The complications in Citrus classification are mostly due to frequent inter-species cross pollination that propagates and stabilizes hybrid taxa, bud mutations, adventitious nucellar embryony
, polyploidy (Scora, 1975).
Reproduction mechanisms, including categories of adventitious/nuclear embryony
, development of embryos adventitious from the outer integument, without of stimulation of sexual development (Richard 1990).
The taxonomy and phylogeny of Citrus are complicated due to the high rate of bud mutation and the sexual compatibility between Citrus and related genera and the asexual reproduction through nucellar embryony
, which is characteristic in several Citrus species and most rootstock (Frost, 1943; Cameron, 1979).
took 1.48 [+ or -] 0.3 days while egg-hatching rate was 63.18 [+ or -] 23.94%.
Genetics, breeding and nucellar embryony
. In: REUTHER, W.; BATCHELOR, L.D.; WEBBER, H.J.
as a means of fneeing citrus clones of viruses In: Wallace, J.
Although there is a large amount of variability within the Citrus genus with which the breeder can work, and closely related genera provide an even wider selection of characters, there are several barriers to the full utilization of this variability (sterility, incompatibility, nucellar embryony
Naumova (1993) tabulated only adventitious embryony
and ended up with 57 families, 121 genera and 250 species.
With molecular reports of independent loci controlling parthenogenesis and diplospory (Noyes and Rieseberg, 2000), as well as six QTLs influencing nucellar embryony
(Garcia et al., 1999), it is likely that modifiers affect the expression of apomixis in many plants.
Regeneration and adventive embryony
. Canadian Journal of Botany 47:1643-1649.
Data obtained from three maize genotypes suggest high endogenous hormone levels in ovules during early embryony
reduce embryogenic competence of immature embryos (Carnes and Wright, 1988).
The usual reduced embryo sac degenerates and is replaced by an unreduced somatic embryo, a type of apomixis called nucellar embryony
(den Nijs & van Dijk, 1993).