Three RFLP maps, as well as several RAPD maps have been developed in common bean (Phaseolus vulgaris L.). In order to align these maps, a core linkage map was established in the recombinant inbred population BAT93;Jalo EEP558 (BJ). This map has a total length of 1226 cM and comprises 563 markers, including some 120 RFLP and 430 RAPD markers, in addition to a few isozyme and phenotypic marker loci. Among the RFLPs mapped were markers from the University of California, Davis (established in the F of the BJ cross), University of Paris-Orsay, and University of Florida maps. These shared markers allowed us to Communicated by P. M. A. Tigerstedt

We examined reproductive isolating barriers at four postmating stages among 11 species from the morphologically diverse genus Nolana (Solanaceae). At least one stage was positively correlated with both genetic and geographic distance between species.Postzygotic isolation was generally stronger and faster evolving than postmating prezygotic isolation. In addition, there was no evidence for mechanical isolation, or for reproductive character displacement in floral traits that can influence pollinator isolation. For sexually reproducing plants and animals, the origin of new species involves the evolution of reproductive isolating barriers between diverging lineages. Studying these isolating barriers therefore provides insight into the process of speciation (Coyne and Orr 2004). Several approaches have been used to examine the evolution of reproductive isolation within the same closely related group of species, including examining the relative strength of isolating barriers operating at different reproductive or developmental stages among different species pairs, across different degrees of evolutionary divergence, and/or among reciprocal crosses (Coyne and Orr 2004, and see below). These approaches aim to evaluate how rapidly barriers accumulate and which isolating barriers contribute most during initial divergence between lineages, among other questions. In combination, they can provide insight into the evolutionary forces and the genetic mechanisms responsible for the evolution of new, reproductively independent, lineages.First, examining the reproductive compatibility of a single species pair at multiple developmental stages (e.g., premating, postmating prezygotic, and postzygotic) can be used to infer which stages are most effective at reducing current gene flow between these species, and therefore which stages might have been more or less influential during their initial divergence (e.g., Ramsey et al. 2003;Kay 2006;Martin and Willis 2007;Mendelson et al. 2007;Maroja et al. 2009;Dopman et al. 2010). For example, based on the estimated contributions of multiple preand postzygotic reproductive barriers between two monkeyflower sister species, Mimulus lewisii and M. cardinalis (Ramsey et al. 2003), factors acting prior to hybridization (specifically ecogeographic isolation and pollinator isolation) were inferred to be the primary isolating barriers in this system. Data such as these can also suggest the evolutionary forces that are most likely responsible for reducing gene flow between species. For example, estimates of pre-and postzygotic barriers between M. guttatus and M. nasutus (Martin and Willis 2007) revealed that prezygotic barriers contributed most to total isolation, likely as a result of adaptive divergence in mating systems (i.e., shift to self-pollination) and edaphic ecology (i.e., drought avoidance via phenological acceleration).

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Quantitative trait locus (QTL) analysis for tuber dormancy was performed in a diploid potato population (TRP133) consisting of 110 individuals. The female parent was a hybrid between haploid S. tuberosum (2x) and S. chacoense, while the male parent was a S. phureja clone. The population was characterized for ten isozyme loci, 44 restriction fragment length polymorphisms (RFLPs) and 63 random amplified polymorphic DNAs (RAPDs). Eighty-seven of these loci segregating from the female parent were utilized to develop a linkage map that comprised 10 of the 12 chromosomes in the genome. Dormancy, as measured by days-to-sprouting after harvest, ranged from 10 to 90 days, with a mean of 19 days. QTLs were mapped by conducting one-way analyses of variance for each marker locus by dormancy combination. Twenty-two markers had a significant association with dormancy, identifying six putative QTLs localized on each of chromosomes 2, 3, 4, 5, 7 and 8. The QTL with the strongest effect on dormancy was detected on chromosome 7. A multilocus model was developed using the locus with highest R(2) value in each QTL. This model explained 57.5% of the phenotypic variation for dormancy. Seven percent of possible epistatic interactions among significant markers were significant when tested through two-way analyses of variance. When these were included in the main-effects model, it explained 72.1% of the phenotypic variation for dormancy. QTL analysis in potato, the methodology to transfer traits and interactions into the 4x level, and QTLs of value for marker-assisted selection, are discussed.