| To satisfy the increasing demand of intensive production, an efficient micropropagation system, genetic stability evaluation to the in vitro plantlets and shoot regeneration from leaves of four strawberry (Fragaria ananassa Duch.) cultivars were carried out in this present study. The main results are as follow:1 Establishment and optimization of aseptic culturesThe shoot tip of stolon showed the best germination after being inoculated in MS + BA(0.5 mg/L) + IBA(0.2 mg/L ) + sucrose (3.0%) + agar (0.7%). MS medium supplemented with BA(0.5-1.0 mg/L) + NAA(0-0.1 mg/L )+sucrose (3.0%)+agar (0.7%) gave the best propagation ratio and considerably improved shoot vigor. Following the shoot elongation stage, shoots of 4-5 cm in height cultured in 1/2MS for 20 d showed the best effect on rooting. With acclimatization of 15 d in autoclaved soil, the plants showed 90 % of survival after transplantation. Using just-mentioned procedure, the optimized in vitro micropropagation system for the four cultivars was established.2 Establishment and optimization of regeneration from leafGenotype, explants, types and concentrations of plant growth regulators, sub-culture cycle and dark duration significantly affected the regeneration rate and quality of adventitious buds.The stipule from in vitro shoots 20-30 d after transfer was used to induce regeneration. MS medium supplemented with BA (2.0 mg/L) + LAA (0.1 mg/L )+sucrose (3.0 %)+agar (0.7 %) and 7-14 d dark treatment gave the best regeneration ratio and the highest bud number per explant. However, no statistical difference in regeneration ratio was investigated among the treatment using different concentration of AgNO3.3 Horticultural performance of in vitro plants grown in field The in vitro propagated plants showed strong growth vigor when they were transferred to the field. Compared with in vivo propagated ones, size and weight of fruit were considerably improved in in vitro propagated plants. The juice yield, soluble solid content and total sugar of fruit yielded from in vitro propagated plant were higher than that from in vivo propagated ones, while the total acid of the former was lower than that of the latter.4 Genetic stability assessment of in vitro shootsUsing 62 and 53 arbitrary primers, RAPD markers were employed to evaluate the genetic stability of different cycles of sub-cultured and different lines at the 15th cycle of transfer in four strawberry genotypes, respectively. No DNA variation was scored in the in vitro plants that had been transferred many as 15 as cycles. |
