暖化下的地下部交互關係與地上部反應：叢枝菌根菌（AMF）、根瘤線蟲（RKN）與暖化交互作用對作物及地上部草食動物表現之影響

Belowground interactions and aboveground consequences under warming: Interactive effects of belowground arbuscular mycorrhizal fungi (AMF), root-knot nematodes (RKN), and warming on the performance of a crop plant and aboveground herbivore

柳智升(Chih-Sheng Liu)

指導教授 ： 何傳愷

國立臺灣大學/生命科學院/生態學與演化生物學研究所/碩士(2021年)

https://doi.org/10.6342/NTU202104015

摘要

糧食安全是目前急迫的全球問題，主要取決於環境變遷下的作物表現。作物表現受到非生物性（例如：暖化）或生物性（例如：物種交互作用）因子的影響，因此，檢驗非生物性和生物性因子如何同時影響作物系統可以幫助了解人類世的作物生產和糧食安全。為回應此議題，本研究檢驗地下部生物（叢枝菌根真菌 「AMF」 和根瘤線蟲 「RKN」）是否會透過單獨和交互作用影響作物和地上部食草動物的表現，並檢驗上述的結果是否會受到氣候暖化的影響。具體而言，我們探討以下三個與農業相關的議題：（壹）暖化下，AMF是否仍具有生物肥料的作用；（貳） 暖化下，是否會加劇 RKN 對農作物的負面影響；（參） 暖化下，AMF是否會抵消RKN對農作物和地上草食動物的影響。為釐清上述的議題，我們研究一個常見的農業系統，包含地下部叢枝菌根箘（Claroideoglomus etunicatum）、根瘤線蟲（Meloidogyne enterolobii）、大豆（Glycine max）、以及地上部斜紋夜蛾（Spodoptera litura）。田間的大豆可能會自然地遇到這些叢枝菌根菌、根瘤線蟲和地上部草食動物。我們在實驗室執行一個3×2×2的複因子實驗，操控溫度（控制組、+2°C、+4°C）、叢枝菌根菌（接種、不接種）與根瘤線蟲（接種、不接種）。我們測量叢枝菌根感染率、線蟲密度、植物表現（營養、生長、水分使用效率、生殖、以及物理與化學防禦）、地上部草食物動物的表現（生長與發育）。結果顯示：（甲）關於作物的表現， AMF基本上在控制組溫度和暖化溫度下都會幫助作物表現，代表AMF在暖化下仍能具有生物肥料的作用。具體來說，AMF單獨地影響植物生長（增加地上/地下生重量比值），幫助植物繁殖（增加豆莢重量），改善植物營養情況（較高的無機磷含量和較低的C/N比值），並減少植物物理防禦（減少葉片硬度）。相反地，RKN普遍降低了作物的表現（生長和繁殖），而其對作物繁殖（豆莢數）的傷害，會在+2℃暖化下加劇。具體來說，RKN的單獨作用降低植物生長（降低地上部重量和地上部/地下部重量比值），傷害植物的繁殖（降低豆莢重量），但會改善植物營養狀況（葉無機磷含量「Pi」含量增加，此增加僅是AMF所造成增加的19%）。此外，本研究沒有發現AMF和RKN沒有透過交互作用進而影響作物表現。（乙）暖化與AMF或暖化與RKN的交互作用會改變作物的表現（生長、水份使用效率和繁殖），暗示AMF和RKN對作物影響的方向或程度會隨氣候暖化而發生變化。（丙）關於地上部食草動物的表現，AMF的單獨作用會幫助斜紋夜蛾的表現（增加生長率或略微增加relative growth rate），然而RKN不影響地上部食草動物的表現。（丁）AMF在控制組溫度下會對RKN產生正面的影響，但在暖化下會抑制 RKN，顯示AMF和RKN的關係會隨溫度改變。因此，傳統上認為AMF可以抑制作物害蟲（如RKN和土壤病原）的觀點可能需要被重新檢視，加入溫度的考量，以便提供更精準的農業害蟲管理措施。整體而言，本研究結果顯示農業系統管理需要考量植物地上部系統與地下部系統之間的交互作用，且此交互作用很有可能會隨著全球暖化而改變。

關鍵字

微生物 ； 植物與動物交互作用 ； 叢枝菌根菌 ； 根瘤線蟲 ； 作物 ； 全球暖化

並列摘要

Food security is a pressing global issue and depends largely on the crop performance in a changing environment. Crop performance is affected by abiotic (e.g., climate warming) and biotic (e.g., species interactions) factors; therefore, examining the combined effects of abiotic and biotic factors will provide critical insights for understanding crop production and food security in the Anthropocene. Here, we examined whether belowground organisms (e.g., arbuscular mycorrhizal fungi [AMF] and root-knot nematodes [RKN]) individually and interactively affect crops and herbivores, and whether the effects are mediated by climate warming. Specifically, we investigated the following three questions related to agriculture: a) whether AMF will still work as bio-fertilizer under warming, b) whether the effects of RKN on crops will exacerbate under warming, and c) whether AMF will counteract the RKN effects on crops and aboveground herbivores under warming. We studied an agricultural system comprising AMF (Claroideoglomus etunicatum), RKN (Meloidogyne enterolobii), soybean (Glycine max), and an aboveground leaf chewing herbivore (Spodoptera litura). Soybean plants in the field may naturally encounter the AMF, RKN, and aboveground herbivores. We conducted a laboratory experiment with a 3×2×2 factorial design crossing temperature (control, +2°C, +4°C), AMF (presence, absence), and RKN (presence, absence) treatments. Traits to measure included AMF infection rate, RKN density, plant performance (nutrients, growth, water use efficiency, reproduction, and chemical and physical defense), and aboveground herbivore performance (growth and development). The results showed that 1) Regarding crop performance, in general, AMF benefited crop performance at control and warming temperature, suggesting that AMF work as bio-fertilizer under warming. Specifically, AMF individually affected plant growth (increased above-/belowground biomass ratio), benefited plant reproduction (increased pod biomass), improved plant nutrient status (higher Pi content and lower C/N ratio), and reduced plant physical defense (reduced leaf toughness). In contrast, RKN generally reduced crop performance (growth and reproduction), and its negative effect on crop reproduction (pod number) exacerbated under a +2°C warming. Specifically, RKN individually reduced plant growth (reduced aboveground biomass and above-/belowground biomass ratio), damaged plant reproduction (reduced pod biomass), but improved plant nutrient status (higher Pi content). Note the Pi increase induced by RKN was only 19 % of that induced by AMF. We did not detect the interactive effect of AMF and RKN on crop performance. 2) Warming interacted with AMF or RKN and affected crop performance (growth, water use efficiency, and reproduction), suggesting that the direction or degree of AMF and RKN effects on crops may shift under climate warming. 3) Regarding aboveground herbivores, AMF individually benefited tobacco cutworm performance (increased growth rate or marginally increased relative growth rate). RKN did not affect the aboveground herbivores. 4) AMF benefited and suppressed RKN at control and warming temperature, respectively, suggesting that the AMF-RKN relationship is temperature dependent. Therefore, a conventional wisdom that AMF can suppress crop pest (e.g., RKN and soil borne pathogen) may need to be refined with a temperature aspect. Overall, the results imply that agricultural management should consider the interplay between above- and belowground systems, which is likely mediated by climate warming.

並列關鍵字

Microbe-plant-animal interactions ； Arbuscular mycorrhizal fungi ； Root- knot nematodes ； Crops ； Climate warming

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