Occurrence, inheritance and use of reproductive mutants in alfalfa improvement

摘要: The widespread occurrence of 2ngametes (i.e. gametes with the somatic chromosome number) in Medicago sativa-coerulea-falcata complex supports concept that gene flow from diploid to tetraploid species occurs continuously nature and plays a key role alfalfa evolution. Breeders realized early transfer between ploidy levels via 2n pollen eggs would have had potential use cultivated improvement. Cytological investigations provided insights into types meiotic abnormalities responsible for production gametes. Alterations were defined as genetically equivalent first (FDR) or second division restitution(SDR) mechanisms. For breeding purposes,data proven FDR type are more advantageous than those obtained by SDR transferring parental heterozygosity retaining epistatic interactions. mutants produce is now recognized one most effective methods available exploiting heterosis introgressing wild germplasm traits unilateral (USP) bilateral sexual polyploidization (BSP) schemes. Both2n egg producers could be used direct relatives means 2x-4x and4x-2x crosses. Although data shown forage yield improvement can achieved when plants sexually tetraploidized, problems related reduced plant fertility seed remain largely unexplained. Apomixis has cloning through thus provides unique opportunity developing superior cultivars permanently fixed effects. A main goal introduction functional apomixis Apomeiosis parthenogenesis) stocks. In future, efficiency programs based on reproductive improved selection at genotype level using RFLPs PCR-based markers. Suitable DNA markers detailed linkage maps should help discover apomictic address basic genetic issues such extent genomicre combination polyploid hybrids effect heterosis. Molecular recently been studying inheritance gamete formation identifying polymorphisms associated genes involved abnormalities. tagging not only explain control regulation these traits, but may also an essential step towards marker-assisted implementation USP BSP Future perspectives include strategies map-based genomic markers,and screening EST mini-libraries flowers different developmental stages wild-type scan lead identification mRNAs candidate alfalfa.