Abstract

Non-parametric selection indexes (that is, require no estimation of parameters) can be used to help the selection process in the final stage of genetic enhancement. In this context, the objective of this study was to evaluate the efficiency of non-parametric selection indexes to choose promising lineages of loose-leaf lettuce, so that genetic gain of each lineage can be estimated and then registered in the Ministry of Agriculture. The indexes of Mulamba and Mock, Elston and Schwarzbach were used in the analysis. Ten genotypes of loose-leaf lettuce were evaluated, with eight of them being lineages (L₁, L₂, L₃, L₄, L₅, L₆, L₇, L₈) and two commercial cultivars (Vanda and Vera). The experiments occurred in six different locations of cultivation during the autumn and winter seasons of 2014. Experimental delineation was composed of random blocks, with four repetitions and the evaluated characteristics were: total production, commercial production, number of leaves, plant volume and stem length. The effects of genotype (G), location (L), and G x L interaction were significant for all characteristics. Indexes were correlated to classify the genotype. The Mulamba and Mock index stood out because it enabled good direct gains for the evaluated characteristics and because of its easy construction. Therefore, this index is recommended for selection of loose-leaf lettuce genotypes in the stage of cultivar recommendation in different locations. As the best lineages of loose-leaf lettuce were L₂, L₃, L₇ and L₈, these lineages have been considered promising and are recommended for registration.

Key words: Agronomic performance, Lactuca sativa, nonlinear indexes, spearman correlation.