Germination and seedling growth at low temperature: comparisons of Lotus species and effects of selection and seed source in L. pedunculatus Cav.

Abstract

The association of seed size, type of life cycle (annual/perennial), and ploidy (diploid/tetraploid) with low temperature (5˚C), germination rate, and seedling growth was examined under controlled conditions in 9 Lotus species. Seeds harvested at 2 localities from 2 populations of L. pedunculatus, one selected for early flowering and the other unselected for flowering time, were included in the study to examine the influence of selection history and seed provenance on cold temperature germination rate and seedling growth. Seed size and ploidy level were not significant factors influencing germination rate of the Lotus species, but both seed size and life cycle had significant associations (P< 0.01) with seedling dry weight. Seed of the selected, early flowering population of L. pedunculatus germinated significantly faster than that of the unselected population (P< 0.01), and this difference was more pronounced in seed from the site where early flowering would confer advantages of better seed production and the potential for better persistence through seedling recruitment. Anarrow-sense heritability estimate for the germination rate of L. pedunculatus was high at the 2 localities (0.84 ± 0.17 and 0.65 ± 0.16) and it was thus promising as a selection criterion for improved establishment. If interspecific hybridisation can be achieved between the annual and perennial species, a longer term prospect exists to utilise the high capacity of annual species to germinate and grow at low soil temperatures.