Tolerância ao florescimento precoce e à termoinibição em genótipos de alface

Abstract

Lettuce is a leafy vegetable most consumed in the world, being used in alimentation as a source of vitamins and minerals. In warm climates growing lettuce can be made impossible due to the early flowering. Moreover, seeds typically do not exhibit satisfactorily germination at elevated temperatures. In this study we evaluated 16 cultivars of lettuce, together with thermotolerant cultivar Everglades, with a view to identifying promising genotypes for use in breeding programs of lettuce to regions with higher temperatures. Seeds were obtained in plants cultured during spring/summer. The planting was done in greenhouse in a randomized complete block design with three replications and six plants per plot, and evaluated the number of days to the first anthesis of each plant. The seeds from each cultivar were harvested, dried and treated, being part used for evaluation immediately after harvest and part used for another experiment realized six months after. In these experiments we evaluated the germination and germination speed index (GSI) of each cultivar at four temperatures: 20, 25, 30 and 35°C under a completely randomized in a factorial design. The emergence speed index (EVI) was also assessed, using the standards of the RAS. Both experiment in post-harvest, as was made in six months after harvest. Everglades was the only cultivar that showed satisfactory germination temperature above 30°C. The occurrence of primary dormancy may be evidenced by the low germination of some cultivars even at 20 ° C. At six months after harvest to cultivate Luisa was statistically equal to Everglades to 35 ° C, but not with standard commercial germinates. No relationship was evident between early flowering and germination at high temperatures. Everglades is a promising material for breeding to feature thermoinhibition.