采用抗旱品种和机械化旱直播栽培体系可使稻作大幅度节水，现有品种多按移栽或水直播条件选育，未按旱直播优化特性。幼苗通过中胚轴和胚芽鞘的伸长提高出苗速度和整齐度，是对杂草竞争力和高产群体的基础。中胚轴黑暗伸长，见光后停止，形成幼苗对播深自适应机制。本研究拟综合考虑播种深度、中胚轴长度和胚芽鞘长度及比例，提出适应旱直播的早期幼苗形态性状的优化模式，分析土壤水分不足和低温影响以及补偿性状参数。利用我国水稻微核心种质、抗旱水稻品种和全球水稻品种等自然变异群体，已获得全基因组SNP基因型数据，拟开展中胚轴和胚芽鞘长度及其比例、适度深播条件下出苗率和秧苗素质等性状的关联定位。以节水抗旱稻优良恢复系为受体亲本，利用回交后代及其次级分离群体进行QTL精细定位，同时转育适应旱直播条件的节水抗旱稻新种质。采用中胚轴延长受光抑制过程中差异表达基因分析等手段加快候选基因鉴定和克隆，开展目标基因的功能和调控机制研究。

Irrigation water could be largely saved in rice production after application of drought resistant varieties and mechanized dry direct sowing method. Most present varieties were developed for transplanting or wet direct sowing system without optimizing their characteristics for dry direct sowing. Elongation of both mesocotyl and coleoptile increases the speed and uniformity of seedling emergence of deep-sown seeds that is the basis of competition against weeds and high-yielding population structure. Mesocotyl elongated at the dark that stopped after exposure to light. This characteristics support the self-adaptation of seedlings to sowing depth. This study take comprehensive considerations on sowing depth, final lengths of mesocotyl and coleoptile (and their ratio) to propose a optimized pattern of early seedling morphological characteristics. The influence of low soil water content and low temperature are analyzed to estimate compensation of seedling characteristics. Using natural varied populations like mini- core-collection of Chinese rice germplasm, drought resistant varieties and collection of global rice germplasm and ready-to-use SNP genotypic data, association mapping will be conducted for mesocotyl length, coleoptile length, their ratio, seedling emergence rate and quality after properly deep-sowing. Using backcross progenies and derived segregation populations with elite restorers of water-saving and drought-resistant rice (WDR) as the recurrent parents, QTL fine mapping and development of new WDR materials adapting to dry direct sowing will be conducted. Analysis of differential gene expression during the procedure of light inhibition to mesocotyl elongation will be used to accelerate the identification and cloing of candidate genes. Researches on functions of target genes and the regulation mechanism will be conducted in this study.