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

FRANCISCO ESPINOZA; PESSINO, S. C.; QUARIN, C. L.; VALLE, E. M.

ANNALS OF BOTANY

OXFORD UNIV PRESS

Año: 2002 vol. 89 p. 165 - 170

0305-7364

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 about 30 plants each  were generated at 5 different pollination times: 1-3 days pre-anthesis, at anthesis, 2, 4 and 6 days post-anthesis. Cytoembryological analyses indicated that approximately 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 by using RAPD molecular markers. Ninety-five total oligonucleotides were assayed on the progenitors 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 %) out 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 shortly as 2 days after anthesis, only the aposporous sacs develop endosperm through pseudogamy to set seed.