Growth and yield properties of near-isogenic wheat lines carrying different photoperiodic response genes

Near-isogenic lines (NILs), carrying different combinations of Ppd-1 genes in the genetic background of an early-maturity cultivar Abukumawase were grown at two sites for two years to elucidate the effects of photoperiodic response genes on the growth and yield of early-maturity wheat (Triticum aestivum L.) in central and southwestern Japan. Photoperiod-insensitive genes, Ppd-B1a and Ppd-D1a, accelerated young spike development, and this effect was predominant with Ppd-B1 with no additive effect among them. Ppd-B1a and Ppd-D1a also advanced the jointing stage, heading, and maturity, and the effect of Ppd-B1a on the jointing stage and heading was stronger than that of Ppd-D1a. An additive effect of two genes was detected for heading. Besides, Ppd-B1a and Ppd-D1a reduced culm length and grain weight, although the reduction effect on grain weight was not significant. Meanwhile, the mean temperature from double ridge formation stage to heading was lower in NILs with photoperiod-insensitive genes than in NILs with photoperiod-sensitive gene, and there was a significant correlation between mean temperature from double ridge formation stage to terminal spikelet formation stage and spikelet number per spike as well as between mean temperature from terminal spikelet formation stage to heading and grain number per spikelet. Therefore in a genetic background of extremely early-maturity line of spring type wheat, photoperiod-insensitive genes accelerated wheat growth and reduced spikelet numbers in central and southwestern Japan, and the effect of Ppd-B1a was stronger than that of Ppd-D1a.