Genetic Diversity of Seven Deciduous Azalea Species (Rhododendron spp. section Pentanthera) Native to the Eastern United States

Abstract

<jats:p>Despite the ecologic and economic importance of native deciduous azaleas (<jats:italic>Rhododendron</jats:italic> L. section <jats:italic>Pentanthera</jats:italic> G. Don), our understanding of interspecific variation of North American deciduous azalea species comes principally from morphologic studies. Furthermore, little is known concerning intraspecific or interpopulation genetic variation. With ever-increasing loss and fragmentation of native azalea habitat in the eastern United States due to anthropogenic activity, it is imperative that an understanding of natural genetic variation among and within species and populations is acquired. The present study addresses questions of genetic diversity through the use of amplified fragment length polymorphism (AFLP) analysis. Twenty-five populations of seven species of native azalea were analyzed using three primer pairs that amplified a total of 417 bands. Based on analysis of molecular variance (AMOVA) and estimates of Nei's coefficients of gene diversity (<jats:italic>H</jats:italic> <jats:sub>S</jats:sub>, <jats:italic>H</jats:italic> <jats:sub>T</jats:sub>, and <jats:italic>G</jats:italic> <jats:sub>ST</jats:sub>), the majority of variation found in deciduous azalea occurs within populations. Variation both among species and among population was low, likely the effect of common ancestry as well as frequent introgression among members (and populations) of section <jats:italic>Pentanthera</jats:italic>. The latter was evident in four populations of <jats:italic>R. prunifolium</jats:italic> (Small) Millais and <jats:italic>R. canescens</jats:italic> (Michaux) Sweet that were highly related to <jats:italic>R. austrinum</jats:italic> (Small) Rehder and <jats:italic>R. viscosum</jats:italic> (L.) Torrey, respectively. Despite these outliers, most populations were grouped into species based on Nei's unbiased genetic distances viewed as an unweighted pair group method with arithmetic mean (UPGMA) phenogram. The significance of these results is discussed in relation to breeding in section <jats:italic>Pentanthera</jats:italic>.</jats:p>

Genetic Diversity and Population Structure of Rhododendron canescens, a Native Azalea for Urban Landscaping

“…An analysis of R. canescens genetic diversity was included in a prior study (Chappell et al, 2008) that examined four R. canescens populations (six accessions each) with AFLP markers. Similar to that study, our investigation found a low G ST value, indicating that the proportion of diversity between populations was low, while the proportion of diversity within populations was high.…”

“…Minimal differentiation between R. canescens populations was also indicated by the low F ST value. Chappell et al (2008) suggested that this may be the result of gene flow between populations due to insect pollination. R. canescens is known to be pollinated by bumblebees, adrenid bees, butterflies, and hummingbirds.…”

“…These studies found little sequence variation among species of the section Pentanthera, suggesting that they are a closely related group. Low genetic diversity among section Pentanthera species was further observed in a study with several hundred amplified fragment length polymorphism (AFLP) markers (Chappell et al, 2008). In that study, AFLP analysis was also used to investigate variation between and within populations of individual azalea species, including R. canescens.…”

“…In contrast to the low level of variation found between populations and species, a high level of variation was observed within populations. Variation within R. canescens populations may be due in part to hybridization and introgression from other native azalea species (Chappell et al, 2008).…”

Molecular Genetic Variability of Spigelia marilandica and S. gentianoides

“…(Zhang et al, 2010), sweetpotato [Ipomoea batatas (Cervantes-Flores et al, 2008)], pecan [Carya illinoinensis (Beedanagari et al, 2005)], Rhododendron sp. (Chappell et al, 2008), barberry [Berberis thunbergii (Lubell et al, 2009)], and Lactuca sp. (Koopman et al, 2001).…”