高代回交QTL分析方法可以使QTL检测和育种相结合，有效利用非适应性种质。在河南郑州春、夏播两种环境条件下，种植以普通玉米自交系丹232和爆裂玉米自交系N04为亲本构建的220个BC2S1家系群体，利用覆盖玉米10条染色体的188对多态性SSR分子标记，采用单标记分析法对控制膨化倍数QTL进行分析。目的在于印证利用F2:3家系的QTL分析结果，检测具有世代稳定性的QTL，同时将QTL分析与爆裂玉米育种相结合，直接从中选育爆裂玉米自交系。研究结果表明，膨化倍数在家系间、环境间均存在极显著差异，家系与环境互作不显著。BC2S1家系呈连续正态分布，且存在超高亲分离，超高亲家系分别占12.27%和19.09%。共检测出16个QTL，其中2个在两种环境条件下均被检测到，单个QTL的贡献率为3%~9%，累计贡献率为42%和33%，增效基因均来自爆裂N04。BC2S1家系的穗粒和植株性状均得到明显改良，各性状优于爆裂亲本N04的家系占10%~100%。两种环境条件下分别有186个和204个家系的穗粒重比爆裂亲本N04高10%以上，其中23个和46个家系的膨化倍数达到或优于N04，可以直接从中选育出优良爆裂玉米自交系。
Advanced backcross QTL (AB-QTL) method can combine QTL detection with elite variety improvement and apply unadapted germplasm efficiently, which has been used in tomato, rice, wheat, and normal maize. Previous studies showed that normal maize inbreds could enrich the germplasm of popcorn through interspecies cross and improve the popping characters and plant traits of hybrids through 1 to 2 cycles of backcrosses with popcorn inbred. When BC1 and F2:3 generations were used, QTL for popping fold have been detected, but no research has been done with advanced backcrosses. In this study, a total of 220 BC2S1 families, derived from the cross between a dent corn inbred Dan 232 and a popcorn inbred N04, were evaluated for their popping fold and other 13 traits of kernel yield component, plant and popping in a replicated experiment under two environments. 188 pairs of SSR markers with polymorphism were selected to analyze their genotypes. QTL were identified, and their genetic effects were estimated with single marker method (SMM). Our first objective was to compare the detection of QTL in the BC2S1 generation with a previous study by F2:3 families of the same population grown at the same location and in the same year. The second objective was to combine QTL analysis with popcorn breeding and develop popcorn inbreds simultaneously. The results are as follows: There were significant differences among BC2S1 families and between two environments for popping fold, but the family × environment interaction was not significant. Its hB2 was 0.60, with confidence interval of 0.43 to 0.72. The values of skewness and kurtosis indicated its normal distributions under both environments with transgressive segregations exceeding the high parent N04. 12.27% and 19.09% of BC2S1 families were higher than N04 in popping fold. Totally, 16 QTL were detected, and only two of them (qBPF-1-2 and qBPF-10-1) shared under two environments. Nine QTL detected in spring were located on chromosomes 1 (three), 2 (two), 4 (one), 8 (one), and 10 (two), whereas seven QTL detected in summer were on chromosomes 1 (three), 7 (one), and 10 (three). Contribution to phenotypic variation of a single QTL varied from 3% to 9%, with qBPF-1-1 the largest, and qBPF-7-1, qBPF-10-1 the next (all 6%). Total contributions of all QTL under two environments were 42% and 33%, respectively. In our previous study using F2:3 generation, we detected 22 QTL (associating with 37 marker loci), among which 7 QTL were detected in the same marker loci and 4 in the near marker loci in this study, totally accounting for 29.73%, and three QTL were only detected in this study. The performance of BC2S1 families for other traits showed that most families were significantly improved in ear-kernel and plant traits, with 10%–100% of the families higher than the popcorn parent N04. The kernel weight per ear of 186 and 204 BC2S1 families in two environments was 10% higher than the popcorn parent N04, among which 23 and 46 families were the same or higher than N04 in popping fold. Therefore, modified N04 could be developed from them and used in popcorn breeding.
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