以人工光源調整番荔枝花期及轉錄體變化與 防治荔枝細蛾技術之研究

Abstract

以人工光源輔助作物生產已行之有年，但因果樹植株普遍較大，較少人工光源應用在果樹方面的研究。本論文使用不同人工光源進行番荔枝 (Annona squamosa cv. Damu) 夜間暗中斷 (night break, NB) 延長花期研究，以瞭解可促進開花的關鍵波長以及轉錄體分子機制；除此之外，利用荔枝細蛾 (Conopomorpha sinensis Bradley) 避光特性，進一步篩選可防治荔枝細蛾又不影響荔枝 (Litchi, Litchi chinensis Sonn.) 果實品質的人工光源。首先進行連續4年番荔枝、冷子番荔枝 (Annona cherimola cv. Spain) 、鳳梨釋迦 (Annona x atemoya cv Gefner) 與牛心梨 (Annona reticulata cv. Red) 的周年開花能力調查，結果顯示，開花數量與平均溫度的相關性較高，與積溫相關性次之，與日照長度及降雨量相關性較低。秋天溫度逐漸降低開花量逐漸減少，若進行暗中斷則可以刺激開花。為了解暗中斷延長番荔枝開花期之分子機制，使用藍光450 nm、紅光660 nm與遠紅光740 nm LED (Light-emitting diodes) 燈暗中斷處理，並進行生育調查與轉錄體分析，結果顯示，紅光 660 nm暗中斷處理的莖葉於秋季可持續生長且開花數量顯著高於藍光 450 nm 、遠紅光 740 nm 與無光對照組。RNAseq轉錄體分析結果顯示，在秋季以紅光暗中斷處理有促進植物生長素 (auxin) 、乙烯 (ethylelne) 、激勃素 (gibberellic acid, GA) 與離層酸 (abscisic acid, ABA) 等植物荷爾蒙相關基因表現，較沒有明顯調控細胞分裂素 (cytokinin) 與光週期路徑相關基因，紅光暗中斷有一些基因顯著增加表現，此些基因功能為減少氧化逆境、去除受損蛋白質、減少低溫損傷與減少老化。番荔枝於短日照的冬季無法順利開花，以紅光660 nm夜間暗中斷與補充4種植物生長調節劑皆無法於12月底促進開花。若以增溫方式於溫室提高白天與夜晚溫度 5.7℃ 與 1.8℃ ，增溫溫室組於1月初的平均開花量為每芽0.49朵，顯著高於露天組與露天紅光組的0朵與0.05朵，結果顯示較高的溫度比紅光暗中斷對於番荔枝花朵形成的影響較大。此外，為篩選可防治荔枝細蛾的最有效波長，本研究使用紫光 400 nm、藍光 460 nm、綠光 520 nm、黃光 600 nm、紅光 660 nm、遠紅光 740 nm、混合白光 MixW 與混合黃光 MixY 等8種不同波長LED燈進行試驗。結果顯示，荔枝細蛾確實對光線相當敏感，於有光環境活動力下降，無光環境則活動力旺盛。夜間使用綠光 520 nm燈照可較無光對照組減少荔枝細蛾 99% 活動力、93% 產卵量以及 91% 果實危害率，若於夜晚使用其它波長燈照，會有荔枝果實較小或是甜度降低的情形，只有綠光 520 nm燈照可同時保持良好的荔枝果實品質。於開花前設置8種不同波長燈具進行玉荷包荔枝全株夜間燈照，並於開花前與果實成熟後採樣調查植體糖類變化。試驗結果顯示，只有夜間綠光 520 nm 燈照的葉片，於果實成熟時至果實成熟後增加5.5% 總可溶性糖的與減少2.5% 的澱粉，顯著高於夜間無燈照及其它燈照處理消耗約 20~50% 葉片的總可溶性糖與澱粉。夜間綠光 520 nm 燈照處理的葉片含有較高的碳水化合物狀態，可能是果實可以保持較佳的可溶性固型物含量以及果實糖酸比的主要原因之一。擴大於3個荔枝產區進行驗證的結果顯示，夜間綠光 520 nm 燈照確實可有效防治荔枝細蛾，大幅減少荔枝細蛾危害損失。本研究依不同的果樹種類與目的，成功篩選適合的人工光源輔助果樹生產。

The application of artificial light sources in crop production has been explored for many years; however, due to the relatively large plant size of fruit trees, there has been limited research on the use of artificial light for fruit trees. This study investigates the extension of the flowering period in sugar apple (Annona squamosa cv. Damu) through night break (NB) treatments using different artificial light sources to identify the key wavelengths that promote flowering and to elucidate the underlying transcriptomic mechanisms. Additionally, the study aims to screen artificial light sources that can control the litchi fruit borer (Conopomorpha sinensis Bradley) without compromising litchi (Litchi chinensis Sonn.) fruit quality, leveraging the photophobic behavior of the pest. The research involved selecting appropriate artificial light sources to support fruit tree production according to the specific crop and objective. Over four consecutive years, we investigated the year-round flowering capacity of sugar apple, cherimoya (Annona cherimola cv. Spain), atemoya (Annona × atemoya cv. Gefner), and Bullock’s-heart (Annona reticulata cv. Red). The results indicated that flowering quantity was most strongly correlated with temperature, followed by cumulative temperature, and was less correlated with photoperiod and rainfall. As temperatures gradually decreased in autumn, the number of flowers diminished; however, night break treatment could stimulate flowering. To understand the molecular mechanisms by which night break extends the flowering period of sugar apple, LED (Light-emitting diodes) lights with wavelengths of 450 nm blue light, 660 nm red light, and 740 nm infrared light were used for night break treatments, followed by phenological observations and transcriptome analysis. The results demonstrated that night break treatment with 660 nm red light significantly promoted stem and leaf growth and increased flowering quantity in autumn compared to 450 nm blue light, 740 nm infrared light, and control groups. RNAseq transcriptome analysis revealed that red light night break treatment in autumn did not significantly regulate genes related to cytokinin and photoperiod pathways, but it did promote the expression of genes associated with plant hormones such as auxin, ethylene, gibberellic acid (GA), and abscisic acid (ABA). Some genes that were significantly upregulated by red light night break were involved in reducing oxidative stress, removing damaged proteins, reducing cold injury, and delaying senescence, which may collectively maintain the plant's growth capacity and facilitate successful flowering. During the short-day conditions of winter, sugar apple faces challenges in flowering. Attempts to promote flowering by employing nighttime red light (660 nm) interruption and supplementation with four types of plant growth regulators failed to induce flowering by late December. However, temperature elevation in a greenhouse, increasing daytime and nighttime temperatures by 5.7°C and 1.8°C, respectively, significantly enhanced flowering. By early January, the average number of flowers per bud in the heated greenhouse treatment reached 0.49, significantly higher than the open-field and open-field red-light treatments, which produced 0 and 0.05 flowers per bud, respectively. These results indicate that elevated temperatures have a greater effect on floral development in sugar apple than red light interruption under short-day conditions. Furthermore, to identify the most effective wavelength for controlling the litchi fruit borer, eight different LED light sources were tested, including 400 nm violet light, 460 nm blue light, 520 nm green light, 600 nm yellow light, 660 nm red light, 740 nm infrared light, mixed white light (MixW), and mixed yellow light (MixY). The results showed that the litchi fruit borer is indeed highly sensitive to light, exhibiting reduced activity in illuminated environments and increased activity in darkness. Nighttime application of green light illumination at 520 nm wavelength demonstrated significant suppression of litchi fruit borer activity, reducing moth mobility by 99%, oviposition rate by 93%, and fruit damage rate by 91% compared to the non-illuminated control (CT). While alternative wavelengths of illumination resulted in adverse effects on fruit size and sugar content, the 520 nm green light treatment uniquely maintained optimal litchi fruit quality. Eight different wavelengths of light were applied for whole-plant nighttime illumination of 'Yu Her Pau' litchi prior to flowering, with sampling conducted before flowering and after fruit ripening to investigate changes in plant carbohydrate levels. The results showed that only leaves exposed to nighttime green light at 520 nm exhibited a 5.5% increase in total soluble sugars and a 2.5% reduction in starch content from fruit ripening to post-ripening. These changes were significantly higher than those observed in leaves under no light or other light treatments, which consumed approximately 20–50% of total soluble sugars and starch. Leaves treated with nighttime green light at 520 nm maintained a higher carbohydrate status, which may be a key factor contributing to the improved soluble solid content and sugar-to-acid ratio in the fruit. Field validation studies conducted across three distinct litchi-producing regions—southern, central, and northern Taiwan—substantiated that green light illumination at 520 nm wavelength effectively controls litchi fruit borer, resulting in substantial reduction of fruit damage and associated economic losses. This study successfully screened suitable artificial light sources to support fruit tree production, based on different fruit tree types and objectives.