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.

Genotypic‐specific responses caused by prolonged drought stress in smooth bromegrass (Bromus inermis): Interactions with mating systems

“…This is based on the utilization of hybrid vigour derived from combining superior clones. In open‐pollinated grasses, genetic parameters are estimated using selfed (S1) and open‐pollinated (OP, half‐sib) populations (Spanani, Majidi, & Hughes, 2018). Mating between closely related individuals is termed "inbreeding", while “inbreeding depression” refers to the relative reduction in inbred progenies’ fitness compared to outcrossed progenies (Husband & Schemske, 1996).…”

“…Inbreeding depression is of great interest to breeders due to its potential role in conservation biology (Allendorf & Leary, 1986; Barrett & Kohn, 1991) as well as its heavy influence on how reproductive systems evolved in natural populations (Husband & Schemske, 1995, 1996; Sakai, Weller, Chen, Chou, & Tasanont, 1997). In both birdsfoot trefoil ( Lotus corniculatus L.; Onokpise, Bowley, Tomes, & Twamley, 1987) and smooth bromegrass (Spanani et al., 2018), polycross progenies have been reported as having increased survival and higher forage yield when compared to selfed progenies. Geiger (1988) and Waser and Price (1989) also found that when crossing distant populations of a species, significant advantages due to outbreeding occurred in the progenies.…”

Pollination system and deficit irrigation affect flavonolignan components of sylimarin, oil, and productivity of milk thistle

“…Decrease traits under self-pollination could be due to inbreeding depression, which occurs when the plant is pollinated with its own pollen. On the other hand, lethal genes (deleterious alleles), whose expression is masked by heterozygous loci have a chance to be revealed at selfpollination (Leroy, 2014;Spanani et al, 2018). Ibrahim et al (2007) documented that self-pollination improved the silymarin content and seed yield in purple Egyptian lines of milk thistle, while it reduced the same traits in white lines.…”

“…In a study of bird's-foot trefoil (Lotus corniculatus L.), Onokpise et al (1987) found that polycross progeny had higher forage and seed yield than selfed progeny, which indicated inbreeding depression for these traits. Similarly, Sulewska et al (2014) showed that a cross-pollinated population of maize (Zea mays L) had higher content of starch and lower protein content, and Spanani and Majidi (2017) and Spanani et al (2018) reported different levels of inbreeding depression due to self-pollination for yield, plant height, and days to flowering in orchardgrass (Dactylis glomerata L.) and bromegrass (Bromus inermis Leyss).…”

“…(2014) showed that a cross‐pollinated population of maize ( Zea mays L) had higher content of starch and lower protein content, and Spanani and Majidi (2017) and Spanani et al. (2018) reported different levels of inbreeding depression due to self‐pollination for yield, plant height, and days to flowering in orchardgrass ( Dactylis glomerata L.) and bromegrass ( Bromus inermis Leyss).…”