About Us
Member Directory
Update Member Information
or Register as New Member
2003 Conference
Related WWWs
Announcements
Newsletter
Abstracts
Proceedings
PROGRESS IN ASSEMBLING A FUNCTIONAL SYSTEM OF APOMICTIC SEED PRODUCTION IN ALFALFA
G. Barcaccia1, E. Albertini2, M. Lucchin1, and .Veronesi2
1Dipartimento di Agronomia Ambientale e Produzioni Vegetali, University of Padova, Agripolis, Via Romea 16, 35020 Legnaro, Padova, Italy; 2Istituto di Miglioramento Genetico Vegetale, University of Perugia, Borgo XX Giugno 74, 06121, Perugia, Italy.
Apomixis has the potential of cloning plants through seed and thus gives a unique opportunity in alfalfa breeding for developing superior cultivars with permanently fixed heterosis. Apomixis «as a whole» has never been detected in the Medicago sativa complex, but features of apomixis have been documented. Cytological and molecular data have independently provided evidence that diplosporic mechanisms of unreduced egg formation would occur in a diploid mutant of M. falcata, named PGF-9. Besides, a morphological and molecular progeny test has indicated that apomeiosis in this case would not be tightly associated to parthenogenesis. Because gametophytic apomixis has shown to be strongly correlated with the occurrence of hybridity and poliploidy, Bilateral Sexual Polyploidization (BSP) schemes were adopted for introgressing the diplosporic mutation at the tetraploid level using unreduced pollen producers of M. coerulea. Tetraploidized F1 plants from BSP were then backcrossed with mutant PGF-9 (employed as unreduced egg donor) and the BC1 progenies screened for level of ploidy, occurrence of diplospory, genetic similarity with diploid parents, and fertility in controlled matings with tetraploid testers of M. sativa. Nine tetraploid BC1 plants out of 15 recovered showed a degree of diplospory ranging from 5.04 to 40.96%. These mutants, named DTA (Diplosporic Tetraploidized Alfalfa), set a few seeds in widecrosses performed with unrelated diploid testers evidencing a null or very low capacity for parthenogenesis. Our goal of eventually assembling an apomictic system of seed production in alfalfa is discussed.
Keywords: Medicago spp.; seed set; diplospory; parthenogenesis; apomixis