Genetic variability for agronomic characteristics in lettuce progenies with heat tolerance

Lettuce progenies with tolerance to early bolting were evaluated in relation to commercially desirable agronomic characters, as well as to estirnate important genetic components for crop breeding. The experimental design was random blocks with three replications and IS treatments (13 progenies F-7, the genitors Verdinha, Regina, and Tinto, and cultivars Luisa and Baba de Verao). The genetic, phenotypic, and environmental variances, the heritability, and the correlation anion g the characters number of leaves, plant and leaves fresh weight, plant diameter, stern length, and bolting, were estimated. The F test was significant (p<0,01) for all the studied characteristics. In the clustering of means by the Scott-Knott test, at 5% probability, treatments were assembled in two groups, except for plant diameter, in which cultivar Tinto remained isolated in a third group. The genetic variance was higher than the environmental variance for all evaluated characteristics, and the heritability, below 90%, revealed the environmental influence over some characters. When bolting was correlated to the other characteristics, results were positive and significant for most combinations, considering the genetic correlations. Under these experimental conditions, progeny 76 stood out for its low stem length and reduced bolting index, although its commercial performance was interior to the control cultivars, genitors, and some other progenies.