Selfing rates in alfalfa seed production fields

Authors: Brunet, Johanne; Riday, Heathcliffe; Dieterich Mabin, Molly; PALMIERI, LUCIANO - Oak Ridge Institute For Science And Education (ORISE); FLICK, ANDREW - Oak Ridge Institute For Science And Education (ORISE)

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/19/2020
Publication Date: 1/29/2020
Citation: Brunet, J., Riday, H., Dieterich Mabin, M.E., Palmieri, L.R., Flick, A. 2020. Selfing rates in alfalfa seed production fields. Meeting Abstract. Winter Seed Conference, 2020 Western Alfalfa Seed Growers Association (WASGA).

Interpretive Summary: n/a

Technical Abstract: Alfalfa is commonly referred to as an outcrosser, but it is a self-compatible plant, meaning that mature seeds can be produced via self-fertilization. Previously reported selfing rate estimates in alfalfa fields have been highly variable, ranging between 9% and 47% selfing. Some of the variation in selfing rate among studies could result from the different methods used to estimate selfing (flower color polymorphism, allozyme, microsatellite) and the fact that estimates were obtained over a 70-year range. A true estimate of selfing rate variation in alfalfa seed production fields should be obtained in the same year using a similar methodology. In the current study, we present selfing rate estimates for 32 alfalfa seed-production fields located in three major areas of alfalfa seed production, the Pacific Northwest (PNW), the Central valley (CENT) of California and the Imperial (IMP) valley of California. Selfing rate of each field was estimated using genotypic data from 15 microsatellite loci on 32 seeds for each of 40 maternal parents per field. Field selfing rate estimates ranged between 5.3% and 30% selfing with no differences in mean selfing rate among the three geographic regions. Selfing is the most extreme form of inbreeding and the coefficient of inbreeding over all progeny or parent was 0.23, suggesting an overall 23% decrease in heterozygosity in alfalfa seed-production fields. Over all fields and regions, we detected two genetic clusters, likely corresponding to the dormant and non-dormant varieties. When each region was examined separately, more than two genetic clusters were often detected. Path analyses and structural equation modeling were used to identify the management factors that most affected selfing rate in alfalfa seed production fields. Preliminary results indicated disease and field age affected flower production while flower production, together with field size and presence of honey bee, influenced selfing rate. This research represents the most comprehensive study of selfing rate in alfalfa seed-production fields.