水稻苗期生长特性的遗传剖析

 以1个水稻重组自交系为作图群体进行盆栽试验，分别在播种后第14、24、34和44天进行第1、2、3和第4次取样，考察秧苗苗高和干物重以及播种前所用种子的千粒重。结合1张高密度的遗传图谱，对性状进行复合区间作图，分别检测到控制秧苗干物重、苗高和种子千粒重的主效应QTL 6、14和3个。其中，位于3号染色体RM148-RM85区段的QTL qGC-3-3同时影响第4期干物重和第1、3和4期苗高，且其对苗高的效应呈逐期递增的趋势。与qGC-3-3相反，位于5号染色体RM163-RM161区段的QTL qGC-5 同时影响第1～3期的干物重和苗高，但其效应由强趋弱。在第1～4期中，秧苗干物重与苗高的相关系数分别为0.60～.70，为极显著（P<0.01）正相关。秧苗干物重和苗高与种子千粒重的相关性均呈逐期递减的趋势、以至于到后期相关性较弱或不显著。QTL定位结果表明，对种子千粒重效应最大的QTL正是上述5号染色体上的qGC-5，该QTL对这3个相关性状的效应方向均一致，但对秧苗干物重和苗高的效应大小是逐期递减。将本研究中定位到的QTL与已报道的利用同一定位群体所检测到的籽粒产量性状QTL相比较，发现有的QTL（如3号染色体上的QTL qGC-3-1和qGC-3-3）尽管在水稻生育早期的效应较小，但其效应随着生育进程的发展而逐期递增，且加性效应的方向在全生育期一致；有的QTL（如5号染色体上的qGC-5）在水稻生育早期的效应相对较大，但其效应逐期减弱，以至于对生育后期的生长发育和产量性状没有直接影响或影响很小。这些QTL的表达具有较强的时期特异性。

Genetic Dissection of Early Growth Characteristics in Rice

The aim of the present study is to dissect the genetic factors controlling early growth characteristics of rice (Oryza sativa L.) by QTL analysis. A RIL (recombinant inbred line) population was directly seeded in plastic pots in a randomized complete block. Seedling height (SH) and dry weight (DW) of seedlings were measured at 14, 24, 34 and 44 days after sowing, respectively. Combined with a linkage map based on this population, composite interval mapping was carried out, leading to the identification of 6, 14 and 3 main-effect QTL for DW, SH and 1 000-grain weight (KGW) of the seeds used in the study, respectively. Among these QTL, qGC-3-3 and qGC-5, located within the interval RM148-RM85 of chromosome 3 and the interval RM163-RM161 of chromosome 5, respectively, showed additive effects on multiple measurements of SH and DW in the same direction, but, as the seedlings grew, the magnitude of the effects of QTL qGC-3-3 appeared to have increased while that of QTL qGC-5 seemed to have declined. DW correlated positively with SH (P<0.01), which was genetically explained by the co-locations of some of the QTL for the two traits with effects in the same direction. Both DW and SH correlated positively with KGW, but the correlation degrees became weaker as the seedlings grew, which was also explained well by the coincidence of the QTL for the traits concerned. In addition, comparison of the QTL detected in the current study with those previously identified for yield related traits with the same population revealed that some of the QTL, such as QTL qGC-3-1 and qGC-3-3 on chromosome 3, seem to produce larger effects on late growth of rice so that they show a greater influence on multiple yield traits, while the others, such as QTL GC-5, show larger effects mainly on early growth. From the point of view of breeding, the former could be better to be used as the potential targets to be manipulated in rice breeding program by marker-aided selection.