Effectiveness of repeated mutagenesis of sesame crosses for enhancing polygenic variability in F2M2 generation

Abstract

The value of combining hybridization and mutagenesis in sesame was examined to determine if treating hybrid sesame plant material with mutagens generated greater genetic variability in four key productivity traits than either the separate hybridization or mutation of plant material. In a randomized block design with three replications, six F2M2 varieties, three F2varieties, and three parental varieties were assessed at Odisha University of Agriculture and Technology, Bhubaneswar, Odisha, India. The plant characteristics height, number of seed capsules per plant, and seed yield per plant had greater variability in the F2M2 generation than their respective controls (F2), however, the number of primary branches per plant varied less than in the control population. The chances for trait selection to be operative were high for all the characteristics examined except the number of primary branches per plant, as indicated by heritability estimates. Increases in the mean and variability of the characteristics examined indicted a greater incidence of beneficial mutations and the breakdown of undesirable linkages with increased recombination. At both phenotypic and genotypic levels strong positive correlations between both primary branch number and capsule number with seed yield suggest that these traits are important for indirect improvement in sesame seed yield. As a result of the association analysis, sesame seed yield and its component traits improved significantly, which may be attributed to the independent polygenic mutations and enlarged recombination of the polygenes controlling the examined characteristics. Compared to the corresponding control treatment or to one cycle of mutagenic treatment, two cycles of mutagenic treatment resulted in increased variability, higher transgressive segregates, PTS mean and average transgression for sesame seed yield. These findings highlight the value of implementing two EMS treatment cycles to generate improved sesame lines. Furthermore, the extra variability created through hybridization may have potential in subsequent breeding research and improved seed yield segregants may be further advanced to develop ever-superior sesame varieties.

Fig 1. Overview of sesame recurrent mutagenesis in the field experiment.

Fig 2

(a) Plant height means in F₂M₂ as a function of the number of EMS (ethyl methane sulfonate) treatment cycles; (b) Plant height standard deviations (SD) in F₂M₂ as a function of the number of EMS treatment cycles.

Fig 3

(a) Primary branches/plant means in F₂M₂ as a function of the number of EMS (ethyl methane sulfonate) treatment cycles; (b) Primary branches/plant standard deviations in F₂M₂ as a function of the number of EMS treatment cycles.

Fig 4

(a) Number of capsules/plant means in F₂M₂ as a function of the number of EMS (ethyl methane sulfonate) treatment cycles; (b) Number of capsules/ plant standard deviations in F₂M₂ as a function of the number of EMS treatment cycles.

Fig 5

(a) Seed yield/plant means in F₂M₂ as a function of the number of EMS (ethyl methane sulfonate) treatment cycles; (b) Seed yield/ plant standard deviations in F₂M₂ as a function of the number of EMS treatment cycles.