Prediction of the breeding value of leaf lettuce mutant lines according to the correlation between the manifestation of qualitative and quantitative traits

Aim. To establish the effect of mutagenic factors on the formation of qualitative traits, defining the phenotype of the leaf blade, and to investigate the correlation between the manifestation of these factors and the variation of quantitative traits of breeding value in mutant lines of leaf lettuce. Methods. Non-parametric statistical and criteria of difference for biological specimens, computational and analytical calculations, correlation analysis. Results. The comparative analysis was conducted on the qualitative characteristics of the original leaf blade form of leaf lettuce, Zhnych variety, alongside 14 mutant lines derived from it through the application of mutagenic agents, including dimethyl sulfate (DMS) and its derivatives (D3MU, DMU-10А, and DMU-9) in two varying concentrations. Notably, the derivatives of DMS exhibited superior mutagenic efficiency, leading to a four to fivefold increase in the number of mutant plant forms compared to the reference compound DMS. Among the derivatives, D3MU proved the most effective, generat- ing five mutant lines. In contrast, DMU-10A and DMU-9 yielded four mutant lines, while DMS produced only one mutant line. All mutant lines exhibited distinct variations from the initial form across 17 qualitative characteristics determining leaf blade phenotype. The analysis of Spearman’s rank correlation coefficient (rs) demonstrated weak to moderate correlation (rs = –0.08...0.62) between the original form and mutant lines. It was determined that three lettuce lines, namely B-7, B-22, and B-38, exhibited the most significant deviations from the initial form in term of leaf blade qualitative traits. Furthermore, it was established that non-parametric indicators of qualitative traits expression exhibited moderate or high correlation (rs = 0.57...0.74) with an essential quantitative trait – the duration from the emergence of mass shoots to plant stem development in mutant lines. Conclusions. The identified correlations between quantitative and qualitative traits provide the opportunity to predictably select mutant genotypes with extended growth period during the early stages of lettuce plant ontogenesis in future breeding work.