Barriers preventing hybridisation of Lathyrus odoratus with L. chloranthus and L. chrysanthus

Abstract

Interspecific hybridisation of the sweet pea, Lathyrus odoratus L., with two yellow flowered relatives, Lathyrus chloranthus Boiss. and L. chrysanthus Boiss., was undertaken with the aim of transferring yellow flower colour into the sweet pea. Initial reciprocal cross pollinations of L odoratus ’Original’, with the two species, produced no viable seed, suggesting the presence of interspecific hybridisation barriers. Observation of events following further reciprocal cross pollinations confirmed the presence of hybridisation barriers which prevented the formation of hybrid embryos in all cross combinations except L. chloranthus × L. odoratus. Post‐fertilisation hybridisation barriers subsequently prevented the maturation of such hybrid embryos. Further crosses using a range of sweet pea cultivars indicated varying degrees of impediment to hybridisation depending on the cultivar used. Pre‐fertilisation hybridisation barriers which prevented the growth of foreign pollen tubes to the bases of styles were observed in L. odoratus × L. chloranthus crosses and reciprocal L odoratus × L chrysanthus crosses involving long‐styled L. odoratus cultivars. Although growth of pollen tubes to the bases of the styles and to ovules was observed when shorter‐styled cultivars were used, hybridisation barriers acting around the time of fertilisation prevented the production of embryos. In L chloranthus × L odoratus crosses, cultivar had no effect on post‐fertilisation barriers causing embryo failure. Endosperm degeneration was presumed to be the cause of embryo failure.

Keywords:

• Lathyrus
• interspecific hybridisation
• breeding barriers
• embryo development
• embryo rescue