RFLPs (restriction fragment length polymorphisms)
of PCR (polymerase chain reaction) -amplified
fragments were used to trace the pattern of plastid DNA
inheritance in the genus Actinidia. A total of 51 progeny
originating from interspecific crosses between three A.
arguta cultivars and A. deliciosa, the kiwifruit, and 12
progeny originating from the cross between A. kolomikta
and A. chinensis were analysed together with their parents.
No reciprocal crosses could be tested since they all
failed to set viable seeds. Attempts to rescue immature
embryos failed in all cases as well. The A. argutaXA.
deliciosa crosses were checked for the RFLP patterns of
a sequence encoding part of the Rubisco large subunit
(rbcL), using either AluI or MseI, and for a sequence
encoding part of the photosystem II D1 protein (psbA),
using Hinfl. The A. kolomikta×A, chinensis cross was
checked for the RFLP patterns of sequences encoding
the spacers between trnT and the 5'-trnL exon (a-b spacer
DNA) and the trnL 3' exon and trnF (e-f spacer DNA),
respectively. The first spacer revealed a natural polymorphism
between the two parent species due to a large deletion
occurring in A. kolomikta detectable without further
restriction enzyme treatment. The e-f spacer DNA was
digested with HinfI. The comparison of the RFLP patterns
in the parents and their progeny showed a strictly
paternal inheritance of chloroplast DNA in Actinidia,
with no exception found in any of the crosses examined.
As the reciprocal crosses were not available, we do not
know whether paternal inheritance of plastids is restricted
to the crosses we analysed or if this is the general rule
for plastid inheritance in the genus Actinidia. Actinidia
is dioecious and is the first purely outbreeding species
for which a paternal plastid inheritance has so far been
documented.
