Changes in seed quality (assessed by potential longevity, i.e. the value of the seed lot constant K1 of the seed viability equation) in three contrasting cultivars of rice (Oryza sativa L.) were monitored during seed development and maturation in two temperature regimes, viz 28/20°C and 32/24°C (12/12 h), provided by controlled environments. Mass maturity (defined as the end of the seed-filling phase) varied only between 18 and 20 d after 50% anthesis. In five of the six treatment combinations maximum potential longevity was not achieved until 12-19 d after mass maturity. In contrast, the maximum potential longevity of seeds of a japonica rice cultivar produced in the warmer regime was obtained in the first harvest after mass maturity. After mass maturity, the potential longevity of the japonica rice seed lots produced in the warmer environment was much less than that for the cooler environments. Maximum potential longevity was also consistently greater in the cooler than the warmer regime for the two indica cultivars, although the difference in K1 was small (0·3-0·5). The deleterious effect of increase in temperature on seed quality development was not detected until after mass maturity. Maximum potential longevity in the cooler regime was greatest in the glutinous indica (K1 = 3·9) and least in the japonica cultivar (K1 = 3·1). It is concluded that the japonica cultivar is not as well adapted to warm seed production regimes as the indica cultivars. Consequently, subject to confirmation, this research suggest that the seed production of japonica cultivars for long-term genetic conservation should be undertaken, whenever possible, in warm temperate environments.
Ellis, R.H.; Hong, T.D.; Jackson, M.T. Seed Production Environment, Time of Harvest, and the Potential Longevity of Seeds of Three Cultivars of Rice (Oryza sativa L.). Annals of Botany (1993) 72 (6) 583-590. [DOI: 10.1006/anbo.1993.1148]