Analysis of Spike Development of Three Spring Wheat Genotypes under Various Cultural Conditions

Abstract

The spike development in three spring wheat genotypes was studied under various cultural conditions. Two genotypes weakly responsive to cultural conditions in spikelet number per spike (T1 from Nepal and Haruyutaka from Japan) and one weakly responsive to cultural conditions in spike length (U6 from Xinjiang Uygur district of China) were grown under three cultural conditions with different seeding density and fertilization levels : 680 seeds m−2 without fertilizer (unfavorable), 340 seeds m−2 with common fertilizer (common) and 170 seeds m−1 with double fertilizer (favorable). The durations of the vegetative phase, spikelet phase and the spike elongation phase were scarcely influenced by these cultural conditions, although the leaf number was influenced. The development of spikelets seemed to be determined by several factors other than those affecting the developmental processes of the spike. In U6, the increase in shoot apex length during the floral initiation period under the favorable condition was accompanied with an increase in double ridge number and spikelet number per spike, but such a relationship was not observed in T1 and Haruyutaka. T1 and Haruyutaka had a higher rate of spikelet formation under the favorable condition than under the unfavorable condition, but U6 showed a rather lower rate of spikelet formation under the favorable condition. Thus, the effects of the cultural conditions on the spikelet number per spike differed with genotype. At the time of terminal spikelet formation, U6 tended to have a longer spike than T1 and Haruyutaka. However, since the rate of spike elongation was higher in T1 and Haruyutaka than in U6, the spike length at anthesis was shorter in U6.