Evaluation of diverse elite and landrace maize lines for testcross hybrid performance and combining ability under low and high phosphorus fertilization regimes

Abstract In the context of over‐fertilization, especially of phosphorus (P), the debate about the usefulness of applying starter fertilization to maize ( Zea mays L.) must be revisited. One solution is to breed crops with an enhanced phosphorus use efficiency, which require less fertilizer yet are high‐yielding. This study examined a diverse panel of Flint elite lines and double haploid lines from six European landraces, which were crossed with two Dent testers. The resulting 588 testcross hybrids were evaluated under two fertilization treatments: with and without the addition of a di‐ammonium phosphate starter fertilization. The omission of the starter fertilization led to a decrease in early developmental traits, like plant height and biomass, in all four tested environments. Surprisingly, grain yield increased in three out of four environments, an effect that was especially noticeable in the landrace line testcrosses and is possibly caused by the increased ability to cope with environmental stress occurring at later developmental stages. Importantly, there is substantial genetic variation that can be exploited in breeding for the response to fertilizer levels, with some landrace testcrosses performing in the range of the Flint elite testcrosses. Furthermore, additive genetic effects were found to be the main contributor to early developmental traits and grain yield under both fertilization treatments. These results suggest that landraces may offer valuable genetic variation for breeding for reduced phosphate fertilizer input. In conclusion, breeding programs should include breeding for nutrient acquisition but combined with a tolerance to withstand seasonal climate variations.