K. Havens et Lf. Delph, DIFFERENTIAL SEED MATURATION UNCOUPLES FERTILIZATION AND SIRING SUCCESS IN OENOTHERA-ORGANENSIS (ONAGRACEAE), Heredity, 76, 1996, pp. 623-632
This study examines ovule fertilization and seed maturation success in
an evening primrose, Oenothera organensis, using transgenic plants. T
he reproductive success of several pollen donors was compared using in
dividuals transformed with the GUS (beta-glucuronidase) marker ne whic
h allowed the genotype of developing ovules to be determined prior to
seed abortion. This marker gene allowed us to discriminate between a p
ollen donor's success in fertilizing ovules and its success in siring
seeds. Transformed plants had decreased microgametophytic vigour, as e
videnced by lower than expected fertilization success in vivo and slow
er pollen tube growth rates in vitro. However, transformation had no a
pparent effect on offspring sporophytic vigour, including seed mass, s
eedling emergence and dry weight. This illustrates the effectiveness o
f fertilization competition in screening out poorly functioning haploi
d genomes as suggested by Mulcahy (1979). We found significant differe
nces between the percentage of ovules fertilized and the percentage of
seeds sired by a pollen donor in four of eight cases. Hence, fertiliz
ation success does not always predict seed paternity. The proportion o
f seeds sired by the transformed donor with very low fertilization suc
cess increased, whereas the proportion sired by the donor with relativ
ely high fertilization success was reduced. This resulted in nearly eq
ual siring ability for the two donors in spite of their difference in
fertilization ability.