Pan African University Life and Earth Sciences Institute (Including Health and Agriculture), University of Ibadan, Ibadan, 200284, Nigeria.
International Institute of Tropical Agriculture (IITA), PMB 5320, Ibadan, 200001, Nigeria.
BMC Plant Biol. 2022 Jun 10;22(1):286. doi: 10.1186/s12870-022-03662-1.
Temperate maize inbred lines with expired Plant Variety Protection Act certificates (Ex-PVP) are potential sources of desirable alleles for tropical germplasm improvement. Up to now, the usefulness of the Ex-PVP inbred lines as a potential source of novel beneficial alleles for Striga hermonthica resistance breeding to enhance genetic gain in tropical maize has not been reported.
This study was thus conducted to characterize the combining ability of 24 Ex-PVP inbred lines in crosses with two tropical Striga resistant inbred testers under Striga-infested and non-infested conditions and across three locations for 2 years. Many testcrosses between Ex-PVP inbred lines and the first tester (T1) produced competitive or significantly higher grain yields compared to the hybrid between the two resistant testers under Striga infested and non-infested conditions and across multiple test locations. Also, most of the testcrosses with positive heterosis for grain yield and negative heterosis for Striga damage and emerged Striga count involved T1 as a tester. Our study identified six Ex-PVP inbred lines with positive GCA effects for grain yield under Striga infested and non-infested conditions and across multiple test locations. Amongst these, inbred lines HB8229-1 and WIL900-1 also displayed negative GCA effects for emerged Striga count and Striga damage rating. The inbred line HB8229-1 showed positive SCA effects for grain yield with T2, whereas WIL900-1 had positive SCA effects for grain yield with T1. Over 70% of the Ex-PVP inbred lines were consistently assigned to specific heterotic groups using yield-based classifying methods (mean grain yield and SCA effects).
These results could facilitate systematic introgression of the Ex-PVP inbred lines into the existing Striga resistant heterotic groups in IITA. The Ex-PVP inbred lines with positive GCA effects and producing high grain yields in hybrid combinations could be useful parents for enhancing Striga resistance and agronomic performance of tropical maize hybrids.
已过期植物品种保护法证书的温带玉米自交系（Ex-PVP）是热带种质改良中理想等位基因的潜在来源。到目前为止，还没有报道过 Ex-PVP 自交系作为提高热带玉米中 Striga 抗逆性遗传增益的新型有益等位基因的潜在来源的有用性。
因此，本研究旨在对 24 个 Ex-PVP 自交系在受 Striga 侵染和未侵染条件下与两个热带 Striga 抗性自交系 tester 杂交的配合力进行表征，在 2 年的 3 个地点进行。与受 Striga 侵染和未侵染条件下及多个测试地点的两个抗性 tester 之间的杂交相比，许多 Ex-PVP 自交系与第一个 tester（T1）之间的测验交产生了有竞争力的或显著更高的籽粒产量。而且，大多数具有籽粒产量正杂种优势和 Striga 损伤和萌发 Striga 计数负杂种优势的测验交都涉及 T1 作为 tester。我们的研究鉴定了 6 个在受 Striga 侵染和未侵染条件下及多个测试地点具有正一般配合力效应的 Ex-PVP 自交系。在这些自交系中，HB8229-1 和 WIL900-1 也表现出负的一般配合力效应，对萌发的 Striga 计数和 Striga 损伤评分。HB8229-1 自交系与 T2 表现出正的特殊配合力效应，而 WIL900-1 自交系与 T1 表现出正的特殊配合力效应。超过 70%的 Ex-PVP 自交系使用基于产量的分类方法（平均籽粒产量和 SCA 效应）被一致地分配到特定的杂种优势群中。
这些结果可以促进 Ex-PVP 自交系系统地导入 IITA 现有的 Striga 抗性杂种优势群中。在杂种组合中具有正一般配合力效应和产生高籽粒产量的 Ex-PVP 自交系可以作为增强热带玉米杂种的 Striga 抗性和农艺表现的有用亲本。
