抗鹽細菌 Pseudomonas sp. T1C2 提升番茄鹽害耐受性之潛力研究

Abstract

隨著全球氣候變遷以及耕作面積增加，農用地鹽鹼化問題日益嚴峻。鹽害是作物栽培中僅次於乾旱的非生物性逆境，會對作物造成多方傷害，如滲透壓影響植株水分吸收、Na+ 在組織內累積對細胞造成離子毒性並同時影響細胞胞器活性，以及阻礙植物光合作用與生長發育，進而嚴重影響農作物品質和產量，對農業經濟造成巨大損失。耐鹽性促進植物生長根棲細菌 (Halotolerant Plant Growth-Promoting Rhizobacterium, HT-PGPRs) 可透過多種途徑提升植物耐鹽性，如調節植物激素生合成、增加植株內部調滲物質 (Osmoprotectants) 含量，以及誘導逆境相關基因表現。本研究利用誘釣法從臺灣濱海地區土壤與植物根圈土中分離出 261 株菌株，並通過菌株耐鹽性分級、優勢程度以及接種後植株於 500 mM 鹽處理下的生長狀況等指標，最終篩選出 T1C2 分離株。經過 16S rRNA、gyrB、rpoB 以及 rpoD 等基因序列與 GenBank 資料庫比對，T1C2 應為 Pseudomonas citronellolis，其可在 500 mM 鹽濃度下生長，並且具由螯鐵能力。然而，經過根組織切片與菌數計算後發現，T1C2 可能不具植物內生性，但能有效促進番茄 (農友 301) 於 200 mM 鹽濃度下的幼苗乾鮮重，並提升植株乾鮮重、葉綠素、脯胺酸含量、SOD、POD 與 CAT 抗氧化酵素活性，同時顯著降低 MDA 含量和細胞膜離子滲漏率。在植體元素分析中，T1C2 有效降低番茄於鹽害下的 Na+ 含量，並且提升 K+ 含量與K+/Na+ 比率；此外，T1C2 在番茄滲透壓逆境中也顯示出提升植株乾鮮重以及延緩滲透壓損傷發生的潛力。總言之，本研究篩選出 1 株可以有效提升番茄鹽耐受性及滲透壓耐受性潛力的 HT-PGPR。本研究盼望未來能通過施用此類 HT-PGPR 的方式，提升鹽鹼化田地的利用率，減輕鹽害對作物造成的影響，並作為後續相關研究的參考。

With global climate change and agricultural expansion, the issue of agricultural soil salinization is becoming severe. Salt stress is the second most significant abiotic stress after drought in crop cultivation, causing multiple harms to crops such as osmotic stress affecting plant water absorption, Na+ accumulation in tissues leading to ion toxicity and impaired organelle activity, and disruption of photosynthesis and plant growth. All these severely impact crop quality and yield, causing substantial economic losses in agriculture. It has been shown that halotolerant plant growth-promoting rhizobacteria (HT-PGPR) can enhance plant salt tolerance through various mechanisms, including regulating plant hormone biosynthesis, increasing the content of osmoprotectants within the plant, and inducing the expression of stress-related genes. In this study, 261 bacterial strains were isolated from the roots and rhizosphere soil of coastal plants using the baiting method. Through assessing salt tolerance, predominance in soil, and performance on growth indices after inoculating plants under 500 mM salt treatment, T1C2 was finally selected. Multilocus sequence typing analysis using 16S rRNA, gyrB, rpoB, and rpoD genes agains the GenBank database indicates that T1C2 should be Pseudomonas citronellolis. T1C2 can grow under 500 mM NaCl and has siderophore production capability. However, root tissue sectioning and bacterial count revealed that T1C2 might not be an endophyte but can effectively promote dry and fresh weight of tomato cv. 'Knowyou 301' under 200 mM NaCl. T1C2 treatment enhanced plant dry and fresh weight, chlorophyll and proline contents, and the activities of antioxidant enzymes SOD, POD, and CAT, while significantly reduced MDA content and electrolyte leakage rate. Plant element analysis showed that T1C2 effectively reduced the Na+ content in tomato under salt stress, while increased the K+ content and the K+/Na+ ratio. Additionally, T1C2 was found to increase plant dry and fresh weight and delay osmotic stress damage in tomato under osmotic stress. In conclusion, this study identified an HT-PGPR strain that can effectively enhance tomato tolerance to salt and osmotic stresses. In the future, halotolerant bacteria were recommended to increase the utilization of saline-alkaline fields, mitigate the impact of salinity on agriculture, and serve as a reference for future related studies.