水稻亚种间F_1杂种优势在不同播期下的表现

Analysis of heterosis in inter-subspecific F_1 hybrids under three different sowing dates in rice.

以６份籼型不育系和７份粳型或偏粳型广亲和系配制成不完全双列杂交，将杂种Ｆ_１及其亲本在３个播期（早播５／２０，中播６／１０，迟播６／３０）下试验．结果表明，籼粳交Ｆ_１在多数性状上其群体平均优势和群体超亲优势均随播期推迟而呈下降的趋势；Ｆ_１性状的平均基因型预测值显示了早播常出现植株偏高、剑叶披和生育期延长，而迟播导致主穗总粒数减少；Ｆ_１杂种在株高、抽穗天数、剑叶长、主穗长、主穗总粒数和着粒密度性状间均表现显著显性正相关．

Six indica cytoplasmic male sterile lines and seven japonica widely compatible varietieswere used to make a set of incomplete diallel crosses.The field experiment was carried out at threediffrent sowing dates （early 5/20,middle 6/10, late 6/30） in 1993.F1 hybrids showed the differ-ent degree of heterosis under the three sowing dates. The heterosis over both mid-parent and bet-ter-parent based on population means decreased with the postpondment of planting for most ofcharacters. The predicted genotype values of hybrid showed that plant height,flag leaf length andheading time increased at early date but total number of grain per main panicle decreased at latersowing date. Analysis of dominant correlation between traits revealed positive corralations amongplant hight,days to heading,flag leaf length, main panicle length,total grain nuber per main pan-icle and panicle density.