戀香草莓組織培養苗生物健化有益細菌之研究

Abstract

草莓為臺灣高經濟價值之作物，育苗期為五月初至九月底，此時期因夏季高溫多濕，可能導致病蟲害發生嚴重的情形，進而影響種苗的品質與產量。為降低田間病害發生率，政府推行草莓健康種苗制度，欲藉由組織培養苗作為母株培育無病原菌之健康種苗。然而組織培養苗出瓶後易暴露在非生物及生物性逆境中而死亡，為了提高組織培養苗在馴化階段的生長及存活率，可以利用如促進植物生長根棲細菌 (plant growth promoting rhizobacteria, PGPR) 進行生物健化 (biohardening)，來幫助植株生長、誘導抗病性或提高耐受非生物逆境之能力。本研究首先評估草莓植株生長勢的生長指標，以找出後續盆栽試驗及田間試驗之監測準則，同時利用誘釣法分離並篩選具有促進戀香草莓組織培養苗生長、可應用於生物健化之有益細菌。結果顯示，葉面積、葉柄長及根冠直徑均與草莓植株生物量 (biomass) 呈高度正相關，較適合作為草莓組織培養苗生長指標。本研究自根圈土壤分離的 116 個菌株中，Pseudomonas sp. NA-3-1 及 Pseudomonas sp. KBM-3-9-2 兩菌株具有促進戀香草莓苗生長的效果；而先前研究對豐香草莓有促進生長效果之菌株中，經測試 P. fluorescens K1-3-1 及 Serendipita indica 兩個菌株對戀香草莓亦具有促進生長效果。進一步測試對炭疽病的耐受能力及可能機制，發現預處理 P. fluorescens K1-3-1 病害嚴重度雖仍高，但可誘發較高的過氧化氫酶 (Catalase, CAT) 及過氧化酶 (Peroxides, POD) 活性，同樣的情況也發生在菌株 Pseudomonas sp. NA-3-1 處理的植株上。本研究篩選出 Pseudomonas sp. NA-3-1、Pseudomonas sp. KBM-3-9-2、P. fluorescens K1-3-1 及 S. indica 等 4 支有益微生物，盼能以生物健化的方式優化新品種戀香草莓健康種苗繁殖過程，透過提升健康種苗使用率，達到降低田間病害嚴重度之最終目標。

Strawberry is a profitable cash crop in Taiwan. During seedling production from early April to late September, hot and humid summer may increase disease severity and pest infestation, reducing seedling quality and quantity. To decrease disease severity in the field, the government implemented a healthy seedling production system for strawberries to alleviate such problems by producing healthy strawberry seedlings from acclimatized micropropagated plantlets. However, high mortality can be observed during the acclimatization of tissue culture plants due to exposure to abiotic or biotic stresses. Thus, to increase their survival rates, we can use biohardening with beneficial rhizobacteria such as plant-growth promoting rhizobacteria (PGPR) to improve seedling growth, induce resistance and enhance plant ability to tolerate abiotic stresses. In this study, we evaluated the growth index of strawberry vigor to identify monitoring standards for pot and field experiments. In the meantime, the baiting method was used to isolate and screen beneficial bacteria for strawberry growth promotion and biohardening. The results showed that leaf area, petiole length, and crown diameter are better growth indexes for strawberry micropropagated seedlings. Among one hundred and sixteen strains isolated from strawberry rhizospheric soil, only Pseudomonas sp. KBM-3-9-2 and Pseudomonas sp. NA-3-1 can promote strawberry growth. P. fluorescens K1-3-1 and Serendipita indica, which showed growth-promoting ability to strawberry cultivar ‘Toyonoka’ in a previous study, also work on strawberry ‘Miaoli No.1’. Further investigation of strawberry tolerance to anthracnose and its possible mechanisms revealed that, although disease severity was high, P. fluorescens K1-3-1 pretreatment could induce higher catalase and peroxidase activities, similar to Pseudomonas sp. NA-3-1. In conclusion, four beneficial microorganisms, including Pseudomonas sp. KBM-3-9-2, Pseudomonas sp. NA-3-1, P. fluorescens K1-3-1, and S. indica were identified in this study. Hopefully, they can be used to optimize the healthy seedling production system of strawberries, raising the utilization rate of healthy seedlings and finally achieving the goal of reducing disease severity in the field.