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

ESPINOZA F; PESSINO SC; QUARIN CL; VALLE EM

ANNALS OF BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; 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 offsrping 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 analysis 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 sexualy 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 yhe aposporous sacs develop endosperm through pseudogamy to set seed.