Lateness Gene Concerning Photosensitivity Increases Yield, by Applying Low to High Levels of Fertilization, in Rice, a Preliminary Report

Various genes controlling heading time have been reported in rice. An isogenic-line pair of late and early lines “L” and “E” were developed from progenies of the F1 of Suweon 258 × an isogenic line of IR36 carrying Ur1 gene. The lateness gene for photosensitivity that causes the difference between L and E was tentatively designated as “Ex(t)”, although it's chromosomal location is unknown. The present study was conducted to examine the effects of Ex(t) on yield and related traits in a paddy field in two years. Chemical fertilizers containing N, P2O5 and K2O were applied at the nitrogen levels of 4.00, 9.00 and 18.00 g/m2 in total, being denoted by "N4", "N9" and "N18", respectively, in 2014. L was later in 80%-heading by 18 or 19 days than E. Regarding total brown rice yield (g/m2), L and E were 635 and 577, 606 and 548, and 590 and 501, respectively, at N18, N9 and N4, indicating that Ex(t) increased this trait by 10 to 18%. Ex(t) increased yield of brown rice with thickness above 1.5mm (g/m2), by 9 to 15%. Ex(t) increased spikelet number per panicle by 16 to 22% and spikelet number per m2 by 11 to 18%. Thousand-grain weight (g) was 2 to 4% lower in L than in E. L was not significantly different from E in ripened-grain percentage. Hence, Ex(t) increased yield by increasing spikelet number per panicle. It is suggested that Ex(t) could be utilized to develop high yielding varieties for warmer districts of the temperate zone

Gravitropic Response of Acetylcholinesterase and IAA-inositol Synthase in Lazy Rice

We previously observed that gravistimulation changes the localization of acetylcholinesterase (AChE) and IAA-inositol synthase in maize shoots. In the present study, we analyzed the localization patterns of these enzymes in a lazy strain of rice, which lacks gravitropic responses. AChE was detected by color development due to enzymic reaction in the coleoptile of dark-grown rice plants under a light microscope. IAA-inositol synthase was detected immunochemically using an anti-IAA-inositol synthase polyclonal antibody. Gravistimulation was given by moving 5-d-old rice seedlings from a vertical to a horizontal position. AChE and IAA-inositol synthase in both normal and lazy rice strains were both distributed asymmetrically in the vascular bundles in the lower half of the horizontally oriented coleoptile at the 90th min. At the 4th h, they were distributed asymmetrically in normal rice, but symmetrically in the lazy rice. The immunoreaction of IAA-inositol synthase in the lazy rice was weak compared to that of the normal rice. Neostigmine bromide inhibited AChE activity and asymmetric distribution of IAA-inositol synthase in both normal and lazy rice strains. The results showed that AChE responded to gravistimulus, and consequently controlled the distribution of IAA-inositol synthase in both normal and lazy rice strains