【作者】 王冲；

【导师】 齐红岩；

【作者基本信息】 沈阳农业大学 ， 蔬菜学， 2020， 硕士

【摘要】 西瓜(Citrullus lanatus)对低温极其敏感,是典型的喜温耐热植物,在中国北方地区的设施反季节栽培中,西瓜冷害时有发生,降低西瓜产量的同时也影响了果农的收益,嫁接技术的应用使这一问题得到了极大改善,而耐低温砧木和耐低温嫁接组合的筛选更是提高嫁接西瓜幼苗耐低温性的关键,因此,筛选耐低温砧木和耐低温嫁接组合并探究嫁接西瓜幼苗提高耐低温性的生理机制具有重要意义。本试验以27份西瓜砧木为材料,对它们芽期的耐低温性进行评价,建立西瓜砧木芽期耐低温评价体系并筛选出芽期耐低温差异砧木,然后以筛选出的耐低温差异砧木为材料,自根苗为对照,探究耐低温差异砧木经过嫁接得到的嫁接组合对低温处理的生理响应,并筛选出最耐低温的嫁接组合,最后以筛选出的嫁接组合为材料,自根苗为对照,探究脱落酸(ABA)在嫁接中提高西瓜幼苗耐低温性的生理机制。具体结果如下:1.以28℃的常温条件为对照,采用15℃的低温条件处理砧木种子,时间为10 d。结果显示:低温会推迟种子出芽的开始时间,降低不同西瓜砧木种子的发芽率、发芽势、发芽指数、胚根长度和活力指数,且不同种类西瓜砧木种子耐低温性差异较大,南瓜砧木种子耐低温性最强,葫芦砧木种子耐低温性次之,西瓜砧木种子耐低温性最弱;利用主成分分析、聚类分析和逐步回归分析等方法综合评价了27份西瓜砧木种子芽期的耐低温性,建立了西瓜砧木芽期耐低温评价体系,并筛选出了4种芽期耐低温性差异较大的砧木,即:强耐低温型品种为LFCX和JXZ9,低温敏感型品种为JXZ1和ZS,其中LFCX、JXZ9和ZS为南瓜砧木,JXZ1为葫芦砧木。2.以西瓜品种‘京欣2号’为接穗,以芽期筛选出的4种耐低温性差异较大的LFCX、JXZ9、JXZ1和ZS为砧木,经过嫁接得到4种嫁接组合,以自根苗‘京欣2号’为对照,于28℃/18℃(昼/夜)的温度下培养至三叶一心时期,将幼苗分别移到15℃/6℃和28℃/18℃的人工气候室中培养7 d,然后在28℃/18℃的温度下恢复3 d,分别在低温处理后的0、1、3、5、7和10 d取样并测定相对电导率、脯氨酸(Pro)、丙二醛(MDA)、可溶性糖(SS)、可溶性蛋白(SP)、光合参数和叶绿素荧光参数等生理生化指标(在处理后7 d测定株高、茎粗、地上部干鲜重、地下部干鲜重和根系形态等生长指标)。结果显示:在低温胁迫下,各处理的地上和地下生长均受到抑制,细胞质膜透性、膜脂过氧化程度以及渗透调节物质含量升高,光合作用下降,但是嫁接苗受低温胁迫影响程度小于自根苗,其中,以南瓜为砧木的嫁接苗受低温胁迫的影响最小,以葫芦为砧木的嫁接苗次之,自根苗最大,南瓜砧木LFCX嫁接组合耐低温性最强。3.以LFCX嫁接组合为处理,自根苗‘京欣2号’为对照,进行10℃低温处理,时间为72 h,在处理的前1 d喷施5 mM的ABA生物合成抑制剂钨酸钠溶液,分别在低温处理后0、6、12、24、48、72 h测定叶片中相对电导率、MDA、Pro和ABA含量,并测定关键时间点ABA合成及信号转导途径中的基因表达量。结果显示:在低温胁迫过程中,各处理的生长受到明显抑制,各处理的相对电导率和MDA含量均呈升高趋势,其中未喷施钨酸钠的嫁接苗增幅最低;除了喷施钨酸钠的自根苗外,其他处理的Pro含量在低温胁迫期间也出现了升高趋势,其中未喷施钨酸钠嫁接苗增幅最高;在胁迫期间各处理的ABA含量均呈升高趋势,未喷施钨酸钠嫁接苗的ABA含量及其合成和信号转导途径中基因表达量始终高于其他处理,认为低温胁迫下嫁接可能通过诱导ABA合成基因Cla009779、Cla005404、Cla019578以及信号转导途径中的正调控基因Cla008802、Cla006604、Cla018017、Cla004235、Cla008760、Cla020180、Cla015990、Cla003005和Cla020167的表达提高叶片中ABA含量,从而提高西瓜幼苗的耐低温性。更多还原

【Abstract】 Watermelon(Citrullus lanatus)is extremely sensitive to low temperature,is a typical thermophilic and heat resistant plant,facilities in northern China anti-season of watermelon,chilling injury occurs frequently,it reduces the watermelon production also influenced the benefits of fruit farmer,the application of grafting technology makes this problem greatly improved,the screening of low temperature resistant rootstocks and low temperature resistant grafting combinations is the key to improve the low temperature tolerance of grafted watermelon seedlings,therefore,it is of great significance to screen the cold-resistant rootstocks and cold-resistant grafting combinations and explore the physiological basis of tolerance in grafted watermelon seedlings.In this experiment,27 watermelon rootstocks were used as materials,the low temperature tolerance of watermelon rootstocks in germination stage was evaluated,establishing a low temperature tolerance evaluation system for watermelon rootstocks and screening rootstocks with different tolerance in germination stage,then the screened rootstocks were used as the materials,own-rooted seedlings were used as the control,the physiological response of grafted rootstocks with different tolerance to low temperature stress was studied,and the most low temperature resistant grafting combination was screened,finally,the screened grafting combination was used as the material,own-rooted seedlings were used as the control,exploring the physiological mechanism of abscisic acid(ABA)in improving the tolerance of watermelon seedlings in grafting.The specific results were as follows:1.28℃ was used as the control,the rootstock seeds were treated at 15℃ for 10 d.Results showed that low temperature could delay the start of seeds germination time and reduce different watermelon root stock seeds germination rate,germination potential,germination index,radicle length and vigor index,in addition,the low temperature tolerance of different watermelon rootstock seeds was significantly different,pumpkin rootstock seeds had the highest tolerance,followed by gourd rootstock seeds,watermelon rootstock seeds had the weakest tolerance;The principal component analysis,cluster analysis and stepwise regression analysis were used to evaluate the low temperature tolerance of 27 watermelon rootstocks at germination stage,a low temperature tolerance evaluation system for watermelon rootstock seeds was established,four rootstocks with great differences in low temperature resistance at germination stage were screened out,the strong low temperature resistant varieties were LFCX and JXZ9,the low temperature sensitive varieties were JXZ1 and ZS,among them,LFCX,JXZ9 and ZS were pumpkin rootstocks,JXZ1 was gourd rootstock.2.The watermelon variety ’JX2’ was used as scion,LFCX,JXZ9,JXZ1 and ZS with greatly different resistance in germination stage were screened as rootstocks,four grafting combinations were obtained after grafted,the own-rooted seedling ’JX2’ was used as the control,it was cultured at 28℃/18℃(day/night)until the three-true-leaf stage,the seedlings were respectively moved to an artificial climate chamber at 15℃/6℃ and 28℃/18℃ for 7 d,then they were recovered for 3 d at 28℃/18℃,the physiological and biochemical indexes such as relative conductivity,proline(Pro),malondialdehyde(MDA),soluble sugar(SS),soluble protein(SP),photosynthetic parameters and chlorophyll fluorescence parameters were sampled and measured at 0,1,3,5,7 and 10 d after treatment(Growth indexes such as plant height,stem thickness,overground dry fresh weight,underground dry fresh weight and root morphology were measured on 7 d after treatment).The results showed that under low temperature stress,the aboveground and underground growth of each treatment were inhibited,the permeability of cytoplasm membrane,the degree of membrane lipid peroxidation and the content of osmotic regulatory substances were increased,and the photosynthesis were decreased,however,the degree of low temperature stress affected the grafted seedlings less than the own-rooted seedlings,among them,the grafting seedlings of pumpkin rootstock were the least affected by the low temperature stress,the grafting seedlings of gourd rootstock were the second,the own-rooted seedlings were the largest,and the LFCX grafting combination of pumpkin rootstock had the strongest resistance to low temperature.3.The LFCX grafting combination was used as treatment,the own-rooted seedling ’JX2’ was used as the control,low temperature treatment was conducted at 10℃ for 72 h,5 m M of ABA biosynthesis inhibitor sodium tungstate solution was sprayed 1 day before low temperature stess,the relative conductivity,MDA,Pro and ABA contents in leaves were measured at 0,6,12,24,48 and 72 h after treatment,the gene expression in ABA synthesis and signal transduction pathays at critical time points was measured.The results showed that the growth of each treatment was obviously inhibited during the low temperature stress,and the relative conductivity and MDA content of each treatment showed an increasing trend,the unsprayed sodium tungstate grafted seedlings increase the least;The Pro content of other treatments also showed an increasing trend during low temperature stress except the own-rooted seedlings sprayed with sodium tungstate,grafted seedlings without sodium tungstate showed the highest increase;The ABA content in each treatment showed an increasing trend during the low temperature stress,and the ABA content and gene expression in the synthesis and signal transduction pathays of the unsprayed tungstate grafted seedlings were always higher than other treatments,it was suggested that grafting under low temperature stress may enhance ABA content in leaves by inducing the expression of ABA synthesis genes Cla009779,Cla005404,Cla019578 and positive regulatory genes Cla008802,Cla006604,Cla018017,Cla004235,Cla008760,Cla020180,Cla015990,Cla003005,Cla020167 in signal transduction pathays,in the last,the low temperature resistance of watermelon seedlings was improved.更多还原