Plant Molecular Biology and Biotechnology Unit, Sart-Tilman, B 22, University of Liege, B-4000 Liege, Belgium.
C R Biol. 2010 Jan;333(1):28-34. doi: 10.1016/j.crvi.2009.11.001. Epub 2010 Jan 25.
The control of field tuber dormancy in the yam (Dioscorea cayenensis-D. rotundata complex) is poorly understood. Although studies have examined single environmental factors and chemical treatments that might prolong tuber dormancy and storage, only a few were focused on further tuber sprouting. The present study concerns microtubers obtained by in vitro culture. When microtubers were harvested (after 9 months of culture) and directly transferred on a new medium without hormones, the tubers rapidly sprouted in in vitro conditions. No dormancy was observed in this case. Harvested microtubers were also stored dry in jars in sterile conditions during 2 to 18 weeks before in vitro sprouting. In this case, microtubers stored during 18 weeks sprouted more rapidly than those stored 8 weeks. A constant "dormancy-like period" (storage duration+sprouting delay) was observed, between 20 and 28 weeks respectively for the more rapid and the slower microtubers. The size of the tubers used for the storage had great influence on further sprouting. The larger they were, the better they sprouted. Light during storage had no effect on the sprouting delay while a temperature of 25 degrees C permit a quicker sprouting than 18 degrees C. The medium used to obtain microtubers could also have an effect on sprouting rate. Ex vitro sprouting was not a problem. There was a delay in sprouting in contrast to in vitro conditions but the rate of 100% was kept. This fact is very important for an agronomical application of this technique to the production of "seeds" directly usable in the field or after culture in the greenhouse.
块茎休眠的田间控制在薯蓣属（薯蓣属-旋花科薯蓣属复合体）中了解甚少。虽然已经研究了可能延长块茎休眠和储存期的单个环境因素和化学处理，但只有少数研究集中在进一步的块茎发芽上。本研究涉及通过体外培养获得的微型块茎。当微型块茎（培养 9 个月后）收获并直接转移到不含激素的新培养基上时，块茎在体外条件下迅速发芽。在这种情况下，没有观察到休眠。收获的微型块茎也在无菌条件下储存在干燥的罐中，在体外发芽前储存 2 至 18 周。在这种情况下，储存 18 周的微型块茎比储存 8 周的微型块茎发芽更快。在更快速和更缓慢的微型块茎中，分别观察到 20 至 28 周之间的恒定“休眠样期”（储存持续时间+发芽延迟）。用于储存的块茎的大小对进一步发芽有很大影响。它们越大，发芽越好。储存期间的光照对发芽延迟没有影响，而 25 摄氏度的温度比 18 摄氏度允许更快的发芽。用于获得微型块茎的培养基也可能对发芽率有影响。外植体发芽不是问题。与体外条件相比，发芽有延迟，但保持 100%的发芽率。对于将该技术直接应用于田间或温室培养后的“种子”生产的农业应用，这一事实非常重要。
