In Vitro Screening And Primary Identification Of Thermotolerant Variants In Gerbera Hybrida

Gerbera hybrida, one of the ten greatest cut flowers in the world, is a kind of cold-half-resistant flower. Because almost all of the varieties in Gerbera are maladjusted to high temperature, it is necessary to breed thermotolerant varieties in practice. In this research, we established an in vitro screening procedure for thermotolerant variants with six varieties of Gerbera including Lilabella(F3), Diablo(F25), Vino(F30), Sangria(F32), Pinkas(F39) and No.5 Shengzheng( S5). 60Co γ irradiation and EMS/PYM treatment were used for mutation of the plants and the proper HYP dosages for screening in the in vitro culture were investigated. .The physiological and biochemical characteristics of the three thermotolerant variant lines from in vitro screening with high temperature or HYP were analyzedcomparing with the control. The main results are summarized as follows:1. The proliferation rates of in vitro shoots increased steadily after 2 h heat shock of 45 ℃. The relative electrolyte leakage of cell membrane showed well relat-ionship to the survival rate of shoots in vitro. The appearance of heat damage and the thermotolerance at 35℃ or 45℃ were different among the different varieties of Gerbera and it is necessary to screen thermotolerant lines under different pressures for them. The results showed that 10 to 25 d at 35℃and 20 h at 45℃ were the proper intimidate pressure ranges for each variety.2. The dosage of 60Co γ irradiation in 5000 rad was proper for thalami mutation and it could be moderately higher for shoots in vitro of all varieties except F3. The thalami were more sensitive to the treatment time than the concentration when EMS was used as a mutagen and 4 h was the proper treatment time under 0.4% EMS. PYM is another mutagen we used and 1.5 h soak with 40 g/ ml PYM was proper for pre-cultured of thalami. The survival rates and the variation of the color and shape in leaves after screening with high temperature showed that our experimental procedurewas effective and several primary thermotolerant lines in S5, F25, F32 were selected after 6 to 9 heat screening.3. The effects of HYP with different concentrations on the culture of thalami and shoots in vitro were investigated. The results showed that 0.4mg/ml HYP was the proper dosage for thalami and shoots in vitro and 0.6mg/ml was appropriate for 25 d precultured thalami. The primary variation lines were isolated from S5 after 5 and 6 HYP screening.4. The shoots in vitro of three thermotolerant lines of SR7, SHP5 and SE6 showed higher survival rates at 35 ℃and 45 ℃ comparing with the control. Among three lines SR7 had a remarkable difference with the control under the treatment of 15 days with35 ℃ and it is a new material of thermotolerant variation we selected. The content of Pro and the activities of POD and SOD in SR7 also increased remarkably indicatingthese biochemical changes may be related to the thermotolerance of Gerbera.Our results showed above demonstrated that it was feasible to isolate thermotolerant variant lines by in vitro screening technique and a large scale of screening was required.