A molecular cytogenetic analysis of chromosome behavior in Lilium ...

Intergenomic recombination and chromosome translocation in Lilium hybridsduplication indicates that there is either a duplication or a reciprocal translocation in thepaternal parent ‘Connecticut King’, and in the latter, a so-called duplication-deficiencygametes has been transmitted to the progeny successfully (Burnham 1962). These twoalternative possibilities need cytological confirmation through the analysis of the Asiaticparent. From the available observations and previous reports (Abe et al. 2002; Khan 2009;Shahin et al. 2011; Van Heusden et al. 2002), it appears that the presence of a reciprocaltranslocation may be more likely. During meiosis of reciprocal translocation, quadrivalentsare normally formed at metaphase I. Chiasma formation and crossing over in such cases willbe suppressed in the area close to the translocation breakpoints, both alternate and adjacentsegregation lead to reduced fertility. When progenies from these gametes are used for geneticmapping, markers will show skewed segregations, which has been found when these LApopulation were used for mapping (Shahin et al. 2011). Furthermore, two translocatedchromosomes usually lead to the formation of ‘pseudolinkage’ (Albrecht and Chetelat 2009;Beeman et al. 1986; Farré et al. 2010; Kamphuis et al. 2007; Larson et al. 2011). One exampleis the linkage maps of an interspecific F2 Solanum ochranthum × S. juglandifolium population.Chromosome 8 and 12 were connected in one large linkage groups, which indicating a likelyreciprocal translocation (Albrecht and Chetelat 2009). In the maps of LA lily, linkage group 1(219 cM) is more than two times longer compared with the average longth of the linkagegrous (95 cM)(Khan 2009), which also indicate a likely reciprocal translocation in‘Connecticut King’. Meanwhile, if crossovers happen in the interstitial segment of thetranslocated chromosome, different types of duplication-deficiency gametes, which aregenerally sterile, will be produced (Fig. 3.3).In conclusion, intergenomic recombination in lily allopolyploids are derived from crossingover events during meiosis; while the non-homologous chromosome pairing in multivalentsand bivalents potentially lead to the production of gametes with real chromosomerearrangements.43