, particularly for those taxa that are narrowly distributed ( Havens, 1998 ; Rogers and Montalvo, 2004 ). When different but cross-compatible taxa are brought into close proximity for seed production or planting, interspecific pollen-mediated gene flow (PMGF
Gene flow between species of different ploidy levels is important in plant evolution and breeding. A cytological study was conducted on a natural population with individuals belonging to the diploid L. purpurea Gay (2n = 10) and to the tetraploid L. coquimbensis F. Phil (2n = 18) species, as well as intermediate phenotypes of apparent hybrid origin. The genus Leucocoryne is endemic to Chile and it exhibits heterogeneity, presumably genetic, for shape, size, and color of its flowers. The objective of the study was to determine if there is gene flow between species having different ploidy levels. From the karyotypic analyses of the seeds, only parental types having 2n = 10 and 2n = 18 individuals were observed. However, from the bulb analyses, 2n = 10, 2n = 18, 2n = 14, and 2n = 22 individuals were encountered. The karyotypes of the 2n = 14 and 2n = 22 individuals suggest the occurrence of natural interespecific hybridization between species with different ploidy levels in nature. Models which may account for the origin of these genotypes are proposed.
It is well known that crossability within section Batatas is a complex phenomenon because of genetic, cytogenetic and physiological implications. During 1988 to 1991 we investigated the factors involved in crossability. In the 1st stage, self-compatibility was determined/verified in I. cynanchifolia (2x), I. grandifolia (2x), I. triloba (2x), I. x leucantha (2x), I. lacunosa (2x), I. tenuissima (2x), I. ramosissima (2x) and I. cordato-triloba (2x). Additionally, self-incompatibility was verified in I. trifida (2x), I. tiliacea (4x) and I. batatas (4x,6x). It is postulated that sexual compatibility is related to a multiallelic sporophytic incompatibility system. In the second stage, 4,162 cross pollinations between 11 species were performed at La Molina and San Ramon, and 76 interspecific combinations from 110 possible theoretic combinations in a diallelic 11 × 11 design were obtained. Of 76 interspecific combinations, 38 succeded with a crossability rate ranging from 0.01 to 1.00 at La Molina. In San Ramon, of 17 interspecific combinations, 11 were succesfull when estimating crossability from 0.01 to 0.71. Considering the factors affecting crossability, it was found that latitude influences flowering synchrony in progenitors, and in the germination process, and the early death of seedlings is related to an unbalanced genome (embryo/endosperm) relationship. In interspecific crosses, it was shown that I. trifida and I. x leucantha act as “bridge species”.
conditions, can contribute to somaclonal variation ( Brar and Jain, 1998 ). Therefore, homogeneity and trueness-to-type of regenerated plantlets should be checked. Several methods are available for this analysis, including chromosome determination, flow
’s genetic identity for analyzed accessions performed on the basis of pairwise comparisons between different countries was evaluated using GenAlEx 6.1 ( Peakall and Smouse, 2006 ). The estimation of gene flow among populations was carried out by calculating
rapid range expansion ( Zong et al., 2014 ), and both restricted gene flow with isolation by distance (IBD) and allopatric fragmentation were crucial processes responsible for shaping the genetic patterns of P. betulaefolia . Although the genetic
Leitch, I.J. Bennett, M.D. 2007 Genome size and its uses: Impact of flow cytometry, p. 153–176. In: Doležel, J., J. Greilhuber, and J. Suda (eds.). Flow cytometry with plant cells: Analysis of genes, chromosomes and genomes. Wiley-VCH, Weinheim, Germany
risk of genetic isolation ( Fahrig, 2003 ; Lienert, 2004 ). Spatial isolation may promote inbreeding and the reduction of gene flow among populations ( den Nijs and Oostermeijer, 1997 ). Moreover, genetic differentiation, gene flow, and levels of
) was 0.25, and the average heterozygosity within populations (H S ) was 0.24. The proportion of species genetic diversity attributed to variation among populations (G ST ) was calculated to be 4.0%, a low value indicating significant gene flow within
Common bean is by far the most widely consumed grain legume in the world ( Singh, 2001 ). Domestication of common bean took place in two, already diverged ancestral wild gene pools distributed from northern Mexico to Colombia (Mesoamerican gene pool