Analysis of inheritance mode in chrysanthemum using EST-derived SSR markers

• We studied segregation type in chrysanthemum.
• EST-SSR markers were developed to study the segregation.
• Hexasomic inheritance was the dominant segregation type in our study population.
• Some evidence for disomic segregation was found.

To study the inheritance mode of hexaploid chrysanthemum (random or preferential chromosome pairing), a segregation analysis was carried out using SSR markers derived from chrysanthemum ESTs in the public domain. A total of 248 EST-SSR primer pairs were screened in chrysanthemum cultivars ‘Dancer’ and ‘Puma White’, of which 49 EST-SSRs were selected as polymorphic and informative markers. These polymorphic markers were used for genotyping a F1-pseudo test cross population derived from a cross between these two cultivars. The 49 EST-SSRs detected 210 marker alleles with an average number of 4.29 marker alleles per locus. For 180 of these polymorphic SSR marker alleles, segregation could be estimated using a χ2 goodness of fit test (α = 0.05) with the expected segregation ratios for hexasomic or disomic inheritance. For 65 SSR marker alleles the segregation ratio was informative for the type of inheritance, 33 marker alleles gave a good fit to the expected segregation ratio for hexasomic inheritance and whereas 24 marker alleles gave a good fit for disomic inheritance showing a higher number of marker alleles supporting autopolyploid segregation in chrysanthemum. In addition, the observed ratio of non-simplex to simplex markers was 20:80 (25 vs. 99) supported hexasomic inheritance. Furthermore, random marker allele assortment was found within the six fully informative markers giving conclusive evidence for hexasomic inheritance in chrysanthemum at these chromosomal regions.