不同品種聖誕紅植株體內植物菌質體之定量追蹤及溫度對植物菌質體之影響

Abstract

聖誕紅(Euphorbia pulcherrima)是大戟科 (Euphorbiaceae) 大戟屬 (Euphorbia)的多年生木本植物。聖誕紅的苞片因為色彩鮮豔而具有觀賞價值，是重要的花卉作物，台灣的年產量約120萬盆，產值約1.2億新台幣，僅次於蘭花。野生的聖誕紅分枝少、枝葉稀疏，且株高可達三公尺，是因為植物菌質體才使得聖誕紅矮化與分枝增加，株型圓潤緊湊而適合製成盆花。近期因聖誕紅種植期間出現突然抽高的現象，造成業者的經濟損失，而此現象的發生推測與植物菌質體有關。本研究蒐集市面較主流的聖誕紅品種，利用real-time PCR定量技術探討植物菌質體數量與聖誕紅分枝性狀的相關性，並追蹤在一般溫室栽培環境下自種植到出貨時期的植物菌質體濃度變化。同時，也利用生長箱，調查聖誕紅植株內植物菌質體在15 ℃、25 ℃、35 ℃等不同環境溫度下，是否會出現不同的消長狀況。本研究發現大多數品種的植物菌質體數量皆與分枝性狀的好壞呈現中高度的正相關，惟尚紅與玫瑰紅星因個體差異導致標準差過大，尚不易看出植物菌質體數量是否會影響該二品種的分枝數量。在自然感染的情況下，一般溫室栽培者，發現經過六個月的定量追蹤，僅在定植初期植物菌質體數量較低，隨著植株成長茁壯，植物菌質體也跟著增加，直到12月的開花期，植物菌質體數量出現顯著的提升，隨後在花期結束後，當苞片與葉片開始掉落，生長勢變的衰退，植物菌質體也跟著減少。於生長箱控溫環境栽培的品種為倍利及尚紅，在為期約半年的追蹤下，最終僅15 ℃處理的倍利於第三個月植物菌質體出現顯著的上升，其餘皆無顯著差異。35 ℃處理的兩個品種，從一開始植物菌質體數量就不斷降低，卻因為高溫對於植物本身造成太大的逆境，至實驗後第三個月時，植株數量已剩下不到一半，故統計上才不具顯著差異，而後續將植物移至溫室中恢復，植物菌質體也隨之增加，因此，雖然無法判定高溫是直接對植物菌質體造成傷害，還是因為植物逆境導致寄主植物狀況不佳，間接影響植物菌質體的生存，但仍可以確定高溫環境並不利於聖誕紅的種植，在商業栽培上應適時利用遮陰等方式改善環境溫度，避免將植株長時間暴露在過度炎熱的環境下。

Poinsettia (Euphorbia pulcherrima) is a perennial woody plant belonging to the family Euphorbiaceae and the genus Euphorbia. Being an important ornamental crop, poinsettia is valuable due to its colorful bracts. Total poinsettia production is about 1.2 million pots and values at 120 million NTD, ranking second only to orchids in Taiwan. Wild poinsettias are few in branches and sparse in leaves. Moreover, the plants can grow up to three meters tall. Phytoplasma is the key factor that induces poinsettia dwarf and free-branching. With these characters induced by phytoplasma, the plant appearance becomes more compact and suitable for pot flower. However, on these days, some of the poinsettia plants somehow start to grow excessively during the growing season and cause huge lost to producers. The reason of excessive growth is supposed to be leaded by phytoplasma. In this study, I collected some common cultivars and employed real-time PCR technology to study the relationship between the number of phytoplasma and poinsettia branching character. Moreover, I examined changes in the concentration of phytoplasma under normal atmospheric temperature in greenhouse. I also quantified the amount of phytoplasma with plants incubated in the growth chamber under 15 ℃, 25 ℃ and 35 ℃ to determine the patterns of growth and decline of phytoplasma. As result, the amounts of phytoplasma are positively correlated to the branching rate of most cultivars except Prima Red & Rose Star. The 2 cases might be due to huge variation from statistics. After six months of tracing, cultivars grown in the normal greenhouse exhibited lower phytoplasma in the beginning of investigation. Along with plant growth, phytoplasma increased as well. During flowering season on December, the amounts of phytoplasma raised. When it comes to the end of flowering season, phytoplasma declines followed by the decay of growth potential which bracts and leaves start to drop. The two cultivars growing in the growth chamber with controlled temperature are Pepride and Prima Red. Within the tracing of about half of a year, only Pepride shows a significant increase of phytoplasma in the third month while others remain no significant difference. The amounts of phytoplasma under 35 ℃ were actually declined continuously from the beginning. Because high temperature poses great threats to plants, less than half of the amounts of plants were sustained since the third month and, in hence, there is no statistically significant difference in the amount of phytoplasma. The plants under 35 ℃ treatment then moved to greenhouse for recovery and phytoplasma increases again. Thus, although we cannot ensure the high temperature either harms phytoplasma directly or indirectly poses effects on the survive of phytoplasma by causing growing threats to the plant hosts, we can still prove that it is not suitable to grow poinsettias under high temperature. For commercial growth, environmental temperature could be properly improved by shading or other methods to avoid plant being exposed under overheated environment.