ABSTRACT
Measures of molecular and morphological genetic variation are often used to set conservation priorities and design management strategies for plant taxa. Evaluated together they can give insights into a taxon's evolutionary status that neither data type alone can achieve. We investigated the distinctness and variability of Sedum integrifolium ssp. leedyi, a federally and state-listed taxon, from its conspecific relatives using 33 random amplified polymorphic DNA (RAPD) markers (253 plants) and 37 morphological characters from 1308 common-garden-grown plants. We included S. integrifolium ssp. leedyi (four populations), its conspecific relatives (11 populations), and S. rosea and S. rhodanthum populations in our study. The morphological and molecular data correspond in showing that S. integrifolium ssp. leedyi populations are highly distinct. However, the data sets differ in their estimates of the relatedness of some S. integrifolium ssp. leedyi populations and in the percentage variation detected due to differences among them (25 and 9-13% for the molecular and morphological data, respectively) suggesting little gene flow among populations and some differentiation, possibly from selective pressures. Given our data, we recommend that S. integrifolium ssp. leedyi merits protection under the U.S. Endangered Species Act and that its populations be managed as distinct units.
ABSTRACT
In order to help establish a basis for assessing the risk associated with the testing and large-scale deploymen of transgenic raspberries, wild and feral raspberry populations in Scotland were surveyed for evidence of the escape of genes introduced into raspberry cultivars by traditional breeding. The genes concerned were introduced into cultivars using traditional breeding techniques and were deployed at known times 20 to 30 years prior to the present survey. Escape of the semidominant L 1 gene, affecting fruit size and plant morphology, could not be detected after 30 years in test plots at the Scottish Crop Research Institute near Dundee. The recessive gene s, conferring spinelessness, was detected at very low frequencies (estimated at 0.004) in wild populations within the commercial production locales where cultivars carrying this gene had been introduced on a large scale beginning 21-years prior to this survey. This gene was not, however, found in any areas remote from the commercial production locales. The results of the survey indicate that escape does occur following large-scale deployment but that gene flow events are probably infrequent and spread is localized for genes having probable neutral selective value.
ABSTRACT
The use of micronuclei frequency per microspore quartet (MF) has been proposed to indicate the relative reduction in chromosome homology among interspecific oat (Avena L.) hybrids. Hybrids with lower MF would presumably undergo greater genetic recombination, providing greater opportunity for breaking linkages that contribute to association, or coherence, of desirable and undesirable characters in progenies. Microspore quartets from 63A. sativa/A. fatua hybrids were observed. Character coherence was examined in progenies of the four hybrids with the highest MF (2.22 to 2.82 micronuclei/quartet) and four hybrids with the lowest MF (0.23 to 0.31 micronuclei/quartet) to determine whether a relationship existed between MF and character coherence. Coherence of seed disarticulation with quantitative characters that differentiate the parental species was more frequent in high MF crosses as was expected if high MF is indicative of reduced recombination. However, incidence of coherence between seed color and the quantitative characters was not related to MF differences among the crosses. Likewise, the degree of coherence among the quantitative characters, as measured by coefficients of concordance, was not associated with differences in MF among the crosses. Thus, coherence of the characters studied was not associated consistently with differences in MF.
