title: Effect of pollination timing on the rate of apomictic reproduction revealed by RAPD markers in paspalum notatum.
abstract: Progeny tests employing molecular markers allow the identification of individuals originated by sexual means among the offspring of a facultative apomict. The objective of this work was to evaluate the effect of the pollination timing on the proportion of sexually formed individuals in progenies of a facultative apomictic Paspalum notatum genotype. Progeny families of approx. 30 plants each were generated at five different pollination times: 1-3 d pre-anthesis; at anthesis; and 2, 4 and 6 d post-anthesis. Cytoembryological analyses indicated that approx. 17% of the ovules carried a meiotic cytologically reduced embryo sac in florets formed simultaneously with those used for crosses. The parental plants and the five F1 families were analysed using RAPD molecular markers. Ninety-five oligonucleotides were assayed on the progenitors in order to search for male-specific bands. Eight primers presenting clear polymorphic bands were selected for use in the progeny tests. The proportion of sexually produced progeny reached 3.4% before anthesis and 20 % at anthesis, while pollination after anthesis generated only maternal plants. A second progeny of 97 plants obtained from pollination at anthesis produced 16 off-type plants (16.5%), of which only one was a B(III) hybrid (2n + n). Our results indicate that pollination at anthesis allows the greatest potential for sexuality to be expressed in this facultative apomictic genotype. When pollination is delayed as soon as 2 d after anthesis, only the aposporous sacs develop endosperm through pseudogamy to set seed.
authors.affiliation: Instituto de Botánica del Nordeste, IBONE-CONICET, Facultad de Ciencias Agrarias, UNNE, Corrientes, Argentina. espinoza@agr.unne.edu.ar
authors.forename: F
authors.initials: F
authors.lastname: Espinoza
authors.forename: S C
authors.initials: SC
authors.lastname: Pessino
authors.forename: C L
authors.initials: CL
authors.lastname: Quarín
authors.forename: E M
authors.initials: EM
authors.lastname: Valle
mesh_terms: D003433:Crosses, Genetic; D016172:DNA Fingerprinting / Q000379:methods; D005819:Genetic Markers; D005838:Genotype; D008540:Meiosis / Q000235:genetics / Q000502:physiology; D008938:Mitosis / Q000235:genetics / Q000502:physiology; D018547:Plant Stems / Q000235:genetics / Q000502:physiology; D006109:Poaceae / Q000235:genetics* / Q000502:physiology; D011058:Pollen / Q000502:physiology*; D011123:Polyploidy; D019105:Random Amplified Polymorphic DNA Technique / Q000379:methods*; D012098:Reproduction / Q000502:physiology; D012639:Seeds / Q000166:cytology / Q000196:embryology; D013997:Time Factors
chemical_list: D005819:Genetic Markers