Induction of Multiple Bud Clumps from Inflorescence Tips and Regeneration of Salt-tolerant Plantlets in Beta vulgaris

We developed an efficient method for sugar beet multiplication in vitro from excised immature inflorescence tips. On Murashige & Skoog medium supplemented with 4.4 μM 6-benzylamino- purine and 1.3 μM naphthaleneacetic acid, multiple bud clumps were induced from segments of inflorescence tips. The clumps proliferated rapidly. By radiation of small bud clumps at an appropriate dose and by directional selection for NaCl tolerance, we obtained salt-tolerant bud clumps and regenerated plantlets. The plants were vernalized and self-pollinated. The seeds of the regenerated plants were sown in pots of sand and irrigated every day with a solution of 342 mM NaCl. Some of the seeds germinated and grew normally in the 342 mM NaCl solution, exhibiting higher salt-tolerance than the control ones; such seedlings after the saline selection were transplanted to soil and the plants grew normally and produced plump root tuber similar to controls. The seeds from two selected lines germinated and grew for a few weeks in 513 mM NaCl solution before the seedlings withered. In saline soil where the salt concentration was about 154 mM, the yields of tuber from the plants of three salt-tolerant lines were about 45–50 tons ha⁻¹, approximately 2.6–2.9 times of the controls. It is concluded that we have got salt-tolerant materials with good agronomic traits for sugar beet breeding via selection in vitro.