Journal Article Intergeneric hybrids between Crataegus L. and Mespilus L.: a fresh look at an old problem Get access J. I. BYATT, J. I. BYATT F.L.S. 1Department of Botany and Biochemistry, Westfield College, London N.W.3 Search for other works by this author on: Oxford Academic Google Scholar I. K. FERGUSON, I. K. FERGUSON F.L.S. 2Royal Botanic Gardens, Kew, Richmond, Surrey Search for other works by this author on: Oxford Academic Google Scholar B. G. MURRAY B. G. MURRAY F.L.S. 3Department of Botany and Biochemistry, Westfield College, London N.W.3 Search for other works by this author on: Oxford Academic Google Scholar Botanical Journal of the Linnean Society, Volume 74, Issue 4, June 1977, Pages 329–343, https://doi.org/10.1111/j.1095-8339.1977.tb01185.x Published: 28 June 2008 Article history Accepted: 01 January 1977 Published: 28 June 2008
Abstract Evolution in the genus Pratia (Campanulaceae) has been studied using a variety of techniques. The distribution of chromosome races in P. angulata has been plotted and results suggest that although they generally occupy different geographic areas there are large areas of overlap. No consistent morphological differences were found between these chromosome races. The existence of hybrids between P. angulata and P. perpusilla with 1 1x and 13x chromosome numbers has been established using genomic in situ hybridization (GISH), and random amplified polymorphic DNA (RAPD) analysis suggests several independent origins for these hybrids. Artificial hybridization studies showed a high degree of compatibility in almost all the combinations that were attempted. DNA sequences derived from both the nuclear genome (internal transcribed spacer of the rDNA locus, ITS) and chloroplast genomes (trnL intron and trnL‐trnF spacer) were used to construct phylogenies. Colensoaphysaloides has been shown to be distinct from the New Zealand species of Pratia and was used as an outgroup to root the phylogenetic trees. A significant finding is that P. macrodon is sister to the other New Zealand species. DNA sequence data also confirm the hybrid origin of the 1 1x and 13x plants and show that P. perpusilla is the maternal parent of the 1 1x plants and P. angulata is the maternal parent of the 13x ones. The origin of the putative hybrid plants with the12x chromosome number remains to be elucidated. Key words: Campanulaceae Pratia Colensoa cytogeneticspolyploidyhybridizationRAPDsGISHphylogenycpDNA sequencesITSNew Zealand flora
B chromosomes have been found in 7 out of 39 populations of Silene maritima With. (Carophyllaceae) studied. These 7 populations are all from the Norfolk coast. The B chromosome is small, 0.8 μm long, telocentric and appears euchromatic. Within plants the B chromosome is highly unstable with different numbers in cells of the same root or pollen mother cells (pmcs) of an anther. The transmission of the Bs is efficient and in controlled crosses progeny plants usually have higher mean B frequencies than the B-containing parents. At metaphase I the pairing behaviour of the Bs is variable and they often appear as univalents. In general the presence of Bs in pmcs results in an increase in chiasma frequency/cell and populations with Bs have higher mean chiasma frequencies than those without Bs. Cloned plants grown under stress conditions induced by the addition of NaCl to a nutrient solution showed no difference in mean B number/cell or distribution when compared with controls grown in nutrient solution only.
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