Evaluation of Interspecific Crossing Experiments in Facultatively Apomictic Blackberries (Rubus subgen. Rubus) Using DNA Fingerprinting

Abstract

A series of interspecific crossing experiments in Rubus was evaluated with DNA fingerprinting to assess the proportion of apomictic vs sexual seed set. A total of 71 seedlings and their putative parents were thus analyzed by hybridization of HaeIII‐digested DNA samples to a minisatellite DNA probe derived from the M13 phage. Of the offspring derived from non‐hybridogenous seed parents, only about 10% appear to emanate from sexual seed set. On the contrary, offspring derived from pollination of hybridogenous plants were in 6 cases out of 10 sexually derived. Pollen stainability with cotton blue was also investigated and could, though to a more limited extent, be used as an indicator of reproductive mode. Taxonomic treatment of Rubus and other apomictic plant groups would clearly benefit from more data on reproduction and dispersal, which may be obtained by DNA fingerprinting.Hilde Nybom, Balsgard‐Department of Horticultural Plant Breeding, Swedish University of Agricultural Sciences, Fjalkestadsvagen 123‐1, S‐291 94 Kristianstad, Sweden

Characterisation of pseudogamous apospory in the reproductive biology of the invasive weedRubus alceifolius(Rosaceae) in its area of introduction

“…The pseudogamous apospory occurring in R. alceifolius in its area of introduction is the same type of apomixis as that described in European species of the subgenus Rubus (Thomas, 1940;Gustafsson, 1943;Nybom, 1988Nybom, , 1995Weber, 1995;Kollmann et al, 2000). To determine whether fruit-set from non-pollinated flowers results from apomixis or autogamy, individuals with heterozygous microsatellite loci are necessary (Amsellem et al, 2001 ).…”

“…Among the 12 subgenera of the genus Rubus, apomixis prevails in the subgenus Rubus, only in polyploid taxa, under the form ofpseudogamous apospory. In this type of apomixis, asexual reproduction takes place, but the endosperm may require fertilisation to develop (Crane, 1940;Thomas, 1940;Gustafsson, 1943;Jennings et al, 1967;Czapik, 1981Czapik, , 1983Nybom, 1985Nybom, , 1988Nybom, , 1995Richards, 1986;Weber, 1996;Kollmann et al, 2000;van Dijk & van Damme, 2000). Apomixis also occurs in polyploid species from other subgenera of Rubus (Petrov, 1939;Pratt & Clausen, 1958;Nybom, 1988).…”

“…Apospory, diplospory, and reduced embryo sacs commonly occur together in the same species. Usually, reduced embryo sacs do not develop until fertilized, and unreduced embryo sacs develop parthenogenetically (Nybom, 1988(Nybom, , 1995. However, exceptions to both phenomena occur, thereby rendering reproduction in the genus Rubus extremely versatile.…”

Concealed diversity : taxonomical, phytogeographical and phytosociological notes on brambles (Rubus L. subgen. Rubus) in north-west Europe

“…Hybridisation between apomictic lineages of Rubus subgen. Rubus is possible as a result of re-sexualisation followed by pollination, as was proved in DNA research (Nybom 1995;Werlemark & Nybom 2003). Lidforss (1905Lidforss ( , 1907 showed that primary hybrids between apomictic species seem to be largely sexual.…”

“…Apomictic reproduction combines both diplospory and apospory, and this mode of reproduction can be influenced by environmental factors (Šarhanová et al 2012). Especially in tetraploids, retained sexuality can be considerable (Antonius & Nybom 1995;Nybom 1995), but triploid and pentaploid taxa are almost obligate apomicts (Šarhanová et al 2012). Artificial hybrids are rather easily obtained, not only when a sexual partner is involved, but also between apomict lineages.…”