Abstract

ALVAREZ-HOLGUIN, Alan et al. Optimal dose of gamma irradiation with ⁶⁰ Co for mutagenesis induction in grasses. Nova scientia [online]. 2017, vol.9, n.19, pp.65-82. ISSN 2007-0705.  https://doi.org/10.21640/ns.v9i19.886.

In plant breeding programs, the lethal dose (LD50) and the median growth reduction (GR50) are parameters used to determine appropriate irradiation doses to induce effective mutations. The objectives were to determine the LD50 and GR50 on seeds irradiated with cobalt 60 (60Co) of blue grama (Bouteloua gracilis), sideoats grama (Bouteloua curtipendula), buffel grass (Pennisetum ciliare) and weeping lovegrass (Eragrostis curvula), as well as determine a weighted average of the LD50 and GR50. Seeds of these species were irradiated with Co60 at seven different doses were evaluated. Doses intensities included: 0 (control, T-0), 100, 200, 300, 450, 600 and 900 Gray (Gy). The variables evaluated were germination percentage (%GE), speed germination index (IVG), plumule length (LP) and radicle length (LR). Regression analysis and means comparison with the Dunnett test were performed with the data. In addition, LD50 was estimated through a regression equation on the data of %GE while the GR50 was calculated with the reamaining variables. Moreover, a weighted average was calculated with the values obtained from both parameters. The LD50 was weighted at 55%, while the GR50 was weighted at 15% for each of the three remaining variables. In general, the values of all the response variables decreased (P<0.05) as the irradiation doses increased, which allowed the estimation of LD50 and GR50, for each species. The weighted average was obtained at 628 Gy, 712 Gy 698 Gy and 411 Gy for wepping lovegrass, buffel grass, sideoats grama and blue grama, respectively. We do recommend the use of these doses in plant breeding programs of these species.

Keywords : cobalt 60; germination; gamma rays; mutagenesis; radiosensitivity.

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