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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVED PLANT GENETIC RESOURCES FOR PASTURES AND RANGELANDS IN THE TEMPERATE SEMIARID REGIONS OF THE WESTERN U.S. Title: Detection of Genetic Variation in Wild Populations of Three Allium Species Using Amplified Fragment Length Polymorphisms

Authors
item Phillips, Nathan - MIDDLE TENNESSEE ST UNI
item Larson, Steven
item Drost, Daniel - UTAH STATE UNIVERSITY

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 20, 2008
Publication Date: June 15, 2008
Citation: Phillips, N.C., Larson, S.R., Drost, D.T. 2008. Detection of Genetic Variation in Wild Populations of Three Allium Species Using Amplified Fragment Length Polymorphisms. HortScience.

Interpretive Summary: Three wild onion species native to the intermountain west in the United States - Allium acuminatum, A. brandegei, and A. passeyi - show horticultural potential, but little is known about patterns of genetic diversity among localized populations and geographical regions. We examinined amplified fragment length polymorphisms (AFLP) within and among five Allium acuminatum, four A. brandegei, and three A. passeyi collection sites in Utah. These three sister species with contrasting abundance and distribution patterns provide an opportunity to investigate the role of geographic distance, altitude, and rarity in patterns of genetic divergence. The collection sites were selected along an altitudinal gradient to reflect ecogeographic variation. Individual plants from each of the 12 sites were analyzed using DNA fingerprinting to determine genetic variation within and among all three species. Genetic differences between species were high enough to render comparisons among species impractical, so each species was analyzed separately for differences between populations and variability within populations. Genetic similarity coefficients were significantly greater within collection sites versus among collection sites indicating divergence between populations. Within-population genetic diversity was not correlated with elevation for any of the three species. Approximately 66% (A. acuminatum), 83% (A. passeyi), and 64% (A. brandegei) of the overall genetic variation was maintained within populations for each of these three species. Genetic divergence among populations was higher in the widely distributed species, suggesting that interpopulation gene flow may be negatively correlated with range size. Allium acuminatum and A. brandegei individuals cluster into groups corresponding strictly to collection sites based on genetic similarity between individual plants. Allium passeyi populations, however, had less overall genetic variation between populations. Geographic distance explained much of the genetic variability among populations, although there was one notable exception showing significant genetic differences between two adjacent A. acuminatum populations.

Technical Abstract: Three wild onion species native to the intermountain west in the United States - Allium acuminatum, A. brandegei, and A. passeyi - show horticultural potential, but little is known about patterns of genetic diversity among localized populations and geographical regions. We examined amplified fragment length polymorphisms (AFLP) within and among five Allium acuminatum, four A. brandegei, and three A. passeyi colleciton sites in Utah. These three congeners with contrasting abundance and distribution patterns provide an opportunity to investigate the role of geographic distance, altitude, and rarity in patterns of genetic divergence. The collection sites were selected along an altitudinal gradient to reflect ecogeographic variation. Individual plants from each of the 12 sites were genotyped using six AFLP primer combinations detecting DNA variation within and among all three species. Genetic differences between species were high enough to render comparisons among species impractical, so each species was analyzed separately for differences between populations and variability within populations. Similarity coefficients were significantly greater within collection sites versus among collection sites indicating divergence between populations. Within-population genetic diversity was not correlated with elevation for any of the three species. Analysis of molecular variance revealed that 66% (A. acuminatum), 83% (A. passeyi), and 64% (A. brandegei) of observed variation is found within populations. Genetic divergence among populations (VST) was higher in the widely distributed species, suggesting that interpopulation gene flow may be negatively correlated with range size. Allium acuminatum and A. brandegei individual cluster into groups corresponding strictly to collection sites based on neighbor-joining analysis of the total number of DNA polymorphisms between individual plants. Allium passeyi populations, however, had less overall genetic variation between populations. Genetic isolation by distance appeared responsible for much of the variability among populations, although there was one notable exception showing significant differences between two geographically close populations in A. acuminatum.

Last Modified: 10/23/2014