| Present research, driven by the demands in seed potato industry for being compatible of seed potato storage to the crop growth in next season, has objectives of controlling the dormancy and sprouting synchronism of stored microtubers grown in vitro and minitubers produced in greenhouses.The dormancy and sprouting of microtubers and minitubers produced in spring and autumn seasons were monitored during storage at 4 and 20℃in darkness or supplied with artificial light. Two potatoes varieties, Favourita and Nanzhong 552, were employed. Main results obtained are below:1. During storage in constant temperature, dormancy of microtubers of Favourita and Nanzhong 552 were 35 and 60 days in 20℃, respectively, and this was prolonged to about 150 days when stored in 4℃. After dormancy breaking, percentage of sprouting followed a sigmoid curve but significant variations were observed between two varieties. From dormancy breaking to 80% sprouting, 110 days in 20℃and 130 days in 4℃were needed for Favourita, while about 85 days and 180 days were respectively needed for Nanzhong 552.2. Alternative-temperature storage of potato microtubers combined with 20℃and 4℃showed that sprouting was relatively slow after dormancy breaking, then increased rapidly when the sprouting reached 20%, and the rate slowed down again after 80% of sprouting. The whole process could be represented by a sigmoid curve. Terminating representative sprouting stages as dormancy breaking (5% sprouting), rapid sprouting (50% sprouting) and full sprouting (80% sprouting), a relationship between the days need in 20℃(y) and that in 4℃(x) in these three stages could be established and described by the function of y = ax~2 +bx + c. For Favorita, the relationships were presented as y = 0.0011x~2- 0.4394x + 42.907, y = 0.0015x~2- 0.6346x + 72.916 and y = 0.0018x~2- 0.8343x + 104.87, respectively; and for Nanzhong552 they were y = 0.0001x~2- 0.1648x + 25.24, y = 0.0003x~2 - 0.2593x + 54.564 and y = -0.0005x~2 - 0.3692x + 75.488, respectively.3. Potato minitubers stored in the constant temperature showed that, spring produced minitubers had shorter dormancy than autumn produced ones as indicated by difference of about 30 days in 20℃and 50 days in 4℃. Exposure to light prolonged dormancy for one week in high temperature storage and for two weeks in low temperature compared with the storage in darkness. After dormancy breaking, percentage of sprouting followed a sigmoid curve but significant variations were observed between production seasons and storage temperatures. A longer period of sprouting was accompanied with spring produced minitubers and those stored in low temperature refering to the minitubers produced in autumn and that stored in high temperature.4. Potato minitubers stored in alternative-temperature had similar patterns as the microtubers in domancy breaking and sprouting. Since only 7 days of difference between storage in darkness and with light in either of the sprouting stages, the model established in darkness storage was applied to estimate the storage under light. Combinding the data of two varieties, a relationship between the days need in 20℃(y) and that in 4℃(x) in dormancy breaking (5% sprouting), rapid sprouting (50% sprouting) and full sprouting (90% sprouting) could be established as y = ax~2 + bx + c. For minirubers of Favorita produced in spring, fumulars caculated respectively for the three sprouting stages were y = 0.0025x~2 -0.5876x + 35.802, y = 0.0021x~2 - 0.7008x + 59.722 and y = 0.0022x~2 -0.817x + 79.129; for minitubers of Nanzhong552 produced in the same season were y = 0.0006x~2 - 0.3737x + 32.048, y = 0.0006x~2 - 0.3484x + 55.988 and y = 0.0003x~2 - 0.346x + 70.358. Regarding the minitubers grown in autumn, the relationships setup respectively in the three storage stages for Favorita were showed as y = 0.0021x~2 - 0.6787x + 55.482, y = 0.002x~2 - 0.7378x + 71.539, and y = 0.0018x~2 - 0.7522x + 84.904; and for Nanzhong 552 were y = 0.0015x~2 - 0.5219x + 51.012, y = 0.0012x~2 - 0.5476x + 64.834, and y = 0.0016x~2-0.6439x +79.175.5. Validation of the model by fitness-analysis of the theoretical data estimated with the functions established and the data investigated in corresponding storage conditions demonstarted that, except for the stage of microtubers in 80% sprouting, all of the estimated and observed data fitted well, indicating that the models are applicable to predict the days needed to reach a certain sprouting rate of microtubers and minitubers under either 4℃or 20℃storage, or in combination of them. When the models developed in the darkness were applied to the data observed in the storage with light, in spite of some measuring points did not fit signifantly such as minitubers of Favorita at 5% sprouting and minitubers of Nanzhong552 at 5% and 90% sprouting, most of the cases were fitted well. |
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