GENETIC VARIABILITY IN LETTUCE (LACTUCA SATIVA) GERMPLASM USING MORPHOLOGIC AND MOLECULAR ANALYSES

Lactuca sativa is one of the most important crops in the intensive agriculture of Southeast Spain. This intensive agricultural production system is often at odds with concerns of growers and consumers about environmental sustainability, and lettuce varieties adapted to a more ecologically friendly agriculture are desirable. In order to identify landrace cultivars with potential for ecological agriculture, a collection of eleven traditional lettuce landraces from Murcia (SE Spain) were characterized by means of agro-morphological traits and ISSR (inter-simple sequence repeat) markers. Accessions were analyzed for quantitative and qualitative characters related to seed, plant, anthocyanin, head type, phenology, and yield. Based on head type, nine were landrace accessions belonging to the cos type and three to the butterhead type. For molecular comparisons there were six commercial varieties of crisphead, cos, leaf and butterhead type were included. Thirteen of twenty ISSR primers amplified DNA fragments from all tested plants. One hundred and ten (65.9%) of 167 fragments scored showed polymorphism, with an average of 8.5 polymorphic bands per primer. The number of bands per primer ranged from 6 to 19, with an average of 12.8. Based on these ISSR markers, genetic similarity coefficients were calculated and a dendrogram was constructed using the Unweighted Pair-Group Method with Arithmetic average (UPGMA). The eleven lettuce landraces and six commercial varieties were divided into three major groups at a similarity coefficient value of 0.81. All the lettuce landraces were grouped with the commercial varieties of cos and butterhead types. Two accessions were indistinguishable by ISSR primers.