Swiss Flint maize landraces—A rich pool of variability for early vigour in cool environments

Today's modern Dent × Flint maize (Zea mays L. ssp. mays) hybrids have a high yield potential but often lack satisfying early vigour under typical low spring temperatures of temperate latitudes. Maize was introduced into Europe already in the 16th century and until the 1950s, landraces evolved and adapted well to various geographically restricted and climatically marginal regions in Europe. Therefore, the objective of this study was to assess representatives of the large pool of Swiss Flint maize landraces for their early vigour under cool conditions in the field. A set of 17 landrace accessions were tested for 2 years at sites on the Swiss plateau (450 and 550 m a.s.l.) and in the foothills of the Swiss Alps (830 and 870 m a.s.l.). Plant emergence (PE), emergence index (EI), the efficiency of the photosystem II (Fv/Fm), leaf greenness (SPAD) and plant dry weight at the three- and six-leaf stages (DW3P, DW6P) were measured.Compared to a modern European Dent × Flint reference hybrid of good early vigour (Magister), superior early growth was found for several accessions that originated in northern alpine valleys. Three of these landraces (176RV, 151RV and 055LV) combined their good early growth with good early establishment (PE) and seemed to break the usually observed negative association between PE and DW3P or DW6P, a prerequisite for high-yielding plant stands. Plant emergence and establishment were often markedly better for landrace accessions from the Southern Alps, mainly from Tessin region, but their growth performance was significantly lower at the three- and the six-leaf stages. We conclude that northern Swiss landrace accessions in particular show good potential for improving early vigour of maize in cool field environments and we propose that the fast, non-destructive early vigour scoring is an efficient tool for assessing differences in growth in the field during these early plant stages.