Effect of pollination timing on the rate of apomictic reproduction revealed by RAPD markers in Paspalum notatum

• Published in: Annals of botany 2002-02, Vol.89 (2), p.165-170
• Main Authors: Espinoza, F, Pessino, S.C, Quarin, C.L, Valle, E.M
• Format: Article
• Language: English
• Subjects: Apomixis; application timing; Crosses, Genetic; DNA Fingerprinting - methods; Embryo sac; endosperm; Flowering; Genetic Markers; Genotype; Genotypes; Hybridity; hybrids; Meiosis - genetics; Meiosis - physiology; Mitosis - genetics; Mitosis - physiology; Ovules; Paspalum notatum; Plant Stems - genetics; Plant Stems - physiology; Plants; Ploidies; Poaceae - genetics; Poaceae - physiology; Pollen - physiology; Pollination; Polyploidy; progeny; random amplified polymorphic DNA technique; Random Amplified Polymorphic DNA Technique - methods; Reproduction - physiology; seed set; Seeds - cytology; Seeds - embryology; sexual behavior; Sexual reproduction; Time Factors
• ISSN: 0305-7364; 1095-8290
• DOI: 10.1093/aob/mcf024

Progeny tests employing 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 Bm 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.