【作者】 刘健；

【导师】 李传友； 陈谦；

【作者基本信息】 山东农业大学 ， 作物学， 2024， 博士

【摘要】 土壤盐碱化对我国乃至全球粮食安全造成严重威胁。与研究较多的盐胁迫相比,盐碱胁迫给作物造成的危害更为复杂和严重,但目前对作物耐盐碱性状的形成机制所知甚少。番茄是一种重要的蔬菜和水果兼用型经济作物,同时也是重要的模式植物。尽管栽培番茄被认为是中度耐盐碱作物,但包括其起源种在内的许多野生番茄具有超强的耐盐碱胁迫能力,说明番茄的耐盐碱能力在驯化过程中发生了严重退化。因此,发掘耐盐碱番茄资源的优异自然变异,进行功能研究和机理解析,既有利于阐释人工选择和耐盐碱性状之间的关系,又有助于为番茄耐盐碱性状的遗传改良提供关键功能基因和创新性的种质资源。主要研究结果如下:1、驯化和人工选择导致番茄的耐盐碱能力降低。我们发现,在盐碱处理下,栽培番茄（BIG）的叶绿素含量和存活率显著低于醋栗番茄（PIM）和樱桃番茄（CER）;醋栗番茄和樱桃番茄之间的存活率存在显著差异,但叶绿素含量则无显著差异。这些结果表明,在驯化和改良过程中,番茄对盐碱胁迫的耐受性降低。2、耐盐碱野生番茄渐渗系材料的筛选。从LA0716/M82渐渗系群体中鉴定出10份在幼苗期具有较强耐盐碱能力的渐渗系和7份在成株期具有较强耐盐碱能力的渐渗系;从LA1589/E6203渐渗系群体中鉴定出14份在幼苗期有较强耐盐碱能力的渐渗系。3、LA0716/M82渐渗系中SAT7b的图位克隆。目前,我们通过分子标记辅助筛选重组单株,已经筛选到5个IL7-4-1亚渐渗系（Sub-ILs）用于精细定位工作。4、通过转录组分析,揭示了番茄耐盐碱能力降低的潜在机制。我们通过转录组分析发现,盐碱处理下,醋栗番茄LA1589比栽培番茄M82可以更好地维持植物根系的发育、快速地激活ABA信号通路、具有较强的ROS清除能力和Na⁺外排能力,从而使其具有较强的耐盐碱能力。上述结果从转录水平上部分揭示了栽培番茄耐盐碱能力降低的原因。5、SOS信号途径的自然变异导致番茄的耐盐碱能力降低。通过群体基因组学分析,发现SlSOS3和SlSCa BP8在番茄改良过程中受到选择。SlSOS3启动子上2个SNPs与Na⁺/K⁺比值紧密连锁,Hap1（野生型）的Na⁺/K⁺比值显著低于Hap2（栽培型）,并且Hap1分布频率从PIM到CER再到BIG逐渐降低,最终导致番茄的耐盐碱能力降低;同时,SlSCa BP8启动子包含由一个碱基的变异而形成的两种等位基因:SlSCa BP8^-1903G和SlSCa BP8^-1903A。盐碱胁迫下,等位基因SlSCa BP8^-1903G的存活率显著高于SlSCa BP8^-1903A,并且SlSCa BP8^-1903G分布频率从PIM到CER再到BIG逐渐降低,最终导致栽培番茄的耐盐碱能力降低。综上,驯化和人工选择导致番茄的耐盐碱能力降低。我们从LA0716/M82和LA1589/E6203渐渗系群体中筛选到一批耐盐碱渐渗系,并通过正向遗传学对LA0716/M82渐渗系群体中耐盐碱位点SAT7b进行了初定位。我们通过反向遗传学解析了番茄SOS途径基因SlSOS1、SlSOS2、SlSOS3和SlSCa BP8调控盐碱胁迫的的功能。另外,我们通过群体基因组学发现,SlSOS3和SlSCa BP8启动子上的自然变异导致番茄的耐盐碱能力降低。这项工作揭示了番茄耐盐碱能力降低的原因,并从番茄种质中鉴定出一批耐盐碱种质和耐盐碱位点,为发掘耐盐碱功能基因,培育耐盐碱新品种奠定了基础。更多还原

【Abstract】 Saline-alkaline stress is a worldwide problem that threatens the growth and yield of crops and prevents the sustainable development of modern agriculture.Compared to the extensively studied saline stress,saline-alkaline stress has a much more severe effect on plants because it impinges on combined damages of both high salinity and high pH.However,the physiological and molecular mechanisms by which plants adapt to saline-alkaline stress remain less studied.Tomato is an important vegetable and fruit dual-use economic crop,as well as an important model plant.Although some wild tomato species are highly adapted to saline-alkaline stress,domestication has resulted in a significantly reduced saline-alkaline tolerance of cultivated tomatoes.Therefore,exploring the excellent natural variations and molecular mechanism underlying saline-alkaline tolerance,not only helps to elucidate the relationship between artificial selection and saline-alkaline tolerance,but also contributes to providing critical information as well as innovative germplasms for molecular breeding and improving saline-alkaline tolerance in tomato and other crops.The main results are as follows:1.Saline-alkaline tolerance was compromised during tomato domestication and improvement.We measured the chlorophyll content and survival rate of 61 tomato accessions representing different geographical origins and breeding statuses under saline-alkaline stress.We found that the chlorophyll content and survival rate of the BIG group were significantly lower than the PIM group and CER group after saline-alkaline treatments and the saline-alkaline tolerance of tomatoes gradually decreased from PIM to CER and then to BIG.The results indicate that the saline-alkaline tolerance was compromised in the process of tomato domestication and improvement.2.Screening for saline-alkaline tolerant tomato from LA0716/M82 ILs populations and LA1589/E6203 ILs populations.We identified 10 saline-alkaline tolerant ILs during the seedling stage and 7 saline-alkaline tolerant ILs during the adult stage from the LA0716/M82ILs populations.We identified 14 saline-alkaline tolerant ILs during the seedling stage from the LA1589/E6203 ILs populations.3.Map-based cloning of SAT7b.Currently,we have identified five Sub-ILs of IL7-4-1through molecular marker-assisted selection for fine mapping work.4.Explore the mechanism of compromised saline-alkaline tolerance during tomato domestication by transcriptome analysis.We found that compared with M82,LA1589 has strong root development ability,ABA signal transduction ability,ROS scavenging ability,and Na⁺extrusion ability,which endows LA1589 with strong saline-alkaline tolerance.5.Natural variations in the SOS signaling pathway lead to the decrease in saline-alkaline tolerance in tomatoes.Through population genomics analysis,it was found that SlSOS3 and SlSCa BP8 were selected during tomato improvement.Two SNPs on the promoter of SlSOS3are closely linked to the Na⁺/K⁺ratio,dividing it into two major haplotypes:Hap1（wild type）and Hap2（cultivated type）.The Na⁺/K⁺ratio of Hap1 is significantly lower than that of Hap2,and the frequency of Hap1 gradually decreases from PIM to CER and then to BIG,ultimately resulting in the decrease in saline-alkaline tolerance in tomatoes.Meanwhile,the promoter of SlSCa BP8 contains two allelic variants formed by a single base mutation:SlSCa BP8^-1903G and SlSCa BP8^-1903A.Under saline-alkaline stress,the survival rate of the allele SlSCa BP8^-1903G is significantly higher than that of SlSCa BP8^-1903A,and the frequency of SlSCa BP8^-1903Ggradually decreases from PIM to CER and then to BIG,ultimately leading to the decrease in saline-alkaline tolerance in cultivated tomatoes.In summary,domestication and artificial selection have led to a decrease in saline-alkaline tolerance in tomatoes.We have screened a batch of saline-alkaline tolerant ILs from the LA0716/M82 and LA1589/E6203 ILs populations,and rough map-based cloning of saline-alkaline tolerant locus SAT7b through forward genetics.We have elucidated the functions of tomato SOS pathway genes SlSOS1,SlSOS2,SlSOS3,and SlSCa BP8 in regulating saline-alkaline stress through reverse genetics.In addition,we have discovered that natural variations on the promoters of SlSOS3and SlSCa BP8 lead to a decrease in saline-alkaline tolerance in tomatoes through population genomics analysis.This work reveals the reasons for the decrease in tomato saline-alkaline tolerance and identifies a batch of saline-alkaline tolerant germplasm and saline-alkaline tolerant loci,which contributes to breed saline-alkaline tolerant tomatoes.更多还原