DEVELOPMENTAL MORPHOLOGY OF THE INFLORESCENCE IN HEXAPLOID WHEAT CULTIVARS WITH AND WITHOUT THE CULTIVAR NORIN 10 IN THEIR ANCESTRY

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Abstract
The morphological development of the spike in short-statured hexaploid wheats (Triticum aestivum L.) derived from the cultivar Norin 10, and in Norin 10 as well, was markedly different from that in standard hexaploid wheats. In Norin 10 and its derivatives, the single ridges (slowly growing leaf primordia) on the elongating apex were considerably larger and spikelet primordia initiation and expansion were markedly delayed, resulting in a long apex with many single ridges. When spikelet development commenced, it was much more synchronous and hence gave rise to longer heads than in standard wheat in which spikelet development began soon after the start of the elongation of the apex. In most Norin 10 derivatives, more spikelets were initiated than in standard wheat. Apical dominance in the spike appeared to be stronger than in standard wheats. Also, apical dominance within the individual spikelets appeared to be greater, the net result being more fertile florets per spikelet. The developmental pattern of the spike of Norin 10 and its derivatives resembled, to a marked degree, the developmental pattern of rye (Secale cereale L.).