Intercontinental trials reveal stable QTL for Northern corn leaf blight resistance in Europe and in Brazil

Abstract

Key message NCLB is the most devastating leaf disease in European maize, and the introduction of Brazilian resistance donors can efficiently increase the resistance levels of European maize germplasm. Abstract Northern corn leaf blight (NCLB) is one of the most devastating leaf pathogens in maize (Zea mays L.). Maize cultivars need to be equipped with broad and stable NCLB resistance to cope with production intensification and climate change. Brazilian germplasm is a great source to increase low NCLB resistance levels in European materials, but little is known about their effect in European environments. To investigate the usefulness of Brazilian germplasm as NCLB resistance donors, we conducted multi-parent QTL mapping, evaluated the potential of marker-assisted selection as well as genome-wide selection of 742 F1-derived DH lines. The line per se performance was evaluated in one location in Brazil and six location-by-year combinations (= environments) in Europe, while testcrosses were assessed in two locations in Brazil and further 10 environments in Europe. Jointly, we identified 17 QTL for NCLB resistance explaining 3.57–30.98% of the genotypic variance each. Two of these QTL were detected in both Brazilian and European environments indicating the stability of these QTL in contrasting ecosystems. We observed moderate to high genomic prediction accuracies between 0.58 and 0.83 depending on population and continent. Collectively, our study illustrates the potential use of tropical resistance sources to increase NCLB resistance level in applied European maize breeding programs.

Global warming and increasing maize cultivation demand comprehensive efforts in disease and insect resistance breeding in north‐western Europe

“…Fortunately, a recently published study suggests that the introduction of Brazilian resistance donors can efficiently increase the resistance level of European maize germplasm (Galiano‐Carneiro et al, 2021). This is of great interest to maize breeders in NW Europe and elsewhere, because in the subtropics and tropics, maize has already been challenged for a long time by NCLB.…”

“…Nevertheless, in a "near‐final" selection stage, a mycotoxin test might be useful in order to confirm if the promising lines really do have a low mycotoxin content as proposed by GS. To broaden the genetic diversity for ear rot resistance, the exploitation of European landraces (Gaikpa et al, 2021) and of (sub)tropical germplasm is useful (Galiano‐Carneiro et al, 2021).…”

“…Usually, maize is used as grain maize in the warmer regions and as silage maize in the cooler regions. In north‐western (NW) Europe, about 85% of the maize production is designated to silage and biogas maize, while only 15% is grain maize (Galiano‐Carneiro et al, 2021). With the promotion of green energy production via biogas in Germany, silage maize cultivation increased from 1.5 million ha (2000) to 2.7 million ha (2020), illustrating that maize cultivation can profit from both political decisions and from the future due to global warming (see below).…”

Multi‐parental QTL mapping of resistance to white spot of maize (Zea mays) in southern Brazil and relationship to QTLs of other foliar diseases

“…The methodology for QTL detection, LOD threshold determination, confidence interval and the cross-validation used was exactly as described above for MWS. NCLB BLUEs and QTLs were obtained in a separate study based on the same populations (Galiano-Carneiro et al, 2020). Both GLS and NCLB were assessed with the same 1-to-9 scale used for the assessment of MWS (see Section 2.2); therefore, no scale adaptations were necessary.…”

“…They are among the most damaging and widely distributed foliar diseases of maize and constitute a major concern for South America (Brunelli et al, 2008;De Rossi et al, 2017;Kuki et al, 2018). In Europe, GLS has been observed, but is of no relevance at present (Ramos Romero, 2016), whereas NCLB represents the most important foliar disease here (Galiano-Carneiro et al, 2020;Hanekamp, 2016). GLS is caused by the sibling species Cercospora zeina Crous & U. Braun and C. zeae-maydis Tehon & E. Y.…”