Controle genético da tolerância à termoinibição em sementes de alface

Abstract

Lettuce (Lactuca sativa L.) is the most expressive leafy vegetable in the world and national markets, both for its production volume and for its economic importance. Due to the great acceptance of this vegetable by the Brazilians, it presents constant demand, being produced throughout the year and in almost all regions of the country. Considering the climatic variations between the regions of Brazil and the wide geographic distribution of this crop, it is common the occurrence of problems with the germination in places with higher temperature. Normally, the ideal temperature for the germination of lettuce seeds is approximately 20ºC, and temperatures above 28ºC can inhibit germination. One of the main aspects affecting the germination of lettuce seeds at high temperatures concerns the thermoinhibition. Thermoinhibition consists of the loss of the germination capacity of the seeds when exposed to high temperatures, which is a reversible process, since the germination can be resumed with the decrease of the temperature to adequate levels. Most of the lettuce cultivars used in Brazil is sensitive to thermoinhibition, but in the literature there are records of tolerant genotypes, such as the Everglades cultivar, capable of germinating above 70% at a temperature of 35ºC. However, the mechanisms involved in inheriting this trait have not yet been sufficiently studied for this crop. The objective of this work was to study the mechanisms involved in the genetic control of the tolerance to thermoinhibition in lettuce seeds obtained from the crossing between the contrasting lettuce cultivars Everglades and Verônica. From the results obtained, it was possible to infer that the tolerance to the thermoinhibition in lettuce seeds is controlled by one or a few genes with predominant additive effect and with a relatively high heritability in the restricted sense, allowing to anticipate the success with the selection. Thus, it is concluded that the conventional improvement of the lettuce aiming at the tolerance to the thermoinhibition is viable.