Some Aspects of Photoperiodism in Wheat and Its Wild Relatives

Abstract

Experiments with plants grown in controlled environment conditions examine three aspects of photoperiodism in wheat. A survey of the flowering responses of 20 genotypes of diploid, tetraploid and hexaploid wheat cultivars and wild relatives to growth under three daylengths (8, 12, 16 h) after three durations of vernalisation (0, 4, 10 weeks at 20ºC) showed that all were long-day plants and many responded to vernalisation. The requirement for long days was most stringent among the diploid progenitors and most relaxed among the hexaploid cultivars. However, not even the earliest flowering spring wheat cultivars (among eight) were entirely daylength-neutral. Minimum times to inflorescence initiation appeared to be determined independently of the responses to daylength. Whereas leaf initiation and appearance rates were hardly influenced by daylength, the rate of spikelet initiation responded to it from the beginning of floral induction, well before the appearance of double ridges. Comparison of the times to double ridges among near-isogenic lines of four spring wheat cultivars (Ciano 67, Yaqui 50, Rescue and April Bearded) showed that each of the three dwarfing genes Rht1, Rht2 and Rht3 advanced inflorescence initiation but without changing the response to daylength.