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Rate and Duration of Spikelet Initiation in 10 Winter Wheat Cultivars¹

Number of splkelets per spike and florets per spikelet are determined early in the life cycle of winter wheat (Triticum aestivum L.). Rate and duration of spikelet formation developmentally precedes and thus directly influences spikelets per spike and fertile florets/spikelet. To study differences among cultivars for rate and duration of spikelet initiation, 10 cultivars varying in phenotype were planted at two dates with four replications each. Plants were sampled and dissected two or three times weekly in the spring to determine the stage of development of the spike. Duration of spikelet initiation was defined as the number of days from double ridge formation to terminal spikelet formation. At harvest, total spikelets per spike were counted. Rate of spikelet initiation was computed as total spikelet number divided by duration of spikelet initiation. Comparisons of interest included differences among benchmark cultivars, between semidwarf and standard height wheats, and between semidwarf pure lines and hybrids. Differences among cultivars for duration of spikelet initiation were significant. Values ranged from 15.3 days for the hybrid ‘DKI04A’ to 21.5 days for ‘Turkey’. Rate of spikelet initiation was also significantly different among cultivars and ranged from 1.4 spikelets/day in DK104A to 0.82 spikelets/day in Turkey. With yield improvements, benchmark cultivars have progressed towards a shorter duration and a faster rate of spikelet initiation. Semidwarf wheats had a longer duration than the standard height wheats but maintained a high rate. Hybrids had a short duration and a fast rate of spikelet initiation. These results suggest the possibility of improving wheat spike types and yield through manipulation of the spikelet initiation stage.

Key Words: Triticum aestivum • Spikelet development • Floret • Yield components

² Former graduate student, now assistant station manager, Pioneer HiBred Int.; associate professor and professor, Dep. of Agronomy, Kansas State Univ., Manhattan, KS 66506.

Received for publication November 18, 1983.