A programme of interspecific hybridization, involving species from subsections
Pachyspirae, Leptospirae, and Rotatae of section Spirocarpos, resulted in only one
successful combination out of the 20 attempted.
Viable hybrids were obtained with ease in crosses between different accessions
of M. littoralis and M. truncatula. The morphology, fertility, and cytological behaviour
of interspecific hybrids involving seven strains of M. truncatula and three strains of
M. littoralis was compared with intraspecific hybrids of each species. With the
exception of those with N.2829, which was differentiated from the other strains by one
chromosome translocation, intraspecific hybrids of M. truncatula were fully fertile.
Considerable pollen sterility and reduced seed set were observed in intraspecific
crosses of M. littoralis, but there was no evidence of chromosomal rearrangements.
The morphology of the hybrids between M. littoralis and M. truncatula was
intermediate between the parents. Chlorophyll deficiency in seedlings and adult plants,
dwarfism, and other morphological irregularities were observed in F2 plants. In some
FT1s failure of pairing, multivalent formation at metaphase I, and other irregularities
at meiosis indicated chromosome rearrangements. Up to three independent
translocations and one inversion in the hybrid combinations and pronounced
sterility were observed in both FT1s and FT2s. The pollen sterility of the hybrids could
be explained in several instances by structural differences, but these do not account
completely for the results obtained.
Inheritance studies of three possible strain markers indicated simple monohybrid
segregation in most intraspecific crosses, but in the interspecific and partially fertile
intraspecific crosses, ratios were disturbed and phenotypes abnormal.
The agronomic implications of these studies are discussed.
Assessment of intergenomic recombination through GISH analysis of F1, BC1 and BC2 progenies of Tulipa gesneriana and T. fosteriana
