Evaluation of AFLPs for germplasm fingerprinting and assessment of genetic diversity in cultivars of tomato (Lycopersicon esculentum L.)

Cultivated tomato (L. esculentum L.) germplasm exhibits limited genetic variation compared with wild Lycopersicon species. Amplified fragment length polymorphism (AFLP) markers were used to evaluate genetic variation among 74 cultivars, primarily from California, and to fingerprint germplasm to determine if cultivar-specific patterns could be obtained. All 74 cultivars were genotyped using 26 AFLP primer combinations; of the 1092 bands scored, 102 AFLP bands (9.3%) were polymorphic. Pair-wise genetic similarity coefficients (Jaccard and Nei-Li) were calculated. Jaccard coefficients varied from 0.16 to 0.98 among cultivar pairs, and 72% of pair-wise comparisons exceeded 0.5. UPGMA (unweighted pair-group method with arithmetic averaging) clustering and principle component analysis revealed four main clusters, I-IV; most modem hybrid cultivars grouped in II, whereas most vintage cultivars grouped in I. Clusters III and IV contained three and two cultivars, respectively. Some groups of cultivars closely related by pedigree exhibited high bootstrap values, but lower values (<50%) were obtained for cluster II and its four subgroups. Unique fingerprints for all 74 cultivars were obtained by a minimum of seven AFLP primer pairs, despite inclusion of some closely related cultivars. This study demonstrated that AFLP markers are effective for obtaining unique fingerprints of, and assessing genetic diversity among, tomato cultivars.