Variation in alfalfa (Medicago sativa L.) for germination and seedling vigor at suboptimal temperatures: and laboratory and field response to selection within six alfalfa populations

Abstract

Successful establishment of alfalfa (Medicago sativa L.) in the early spring, particularly with no-till seeding, requires rapid germination and vigorous growth at cool temperatures. This study was conducted (i) to evaluate the extent of variation among ten alfalfa cultivars, 'Marathon' red clover (Trifoliumpratense L.), and 'Norcen' birdsfoot trefoil (Lotus comicukuus L.) for germination time (GT) and initial radicle growth rate (IRGR) at three temperatures considered suboptimal for germination; (ii) to evaluate variation among seed lots within seven alfalfa cultivars for GT at 5 and 10 C; and (iii) to determine if field emergence was correlated with traits measured in the laboratory. The IRGR of cultivars increased with temperature and the GT of cultivars decreased, as did the GT of seed lots within cultivars. When seed lots within cultivars were evaluated, differences among cultivars for GT were seen only at 5 C. Both GT and IRGR measured in the laboratoiy were correlated with field emergence 8 d after planting at one of two locations tested. Cultivars with superior laboratory GT and IRGR may perform better under cool field conditions. Abbreviations: GT = Germination Time; IRGR = Initial Radical (jrowth Rate; FD = Fall Dormancy.