【作者】 任旭琴；

【导师】 曹碚生；

【作者基本信息】 扬州大学 ， 作物栽培学与耕作学， 2008， 博士

【摘要】 早春和秋冬季节的低温冷害常造成辣椒大面积落花落果,使产量和品质下降,经济效益降低,严重影响辣椒的周年生产。因此,开展辣椒耐低温品种鉴定和低温生理机制研究有非常重要的理论和现实意义。本文在研究不同辣椒品种耐低温性的基础上,从授粉受精角度对不同时期低温造成辣椒落花落果的原因进行了剖析,研究了碳水化合物、内源激素、细胞膜损伤及膜脂过氧化等的变化,探讨了通过施用外源物质减轻辣椒伤害的效应,克隆了低温诱导基因——辣椒肌醇半乳糖苷合成酶基因并研究了其在低温下的表达规律,以期为辣椒耐低温品种选育和栽培提供理论依据。主要研究结果如下:低温能显著抑制辣椒的营养生长和产量形成,10个辣椒品种的耐低温性存在显著差异,其中苏椒5号的耐低温性最强,苏长红最差;4℃处理4叶1心期幼苗的冷害指数和15℃时的发芽指数与产量形成耐低温指数间存在显著相关性,可以作为辣椒品种耐低温性的评价指标。现蕾期和开花期的花器官对低温的敏感性不同。现蕾期的雄蕊较雌蕊更容易受到低温伤害,开花期低温对雌蕊及受精过程的影响较大,对雄蕊影响较小。不同基因型辣椒的花器官对低温的敏感性不同,与苏椒5号相比,苏长红的花器官更容易受到低温的不利影响。随着果实发育成熟,叶肉、节间、果肉和根部的淀粉、总糖和蔗糖含量不断增加,叶肉、节间、果肉中的葡萄糖和果糖以果实膨大期含量最高,各器官酸性转化酶和中性转化酶活性呈先增强后减弱的趋势,与蔗糖水平的提高相关联,SPS活性也表现出逐渐增强趋势。低温抑制了各部位淀粉和蔗糖的合成,促进了总糖、葡萄糖和果糖的积累,低温也使植株各部位的酸性转化酶活性和中性转化酶活性增强,蔗糖磷酸合成酶活性降低。随着处理温度降低和低温时间延长,辣椒叶片中的脯氨酸（Pro）含量、过氧化物酶（POD）活性、丙二醛（MDA）含量和根系的不饱和脂肪酸含量不断增加,根系饱和脂肪酸含量不断下降;随着低温程度的加强,苏椒5号的Pro含量和POD活性的增加速度比苏长红快,而MDA含量的增加速度则相对较慢。辣椒植株抗低温能力的产生与低温诱导有关,低温胁迫后,辣椒可产生相对迁移率（Rf）为0.3145的POD同工酶电泳新谱带。低温处理后辣椒叶片中的腐胺（Put）、精胺（Spm）、亚精胺（Spd）和脱落酸（ABA）的含量有不同程度增加,而赤霉素（GA₃）和生长素（IAA）含量则有所降低。随着低温条件的解除,Put含量和ABA含量迅速下降至对照水平,表明二者含量变化是植株自身对低温作出的一种应激反应,而Spm和IAA含量在低温解除一段时间后才恢复至对照水平,说明Spm和IAA含量的变化可能是植株对低温的一种适应性反应。早春栽培中,在定植前后及低温发生时叶面喷施1 mmol·L^-1 Put或150 mg·L^-1ABA,有助于提高辣椒产量;在秋延迟栽培中,低温来临时,可使用200 mg·L^-1 Pro或100mg·L^-1ABA进行保花保果。喷施ABA可提高辣椒植株的净光合速率、气孔导度、胞间CO2浓度及根、茎、叶中的N、P、K含量,在一定程度上缓解了低温伤害。采用RT-PCR结合RACE技术从经低温处理的辣椒品种苏长红叶片中克隆得到肌醇半乳糖苷合成酶基因（GS）的cDNA序列,其全长1444bp,编码336个氨基酸,该基因与其他植物的GS具有较高的同源性。该基因常温下在辣椒各组织中均无表达,经4℃或10℃处理6 h后在叶片中开始表达,而茎和根系中不表达。Southern杂交结果表明辣椒基因组中可能还存在其他形式的GS。更多还原

【Abstract】 Chilling stress during winter and early spring usually causes flower abscission and other injuries of pepper （Capsicum annuum L.）, and then has a significant negative effect on year-round production of this crop. So it is important to study the physiology mechanism and cultivation techniques of pepper under low temperature conditions. In this paper, 10 varieties with different cold tolerance were selected, and the effect of low temperature on the pollination, fertilization, carbohydrate metabolization, membrane injury peroxidation and endogenous hormones of pepper were investigated, and the effect of exogenous regulators on the pepper production during cold season was studied. Furthermore, galactinol synthase, a cold induced gene, was cloned and the exprerssion pattern of this gene under chilling stress was studied. The results provided some beneficial clues for pepper cold tolerant breeding and cultivation. The main results showed as follows:The chilling stress inhibited the vegetation growth and field formation of pepper significantly. Among the ten varieties, SCH and SJ-5 has the lowest and highest cold tolerance, respectively. The correlation analysis among vegetative- chilling- tolerant index, yield- formation- chilling- tolerant index, germination index and seedling chilling injury index indicated that the seedling chilling injury index and the germination index at 15℃were feasible to identify the chilling tolerance of pepper varieties.The chilling sensitivity of stamen, pistil and fertilization of pepper at different stages was studied. According to the investigation of fruit-set, seeds number per fruit, at alabastrum stage the stamen were more sensitive than the pistil to chilling stress, while at anthesis, the pistil and fertilization were more susceptible than the stamen.With the development of pepper fruit, the content of starch, total soluble sugars and sucrose in mesophyll, internode, pulp and root were all improved, and the content of glucose and fructose of mesophyll, internode and pulp were highest in swelling time of fruit. AI and NI activity showed a low-high-low trend and SPS activity increased is similarly with sucrose. Because of chilling stress, the content of starch and sucrose in different organs were significantly decreased, while the content of total soluble sugars, glucose and fructose in leaf were increased. Low temperature enhanced AI and NI activity and reduced SPS activity.Pro content, POD activity and MDA content in leaves increased significantly under cold stress. The content of USFA was adding and that of SFA was decreasing continually with the falling of temperature. Under chilling stress, A new POD isozyme band （Rf =0.3145） in leaves of pepper just were the production of chilling stress.Chilling stress increased the level of Put, Spd, Spm and ABA and reduced the level of GA₃ and IAA in leaves. Changes of Put and ABA might be an emergency response of plant to low temperature because their contents would come back to the control level as soon as the chilling stress stopped. While the changes of Spm and IAA may be an adaptitude response because they can not restored to the normal level until days after normal temperature condition begin.1 mmol·L^-1 Put and 150 mg·L^-1ABA applied at seedling stage with six or seven leaves were helpful to increase fruit-set and yield, while 200 mg·L^-1Pro and 100 mg·L^-1ABA had the best effect at anthesis. Exogenous ABA application can relievd the chilling injury of pepper remarkably by enhancing Pn, Gs and Ci in leaves and improving assimilation rate and N, P and K utilization.Full length cDNA sequence of a galactinol synthase gene （GS） （GenBank locus: EF566470） was cloned from cold-stressed pepper （Capsicum annuum L.‘SCH’） leaves using RT-PCR and rapid amplification of cDNA ends （RACE）. The gene consists of 1444 bp encoding a protein of 336 amino acids. Phylogenetic analysis revealed that pepper GS is high homologous to reported GS of other plants. RT-PCR analysis showed that GS mRNA was induced in pepper leaves after 4℃or 10℃cold- stress for 6 h, but not accumulated in cold -stressed stems and roots, no GS mRNA can be detected in pepper tissues under normal temperature. Southern blot analysis indicated that there may be several GS copies in the pepper genome.更多还原