Submitted to: Euphytica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/7/2014
Publication Date: 7/14/2014
Citation: Mccord, P.H., Gordon, V.S., Saha, G., Hellinga, J., Vandemark, G.J., Larsen, R.C., Smith, M., Miller, D. 2014. Detection of QTL for forage yield, lodging resistance and spring vigor traits in alfalfa (Medicago sativa L.). Euphytica. 10:2134. Interpretive Summary: Alfalfa is an internationally significant forage crop. Traits such as high yield, rapid spring growth, and resistance to falling over (lodging) are important for alfalfa. It is currently difficult to breed for these traits, because they are controlled by many genes and are influenced by environmental effects. The objective of this experiment was to identify regions of chromosomes and specific DNA markers that are associated with these traits. A population of 128 individuals was developed by crossing a lodging-susceptible parent with a lodging-resistant parent, and using one of these individuals to back-cross with the original lodging-susceptible parent. A total of 222 DNA markers were used to develop a genetic linkage map of these individuals. Replicated tests of the parents and progeny were evaluated in the field for estimated forage yield, lodging, and spring growth in Washington and Wisconsin in 2007 and 2008. By evaluating the marker information and field data, important chromosomal regions and DNA markers were identified for all three traits. Most importantly, several of these regions and markers were identified in all years and locations of the study. The chromosomal regions can be investigated further to identify additional DNA markers, and the existing markers can now be tested in other alfalfa to determine their usefulness in breeding across a wide range of alfalfa types.
Technical Abstract: Alfalfa (Medicago sativa L.) is an internationally significant forage crop. Forage yield, lodging resistance and spring vigor are important agronomic traits conditioned by quantitative genetic and environmental effects. The objective of this study was to identify quantitative trait loci (QTL) and molecular markers associated with increased forage yield, resistance to lodging, and spring vigor.A backcross population composed of 128 progeny was developed by crossing the breeding parents DW000577 (lodging susceptible) and NL002724 (lodging-resistant) and back-crossing an individual F1 plant to the maternal parent (i.e. DW000577). A linkage map of NL002724 was developed based upon the segregation of 222 molecular markers among the backcross progeny. The markers were distributed among 13 linkage groups, covering an estimated recombination distance of 1382.1 centiMorgans (cM). Replicated clones of both parents and backcross progeny were evaluated in the field for estimated forage yield, lodging, and spring vigor in Washington and Wisconsin during 2007 and 2008. Significant QTL were found for all three traits. In particular, two QTL for lodging resistance were identified that explained =14% of trait variation, and were significant in all years and locations. Major QTL explaining over 25% of trait variation for forage yield were detected in multiple environments at two separate locations on chromosome III. Several QTL for spring vigor were located in the same or similar positions as QTL for forage yield, possibly explaining the significant correlation between these traits. Molecular markers associated with the aforementioned QTL were also identified.