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United States Department of Agriculture

Agricultural Research Service

Research Project: ALLIUM, CUCUMIS, AND DAUCUS GERMPLASM ENHANCEMENT, GENETICS, AND BIOCHEMISTRY Title: Genetic diversity among cucumis metuliferus populations revealed by cucumber microsatellites

Author
item Weng, Yiqun

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 16, 2009
Publication Date: March 1, 2010
Citation: Weng, Y. 2010. Genetic diversity among cucumis metuliferus populations revealed by cucumber microsatellites. HortScience. 45(2):214-219.

Interpretive Summary: African horned cucumber (AHC) or horned melon is native to tropical and sub-tropical Africa and is a relative of cucumber and melon. AHC is being promoted as a specialty crop in several countries including the US. Cucumber and melon breeders have much interest in this species because horned cucumber has a number of useful traits such as high level of resistance to several nematode species and viruses. However, attempts in the past to cross horned cucumber with either cucumber or melon were unsuccessful. Recent development in plant genomics is providing new avenues to explore useful genes in horned cucumber. This requires better understanding the genetics of horned cucumber populations. In the present study, genetic diversity among the USDA horned cucumber collection was evaluated with molecular markers (microsatellite or simple sequence repeat, SSR) derived from cucumber genomic DNA sequences. Of the 564 cucumber SSRs tested, 51.8% were able to amplify products from horned cucumber suggesting high degree DNA sequence homology between the two species. Forty-two cross-species transferable SSRs were selected to investigate genetic variability among 35 accessions from USDA collection and one line of commercial source. Genetic diversity among these accessions was low. Of the 42 markers tested, 13 were not informative among the 36 lines tested, and each marker, on average, was able to detected only 3.4 alleles. A positive relationship of genetic divergence and geographic distance was found among these accessions. Information from this study could be used as a guide for selection of parental lines to develop segregating population for genetic mapping of useful genes in this species.

Technical Abstract: Cucumis metuliferus E. Mey. ex Naud (African horned cucumber, AHC) is native to Africa and is a relative of cultivated cucumber (C. sativus L.) and melon (C. melo L.). AHC is being promoted as a specialty fruit crop in a number of countries. In addition, several traits in C. metuliferus such as high level resistance to the several nematode species and papaya ring spot virus, sequential and concentrated fruiting are very attractive for improving cucumber or other cucurbit crops. However, attempts in the past to cross AHC with either cucumber or melon were unsuccessful. In the present study, genetic diversity among the USDA C. metuliferus collection was evaluated with microsatellite (simple sequence repeat, SSR) markers derived from cucumber genomic DNA sequences. Of the 564 cucumber SSRs tested, 51.8% were able to amplify PCR products from C. metuliferus genomic DNA templates suggesting high degree DNA sequence homology between the two species. Forty two cross-species transferable SSRs were selected to investigate genetic variability among 35 accessions from USDA collection and 1 commercial source C. metuliferus selections. Genetic diversity among these C. metuliferus accessions was low. Of the 42 markers tested, 13 were monomorphic among the 36 accessions, and each marker, on average, was able to detected only 3.4 alleles. Clustering analysis support a positive relationship of genetic distance and geographic distance among these accessions. The possible reasons of the low genetic diversity among C. metuliferus accessions and the implications of this finding with regard to use of C. metuliferus resources for cucurbit improvement were discussed.

Last Modified: 11/26/2014
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