Fig. 3

General scheme of the fertility transition for two-line male sterile rice. The position of red-colored section (from P4 to P6) was modified (added) according to Yao et al. (1995). The horizontal bars represent temperature and day length. The zig-zag lines and the red arrow indicate that the interval lengths between P4 and P3, P6 and P7, P8 and P9, and P4 and P6, respectively, fluctuate due to the changes of photo-thermo-conditions, which constitute the “sterility-fluctuation zone”. P6 indicates the CSIT (daylength). The transition from P6 to P9 corresponds the stable-fertility zone under optimal photo-thermo-conditions while the transition from P3 to P2 corresponds to the stable-sterility zone due to high temperatures and long days. The transition from P9 to P10, or from P2 to P1 is not recommended for self-pollination (propagation) or hybrid seed production because of the extremely low or high temperature, respectively. The transition from P4 to P6, which was not reported by Yao et al. (1995), is the zone of the effect of cumulative ELT which may explain the fertility restoration observed in two-line male sterile rice under ALT (The DAT of the ALT is higher than the CSIT of two-line male sterile rice, but the nighttime temperature is lower than the CSIT)