Mean lethal dose (LD50) and growth reduction (GR50) due to gamma radiation in Wilman lovegrass (Eragrostis superba)

Gamma radiation can be utilized as a mutagenic agent for inducing genetic variability in plant species. However, the adequate dose of radiation must be established before starting a mutagenesis-based breeding program. The objective was to determine the mean lethal dose (LD50) and the dose for the mean growth reduction (GR(50)) in Wilman lovegrass (Eragrostis superba Peyr.). For this purpose, the seeds were radiated with doses of 0 (control treatment), 100, 200, 300, 450, 600, 900, 1400, 2000 and 4000 Gray. The evaluated variables were germination percentage, germination speed index, plumule length, radicle length, forage yield, seed production, leaf-stem ratio and chlorophyll concentration index. The data were analyzed through regression analyses and the Dunnett's mean comparison test. The LD50 and GR(50) generated for each of the evaluated variables were calculated with the resulting regression equation. Based on the values of LD50 and GR(50), a weighted mean was estimated; the LD50 was weighted with 30 % while the GR(50) with 10%. In general, all the evaluated characteristics were affected by the radiation treatment (P<0.05), and their behavior was adjusted to linear square models (P<0.05), allowing the determination of the LD50 and the GR(50). The weighting average of both parameters, estimated at 2486 Gy, is recommended for the genetic breeding of Wilman lovegrass. The results of this study will allow implementing mutagenesis-based plant breeding programs in Wilman lovegrass.