Interspecific reproductive barriers and genomic similarity among the rough-seeded Lupinus species

The nature of reproductive barriers and meiotic behaviour of chromosomes were studied in interspecific hybrids among the six rough-seeded Lupinus species. Out of 30 different interspecific crosses attempted in all possible combinations, eight produced viable F, seeds. These successful crosses involved L. cosentinii, L. digitatus, L. atlanticus and L. pilosus. Crosses of L. princei with other species resulted in shrivelled F, seed in all combinations. In contrast to previous reports, crosses of L. palaestinus with all other rough-seeded lupins were incompatible as no F1 hybrids were obtained. Barriers to interspecific reproduction were identified as nucleo-cytoplasmic and embryo-endosperm incompatibility in unsuccessful crosses, and chromosomal imbalances in F1 hybrids. Gene transfer is possible among L. cosentinii, L. digitatus and L. atlanticus, which produced F2 seed. Patterns of chromosome configurations in F1 meiotic cells suggested that these species have at least two genomes partially in common, but include inversions and translocations. The genome of L. atlanticus is closer to L. digitatus than to L. cosentinii, and that of L. pilosus is closer to L. atlanticus than to L. cosentinii. L. princei appears to have an isolated genome within the rough-seeded Lupinus species