Genetic dissimilarity for thermoinhibition in seeds of lettuce lines after defoliation

Removal of lettuce basal leaves is a technique used by the seed industry; however, the effects on seed production and physiological potential are unknown. Genetic dissimilarity is fundamental in the identification of individuals in terms of traits of interest, although it is rarely considered in relation to seeds that are tolerant to thermoinhibition. The aim of this study was to ascertain the relationship between defoliation of lettuce plants and seed yield/physiological quality, as well as the genetic dissimilarity among genotypes with regard to seed thermoinhibition. We used 35 lines of biofortified lettuce, the cultivars Uberlândia 10000, Belíssima, UFU MC BIOFORT1, and Everglades (tolerant to thermoinhibition), and Grand Rapids and Verônica (susceptible to thermoinhibition). The seed yield and physiological quality of the genotypes with and without defoliation were evaluated, artificially aged, and germinated at four temperatures in a factorial arrangement. The genetic dissimilarity was estimated by Tocher graphing and the UPGMA clustering method, based on the Mahalanobis generalized distance (D 2 ii). Four UFU genotypes and Grand Rapids had high seed yields. With removal of basal leaves, there was higher seed yield per plant and there was an effect on their physiological quality. The genotypes exhibited genetic variability for thermoinhibition, with UFU-86#2#1#1 and Everglades showing similar performance.