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Title: DEVELOPMENT AND UTILIZATION OF SSRS TO ESTIMATE THE DEGRESS OF GENETIC RELATIONSHIPS IN A COLLECTION OF PEARL MILLET GERMPLASM.

Author
item BUDAK, H - UNIVERSITY OF NEBRASKA
item PEDRAZA, F - UNVIERSITY OF NEBRASKA
item Cregan, Perry
item BAENZIGER, P - UNIVERSITY OF NEBRASKA
item DWEIKAT, I - UNIVERSITY OF NEBRASKA

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/30/2003
Publication Date: 3/30/2003
Citation: Budak, H., Pedraza, F., Cregan, P.B., Baenziger, P.S., Dweikat, I. 2003. Development and utilization of ssrs to estimate the degress of genetic relationships in a collection of pearl millet germplasm. Crop Science. 43:2284-2290.

Interpretive Summary: Narrow genetic diversity within a cultivated crop species limits the amount of genetic improvement that can be made by plant breeders. Pearl millet has a narrow gene pool and one approach to increase available genetic diversity is to identify unimproved exotic pearl millet germplasm that is demonstrably different from the cultivated gene pool. A commonly used way to quantify genetic variation is by the use of DNA markers. In this study we developed a set of 11 simple sequence repeat (SSR) or microsatellite DNA markers and used these along with 19 other SSR markers to assess molecular genetic variability in a set of 53 pearl millet accessions derived from many origins around the world. A cluster analysis of the DNA marker data revealed a number of accessions that were genetically distinct from the highly bred cultivated pearl millet germplasm pool. This work demonstrated that SSR markers could be successfully used to assess genetic variability in a diverse spectrum of pearl millet germplasm. This information will be of use to pearl millet geneticists and breeders who desire to broaden the genetic base of cultivated pearl millet.

Technical Abstract: Pearl millet [Pennisetum glaucum (L.) R. Br.] cultivars derive from a narrow gene pool, and studies of genetic diversity in Pennisetum germplasm suggest promising opportunities for the use of undomesticated materials for improving pearl millet varieties. However, efficient utilization of wild germplasm will require effective DNA marker-based fingerprinting strategies for rapid assessment of genetic relationships. The present study aims at development and utilization of a collection of microsatellite (SSR, simple sequence repeat) markers for assessing the genetic diversity of 53 lines of millet. A small insert genomic library was screened with a (CT)15 oligonucleotide probe. A total of 34 (CT)n'containing clones were identified, and specific primers were designed for 18 of these. Of 18 new microsatellites developed as a part of this work, 11 were used to estimate the genetic diversity, along with 19 from other sources. Cluster analysis by the unweighted pair-group method with arithmetic averages (UPGMA) showed two major and eight minor clusters, suggesting that the millet germplasm could readily be distinguished by UPGMA. The coefficients of genetic distance among germplasm lines were high and averaged D = 0.60 (range 0.28'0.92). Genetic diversity averaged 0.38. These results demonstrated that genotypes with potential traits are maximally different from the cultivated gene pool and could readily be distinguished. Development and utilization of polymerase-chain-reaction-(PCR)-based markers such as SSRs is a valuable asset for estimating genetic diversity, the identification of unique genotypes as potentially important new sources of alleles for enhancing important characteristics, and analyzing the evolutionary and historical development of cultivars at the genomic level in pearl millet breeding programs.