria, among which Pseudomonas putida L5 has the best activities, could effectively increase vegetative growth and resistance to anthracnose. Biohardening with P. putida L5 in combination with Serendipita indica, the endophytic fungus which also has the ability to enhance strawberry growth and resistance to anthracnose, could accelerate the seedling raising process, and produce abundant seedlings quickly and stably. Furthermore, four strains were selected on its ability to enhance resistance of micropropagated strawberry seedlings to anthracnose, all of which have activities superior to S. indica. Among those strains, P. fluorescens K1-3-1 has the best performance. In addition, P. fluorescens K1-3-1 could also inhibit mycelial growth of C. gloeosporioides and F. o. f. sp. fragariae in an antagonistic assay. At last, biohardening with P. putida L5 and S. indica, the best choice among all different combinations, created an excellent effect on promoting vegetative growth of micropropagated strawberry seedlings as well as increasing resistance against anthracnose at the same time.