由于水稻直播在节约劳动力、节约水资源、保护环境和大幅减少温室气体排放等方面具有巨大潜力。因此，正成为许多国家水稻生产的主要栽培技术。挖掘和利用中胚轴伸长基因是加快直播稻育种和满足直播水稻生产要求的最有效途径之一。黑龙江省农业科学院利用丽江新团黑谷（LTH）和沈农265（SN265）衍生的144个重组自交系(RIL)群体及其配套的包含2,828个bin标记的连锁图谱分别在2019年和2020年检测了与中胚轴长度相关的数量性状基因座(QTL)。采用30°C黑暗环境下培养10天后测量中胚轴长度。在第1(2)、2(4)、3(2)、4、5、6、7、9、11(2)和12号染色体上共鉴定出16个中胚轴长度QTL。其中7个QTLs可以在两年中被重复检测到，包括qML1a、qML1b、qML2d、qML3a、qML3b、qML5和qML11b。主效QTL-qML3a还可以在不同作图方法中被重复检测到。进一步分析发现，qML3a被定位在88.18kb的范围内，这一区间包含13个预测基因。利用近等基因系也证明了qML3a的真实存在和调控中胚轴伸长的效果。最后，通过分析SN265、LTH 和日本晴之间的DNA序列变异，表明LOC_Os03g50550是qML3a的候选基因。该基因编码有丝分裂原活化的蛋白激酶。使用qRT-RCR分析进一步揭示了LTH中胚轴中LOC_Os03g50550基因的表达水平显著低于SN265中胚轴中的表达水平。这些结果进一步加强了我们对水稻中胚轴伸长遗传机制的认识，也将有助于加快直播专用新品种的育种进程。

Abundant genetic diversity and rational population structure of germplasm benefit crop breeding greatly. To investigate genetic variation among geographically diverse set of japonica germplasm, we analyzed 233 japonica rice cultivars collected from Liaoning, Jilin and Heilongjiang provinces of China, which were released from 1970 to 2011 by using 62 simple sequence repeat (SSR) markers and 8 functional gene tags related to yield. A total of 195 alleles (Na) were detected with an average of 3.61 per locus, indicating a low level of genetic diversity level among all individuals. The genetic diversity of the cultivars from Jilin Province was the highest among the three geographic distribution zones. Moreover, the genetic diversity was increased slightly with the released period of cultivars from 1970 to 2011. The analysis of molecular variance (AMOVA) revealed that genetic differentiation was more diverse within the populations than that among the populations. The neighbor-joining (NJ) tree indicated that cultivar clusters based on geographic distribution represented three independent groups, among which the cluster of cultivars from Heilongjiang is distinctly different to the cluster of cultivars from Liaoning. For the examined functional genes, two or three allelic variations for each were detected, except for IPA1 and GW2, and most of elite genes had been introgressed in modern japonica rice varieties. These results provide a valuable evaluation for genetic backgrounds of current japonica rice and will be used directly for japonica rice breeding in future.