玉米基因型×密度互作及耐密育种策略研究

在假定玉米产量与密度关系为抛物线基础上，以已发表文献所反映的基因型×密度互作研究结果为基础，选取历史数据的平均数，以高产基因型的目标密度为参照，按照“正确、错误、漏选”的选择结果，分析基因型差异的27个可能组合。根据基因型之间产量关系以及对选择的干扰程度，将玉米基因型×密度互作划为3种类别，即交点干扰型、产量差干扰型、无干扰型，进一步细分为14种亚类。高密度育种和低密度育种各受到交点干扰型3个亚类的影响，其中只有第8亚类同时影响两种育种策略；高密度育种和低密度育种各受到产量差干扰型2个亚类的影响，其中只有第3亚类同时影响两种育种策略。产量曲线交点的存在，严重干扰杂交组合的单密度选择效果。虽然从产量-密度数量关系看两种育种策略的优劣相当，但是，高密度育种具有逆境选择优势。正偏移密度加目标密度的双密度选择，能够进一步降低杂交组合和品种筛选阶段的选择风险。

Genotype × Density Interaction and Its Application in High Density Breeding Strategy in Maize

Based on historical summaries of genotype × density interactions associated in published papers, parabola models were used to set the reference to target plant density for higher crop yield in cultivar screening in maize. Output for screening was denoted as correct, wrong and missing. Genotypic difference in model parameters displayed 27 combinations, which fell into 14 cases. Genotype × density interactions were classified into 3 categories, namely cross interference, yield gap interference and non-interference, according to their interference to screening and genotypic difference in crop yield. For high density breeding strategy, the category of cross interference was limited to cases 5, 7 and 8, the category of yield gap interference to cases 2 and 3. For low density breeding strategy, the category of cross interference was limited to cases 4, 6 and 8, the category of yield gap interference to cases 1 and 3. Selection based on a single plant density was heavily disturbed because of yield cross between two genotypes. High density breeding strategy in maize had an advantage of simultaneous selection for stress tolerance over low density breeding strategy although risks of both strategies seemed the same in terms of yield-density relationship. Selection risks may lower down further when double densities of target density plus positive offset were applied to breeding program.