苜蓿幼苗期耐旱性篩選之建立

Screening drought tolerance of alfalfa in early growing stages

巴雅欣(Bolormaa Bayarchimeg)

指導教授 ： 謝清祥

國立屏東科技大學/國際學院/熱帶農業暨國際合作系/碩士(2016年)

摘要

在世界各地皆存在乾旱逆境的環境問題，其對於作物的生長和產量造成不良影響。紫花苜蓿是重要的飼料作物之一，在不同氣候中皆具有非常良好的適應性，其中包含不同程度上的耐旱能力。本試驗在乾旱逆境下種植來自四個不同國家的紫花苜蓿，並比較品種間之抗旱性，以建立種苗篩選方法。首先，對於不同比例混合之介質在中斷供水下進行試驗，以確立何種介質為種植紫花苜蓿在抗旱性篩選測試中具有最佳的乾燥斜率曲線。接著，在乾旱逆境下將不同品種苜蓿於幼苗期進行篩選，並測定逆境植物之脯胺酸含量。此外，亦在生長期中斷供水下測定紫花苜蓿於生長箱中的抗旱性。最後，通過不同濃度的PEG6000的乾旱逆境刺激，以測定苜蓿分別在萌發期與幼苗期的抗旱性。而結果表明顯示，以砂：蛭石(1:1)及砂：珍珠石(1:1)之混和比例的介質，於處理後第二天至第七天的乾旱斜率曲線最平緩而最佳。於苜蓿幼苗篩選試驗的結果則顯示：在介質混合比例為砂：蛭石(1:1)的根和株高較砂：珍珠石(1:1)低約1至2公分。全數四個品種表現出的存活率大抵相似，其中“Middle East”和“Known-You”品種可存活較久，平均為7天。而其脯胺酸含量品種間差異顯著：最高者為“Burgaltai”品種(0.46 µmol g-1)；最低者則是“Middle
East”品種(0.34 µmol g-1)。而不同濃度PEG 6000 (0、10、20及30%)對於苜蓿萌發及幼苗生長的情形，經調查後結果顯示：在濃度30%之PEG處理中，所有的品種皆無法發芽；在濃度20%之PEG處理中，所有的品種發芽率皆很低；而在對照組以及10%PEG處理中，其發芽率皆很高且相近。在苜蓿幼苗期分別以0、10、20和30%之PEG進行灌溉，並測定發現：在各品種間之脯胺酸含量並無顯著差異；“Nutag Belcheer”品種和“Burgaltai”品種在所有PEG灌溉濃度處理中具有最低的脯胺酸含量；20% PEG處理具有最高的脯胺酸含量(1.322 mg/g)。在生長箱試驗中，紫花苜蓿則在一個月不進行灌溉的條件下持續生長直到採收，其中最高者為34公分，然而，其地上部與地下部之重量未達1公克。於間隔一周前後共進行兩次脯胺酸含量的測定，所有品種的含量均增加（第一次為0.1 to 0.2 mg/g，第二次的則為0.7 to 0.9 mg/g），然而，各品種間之含量則無顯著差異。總體而言，所有四個品種根據生長期和處理表現出不同的抗逆性。“Middle East”品種與“Known You”品種之紫花苜蓿在早期的生長階段之耐旱性表現較其他品種為佳，而在長期乾旱逆境下，“Burgaltai”品種和“Nutag Belcheer”品種則相較於其他兩個品種更好。此外，在PEG模擬乾旱條件下，20%PEG處理可能為測試植物耐旱性的最佳濃度。相較於PEG模擬乾旱和生長箱試驗，生長箱試驗賦予較較佳的耐旱性篩選條件。

關鍵字

紫花苜蓿 ； 乾旱 ； PEG ； 脯胺酸 ； 中斷供水

並列摘要

Drought stress is an environmental problem throughout the world which may adversely affect crop growth and yield. Alfalfa is an important forage crop with high adaptation to different climate and is expected to show different levels of drought tolerance. In order to differentiate levels of drought tolerance on alfalfa varieties, several experiments were conducted to establish seedling screening method under drought stress and compare different drought resistance among alfalfa varieties from 4 different countries. First, different types of medium ratios were tested under withholding irrigation condition to determine best drying slope curve for drought screening and test sufficiency of chosen medium for growing alfalfa. In next step, screened alfalfa varieties at seedling stage under drought stressed condition and
measured proline accumulation of stressed plants. Also alfalfa’s drought tolerance was tested in growing stage in box by withholding irrigation. Finally, drought stress stimulated by different concentrations of PEG6000 to determine alfalfa’s drought tolerance in both germination and seedling stages. As a result it revealed that medium ratio of sand: vermiculite (1:1) and sand: perlite (1:1) had shown a best slower drying slope curve at second day to seventh after drought treatment. For seedling screening test the result showed that in sand: vermiculite ratio (1:1) root and plant height were one to two centimeters lower than sand: perlite ratio. In case of survival rate, all four varieties showed same results. “Middle East” and “Known-You” varieties lived longer and showed average of 7 days of survival rate. Proline accumulation showed significant differences among varieties. The highest result was “Burgaltai” variety (0.46 µmol g-1) and the lowest result was detected in “Middle East” variety (0.34 µmol g-1). How PEG 6000 in different concentrations (0, 10, 20 and 30%) effected on germination and seedling growth of alfalfa were investigated. In 30% PEG none of the varieties were germinated, in 20% PEG all of varieties germinated in low percentage and control, 10% PEG treatments showed similar high germination rate. In seedling stage watered with 0, 10, 20 and 30% PEG and measured proline content. Proline content was found no significant difference among varieties. “Nutag Belcheer” and “Burgaltai”, showed lowest proline content in all PEG treatments irrigated condition. Moreover, the 20% PEG treatment has the highest proline content (1.322 mg/g). In box test alfalfa was keep growing without irrigation condition for a month period until harvest and the tallest one was grown up to 34 cm. On the other hand the weight of shoot and root did not reach 1 gram. The proline content was measured twice with interval of a week and proline content increased in all varieties (first time fluctuated between 0.1 to 0.2 mg/g and second time 0.7 to 0.9 mg/g). Also there was no significant difference among proline content of varieties. Overall, all four varieties showed different stress tolerance depending on growing stage and treatment. In early growing stage variety “Middle East” and “Known You Alfalfa” had better drought tolerance than other varieties. In long term drought stress, varieties “Burgaltai” and “Nutag Belcheer” were better than other two varieties. Furthermore, in PEG drought simulated condition, 20% PEG treatment could be the best concentration to test drought tolerance of plants. In comparing PEG simulated drought and box tests, the box test which gives opportunity to screen drought longer is preferred.

並列關鍵字

alfalfa ； drought ； PEG ； proline ； withholding irrigation

參考文獻

Antolín, M. C., I. Muro, M. Sánchez-Díaz. 2010. Application of Sewage Sludge Improves Growth, Photosynthesis and Antioxidant Activities of Nodulated Alfalfa Plants under Drought Conditions. Environmental and Experimental Botany 68 (1): 75–82.

Aranjuelo, I., G. Molero, G. Erice, J. C. Avice, and S. Nogue. 2011. Plant Physiology and Proteomics Reveals the Leaf Response to Drought in Alfalfa ( Medicago Sativa L .). Experimental Botany 62(1): 111–23.

Ashraf, M., and P. J. C. Harris. 2013. Photosynthesis under Stressful Environments :An Overview. Photosynthetica 51 (2): 163–90.

Bates, L. S., R. P. Waldren, and I. D. Taere. 1973. Rapid Determination of Free Proline for Water Stress Studies. Plant and Soil. 39(1): 205-207.

Chaves, M M, J. Flexas, and C. Pinheiro. 2009. Photosynthesis under Drought and Salt Stress : Regulation Mechanisms from Whole Plant to cell. Annals of Botany 103: 551-560