以泰国玉米品种与适应种质共122份为素材, 采用改良穗行、顶交或测交方案, 按精准的育种目标与定向设计, 创制出具有鲜明独特特征的开放授粉品种(Open pollinate varieties, OPVs)。育种素材选择考虑表现优良、广适性、遗传多样性等3个因素; 合成系统考虑实现遗传混合与重组、均等比较遗传贡献、施之温和选择压力、充分交配达到遗传平衡(遗传组成母本性状相近)等4条要素。相继创制Suwan 1复合种及其(半)硬粒型衍生种(Suwan 2、3复合种, Suwan 5、KS24综合种), 含有不同血缘的马齿型KS6、KS28, Non-Suwan 1血缘的马齿型Caripeno DMR、KS27、KS23等。对10个OPVs采用S1选择法分别实施了C2～C13轮选择, 从中育成近50个自交系, 组配并发放16个优良单(三)交种。目前泰国各单位育成的每个杂交种中, 至少有一个亲本系来源于Suwan(KS)种质。文章还依据合成OPVs及选系理论, 对合成OPVs遗传成分适度多样化、亲缘关系、优势群与模式和合成OPVs对杂交优势育种的启示问题加以探讨。
In the present study, 122 maize local cultivars and adapted exotic germplasm from Thailand were used to develop open pollinate varieties (OPVs) using modified ear-to-row scheme, top-cross or test-cross programmes. Ten new maize OPVs with distinct characters were created based on the precise breeding objectives and directional design. The selection of breeding materials was based upon three factors: elite performance, broad adaptability, and genetic diversity. The synthesizing system provided four features: genetic mixing and recombination, equal comparable genetic contribution, mild selection pressure, and maximum intermating for genetic equilibrium (i.e., the female traits were close for the genetic compositions). Subsequently, Suwan 1 composite and its deritives (Suwan 2, Suwan 3 composite, Suwan 5 and KS24 synthet-ics), KS6 and KS28 synthetics with the dent type of different origins, and Caripeno DMR composite, KS23, and KS27 syn-thetics with the dent type of Non-Suwan 1 origin were developed. These OPVs had been improved for 2~13 cycles using S1 recurrent selection method. About 50 inbred lines were developed from these OPVs, and 16 elite single (three-way) crosses were combined and released from these inbred lines. At present, at least one parental inbred line of all the tropical hybrids was derived from Suwan (KS) germplasm in Thailand. Based on the theory of the synthesizing OPVs and developing inbred lines, this paper discussed the genetic moderate diversity, relationship, heterotic group, and patterns for synthesizing OPVs, and inspiration for composed OPVs to heterosis breeding.
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