Evaluation of the effect of chronic gamma irradiation on taro (Colocasia esculenta L. cv Wangi) for agronomic, genomic, antioxidant and oxalate content characteristics / Nor Farah Nadirah Ahmad Noruddin

Taro (Colocasia esculenta L.) is an important staple food crop in developing countries which has a great potential in terms of high-quality food and has a higher nutritive value. Mutation breeding can be used for selection and improvement of desirable morphological traits of taro. This study was attempted to induce mutation on taro in order to determine the effect of gamma irradiation on morphological traits of taro cv “Wangi”. Suckers of taro cv “Wangi” that had previously been exposed with seven doses (0 Gy, 12.01 Gy, 16.02 Gy, 28.03 Gy, 44.05 Gy, 68.07 Gy, 120.12 Gy and 268.28 Gy) under chronic gamma ray radiation were propagated until M1V4 generations. The genetic diversity of taro mutant lines was analyzed among irradiated taro based on the genetic analysis by using Simple Sequence Repeat (SSR) molecular markers. It was observed that chronic gamma irradiation had tremendously affected the growth performance of taro plant. In M1V1 generation, a decreasing trend in the plant height, leaf width, number of suckers per plant and corm weight characters was observed in all the treatments when compared to unirradiated plant (control). In M1V2, M1V3 and M1V4 generation, all the trait studied exhibited significantly better performance in mutant taro as compared to the control. Moreover, those generations also exhibited wide spectrum of viable mutants including shape of laminar, laminar orientation, colour of laminar, vein colour, shape of leaf vein and laminar variegation and corm shape. Correlation analysis revealed the strong and positive correlation between corm weight with corm diameter. Heritability analysis showed the phenotypic coefficients of variation in general for all the characters were higher than genotypic coefficients of variation indicating the influence of environmental factors on these traits. Highest level of heritability was observed in 16.02 Gy for trait number of suckers, number of leaves per plant, corm weight and diameter of corm meanwhile taro mutant at 44.05 Gy, 67.05 Gy and 120.02 Gy recorded highest heritability for trait plant height, leaves length, number of stolon and corm length. The total phenolic content (TPC), total flavonoid content (TFC) and radical scavenging activity showed a significant difference (p<0.05) on different irradiation doses which plant exposed in12.01 Gy showed the highest in TPC and TFC with 299.37 ± 8.87 mg GAE/ 100g and 1680.75± 64.69 mg GAE/ 100g respectively while the highest radical scavenging percentage was recorded in plant treated with 268.28 Gy in both methanol and aqueous extract. The highest oxalate content was recorded in plant exposed with 120.12 Gy (13686.06 ± 356.32 mg/100g) and the lowest was found in plant treated at 12.01 Gy (6092.78 ± 344.54 mg/100g). The PCR-based SSR analysis showed that out of 10 SSR primers tested, 7 primers successfully amplified a total number of 42 amplicons. The polymorphism information content (PIC) values of SSR markers ranged from 0.20 to 0.80. Cluster analysis classified taro into 3 subgroups as mutant and parent genotypes. The results clearly showed that SSR markers are important tools to distinguish mutant genotypes and confirmed their usefulness for phylogenetic studies. Findings in this study suggested that the mutation induction approach is recommended for taro genotype improvement with lower doses of chronic gamma irradiation produced high antioxidant activity and low oxalate content of taro genotype. Potential taro genotypes develop in this study was considered as potential genotype for future taro breeding program.