Because of the development of heat-tolerant cultivars and resistance to major leaf diseases, carrot production is also increasing in other regions,such as in like north and northeast of Brazil. High temperatures during sowing may decrease carrot seed germination and affect the stand establishment. The aim of this study was to evaluate the effect of high temperatures on seed germination and vigor of various Brazilian carrot cultivars as well as different half-sib families from a carrot cv. Brasilia population. Carrot seeds cv. Brasília were incubated at constant temperatures of 20; 24; 28; 32 and 36ºC. Also, seeds of primary and secondary umbels from 120 half-sib families of 'Brasília' carrot population were evaluated for viability (germination at 20ºC) and supra-optimal temperature (35ºC), vigor (first counting) and seed mass. Finally, seeds from 28 commercial lots were evaluated for germination at 20 and 35ºC. Seed germination decreased when the temperature increased. At 36ºC, seeds germinated only 27%. At 20ºC, germination varied among the commercial seed lots, and, at high temperature conditions (35ºC), germination decreased in almost all lots. The 120 half-sib families of 'Brasília' cultivar had high germination and vigor at 20ºC. However, at 35ºC, only few families germinated above 60%. In addition, seeds from primary umbels germinated better than those from secondary umbels at 35ºC. To obtain a good stand establishment in the field, especially under adverse conditions of high temperatures, the selection and development of thermo-tolerant cultivars as well as the use of primary umbel seeds is recommended.
Daucus carota L.; thermoinhibition; stand establishment; lots; progenies
