淹水對日日春生長之影響及選育大花耐淹水之後裔

Abstract

日日春[Catharanthus roseus (L.) G. Don]為亞熱帶/熱帶重要花壇植物，耐熱但不耐溼。本研究比較淹水對不同品種日日春於穴盤苗期與開花株生長與生理之影響，選拔較耐淹水之雜交後裔，以期了解並改善日日春之生產及景觀應用問題。 冬季淹水16天後排水四天，參試日日春品種之開花株葉片黃化、葉片萎凋下垂反捲或甚至呈水浸狀，花朵變小且變少。參試品種中，外觀表現以 ‘Cora Cascade Magenta’ (CCM)維持較佳，‘Jams ‘N Jellies Blackberry’ (JBlack) 與 ‘Cora Cascade Strawberry’ (CCS) 較差。罹病程度 CCM最低，JBlack 次之，CCS 最高。CCM 較耐淹水，JBlack 與 CCS 較不耐淹水。於淹水處理後，較耐淹水的 CCM 光合作用較佳，較不耐淹水的 CCS 較差，且淨光合作用速率(net CO2 assimilation rate, Pn)、氣孔導度(stomatal conductance, gs)、蒸散速率(transpiration rate, Tr)於品種對淹水耐受性之排序趨勢一致，淹水逆境使光合作用降低為氣孔因素導致。 於春夏季淹水處理七天後恢復正常澆水十天，參試品種中‘Mega Bloom Lavender’ 植株外觀受逆境影響較不明顯，而 ‘Tattoo Raspberry’與‘Tattoo Papaya’葉片下垂反捲。光合作用及葉綠素螢光調查顯示，淹水處理使Pn、gs、Tr 降低，非光化學淬熄(Non-photochemical quenching, qN) 上升。‘Tattoo Raspberry’與‘Tattoo Papaya’ 之Pn降低 79.8% - 84.7%，qN升高 51.1% - 52.0%，為不耐淹水之品種；‘Mega Bloom Lavender’之Pn降低66.2%，qN升高39.8% 受淹水影響相對較小。本試驗結果顯示Pn與qN可作為耐淹水之生理指標。 於7-8月試驗中穴盤苗淹水抑制所有參試12品種生長，使所有植株外觀矮小，葉片黃化，株高、葉面積、地上部與全株乾重皆低於正常澆水之對照組，但品種之耐受程度有異；1-2月間淹水處理則生長影響不明顯，全株乾重與葉面積可作為穴盤苗期耐淹水性之指標。‘Mega Bloom Polka Dot’穴盤苗於兩次試驗皆較能維持生長，對淹水較不敏感；‘Jams ‘N Jellies Blackberry’穴盤苗生長於兩次試驗皆受淹水處理影響大，為淹水敏感之品種。 將耐開花株淹水之‘Cora Cascade Magenta’ (CCM) 與蔡(2018)選育具淡橘紅色花冠且具有紫色中型眼圈及小型白色眼圈之新穎花色純系TP1701033為親本進行全互交，得CCM⊗、TP1701033 F6、CCM×TP1701033 F5、TP1701033 F5×CCM。四個日日春自交與雜交組合之實生苗於夏季進行穴盤苗期淹水，淹水處理使葉片數、葉綠素計讀值、葉面積、地上下部乾重與全株乾重皆顯著降低。淹水對CCM⊗ 於株高、葉面積、地上下部乾重、全株乾重受淹水影響最小，TP1701033 F6、CCM×TP1701033 F5與TP1701033 F5×CCM三者生長量因淹水而減少之比率較多且相近。CCM×TP1701033 F5、TP1701033 F5 ×CCM 後裔葉面積、地上、地下部與全株乾重於淹水處理與對照組之頻度分布高峰多介於CCM⊗、TP1701033 F6之間，前述之所有授粉組合對提升TP1701033 後代穴盤苗耐淹水性之效果不明顯，未見雜種優勢或母系遺傳現象。 從日日春開放授粉種子選出強健單株，經由自交選出大花強健單株，再進行自交或與TP1701033 F6為種子親雜交，將其360株自交與雜交後裔進行開花株淹水十天後正常澆水十天選拔。選出五株耐淹水單株，分別具有亮粉紅色花冠 (RP 64C)帶有大型白色擴散眼圈；洋紅色花冠(RP 61B)帶有大型白色眼圈；其中三株為淡橘色花冠(R 43C)帶有深紫色中型眼圈且花托筒周圍有小型白色眼圈，具有大花、對比鮮豔且新穎花色等優良性狀，可作為後續耐淹水品種之選育材料。 將日日春大花耐淹水後裔TS1901024、TS1901048、TS1901080與其對照品種‘Valiant Pure White’、‘Mega Bloom Orchid Halo’、‘Pacifica Burgundy Halo XP’ (PBH)扦插苗於日夜均溫17.1ºC/14.6ºC環境涼溫處理或日夜均溫33.4ºC/25.0ºC 生長適溫處理35天。涼溫使日日春生長減緩，開花較晚且花徑與花朵數減少，光合作用降低。TS1901080具紫紅色花冠帶有白色中至大型眼圈，於涼溫處理之花徑較對照品種PBH大，且到花天數提早8天，其光合作用與乾重因涼溫而降低量最小，且生長適溫下栽培花徑可達6.2 cm，顯著高於對照品種，具有大花、耐淹水、較耐低溫等優良特性，深具商業潛力。

Vinca [Catharanthus roseus (L.) G. Don] is an important bedding plant due to its heat-tolerance. However, vinca is rather susceptible to waterlogging (WL) during rainy summer in tropical areas. The objectives of this study were to compare the growth responses of plug seedlings and flowering plants to WL in different vinca cultivars under various seasonal environments, and to select progenies that were WL-tolerant. After 16-d WL followed by 4-d draining, flowering plants of vinca produced chlorotic, wilting, drooping, and even water-soaked leaves, with smaller and fewer flowers. After WL, ‘Cora Cascade Magenta’ (CCM) performed acceptable, with lowest disease symptoms and highest net CO2 assimilation rate (Pn), stomatal conductance (gs), and transpiration rate (Tr). In contrast, ‘Jams ‘N Jellies Blackberry’ and ‘Cora Cascade Strawberry’ grew poorly under WL, were more susceptible to disease, with lowest Pn, gs, and Tr. Decreased photosynthesis by WL was caused by stomatal limitation. After 7-d WL followed by 10-d recovery in early summer, flowering plants of some cultivars produced drooping leaves. Non-photochemical quenching (qN) increased, and the Pn, gs, and Tr decreased in all WL-cultivars tested. The WL-sensitive ‘Tattoo Raspberry’ and ‘Tattoo Papaya’ showed Pn decreased by 79.8% - 84.7%, and qN increased by 51.1% - 52.0 %. In contrast, the WL-tolerant ‘Mega Bloom Lavender’ performed well, Pn decreased by 66.2%, and qN increased by 39.8%. Photosynthesis and qN could be used as indicators to select WL-tolerant cultivars. After sowing for 10 days, young plug seedlings of twelve vinca cultivars were well-drained or WL for 40-50 days. Results show that all WL-treated plants exhibited leaf chlorosis and reduced growth in July to August. However, the WL effects were not so obvious in plants treated in January to February. Plant total dry weight and leaf area could be used as indicators of WL tolerance in plug seedling stage. Plug seedlings of ‘Mega Bloom Polka Dot’ exhibited consistently higher tolerance to WL. In contrast, growth of WL-sensitive ‘Jams ‘N Jellies Blackberry’ was greatly affected by WL. The WL-tolerant ‘Cora Cascade Magenta’(CCM) and TP1701033, a novelty pure line with a pale orange-red corolla, purple mid-size eye zone and small white eye zone selected by Tsai (2018), were used as parents. Plug seedlings of CCM⊗, TP1701033 F6, CCM×TP1701033 F5, and TP1701033 F5×CCM were well-drained or WL for 40 days in summer. The WL treatment reduced the number of leaves, SPAD-502 value, leaf area, and dry weights in progenies from all cross combinations. The WL- CCM⊗ exhibited lowest reductions in plant height, leaf area, and dry weight, as compared with WL-progenies from other three crosses. The leaf area, shoot, root, and total dry weight distribution of CCM×TP1701033 F5 and TP1701033 F5×CCM progenies peaked were often between CCM⊗ and TP1701033 F6, indicating that the above combinations showed limited improvement to the WL-tolerance of plug seedlings. There were no transgressive segregation or maternal inheritance. A vigorous open pollinated vinca progeny was used as self-crossed parent. Twelve vigorous progenies with and large flowers were selected, and thereafter self-crossed or crossed with TP1701033 F6 as male parent. Five WL-tolerant plants were then selected from 360 selfed and crossed pollinated progenies after 10-d WL followed by 10-d recovery. These selected five plants had light pink corolla (RP 64C) with large white diffuse eye zone, magenta corolla (RP 61B) with large white eye zone. Three of the selected plants have light orange corolla (R 43C) with dark purple medium-sized eye zone and small white eye around hypanthium. These selected WL-tolarent and large flowered plants had commercial potential and could be used as breeding materials for WL-tolerance. The cutting seedlings of WL-tolarent and large flowered progenies, TS1901024, TS1901048, and TS1901080, and those similar cultivars, ‘Valiant Pure White’, ‘Mega Bloom Orchid Halo’, and ‘Pacifica Burgundy Halo XP’ were treated in cool temperature (day/night temp. 17.1ºC/14.6ºC phytotron) or optimum temperature (day/night temp. 33.4ºC/25.0ºC phytotron) for 35 days. Plants in cool temperature growed slower, bloomed later, had smaller and fewer flower, and had lower photosynthesis rate. The WL-tolarent and large flowered progeny TS1901080 has magenta corolla with medium to large white eye zone. TS1901080 had larger flower than similar cultivar ‘Pacifica Burgundy Halo XP’, the day to flower get earlier for 8-d, the photosynthesis rate and dry weight reduced fewer in cool temperature. TS1901080 had 6.2 cm flowers in optimum temperature, which was larger than similar cultivar ‘Pacifica Burgundy Halo XP’. TS1901080 has excellent characteristics such as large flower, WL- tolerance, and cool temperature tolerance.