Vernalization in wheat II. Genetic variability for the interchangeability of plant age and vernalization duration

Abstract

Differences in response to vernalization in wheat ( Triticum aestivum L.) were quantified through controlled environment experiments with 26 lines with diverse geographical origins. Vernalization treatments of 0 to 56 d were applied to plants at their first leaf stage. All plants headed irrespective of duration of vernalization treatment. Vernalization response was assessed through the change of final leaf number (FLN) on the main stem at heading. Five lines did not respond to vernalization. FLN for vernalization-sensitive lines generally decreased to a minimum as days of vernalization treatment increased. Plants at and after the stage where additional vernalization did not reduce FLN were vernalization insensitive. The quantitative features of this vernalization response, up to the point of insensitivity, were characterized with a linear regression: ( F i − 6) = α − βT v, where F i is FLN observed for a particular vernalization treatment, T v is the time in days of that vernalization treatment, and α and β are the Y-intercept and the slope of the regression, respectively. This model fitted the experimental results well. The parameters α and β varied among lines, and are useful for quantifying vernalization response in wheat. The implication of each parameter can be interpreted biologically: α is the “changeable number of leaves”, i.e., how many leaves can be potentially decreased by vernalization treatment, and β represents the “exchange rate” between leaf numbers and vernalization days, i.e., how many leaves can be reduced by one day of vernalization treatment.