Annals of Botany 89: 165-170, 2002
© 2002 Annals of Botany Company
Effect of Pollination Timing on the Rate of Apomictic Reproduction Revealed by RAPD Markers in Paspalum notatum
1Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, UNNE, Sargento Cabral 2131, (3400) Corrientes, Argentina and 2Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), División Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Suipacha 531, (2000) Rosario, Argentina
* For correspondence. E-mail espinoza{at}agr.unne.edu.ar
Received: 6 June 2001; Returned for revision: 4 October 2001; Accepted: 20 October 2001.
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: 13 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 BIII 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.
Key words: Apomixis, Paspalum notatum, pollination timing, RAPD fingerprinting.