Segregation patterns of AFLP markers in F1 hybrids of a cross between tetraploid and diploid species in the genus Malus

Malus xiaojinensis, one of the most important wild genotypes in the genus Malus, is resistant to a variety of stresses such as Fe deficiency chlorosis, drought and cold. However, lack of knowledge of its genetic background prevents using genetic analysis to study those agronomic traits and corresponding gene functions. Here, as the first step towards construction of the linkage map of M. xiaojinensis, genetic analysis of the F-1 triploid hybrids (M. xiaojinensis x M. baccata) was performed with amplified fragment length polymorphism (AFLP) markers. Using 15 EcoRI- MseI primer combinations, 1110 AFLPs were identified, with 31.3% of M. xiaojinensis-, 12.7% of M. baccata-specific markers, 54.9% of common markers, and 1.2% of non-parental markers; 93.3% of the AFLP markers exhibit the expected segregation ratio. Thirty-two M. xiaojinensis-specific markers and 47 common markers display a 5 : 1 and 11 : 1 segregation ratios, respectively, suggesting that M. xiaojinensis is an autotetraploid, or at least an isosyndetic allotetraploid.