Induction of mutagenized tomato populations for investigation on agronomic traits and mutant phenotyping

Global demand for tomato production increased tremendously due to its diverse utility in raw, cooked and processed form of food. This necessitates the continued supply of highly nutritious and better yielding improved cultivars to the producers, considering the rapid changing agro-climatic condition. In this study, induced mutant tomato populations of widely recommended tomato genotype Arka Vikas (Sel-22) were generated using chemical mutagen ethyl methane sulfonate (EMS), hydrazine hydrates (HZ) and their combined treatments. In the in vitro study, a gradual reduction in germination percentage and seedling height occurred with the increasing concentrations of mutagens. Combination of EMS and HZ caused maximum biological inhibition followed by EMS and HZ treatments alone in M1 generation. The rate of survival and fertility in M1 plants of tomato was found highly affected due to mutagenic treatment, in which sensitivity toward combined treatment was found highest followed by EMS and HZ. Inspection on induced phenotypic variations in individual plants of M2 population resulted in identification and isolation of wide range of mutants with altered phenotypes. Highest mutation frequency was resulted by combined mutagens followed by the EMS and HZ treatment. Agronomic trait analyses showed intra and inter treatment variations in three quantitative traits (Plant height, fertile branch per plant and fruits per plant) of M2 mutagenized population. Assessment on rate of mutant recovery in M2 population showed highest mutant recovery is possible with combination treatments and then 0.02% HZ followed by 0.02% EMS. In the present study, phenotyping of the mutants revealed that vegetative organs ('plant size', 'plant habit' and 'leaf morphology') was the most sensitive category (69.33%) to which most of the mutant belongs, followed by 'fruit color and size' (20.27%) and 'germination' (9.79%). Comparative investigation on number of mutants and phenotype category in M2 mutant plants confirmed that the number of pleiotropic mutants was more than the non-pleiotropic mutants in all the treatment conditions. Heritability and reproducibility of the 30 putative mutants were checked in M3 generation based on the observed agro-economical traits; results showed 17 complete and 5 partial heritable mutants.