Controlled deterioration and accelerated ageing tests to predict seedling emergence of watermelon under stressful conditions and seed longevity

摘要

The emergence of 19 commercial seed lots (10 in 2005 and 9 in 2006) of watermelon (Citrullus la.na.tus Matsum and Nakai, Thunb.) with laboratory germination >90% were compared in stressful conditions of low temperature (LTE, early spring), mechanicalstress (MSB, 6 cm deep sowing) and salt stress (SSE, 200 mM NaCl). The emergence percentage ranged between 12 - 54% for LTE, 19 -75%, for MSB and 43 - 91% in 2005 and 35 - 80% at LTE, 13 - 82% at MSE, 45 - 92% at SSE in 2006. The radicle emergence of thelots was determined after controlled deterioration (CD) at 40 and 45 deg C in 2005, or at 45 and 47 deg C in 2006, with 20% or 24% moisture content for 48, 72, 96, 120, 144 hours in 2005 and 48, 72, 96, 120, 144, 168 hours in 2006. The accelerated ageing test was also conducted at the same temperatures and ageing durations in both years. The germination range of the seed lots increased in both CD and AA as the ageing period was extended. Germination after all combinations of CD was positively and significantly (p<0.05) correlated with LTE, MSE and SSE. However, most very highly significant correlations (p<0.001) were observed after CD for between 48-96 hours at 45 deg C and at 24% in both years. Germination after the AA test was correlated with LTE, MSE and SSE. This was especially seen at 40 and 45 deg C. The highest number of very highly correlated combinations was found after AA at 47 deg C for 120 or 144 hours. The initial laboratory germination was significantly related to LTE, MSE and SSE, butthe correlation values were much lower than those of both ageing tests. Laboratory germination after 6 month storage at 25 deg C and 12% seed me was closely correlated with germination after both AA and CD tests (p<0.001). The results show that both ageing tests can be used to predict seedling emergence under stressful conditions. The optimum CD conditions of 48 hours and 24% me at 45 deg C and AA conditions of 120-144 hours at 45 deg C are suggested as a routine predictive test of watermelon seed emergence and longevity.