Assessment of genetic diversity and relationships among maize (Zea mays L.) Italian landraces by morphological traits and AFLP profiling

In the present study we have analyzed the genetic diversity pattern in a sample of 54 Italian maize landraces, using morphological traits and molecular markers. Although the 54 landraces surveyed in this study were restricted to Lombardy, the core region of maize production in Italy, our data revealed a large genetic heterogeneity for both morphological and molecular traits in the accessions analyzed. Additionally, our data confirm that the AFLP markers produced a high frequency of polymorphic bands and were able to unequivocally fingerprint each of the landraces considered. Cluster analysis based on AFLP markers displayed a clearer separation of the accessions in comparison to morphological data. Different populations were divided into four major clusters reflecting the geographical origin and seasonal employment of the landraces analyzed. Molecular analysis of variance showed significant (P < 0.01) differences among groups, among populations within groups, and among individuals within populations. Approximately 74% of the total variance could be attributed to differences within populations. Conversely, a lower level of differentiation was detected among groups (similar to 4%). Regarding population structures, the genetic distance between populations (F-ST = 0.25 +/- 0.3) and the degree of inbreeding within groups (F-SC = 0.22 +/- 0.2), did not diverge significantly, while both significantly differed from the degree of relatedness between markers within groups (F-CT = 0.04 +/- 0.03). Results are discussed in relation to a suitable conservation method.