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In vitro radio-sensitivity of different genotypes and explants of rose (Rosa hybrida)

Kahrizi, Z.A., Kermani, M. Jafarkhani, Amiri, M., Vedadi, S., Hosseini, Z.
Journal of horticultural science & biotechnology 2013 v.88 no.1 pp. 47-52
Rosa, explants, gamma radiation, genotype, irradiation, leaves, lethal dose 50, mutagenesis, mutants, plant breeding, regression analysis, survival rate
In vitro techniques, in combination with induced mutations, are used to speed-up plant breeding programmes. One of the important steps when inducing mutations is to determine the radio-sensitivity (i.e., the lethal dose for 50% of samples; LD50) of the species. In order to determine the LD50 of rose (Rosa hybrida), the effects of different doses of gamma-rays on in vitro nodal sections of five rose genotypes ('Apollo', 'Maroussia', 'Dolce Vita', 'Black Baccara', and 'Beauty by Ogre') and on leaf explants of two rose genotypes ('Apollo' and 'Maroussia') were investigated. Nodal sections were exposed to various doses of gamma-irradiation (0 - 100 Gray) and, based on the higher coefficient of determination (R2) in regression analysis, survival rate was selected as a suitable parameter for determining LD50. Leaf explants were also subjected to different doses of gamma-irradiation (0 - 50 Gray) and regeneration percentages were chosen as the parameter to calculate LD50. The results indicated that, as the dose of irradiation increased, growth parameters were significantly affected. The LD50 was determined to be 40 - 50 Gray for 'Dolce Vita', 'Black Baccara', and 'Beauty by Ogre', whereas it was 50 - 60 Gray for 'Maroussia', and 60 - 70 Gray for 'Apollo'. Apart from the effect of genotype, the type of explant was also important when choosing the correct dose of gamma-irradiation. Leaf explants were more sensitive than nodal sections, and the recommended LD50 for leaf explants was 20 - 30 Gray for both 'Apollo' and 'Maroussia'. Morphological observations revealed one mutant in each of the genotypes 'Maroussia' and 'Black Baccara'. Three mutants of 'Apollo' which were significantly different from the original progenitor were also identified. This is the first report on gamma-ray doses suitable for mutation breeding of in vitro nodal sections and leaf explants of rose.