Abstract
Lettuce (Lactuca spp.) is an annual and self-pollinating crop that belongs to the Asteraceae (Compositae) family. It is one of the most globally essential commercial vegetable crops, used in salads and sandwiches. The lettuce leaves are used to make a cigarette without nicotine. Seeds and stems contain edible oil and dried latex. Gene banks have conserved a large pool of lettuce's genetic resources, including wild Lactuca species with the same chromosome numbers 2n = 2x = 18. Lactuca species vary greatly in terms of geographical distribution and morpho-agronomic characteristics. By crossing commercial varieties with locally adapted varieties, novel alleles can be introduced, increasing genetic diversity and making preselection for desirable traits easier. Lettuce breeders and geneticists' main objectives are to improve lettuce for various desirable traits, including tolerance to abiotic and biotic stress and high yield. These targets accomplished with modern genomics tools together with traditional breeding methods. This chapter discusses lettuce conservation and biodiversity, stages of lettuce breeding, agriculture practices, and conventional breeding techniques and their restrictions. It also includes modern plant breeding tools and marker-assisted breeding, editing of genome, and genetic engineering.