Inheritance of reproductive stage cold tolerance and adaptability in two Japonica x indica rice crosses

The inheritance of reproductive stage cold tolerance and adaptability was studied in seven generations of two japonica x indica rice crosses. Plants eannarked for cold treatment were subjected to low-temperature at 20°/15°C for 5 days in the naturally lighted 3-SAL cabinets in the phytotron at the International Rice Research Institute, Manila, Philippines at the first indication of panicle exsertion. The additive-dominance model was not a good fit for flowering duration, percent fertility and depression in percent fertility. Of the three epistatic effects, dominance x dominance and additive x additive types were more important. Complete to overdominance was operative for the three characters. The narrow sense heritabilities ranged from 93% to 98%.