Anatomical, karyotypic, and nuclear DNA content studies in four morphotypes of wild lettuce

Abstract

Wild lettuce (Lactuca aff. canadensis L.), belonging to the Asteraceae family, occurs subspontaneously in Brazil and may originate from Africa, Asia, Europe and North America. Popularly known as Canada lettuce, it is an unconventional leafy vegetable. Studies on this species are scarce in Brazil, and its scientific name is debated among experts. It has high morphological variability and controversial botanical classification. This study characterized the stomata, organized the karyotype, and determined the nuclear DNA content of four morphotypes of wild lettuce to facilitate correct classification. The genetic material used was acquired from the non-conventional vegetable germplasm in UFLA. The leaves of wild lettuce morphotypes are hypoamphiestomatic with a greater number of stomata in the abaxial epidermis. There were similarities between the morphotypes (green and purple) and between the smooth purple types (narrow leaf and broad leaf) for the number and size of stomata. No variation was found in the number of chromosomes (2n = 18) or DNA content among the four morphotypes. The separation of the morphotypes of wild lettuce did not match the morphological classification or the karyological data. The four morphotypes evaluated were placed under the same species, and the results obtained when compared to other studies led us to infer that the four morphotypes of wild Lactuca belonged to the species L. indica and not L. canadensis as previously assumed. Further investigation may provide insights into the evolutionary history of this species.