Inheritance of bolting tendency in lettuce Lactuca sativa L.

Resistance to early flowering is an important attribute of lettuce cultivar s adapted to tropical conditions. Lettuce cultivars may vary widely in the number of days necessary from sowing to inflorescence formation and floweri ng. In this paper, we report on the polygenic inheritance of the number of days to flowering in two crosses among contrasting lettuce cultivars - Vito ria x Brasil-303 and Baba x Elisa. F-1 and F-2 seed were obtained for each cross, and used to estimate broad sense heritabilities. F-3 families were o btained from randonly sampled F-2 plants, and used to estimate narrow sense heritabilities based on parent-offspring regression. Trials were carried o ut in plastic greenhouses in Campos dos Goytacazes, in the Northern part of the State of Rio de Janeiro, Brazil. Broad and narrow sense heritabilities for days to first anthesis were 0.737 and 0.489 for the cross Vitoria x Br asil-303, and 0.818 and 0.481 respectively, for the cross Baba x Elisa. In both crosses, both early and late-flowering transgressive segregants were o btained. Genetic gains based on selection of late flowering transgressive s egregants in the F-2's were estimated to be 10.2 days in Vitoria x Brasil-3 03 cross, and 8.7 days in the Baba x Elisa cross.