The authors gratefully thank Prof. F. Porcelli (University of Bari, Italy) for accession and assistance with a light microscopy facility, Prof. S. Desantis, Dr. G. Accogli (University of Bari), Dr. G. Maglietta (Tecnopolis, Bari) for assistance with SEM and Mr. N. Salatino (IPP, CNR, Bari) for the technical assistance provided. Research partially funded by Bilateral Cooperation Agreement between Consiglio Nazionale delle Ricerche (CNR, Italy) and Consejo Nacional de Ciencia, Tecnologia e Innovacion Tecnologica (CONCYTEC, Peru) and by Project BIOMED (Ministero Politiche Agricole e Forestali, Italy).

Research partially funded by Bilateral Agreement CNR/CONCYTEC and MIPAF, Project BIOMED. Mr Nicola Salatino is gratefully acknowledged for the technical assistance provided during this study.

Research partially funded by CNR-CONCYTEC Bilateral Agreement. We thank I. Abrantes and R. Manzanilla-Lopez for manuscript reading and the reviewers for suggestions. Mr N. Salatino is gratefully acknowledged for the technical assistance provided during this study.