Molecular analysis of genetic relatedness among alfalfa clones differing in levels of self-incompatibility

Abstract

The possibility of increasing hybridity in alfalfa (Medicago sativa L.) cultivars through the use of self-incompatible (SI) parents is being investigated. Prior research has demonstrated that self-incompatibility is a heritable trait and that environmentally stable SI clones can be selected. However, inbreeding depression is very severe in alfalfa, and a potential problem associated with utilizing self-incompatibility to increase hybridity is the purported positive relationship between self-incompatibility and inbreeding. Fifteen stable, partially to fully self-incompatible clones and 18 stable self-compatible (SC) clones were selected from the broad-based population W10-AC3. RAPD, Anchored Microsatellite Priming (AMSP), and Simple Sequence Repeat (SSR) analyses were performed on genomic DNA using 9, 10-mer RAPD primers; the AMSP primers (from the 5' end) CAA(CA)5, CCCC(GA)5, CCG(GA)5, and GCC(GA)5; and eight SSR primer pairs. Based on genetic distance (GD) estimates (computed from RAPD and AMSP markers) and numbers of tri-allelic and tetra-allelic loci from SSR analysis, there is no evidence that SI clones were more closely related than SC clones. Assuming parental GD is positively correlated with heterosis, environmentally stable SI clones with acceptable specific combining ability and separated by large GD's would be a good basis for a hybrid alfalfa system, or for use in other breeding schemes designed to minimize inbreeding while maximizing heterosis. Key words: Anchored microsatellite-priming, heterosis, inbreeding, RAPD, self incompatibility, SSR