Early blooming, genetic dissimilarity and clustering of lettuce cultivars with thermoinhibition tolerant seeds

Resumo

High temperatures interfere lettuce cropping. Thermoinhibition of seed germination and early blooming causes important losses for farmers. The objectives of this work were to evaluate the tolerance to early blooming, to verify the genetic dissimilarity and to select lettuce cultivars tolerant to seed thermoinhibition. 18 cultivars were evaluated. For early blooming was verified the number of days until the first anthesis. Regarding seed thermoinhibition, the first and final germination counting and germination velocity index were evaluated, using temperatures of 20, 25, 30 and 35 ºC. The analyses were performed immediately after harvest and with six months under storage. The study genetic dissimilarity was performed using the Tocher Graph optimization and hierarchical UPGMA methods. Regression models were adjusted, and curves’ clustering was performed by testing the identity of the models. Early blooming was observed in cultivars Floresta, Colorado, Grand Rapids, and Everglades. Cultivars showed genetic variability and are dissimilar regarding tolerance to thermoinhibition. By clustering the regression equations, it was possible to select thermoinhibition tolerant cultivars.