Genetics of Inbreeding Effects in Smooth Bromegrass

Abstract

Limited knowledge is available on the effects of deliberate selfing on morphological traits and genetic parameters in smooth bromegrass (Bromus inermis Leyss). To gain an enhanced understanding of these effects, 25 parental clones of smooth bromegrass along with 25 full‐sib (S1) and 25 half‐sib (open‐pollinated [OP]) progenies were generated in 2012 and used to assess the consequences of first‐generation inbreeding during 2013 and 2014 in a field experiment. A high genetic variation was observed among and within the S1 and OP progenies and parental clones. Different levels of inbreeding depression were observed for traits of days to anthesis, plant height, spread, and dry matter yield. Principal component analysis separated lines into three groups roughly corresponding to S1, OP, and parental clones, indicating that changes in mating system could rapidly change the genetic structure of populations. Large genetic variations were observed for inbreeding depression among the parental clones. Heritabilities ranged from 0.16 for dry matter (%) to 0.85 for spreading ability. The self‐pollinated progenies exhibited a higher heritability than the other progenies. The high correlations of forage yield with plant height, number of shoots per plant, and spread make it possible to improve forage yield via indirect selection. Results indicated that the magnitude of inbreeding depression varied among the genotypes and traits. Therefore, selection for low inbreeding depression rates is possible in this species, which may facilitate development of inbred lines for future breeding studies.