Genetic variability induced by gamma radiation (Cobalt-60) in eggplant (Solanum melongena L.) and morphoagronomic characterization of the mutants

The success of a breeding program based on hybridization depends on the genetic variability available to exploit it through selection. One way of generating variability and increasing genetic diversity is by mutation, artificially using mutagenic agents. Among the mutagenic agents, ionizing radiation has been widely used, however, according to the dose of gamma radiation that the organism is exposed to, it can cause several apparent modifications, such as death, inhibition or stimulation. The objective of this study was to evaluate radiosensitivity of eggplant seeds to gamma radiation with ⁶⁰Co, estimating the genetic variability by means of morphoagronomic characterization for traits uni and multivariate. Eggplant genotype seeds (BGH 2404) were subjected to gamma radiation of Cobalt-60 (⁶⁰Co) at doses of 0, 25, 50, 100, 200, 400, 800 Gy. After the radiation, the seeds were seeded in polystyrene trays. Sixteen quantitative characters and 18 qualitative characters were evaluated, regarding size, inflorescence and fruit, based on the list of eggplant descriptors suggested by the International Institute of Plant Genetic Resources. The experimental design was completely randomized, consisting of seven treatments (radiation doses) and 10 replicates. The quantitative data were submitted to analysis of variance by the F test at the 5% level of significance and the means were compared by the Dunnett test at 5% significance. The data were also submitted to multivariate analysis of variance by the F test at the 5% level of significance, and the dissimilarity measure based on the generalized Mahalanobis distance was adopted, and the data were grouped by the Tocher and UPGMA methods. We also performed the relative contribution of the characters using the criterion proposed by Singh and finally we performed analysis of genetic divergence through canonical variables. According to the results, it was concluded that the gamma radiation with ⁶⁰Co was responsible for morphological alterations in most of the quantitative and qualitative characteristics analyzed, indicating the possibility of the occurrence of mutations in the evaluated individuals. Considering the obtained results, the radiation dose of 25 Gy is indicated to obtain genetic variability in eggplant. Exposure of the seeds to gamma dose radiation of 800 Gy caused deleterious effects detrimental to their germination. The effects of gamma radiation on Solanun melongena L. seeds does not follow a variation pattern according to the doses used. The variability observed in the clusters is indicative of the diversity among the genotypes and is therefore promising for the selection of mutant individuals with the potential to continue the investigation of the occurrence of mutations induced by gamma radiation. (author)