Increasing Genetic Variability of Local Sorghum Yield by Using Gamma-ray Induced Mutation

Abstract

Increasing the genetic variety of a population is very important for the selection process in plant breeding programs. Mutation induction is an alternative method to increase the genetic variability of local sorghum, especially for the character of seed and biomass yield. This study aims to determine the radio-sensitivity of sorghum to applying gamma-ray irradiation in deciding lethal doses, evaluate the emergence of chlorophyll mutations and increase the genetic variation in the M2 generation. The genetic material used was the local sorghum variety Watar Hammu Putih. Seeds were irradiated at a dose of 0–1,000 Gy of gamma rays utilizing a range of 100 Gy. Planting was carried out with a sand chamber. The experimental parameters include survival rate (%), vigor index, and seedling height (cm). After LD50 was determined for sorghum, 100 g of sorghum seeds were irradiated at a dose slightly below that of LD50. Seeds were grown in the field as an M1 population and harvested the panicle individually. A total of 522 panicles were planted in one row per panicle as the M2 generation in two locations (Jakarta and Bogor) and observed their agronomic characters. The radio-sensitivity test result showed that LD50 was found at 433 Gy. Gamma-ray irradiation was carried out at a dosage of 350 Gy for the M1 generation. Chlorophyll mutations appeared in the seedling phase of the M2 population. Two types of chlorophyll mutation were found, namely albino and viridis. The observations on the M2 population showed that gamma-ray irradiation induces an expansion of the range value of all observed agronomic characters. Higher mean values were obtained with a wide range in the panicle length character than the parent at two locations. Some of agronomic characters have a high heritability for the panicle length, chlorophyll content, stem juice % brix, panicle weight and seed yield. Gamma-ray irradiation expanded the genetic diversity of all the agronomic characters of the observed M2 population except plant height, panicle weight and seed yield.