Dermail Abil, Chankaew Sompong, Lertrat Kamol, Lübberstedt Thomas, Suriharn Khundej
Department of Agronomy, Faculty of Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand.
Plant Breeding Research Center for Sustainable Agriculture, Khon Kaen University, Khon Kaen 40002, Thailand.
Plants (Basel). 2021 Dec 19;10(12):2812. doi: 10.3390/plants10122812.
Lacking elite haploid inducers performing high haploid induction rate (HIR) and agronomic performance is one of fundamental factors hindering the rapid adoption of doubled haploid technology in maize hybrid breeding, especially under tropical savanna climate. Breeding haploid inducers for specific agro-ecology, thus, is indispensable yet challenging. We used temperate inducer Stock6 as genetic source for haploid induction ability and eight tropical maize genotypes as principal donors for agronomic adaptation. Three cycles of modified ear-to-row with 5% intra-family selection were applied in a population set of 78 putative haploid inducer families emphasized on agronomic performance, anthocyanin intensity, and inducer seed set. Genetic gains, variance components, and heritability on given traits were estimated. Hierarchical clustering based on five selection criteria was performed to investigate the phenotypic diversity of putative families. Cycle effect was predominant for all observed traits. Realized genetic gain was positive for HIR (0.40% per cycle) and inducer seed set (30.10% or 47.30 seeds per ear per cycle). In this study, we reported the first haploid inducers for regions under tropical savanna climate. Three inducer families, KHI-42, KHI-54, and KHI-64, were promising as they possessed HIR about 7.8% or 14 haploid seeds per tester ear and inducer seed rate about 95.0% or 208 inducer seeds per ear. The breeding method was effective for enhancing the seed set and the expression of anthocyanin marker of inducers, yet it showed a low effectiveness to improve haploid induction rate. Introgression of temperate inducer Stock6 into tropical gene pool followed by phenotypic selections through modified ear-to-row selection on inducer seed set and marker did not compromise the agronomic traits of tropical inducer families. Implications and further strategies for optimizing genetic gain on HIR are discussed.
缺乏具有高单倍体诱导率（HIR）和农艺性能的优良单倍体诱导系是阻碍双单倍体技术在玉米杂交育种中迅速应用的基本因素之一，特别是在热带稀树草原气候条件下。因此，培育适用于特定农业生态的单倍体诱导系不可或缺，但具有挑战性。我们使用温带诱导系Stock6作为单倍体诱导能力的遗传来源，以8个热带玉米基因型作为农艺适应性的主要供体。在一个由78个假定的单倍体诱导系家族组成的群体中，应用了三个轮回的改良穗行法，并进行5%的家系内选择，重点关注农艺性能、花青素强度和诱导系结实率。估计了给定性状的遗传增益、方差分量和遗传力。基于五个选择标准进行层次聚类，以研究假定家族的表型多样性。轮回效应在所有观察到的性状中占主导地位。对于单倍体诱导率（每个轮回0.40%）和诱导系结实率（每个轮回30.10%或每穗47.30粒种子），实现的遗传增益为正。在本研究中，我们报道了首批适用于热带稀树草原气候地区的单倍体诱导系。三个诱导系家族KHI-42、KHI-54和KHI-64很有前景，因为它们的单倍体诱导率约为7.8%或每个测验种穗产生14个单倍体种子，诱导系种子率约为95.0%或每穗208个诱导系种子。该育种方法对于提高诱导系的结实率和花青素标记的表达是有效的，但在提高单倍体诱导率方面效果较低。将温带诱导系Stock6导入热带基因库，然后通过改良穗行法对诱导系结实率和标记进行表型选择，并没有损害热带诱导系家族的农艺性状。本文讨论了优化单倍体诱导率遗传增益的意义和进一步策略。
