Genetic variation for male and female fertilities in alfalfa

Christian Huyghe, Rafik Leneguer, Pierre-Henri Auriel,
Christel Bodin, Christian Ecalle, Bernadette Julier

INRA, Station d’Amélioration des Plantes Fourragères,
F-86600 Lusignan, FRANCE

The seed production in alfalfa is influenced by the fertility of both male and female gametophytes. A lot of efforts have been devoted to the analysis of the pollen fertility but little to the ovules.

To assess the female fertility, a rapid clearing technique based on a fixation with FPA50, rinsing with ethanol and clearing with methylsalicylate was developed. It makes it possible to observe the embryo sac through the ovary structure without any dissection, using a phase contrast microscope. The pollen fertility was measured with Alexander staining.

The position of the flower into the inflorescence did not modify neither pollen nor ovule fertility. The position of the inflorescence on the stems only influenced the female fertility of a single genotype. The position of the ovule within the ovary did not influence the female fertility (figure 1).

The genetic variation available for both characters was analysed on 10 populations, with 9 individual plants per population. The observations were repeated over two years. This analysis confirmed the existence of a wide range of genetic variation for the pollen fertility (from 20 to 96% with an average of 69%). A wide range was also observed for the female fertility (from 36 to 98% with an average of 82%). For both fertilities, the within-population variance was either equal or larger than the between-population variance (Table 1). There was no strict relationship between the male and female fertilities (r=0.40, 88 df).