EFFECT OF PLANT HORMONES ON MICROPROPAGATION POTENTIAL OF SUPERIOR STRAWBERRY GENOTYPES AND THEIR PARENTS VIA SHOOT-TIP CULTURE

Abstract

In this study, the effects of different hormones and their doses on the micropropagation and rooting of two strawberry cultivar candidates (291 and 299) selected from last step of breeding program carried out by Horticulture Department of Cukurova University (Adana, Turkey) and their parents (Rubygem and Kaşka cultivars developed by Horticulture Department of Cukurova University) were investigated using shoot-tip culture. Nodal segments of strawberry runners were sterilized through keeping in 7% sodium hypochlorite solution containing 1–2 drops of Tween-20 for 10 minutes. Five different Murashige ve Skoog (MS) nutrient media combinations containing 6-Benzylaminopurine (BAP) and Thidiazuron (TDZ) at the ratios 0.75 and 1.50 mg L–1 were tested (Medium 1: MS + 30 g L–1 sucrose, 7 g L–1 agar, Medium 2: MS + 30 g L–1 sucrose, 7 g L–1 agar + 0.75 mg L–1 BAP, Medium 3: MS + 30 g L–1 sucrose, 7 g L–1 agar + 1.50 mg L–1 BAP, Medium 4: MS + 30 g L–1 sucrose, 7 g L–1 agar + 0.75 mg L–1 TDZ, Medium 5: MS + 30 g L–1 sucrose, 7 g L–1 agar + 1.50 mg L–1 TDZ). During the study, darkening, infection and rooting rates (%), shoot number per plant in both first and second sub-culture, root number per plant and root length (cm) parameters were examined. Use of four genotypes/cultivars and five nutrient media, this study was planned according to the factorial design of randomized plots with three replications. JMP package program and LSD test were used for statistical evaluation of data obtained. It was found that the media including TDZ was generally more effective than BAP in terms of shoot proliferation in both first and second sub-culture. The number of shoots per explant varied from 0 to 4.18 shoots per explant in the first sub-culture. Regarding to mean of genotypes and media, Kaşka cultivar (2.53 shoots per explant) and medium 5 (2.88 shoots per explant) gave the best results, respectively. In the second sub-culture, the number of shoots per explant changed between 0.33 and 4.83 shoots per explant. According to mean of genotypes and media, Kaşka cultivar (3.23 shoots per explant) and medium 4 (3.63 shoots per explant) were found to be the best material and medium, respectively. Regarding to rooting parameters, it was determined that the hormone-free MS medium was highly efficient. The number of root per in vitro plant varied from 0 to 30 roots per in vitro plant. According to mean of genotypes and media, Rubygem cultivar (9.60 roots per in vitro plant) and medium 1 (22.30 roots per in vitro plant) gave the best results, respectively. Root lenght changed between 0 and 5.04 cm. Regarding to mean of genotypes and media, the best values were obtained from Kaşka cultivar (2.10 cm) and medium 1 (3.89 cm), respectively. The value of 0 obtained from rooting parameters refers to in vitro plants that can not be rooted. Infection rate was low in both sub-cultures. Especially in the first sub-culture, it was observed only in the genotype 299 cultured in the medium 3. In the second subculture, infection was detected at low rates in the genotypes 291 and 299 and Rubygem cultivar cultured media 2, 3 and 5. No darkening was observed in the explants cultured in both sub-cultures. Based on genotypes, Kaşka cultivar developed in the Horticulture Department of Cukurova University (Turkey) was found to be superior in terms of both shooting and rooting criteria. Achieving successful results of this cultivar will speed up its use in breeding studies. Based on the study result and literature, it was concluded that the selection of the appropriate hormone type and dose are genotype-dependent.