Proceedings of the XLV Italian Society of Agricultural Genetics - SIGA Annual Congress

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

AFLP ANALYSIS OF SOMACLONAL VARIATION IN TRANSGENIC MAIZE

BORGO L., TADDEI R.

Department of Agroenvironmental Science and Technology, University of Bologna

laetitia_borgo@hotmail.com

Zea mays L., essentially derived varieties, AFLP, GMO

A debate is presently underway concerning the commercial release of essentially derived varieties (EDV) obtained from previously released cultivars. Molecular fingerprinting is the most powerful tool to investigate the level of genetic similarity to establish essential derivation, provided a suitable threshold of genetic similarity is available. In this context, the EDV issue becomes relevant also to the release of materials obtained through genetic engineering. These materials are usually derived utilizing plants regenerated from callus cultures which are commonly characterized by the presence of somaclonal variation, particularly frequent at the molecular level. Therefore, it becomes relevant to investigate the genetic distance between the original source of the callus tissue and the regenerated transgenic plant. We have started to investigate somaclonal variation at the molecular level using transgenic maize obtained with the biolistic gun.

In total, we have considered 28 plants which were regenerated from three independently derived transgenic calli proliferated from immature embryos of the donor line DABO1. Double-digested (EcoRI–MseI or PstI–MseI) genomic DNA was ligated and preamplified with one selective nucleotide over the adapter restriction site sequence. Overall, the average level of genetic similarity between the original donor and the regenerated transgenic plants was very high (> 99.5%). A slightly higher level of polymorphism was detected with EcoRI + three selective nucleotides as compared to EcoRI + two selective nucleotides and PstI + two selective nucleotides. The correlations between the similarity matrices obtained with the three different restriction enzymes were low, a result likely due to the low level of polymorphism. Therefore, the dendrogram was constructed pooling all the data obtained with the three enzymes. T0 plants were grouped separately from the DABO1 control plants thus confirming the presence of somaclonal variation among the regenerated T0 plants. The T0 plants were prevalently clustered according to their callus of origin. Within each major group, different subclusters were observed, a result which can be reconciled with the chimeric nature (in terms of subsequent somaclonal events) of each one of the three callus cultures from which the T0 plants were regenerated. However, a number of T0 plants showed a similar profile, a finding which suggests their origin from a callus sector either genetically homogeneous or characterized by a very low level of genetic heterogeneity. These preliminary results indicate that somaclonal variation can be detected through the use of AFLP markers.