Phenotyping Gamma‐Irradiated Cassava ( Manihot esculenta Crantz.) Putative Mutant Population Through Morphological, Physiological and Agronomic Markers

ABSTRACT Mutation induction using gamma irradiation is a potent method for enhancing genetic variability in crops like Cassava ( Manihot esculenta Crantz.), which have narrow genetic bases. The process of phenotyping the qualitative and quantitative morpho‐agronomic traits, coupled with multivariate analysis, is an effective method of identifying and selecting variants within the mutant population. This study involved irradiating stem cuttings of three cassava varieties with three doses of gamma rays, resulting in 176 and 140 putative mutants for the M1V1 and M1V2 generations, using an augmented randomized block design. A radiosensitivity test obtained from probit model revealed that the mean lethal dose were 23.15, 25.70 and 28.42 Gy for Melko‐108, Qulleand Kello varieties, respectively; therefore, doses near LD 50 and within 95% confidence intervals were recommended. Qualitative traits such as leaf colour, petiole colour, petiole orientation and leaf retention showed significant variations in the M1V1 generation. Significant variations ( p < 0.05) in quantitative morpho‐physiological and agronomic traits were observed across the two generations of the mutant population. A high genotypic coefficient of variation (GCV) and broad‐sense heritability (H 2 ) value were observed in all studied traits in both generations. The principal component analysis revealed that 80.9% and 78.9% of the total variation were described by the first three PCs in M1V1 and M1V2, respectively. Traits such as plant height, leaf number and chlorophyll contents contributed significantly to the variations in both generations indicating a similar pattern across the generations, supporting their use as primary selection targets in early mutant screening. The populations were categorized into three distinct clusters (C) in both generations based on the morpho‐physiological and agronomic traits. The highest among clusters was ascertained between C2 and C3 (71.18) and C1 and C2 (47.87) in M1V1 and M1V2, respectively. The two generations of gamma‐irradiated cassava putative mutant populations have shown considerable variation based on the evaluated markers, facilitating selections for the next generation and creating desirable novel traits.