Plant & Animal Genome IX Conference

Workshop: Apomixis
W09_03.html

ELEMENTS OF APOMIXIS IN ALFALFA (MEDICAGO SATIVA L.): AN OVERVIEW

¹ Dipartimento di Agronomia Ambientale e Produzioni Vegetali, University of Padova, Agripolis, Via Romea, 16 35020 Legnaro, Padova, Italy

² Dipartimento di Biologia Vegetale e Biotecnologie Agroambientali, University of Perugia, Borgo XX giugno, 74 06122 Perugia, Italy

The Medicago sativa-coerulea-falcata complex includes species that have a versatile and dynamic reproductive system. It is likely that as alfalfa breeding programs become more sophisticated, future varieties may be genetically uniform because of the constitution of hybrids or the utilization of apomixis. Unreduced gamete producers of diploid relatives are now recognized as one of the main tools available for introgressing wild germplasm traits and exploiting heterotic vigor in cultivated tetraploid forms of alfalfa via sexual polyploidization schemes based on 4x-2x crosses and reciprocals. Apomictic reproduction has the potential of cloning plants through seed and thus it could provide in the future a unique opportunity for developing superior monogenotype tetraploid cultivars with permanently fixed heterosis. Apomixis as a whole has not been detected in the genus Medicago but elements of apomixis have been documented. The formation of apomeiotic eggs through diplospory has been found in a diploid alfalfa mutant, PG-F9, while the induction of haploid parthenogenesis in tetraploid alfalfa has been widely exploited to obtain CADL populations. Our efforts are addressed to assembling a functional system of apomictic seed formation in alfalfa. Because apomixis is mainly associated with hybridity and polyploidy, diplospory was introgressed at the tetraploid level in combination with cytoplasmic male-sterility and the induction of somatic parthenogenesis through wide-crosses with unrelated diploid materials was attempted. The screening of progenies was based on morpho-cytological trait investigations and it was assisted by mapped RFLPs and PCR-based markers. Experimental achievements towards the selection of apomictic alfalfa mutants are presented and theoretical perspectives discussed.