臺灣重要油用山茶屬植物(Camellia spp.)豐產指標篩選之研究

Abstract

茶樹是臺灣重要的經濟作物，種植面積廣大且具有多樣性，茶葉採摘是主要利用方式，2022年臺灣茶葉種植面積達到12,192公頃，但目前茶樹種植油用品種尚未規模化，茶籽油生產主要依賴進口，本土生產的茶籽經濟栽培很少。臺灣的油茶產業包括普通油茶和細葉山茶，主要種植在臺灣中南部和東部地區，2022年生產總面積約1,569.6公頃。油茶的果實在10月至11月成熟，可榨取食用或工業用的茶油，而其它部分如殼、種殼和木材也有其他用途。油茶的種植面積相對不高，如何提高單位面積產量是一個重要的課題。 為發展茶樹油用品種篩選指標，以加速育種時間，並針對不同茶樹品種的含油率及脂肪酸組成，本研究調查超過100個茶樹品種，進行研究以篩選育種指標，並選育高含油率及較佳脂肪酸組成之品種。首先，調查106個茶樹品種，以確定茶樹花朵性狀與果實產量之間的關係，結果顯示雄蕊束外徑寬度為主要影響因素，柱頭寬度為次要影響因素，這兩個性狀有潛力成為茶樹育種計劃中的重要早期篩選指標。接著，比較不同茶樹種類在果實產量、結果率、株高和株寬等性狀上的差異，結果顯示大小葉雜交種和大葉種在果實產量上表現較佳，結果率、株高和株寬與單株果實產量呈現正相關，這些性狀可作為茶樹育種選拔的重要指標。另外，進行比較了不同茶樹種類間果實農藝性狀的差異，結果顯示大小葉雜交種在單顆種子重和種子直徑方面優於大葉種和小葉種，而果實內種子重、種子粒數和種子直徑對單顆果實重有正面影響。最後，比較了104個茶樹品種的種子含油率與脂肪酸組成，結果顯示小葉種具有較高的含油率及較高的亞油酸含量，而大小葉雜交種在棕櫚酸含量上高於大葉種和小葉種。 本研究選取臺東縣鹿野鄉定植的75株實生細葉山茶成木進行研究，結果顯示細葉山茶的產量保持一致，而花朵性狀受氣候和生理調節影響，且開放授粉結果率與套袋結果率呈正相關，套袋結果率可正面影響開放授粉結果率。因此，建議選擇具有較大雄蕊束內徑和突出柱頭的花朵性狀、較高套袋結果率和良好果實產量的單株作為早期篩選標的，以提高細葉山茶的自然結果率和豐產品系的培育。另外進行高產量單株的篩選，依據5年間細葉山茶群體平均產量及2年平均結果率、果實農藝性狀分析。結果顯示，細葉山茶的平均產量為1.68 kg，平均開放授粉結果率為12.48%，最高產量可達9.65 kg。結果率和果實重量對產量有影響，篩選時應考慮果實重量。篩選出的穩定的高產量品系包括B79、B55和B25，它們的平均產量分別達到9.65 kg、5.26 kg和5.26 kg，果實重量達3.79 g、4.05 g及4.96 g，可供將來進入品系比較試驗。 普通油茶花朵性狀在2018年相較於2017年顯示出雄蕊束外徑及內徑減少，雌蕊長度縮短，而雄蕊束外內徑差減少，雄蕊減雌蕊長度差增加的趨勢。2018年普通油茶的自然授粉結果率(8.89%)顯著較2017年(4.26%)提高，而套袋結果率則未有變化。根據2017年和2018年的分析結果顯示，2017普通油茶的花朵性狀對開放授粉結果率的影響不具有統計顯著性，而2018年雄蕊束內徑對開放授粉有正面影響，每增加1 mm的雄蕊束內徑，開放授粉結果率將增加3.951%。然而，其他花朵性狀開放授粉結果率及套袋結果率影響不明顯。普通油茶的套袋結果率與開放授粉結果率呈現顯著正相關，隨著套袋結果率的提高，開放授粉結果率也相應增加。迴歸分析顯示2017年，每增加1%的套袋結果率，開放授粉結果率將增加2.004%；2018年則為每增加1%的套袋結果率，開放授粉結果率將增加1.486%。 本研究中普通油茶，過去三年間的普通油茶單株果實產量呈現相關性，調查平均果實鮮重為17.39 g、平均果實內鮮種子重為6.90 g、平均果實種子粒數為3.24粒、平均果實縱徑為30.00 mm、平均果實橫徑為32.26 mm。過去三年間的普通油茶果實平均單粒重與果實粒數呈現相關性，代表除了產量之外，果實重量與單株果實粒數亦有相關性。2017年自然授粉結果率與單株果實產量以及單株粒數之間呈現顯著正相關。然而，在2015年和2016年的研究中並未觀察到相關性。此外，自然授粉結果率與套袋結果率對平均單粒重並無統計上顯著的相關性，表示平均單粒重不受結果率的影響。 花粉活力檢測對於育種至為重要，本試驗比較了不同花粉發芽培養液與TTC染色配方對茶樹、細葉山茶及普通油茶的花粉活力檢測影響。結果顯示，茶樹、細葉山茶及普通油茶的花粉發芽培養液配方最佳者為「100 g/L蔗糖+150 mg/L硼酸+200 mg/L硝酸鈣」，而茶樹及普通油茶的花粉TTC染色配方最佳者為「100 g/L蔗糖+ 5 g/L TTC」。使用TTC染色法可以獲得較理想的花粉活力檢測結果，且添加蔗糖可以維持花粉外壁的完整性，方便長時間觀察花粉染色。對於75個茶樹品種的TTC染色檢測結果顯示，約80%的品種具有高於70%的花粉活力，僅臺茶19號、水仙和小葉鐵觀音的花粉活力較低，說明絕大多數茶樹品種的花粉可用於育種。在28個細葉山茶單株的檢測中，超過90%的單株花粉活力高於全體的89.3%，超過80%的單株占96.4%，最低花粉活力為60%，這表示大多數的細葉山茶具有正常的花粉可供授粉使用。將來發展本土油用山茶屬植物品種，選育高產量甚至高自交親和性的細葉山茶及普通油茶品系，以提升油茶整體產量，應是重要的課題。

Tea tree is an important economic crop in Taiwan, with a large and diverse cultivation area. Tea leaf picking is the main utilization method. In 2022, the tea cultivation area in Taiwan reached 12,192 hectares. However, the cultivation of oil-producing tea tree varieties has not been scaled up, and the production of tea seed oil relies mainly on imports, with very little locally grown tea seeds for economic cultivation. Taiwan's oil tea industry includes Camellia oleifera and C. tenuifolia, primarily grown in central and southern Taiwan, as well as the eastern region. The total production area in 2022 was approximately 1,569.6 hectares. The fruits of oil tea ripen from October to November and can be pressed to extract edible or industrial tea oil. Other parts, such as shells, seed coats, and wood, also have various uses. The cultivation area of oil tea is relatively low, making it an important challenge to increase the yield per unit area. To develop selection criteria for oil-producing tea tree varieties and accelerate the breeding process, this study investigated over 100 tea tree varieties to screen for breeding indicators and select varieties with high oil content and desirable fatty acid composition. Firstly, 106 tea tree varieties were surveyed to determine the relationship between floral traits and fruit yield. The results showed that the outer diameter of the stamen bundle was the main influencing factor, followed by the width of the pistil head. These two traits have the potential to become important early selection indicators in tea tree breeding programs. Next, the differences in fruit yield, fruiting rate, plant height, and plant width among different tea tree types were compared. The results showed that hybrids between large and small leaf varieties and large leaf varieties performed better in terms of fruit yield. The fruiting rate, plant height, and plant width were positively correlated with individual fruit yield, indicating that these traits could serve as important indicators for tea tree breeding and selection. Furthermore, the differences in agronomic traits of fruits among different tea tree types were compared. The results showed that hybrids between large and small leaf varieties had superior individual seed weight and seed diameter compared to large leaf and small leaf varieties. The seed weight, number of seeds, and seed diameter within the fruit had a positive impact on individual fruit weight. Finally, the seed oil content and fatty acid composition of 104 tea tree varieties were compared. The results showed that small leaf varieties had higher oil content and higher linoleic acid content, while hybrids between large and small leaf varieties had higher palmitic acid content compared to large leaf and small leaf varieties. This study selected 75 seed-grown C. tenuifolia trees in Luye Township, Taitung County, for research. The results showed consistent yield in C. tenuifolia, while floral traits were influenced by climate and physiological regulation. Furthermore, the fruiting rate through open pollination was positively correlated with the fruiting rate through bagging, indicating that bagging can have a positive impact on the fruiting rate in open pollination. Therefore, it is suggested to select individual plants with larger inner diameter of stamen bundles and prominent pistil heads, higher bagging fruiting rate, and good fruit yield as early screening targets to improve the natural fruiting rate and cultivate high-yielding germplasms of C. tenuifolia. Additionally, selection of high-yielding individual plants was conducted based on the analysis of the average yield and fruit agronomic traits over a 5-year period and the average fruiting rate over 2 years. The results showed that the average yield of C. tenuifolia was 1.68 kg, with an average open pollination fruiting rate of 12.48%. The highest yield recorded was 9.65 kg. The fruiting rate and fruit weight had an impact on the yield, and fruit weight should be considered during selection. Stable high-yielding strains selected included B79, B55, and B25, with average yields reaching 9.65 kg, 5.26 kg, and 5.26 kg, and fruit weights of 3.79 g, 4.05 g, and 4.96 g, respectively. These strains can be further evaluated in comparative trials in the future. In comparison to 2017, the floral traits of C. oleifera in 2018 showed a decrease in the outer and inner diameter of stamen bundles, as well as a reduction in the length of pistils. Additionally, there was a decrease in the difference between the outer and inner diameter of stamen bundles, while the difference in length between stamens and pistils increased. The natural pollination fruiting rate of C. oleifera significantly increased from 4.26% in 2017 to 8.89% in 2018, while the bagging fruiting rate remained unchanged. The analysis of 2017 and 2018 data revealed that the floral traits of C. oleifera in 2017 did not have a statistically significant impact on the open pollination fruiting rate. However, in 2018, the inner diameter of stamen bundles had a positive effect on open pollination, with an increase of 3.951% in the fruiting rate for every 1 mm increase in the inner diameter of stamen bundles. However, the influence of other floral traits on the open pollination fruiting rate and bagging fruiting rate was not significant. There was a significant positive correlation between the bagging fruiting rate and the open pollination fruiting rate in Camellia oleifera. As the bagging fruiting rate increased, the open pollination fruiting rate also increased accordingly. Regression analysis indicated that in 2017, for every 1% increase in the bagging fruiting rate, the open pollination fruiting rate would increase by 2.004%. In 2018, for every 1% increase in the bagging fruiting rate, the open pollination fruiting rate would increase by 1.486%. In this study on C. oleifera, there was a correlation observed in the individual fruit yield of C. oleifera over the past three years. The average fresh fruit weight was recorded as 17.39 g, average fresh seed weight within the fruit was 6.90 g, average number of seeds per fruit was 3.24, average fruit length was 30.00 mm, and average fruit width was 32.26 mm. The average weight per individual fruit and the number of seeds per fruit showed a correlation over the past three years, indicating that fruit weight is correlated with the number of seeds per individual fruit, in addition to overall yield. In 2017, there was a significant positive correlation observed between the natural pollination fruit set rate and the individual fruit yield as well as the number of seeds per individual plant. However, no significant correlation was observed between these factors in the studies conducted in 2015 and 2016. Furthermore, there was no statistically significant correlation observed between the natural pollination fruit set rate, bagging fruit set rate, and the average weight per individual seed, indicating that the average weight per individual seed is not influenced by the fruit set rate. Pollen viability testing is crucial for breeding purposes. In this experiment, the effects of different pollen germination media and TTC staining formulations on the pollen viability testing of tea plants, C. tenuifolia, and C. oleifera were compared. The results showed that the optimal pollen germination media for tea plants, C. tenuifolia, and C. oleifera were "100 g/L sucrose + 150 mg/L boric acid + 200 mg/L calcium nitrate." As for the TTC staining formulation, the optimal one for tea plants and C. oleifera was "100 g/L sucrose + 5 g/L TTC." Using the TTC staining method yielded more desirable results for pollen viability testing, and the addition of sucrose helped maintain the integrity of the pollen exine, facilitating long-term observation of stained pollen. The TTC staining results for 75 tea plant varieties showed that approximately 80% of the varieties had pollen viability above 70%. Only Taiwan Tea No. 19, Shui Xian and Xiao Ye Tie Guan Yin had lower pollen viability, indicating that the majority of tea plant varieties can be used for breeding purposes. Among the 28 tested C. tenuifolia individual plants, over 90% of them had higher pollen viability than the overall average of 89.3%, with over 80% of the individual plants accounting for 96.4%. The lowest pollen viability recorded was 60%, indicating that the majority of C. tenuifolia plants have normal pollen that can be used for pollination. In the future, the development of local oil-bearing Camellia species, selecting high-yielding and even high-selfing affinity varieties of C. tenuifolia and C. oleifera, to enhance the overall yield of oil tea, should be an important task.