Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 20, 2006
Publication Date: February 16, 2007
Citation: Hu, J., Mou, B., Vick, B.A. 2007. Genetic diversity of 38 spinach (Spinacia oleracea L.) germplasm accessions and 10 commercial hybrids assessed by TRAP markers. Genetic Resources and Crop Evolution. 54:1667-1674. Interpretive Summary: This project was conducted in collaboration with an ARS scientist from Salinas, CA. Target region amplification polymorphism (TRAP) marker technique was employed to generate DNA markers for assessing genetic variation of a germplasm collection containing 36 spinach accessions from the USDA National Plant Germplasm System (NPGS) and ten commercial hybrids. A considerable amount of genetic variability was detected within accessions using DNA from 12 individual seedlings from each of eight entries. Ninety-six polymorphic markers obtained from six PCR analyses (12 primer combinations) were able to distinguish all the entries. Among a total of 1128 pairwise comparisons, the genetic similarity varied from 23.2 to 85.3%, and the average was 57.5%. The mean value of the similarity coefficients of an accession with each of the remaining 47 accessions ranged from 42.0 to 64.4%. These statistics suggested substantial genetic variability among accessions examined. Cluster analysis based on these polymorphic markers grouped the 48 entries into eight clusters, but a close association between geographical origin and TRAP patterns was not apparent. One implication of this study is the need for a relatively larger number of plants to maintain the genetic variation within an accession when regenerating spinach germplasm.
Technical Abstract: Target region amplification polymorphism (TRAP) markers were used to assess genetic variability among 38 germplasm accessions and ten commercial hybrids of spinach (Spinacia oleracea L.), an economically important leafy vegetable crop in many countries. Germplasm accessions with different geographic origins and ten commercial hybrids were examined. For assessing genetic diversity within accessions, DNA was extracted from 12 individual seedlings from six germplasm accessions and two hybrids. A relatively high level of polymorphism was found within accessions based on 59 polymorphic TRAP markers generated from one fixed primer derived from the Arabidopsis-like telomere repeat sequence and two arbitrary primers. For evaluating inter-accession variability, DNA was extracted from a bulk of six to 13 seedlings of each accession. Of the 492 fragments amplified by 12 primer combinations, 96 (19.5%) were polymorphic and discriminated the 48 accessions from each other. The average pair-wise genetic similarity coefficient (Dice) was 57.5% with a range from 23.2 to 85.3%. Dendrogram indicated that the genetic relationships among the accessions were not highly associated with the geographic locations in which the germplasms were collected. The seven commercial hybrids were grouped in three separate clusters, suggesting that the phenotype-based breeding activities tended to reduce the genetic variability. This study demonstrated that TRAP markers are effective for fingerprinting and evaluating genetic variability among spinach germplasms.