The emergence of 22 commercial seed lots (12 in 2005 and 10 in 2006) of melon (Cucumis melo L.) with laboratory germinations greater than 90% were compared in low temperature (LTE), mechanical stress (MSE), high temperature (HTE), and salt stress (SSE) sowing conditions. The seedling emergence percentage ranged between 18% and 79% for LTE, 15% and 90% for MSE, 27% and 84% for HTE, and 49% and 92% for SSE in 2005; and 43% and 85% for LTE, 30% and 82% for MSE, 56% and 91% for HTE, and 49% and 89% for SSE in 2006. The germination of the lots was determined after controlled deterioration (CD) with 20% or 24% moisture content (MC) and accelerated aging (AA) at 40 and 45 °C in 2005; or at 45 and 47 °C in 2006 for 48, 72, 96, 120, and 144 h. Germination after various combinations of CD and AA was positively and significantly (P < 0.05) correlated with LTE, MSE, HTE, and SSE. Correlation values (0.17 to 0.78) of the initial laboratory germination were much lower than those of both aging tests. The optimum CD conditions of 48 h and 20% MC at 45 °C and AA conditions of 120 h at 45 to 47 °C are suggested as vigor tests to estimate relative seedling emergence of melon seeds.
The laboratory germination (radicle emergence) percentages of 9 watermelon, 12 melon, and 7 cucumber seed lots were tested after storing in relatively adverse storage conditions of 25 °C and 12% mc for 6, 12, and 18 months in sealed aluminum foil packets. The laboratory germination (radicle emergence) of lots was determined after controlled deterioration (CD) at 45 °C with 20% or 24% moisture content (mc) for 48, 72, 96, 120, and 144 h. The accelerated aging test (AA) was conducted at 45 °C for the same aging periods. A number of seed lots was dead by 12 and 18 months in watermelon and cucumber, respectively. Various combinations of test regimens were found to be correlated with laboratory germination after 6 months storage, but the most consistent regimens for AA tests was 96 h at 45 °C in all species (r = 0.71 to 0.98). In the CD tests, 72 h with 20% mc at 45 °C gave the best correlation (r = 0.86 to 0.96). These conditions of highest correlation were observed after laboratory germination after 6 months storage and are suggested as good predictors of storage life in cucurbit seed lots. The initial standard germination before storage was also significantly correlated with seed longevity, but the correlation coefficient was generally lower (r = 0.60 to 0.83) than the AA and CD test results and separation of lots less clear.
The effect of moisture on seed longevity during experimental storage was investigated in pepper (Capsicum annuum) cultivar Demre. Seeds were stored hermetically at 7.0%, 8.6%, 9.5%, 10.5%, and 12.1% moisture content (MC; percent fresh weight basis) and 35 °C for up to 306 d. Viability (normal germination) was assessed periodically and the seed viability equation moisture constants, KE and CW, estimated by regression of log σ (the sd of distribution of seed death in time) with log MC. KE and CW values were found to be 7.767 and 4.670, respectively. The newly found moisture constants were combined with the temperature constants that had already been proposed as universal for all orthodox seeds (CH = 0.0329, CQ = 0.000478) and their validity was tested by predicting the viability loss in another pepper cultivar, Carliston. The Ki of the Carliston cultivar was determined by controlled deterioration at 40 °C and 14% MC. The observed viability loss between 30 and 270 d at 25 °C and 10% seed MC was closely related to that predicted by the equation R2 = 0.982 (P < 0.001).