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首页> 外文学位 >Natural variation and genetic analyses of seed and seedling traits in lettuce: Discovery, confirmation and proposed role for a quantitative trait locus in regulating seed dormancy at high temperature.
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Natural variation and genetic analyses of seed and seedling traits in lettuce: Discovery, confirmation and proposed role for a quantitative trait locus in regulating seed dormancy at high temperature.

机译：生菜种子和幼苗性状的自然变异和遗传分析：发现，确认和提出定量性状基因座在调节高温种子休眠中的作用。

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Genetic analyses of natural variation can provide insight into the regulation of important agronomic or physiological traits of plants. A survey of the natural variation present in four species of Lactuca identified species-specific differences in seed weight, oil content, fatty-acid composition, and germination in response to light and temperature. A QTL analysis was performed in a recombinant inbred line (RIL) population derived from L. sativa cv. Salinas x L. serriola UC96US23. QTL were identified for seed oil content, seedling growth and quality, and germination in response to light and temperature. The Htg6.1 QTL described ∼55% of phenotypic variation for germination at high temperature (35°C) in multiple environments. The failure of seeds to germinate when imbibed at warm temperatures (thermodormancy) results in yield losses in major lettuce growing areas, thus making the alleviation of thermodormancy a valuable breeding goal.;Marker-assisted backcrossing/selection was utilized to introgress the Htg6.1 QTL-allele originating from UC96US23 into the Salinas background and develop near-isogenic lines (NILs). The QTL increased the mean upper temperature limit (UTL) of seed germination in NILs by an average of 2.3°C, confirming its role as a significant source of germination thermotolerance in lettuce. Thirty-four candidate genes for germination/dormancy and seed oil biosynthesis/metabolism were mapped. Genes in the ABA, GA and ethylene biosynthetic or response pathways were collocated with QTL for germination in the absence of light and germination at 25°C. A gene critical for ABA biosynthesis, 9-cis-epoxycarotenoid dioxygenase (LsNCED4), collocated with Htg6.1. Expression of LsNCED4 was significantly lower in thermotolerant NILs homozygous for the UC96US23 allele at Htg6.1 compared to expression in thermosensitive NILs homozygous for the Salinas Htg6.1 allele.;In Salinas and UC96US23, gene expression patterns contrasted at germination-permissive and -inhibitory temperatures. Increased ABA content, sensitivity, and ABA-related gene expression in Salinas seeds was associated with the inability to germinate at 33°C and with corresponding repression of genes in the GA and ethylene biosynthetic pathways. These results suggest that when the UC96US23 allele of LsNCED4 at Htg6.1 is present, imbibition at high temperature does not increase ABA synthesis, allowing expression of GA and ethylene biosynthetic genes and promotion of germination.
机译：对自然变异的遗传分析可以提供对植物重要农艺或生理性状调控的见识。一项对四种莴苣属植物存在的自然变异的调查发现，种子的重量，油含量，脂肪酸组成和发芽率随温度和温度的变化因种而异。在源自L. sativa cv的重组近交系（RIL）群体中进行了QTL分析。盐沼x L.serriola UC96US23。确定了QTL的种子油含量，幼苗生长和质量以及对光和温度的响应而发芽。 Htg6.1 QTL描述了在多种环境中高温（35°C）下发芽的约55％的表型变异。种子在温暖的温度下吸收后无法发芽（高温休眠），导致主要生菜生长区的产量下降，因此减轻热休眠成为重要的育种目标。利用标记辅助的回交/选择对Htg6.1进行渗入源自UC96US23的QTL等位基因进入盐沼背景，并发育近等基因系（NIL）。 QTL使NIL中种子发芽的平均温度上限（UTL）平均提高2.3°C，从而确认了其作为生菜中发芽耐热性的重要来源。绘制了34个用于萌发/休眠和种子油生物合成/代谢的候选基因。 ABA，GA和乙烯的生物合成或响应途径中的基因与QTL并置，以便在无光照和25°C的条件下发芽。 Htg6.1与ABA生物合成有关的关键基因9-顺式-环氧类胡萝卜素双加氧酶（LsNCED4）。与在Salinas Htg6.1等位基因纯合的热敏性NILs中的表达相比，在Htg6.1中UC96US23等位基因纯合的耐热NILs中的LsNCED4的表达显着降低。温度。盐沼种子中ABA含量，敏感性和ABA相关基因表达的增加与33°C下无法发芽以及GA和乙烯生物合成途径中基因的相应抑制有关。这些结果表明，当在Htg6.1处存在LsNCED4的UC96US23等位基因时，在高温下吸收不会增加ABA的合成，从而可以表达GA和乙烯生物合成基因并促进发芽。

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