(1) Mesocotyl elongation is responsive to abiotic stresses, such as deep sowing drought, submergence, chilling, and salinity. (2) Humus soil culture with a burial depth of 6 cm and at the temperature of 30 °C could be the optimum method for mesocotyl length phenotyping, The frequently colocalized quantitative trait loci (QTL) controlling mesocotyl elongation were located on chromosome (3) 1 (RM562-RG146), chromosome 2 (RZ288-RM145), and chromosome 3 (RM426-RM520). Dry direct-seeding is becoming a popular rice cultivation technology in many countries, which reduces water use and labor costs enormously. Meanwhile, direct-seeding rice is also facing the problems of low seedling emergence rate, poor seedling establishment, weed infestation, and high crop lodging rate. To take the full advantages of direct-seeding, both agronomic and genetic solutions are needed. Varieties with optimum mesocotyl length are desired for improving rice seedling emergence rate, particularly under deep sowing and submergence, which is adopted to reduce lodging and increase tolerance to abiotic stresses. In this review, we summarized the physiological and genetic mechanisms of mesocotyl elongation in rice. The elongation of mesocotyl is affected by light, temperature, and water, and, as a result, is responsive to sowing depth, water content, and soil salinity. Plant hormones such as abscisic acid (ABA), brassinosteroid (BR), strigolactones (SLs), cytokinin (CTK), ethylene (ETH), jasmonic acid (JA), gibberellin (GA), and indole-3-acetic acid (IAA) play important roles in regulating mesocotyl elongation. A humus soil culture protocol developed by our team was shown to be a better high-throughput method for measuring mesocotyl length in large scale. Sixty-seven QTL controlling mesocotyl length were reported, which are distributed on all the 12 chromosomes. Twelve chromosomal regions were repeatedly found to have QTL using various mapping populations and methods. These regions should be targeted in future studies to isolate genes and develop markers for molecular breeding. Two genes with very different molecular functions have been cloned, highlighting the genetic complexity of mesocotyl elongation.

中文翻译：

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中胚轴伸长，干种水稻（Oryza sativa L.）的一个基本特征：生理和遗传基础综述

(1) 中胚轴伸长对非生物胁迫有响应，如深播干旱、淹没、寒冷和盐度。(2) 埋藏深度6 cm、温度30 °C的腐殖质土壤培养可能是中胚轴长度表型分析的最佳方法，控制中胚轴伸长的频繁共定位数量性状基因座(QTL)位于染色体(3)上。 1 (RM562-RG146)、2 号染色体 (RZ288-RM145) 和 3 号染色体 (RM426-RM520)。干直播正成为许多国家流行的水稻栽培技术，极大地减少了用水和劳动力成本。同时，直播稻还面临出苗率低、成苗差、杂草丛生、作物倒伏率高等问题。为了充分发挥直播的优势，需要农艺和遗传解决方案。需要具有最佳中胚轴长度的品种来提高水稻幼苗的出苗率，特别是在深播和淹没情况下，这被用来减少倒伏并增加对非生物胁迫的耐受性。在这篇综述中，我们总结了水稻中胚轴伸长的生理和遗传机制。中胚轴的伸长率受光、温度和水的影响，因此对播种深度、含水量和土壤盐度有反应。植物激素，如脱落酸 (ABA)、油菜素类固醇 (BR)、独脚金内酯 (SLs)、细胞分裂素 (CTK)、乙烯 (ETH)、茉莉酸 (JA)、赤霉素 (GA) 和吲哚-3-乙酸 (IAA) ) 在调节中胚轴伸长中起重要作用。我们团队开发的腐殖质土壤培养方案被证明是一种更好的高通量方法，用于大规模测量中胚轴长度。报道了67个控制中胚轴长度的QTL，分布在所有12条染色体上。使用各种定位群体和方法反复发现十二个染色体区域具有 QTL。这些区域应成为未来研究的目标，以分离基因并开发分子育种标记。已经克隆了两个分子功能非常不同的基因，突出了中胚轴伸长的遗传复杂性。使用各种定位群体和方法反复发现十二个染色体区域具有 QTL。这些区域应成为未来研究的目标，以分离基因并开发分子育种标记。已经克隆了两个分子功能非常不同的基因，突出了中胚轴伸长的遗传复杂性。使用各种定位群体和方法反复发现十二个染色体区域具有 QTL。这些区域应成为未来研究的目标，以分离基因并开发分子育种标记。已经克隆了两个分子功能非常不同的基因，突出了中胚轴伸长的遗传复杂性。