Clarification of the mechanisms of growth response to cultivation methods in rice plants with genome information

为了从QTL水平上分析深水灌溉对水稻分蘖数(TN)、茎粗(CT)和每穗颖花数(SPP)的影响，于2004年和2005年在宫城大学试验场对秋光(Akihikari)和IRAT109(热带粳稻)回交自交系群体的分蘖数(TN)、茎粗(CT)、每穗颖花数(SPP)及其构成因素进行了研究。在控制全氮和穗数的QTL中，有一些QTL与灌溉互作(两种水分条件下LOD得分差异较大的QTL或相关参数LOD得分较高的QTL)，此外，CT和SPP的QTL与其共定位，对相关参数的影响相反。这表明深水灌溉抑制分蘖、增大CT与提高SPP之间存在因果关系。CT与灌溉互作的一个QTL不对应于TN的任何一个QTL，这表明深水灌溉直接扩大CT的机制(=不仅通过分蘖抑制)也存在。在QTL水平上考察产量形成，12号染色体上Pn的QTL在一年内对应于YD的大效应QTL，这表明Pn在QTL水平上对YD有很强的调控作用。但其对YD的影响被SPP的相反作用所抵消，因此在其他年份没有检测到YD的QTL。Pn和SPP在QTL水平上补偿机制的不适应性决定了YD的QTL表达模式。

To analyze the effect of deep water irrigation on tiller number (TN), culm thickness (CT) and spikelet number per panicle (SPP) at QTL level, TN, CT, grain yield (YD) and its components of backcross inbred population from the cross between Akihikari (temperate japonica) and IRAT109 (tropical japonica) were investigated under two different water regimes (the standard irrigation and the deep-water irrigation) at the experimental farm of the Miyagi University in 2004 and 2005.Two-way ANOVA revealed significant genotype-by-irrigation interactions for almost all traits. Among QTLs for TN and panicle number (PN), some QTLs interacted with irrigation (QTLs with great difference in LOD score between two different water regimes or high LOD score in relative parameter [the ratio of the parameters under the standard irrigation and the deep-water irrigation]).In addition, QTLs for CT and SPP were co-localized with them and had an opposite effect in relative parameter. This suggests the causal relationship between tiller suppression, enlargement of CT and increment of SPP by deep water irrigation. One QTL for CT interacting with irrigation was not corresponded to any QTLs for TN, suggesting the mechanism that deep water irrigation enlarges CT directly (=not only through tiller suppression) also exists. Examining the yield formation at QTL level, QTL for PN on chromosome 12 corresponded to large-effect QTL for YD in a year, suggesting that PN strongly regulates YD at QTL level. But its effect on YD was cancelled out by the opposite effect of SPP, thus QTL for YD is not detected in the other year. The unsuitability of compensatory mechanism at QTL level between PN and SPP determines the expression pattern of QTL for YD.