Self and cross pollination effects on pollen tube growth and fertilizationin self-compatible almond Prunus dulcis 'Tuono'

The inbreeding consequences linked to self compatibility in the cultivated almond, Prunus dulcis (Mill) D. A. Webb were evaluated histologically in th e self-compatible cv. Tuono. Self and cross pollen tubes grow at similar sp eeds in the pistil of 'Tuono'. The pollen tubes reach the style base 4 d af ter pollination. The gametophytic interactions did not help in reducing the occurrence, at this level, of inbreeding effects. The development of the e mbryo sac stimulated by two types of pollination is differentiated when the pollen tubes reach the style base. However, the fertilization process, mar ked by the fusion of polar nucleus and the elongation of the embryo sac, sh ows a delay in the case of the selfed ovule. The differentiation of the pol len sac is in fact realized for 20% of the ovules 5 d after self pollinatio n. In this case 80% of the embryo sacs have unfused polar nuclei. For the s ame period, 80% of the crossed ovules have polar nuclei which are already f used. The type of pollination seems to have a potential effect on ovule via bility of embryo sacs which suggest that the inbreeding effects are reveale d after fertilization.