Evaluation of the optimum threshold of gamma-ray for inducing mutation on Polianthes tuberosa cv. double and analysis of genetic variation with RAPD marker

Abstract

Purpose This experiment aimed to investigate the effect of gamma irradiation on morpho-physiological characteristics and molecular-induced variations in Polianthes tuberosa L. Methods Experiments were designed according to a completely randomized design with eight different gamma-ray doses (0, 20, 30, 40, 50, 60, 70, and 80 Gy) via a source of cobalt-60 with three replications. Some morpho-physiological characteristics of tuberoses were screened and evaluated at the end of the flower growth and development phases. The RAPD-PCR molecular marker technique was further used to identify the mutants of phenotypic variation flowers. Results Results indicated that the effect of different levels of γ-rays on some morphological and physiological traits was significant as the gamma-ray level was increased up to 50 Gy. The doses higher than 50 Gy were found to cause stand or no growth. The 50 Gy gamma irradiation reduced germination by 70.59%, germination rate by 66.36%, dry weight by 88.15%, fresh weight by 87.41%, flowering stem height (cm) by 69.22%, leaf area (cm2) by 57.35%, leaf number by 34.41%, chlorophyll content (mg g−1 FW) by 44.79%, number of florets by 92.57%, spike height (cm) by 27.80%, bulblet number by 32.57%, and bulblet diameter (mm) by 30.21%. On the contrary, gamma radiation at 50 Gy increased relative water content (%) and electrolyte leakage (ds m−1) by 41.27 and 237.65%, respectively. The results also showed that bulbs treated with 20 Gy gamma ray had the highest germination percentage and dry weight. The RAPD analysis indicated that among 10 primers tested, nine primers showed clear bands as the highest number of amplified fragments (90) was related to the OPM13 primer and the lowest number (40) to the OPM10 primer. However, the DNA polymorphism was dose-dependent. Conclusion Overall results showed that although the plant morphology was changed with gamma-ray level, no changes occurred in tuberose color.