Cytological study of chromosome and genome composition of Iranian lettuce (Lactuca sativa L.) accessions

In this study, 15 different accessions of Iranian lettuce cultivars and varieties that were collected from different regions were investigated. Starting from the root apical meristem, we measured the number and size of the chromosomes. The karyotypic formula was determined. The basic chromosome number was n = 9 in all accessions, possibly due to ancient origin, also all accessions had morphological dissimilarity, and heteromorphisms between chromosomes and their chromosomal types were metacentric, submetacentric and subtelocentric. Analysis of variance showed significant differences between chromosomal characteristics. The maximum size of the estimated genome (in terms of chromosome length) was that of the Qom accession (62.45 μm). The minimum size was that of the Babol accession (19.94 μm). Symmetrical and asymmetrical karyotypes were observed between the accessions. The formula of the Ahwaz accession was 12m + 4sm + 2t with the maximum centromic index (40.93%), while the Fasa accession had a 4m + 10sm + 4st karyotypic formula and the minimum value (28.73). There were different numbers of satellites present on the chromosomes in the different accessions. Some of them had two satellites, some one and the others none. In principle component analysis two components had more than 82.75% of the data variations. Based on the first and second components the accessions separated into three groups. Cluster analysis of karyotypic traits based on the unweighted paired group method using arithmetic average (UPGMA) separated the accessions in three groups. The results of this study will be useful for accession classification and identification.