Early growth of flint maize landraces under cool conditions
Cold stress is a major factor that limits the success of environmentally sound cultivation of maize in central and northern Europe. This study evaluated the early growth of seven groups of Swiss Flint maize landraces (Zea mays L. ssp. mays) of different geographic origin under controlled cool conditions by assessing shoot and root traits. Measurements of plants, subjected to a permanent cold stress of 15/13°C (day/night), were made at the three-leaf stage of the check Magister, a hybrid of approved good early vigor. The ranking (univariate analysis of variance) and the multivariate clustering of the groups of landraces differed when root and shoot traits were included in the evaluation. Furthermore, the association of phenotype with geographic parameters was successful only when root traits were considered. Groups of Swiss landrace accessions expressed three types of phenotypes under cold conditions: (i) large leaf area and an extensive axile root system for landraces from the Tessin and the Poschiavo valley (i.e., south of the Alps), (ii) large leaf area and a short axile root system in landraces from the Linth valley, the lower Rhine valley, and the posterior Rhine valley, all of which are north of the Alps, (iii) small leaf area and a short axile root system in landraces from the anterior Rhine valley and the Swiss Rhône valley. The method of root phenotyping (i.e., a simple and rapid determination of traits of axile roots) proved suitable for the characterization of a large number of samples, as is typically required in quantitative genetic analysis.