Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 4, 1996
Publication Date: N/A
Interpretive Summary: Cucumber collections from other countries are held at the USDA/ARS North Central Regional Plant Introduction Station in Ames, Iowa. This collection represents a sample of the genetic heritage of this crop since it is the most complete collection worldwide. Only 14% of the collection consists of samples coming from the crop's center of origin and diversity. Therefore, a U.S./Indian government sponsored collecting expedition was made in 1992 to India to acquire more samples to increase the genetic diversity of the U.S. national cucumber collection. These samples were analyzed using biotechnological tools and were found to be different from collections made before 1992, thus showing the potential for acquiring genetic diversity in India. The information will be used by plant geneticists and plant breeders interested in studying genetic diversity and improving cucumber. The importance of the 1992 collection is documented by the results and increases the likelihood of closer cooperation between the U.S. and India regarding the exchange of genetic material.
Technical Abstract: Genetic variation in cucumber (Cucumis sativus var. sativus L.) accessions from India was assessed by examining variation at 21 polymorphic isozyme loci. Forty-six accessions acquired by the U.S. National Plant Germplasm System (NPGS) before 1972 were compared with 146 accessions collected during a 1992 U.S.-India expedition to the states of Rajasthan, Madhya Pradesh and Uttar Pradesh, India. Two distinct groups were identified with accessions collected in 1992 (0.025<P<0.01). Variation at Ak-2, Fdp-2, Gr, Mdh-2, Mpi-1, Per, Pgm, and Skdh was important in the detection of this difference. A previously unreported Pgm allele [Pgm(3)-105] was detected in accessions collected in a market in Pali, Rajasthan. One group contained 37 accessions and the other group contains 102 accessions. Seven accessions were not associated with either group. The accessions 20664 (Tonk, Rahjasthan), 20666 (Jaipur, Rahjasthan), 20872 (Sehore, Madhya Pradesh), 20881 (Ashtok, Sehore, Madhya Pradesh) and 21026 (Bhatta, Dehra Dun, Uttar Pradesh) were heterozygous for at least nine loci and represent the genetic diversity within this collection. Isozymic variation in U.S. NPGS accessions acquired before 1972 differed significantly (P<0.005) from those collected during 1992. All loci were important in the detection of this difference, except Ak-2, Pep-pap, and Pgd-2.