The consequences of recurrent drought events compared with a single drought, and drought's interaction with deliberate selfing compared with open‐pollination on postdrought recovery and persistence of smooth bromegrass, are not clear. This research was conducted to investigate the effects of recurrent drought stresses compared with a single drought on stress response, poststress recovery and persistence of full‐sib and half‐sib progenies of smooth bromegrass. During this study, 25 selfed (S1) and 25 open‐pollinated (OP) progenies of smooth bromegrass created in 2012 were evaluated in the field under normal and recurrent drought stress during 2013–2016. After the first harvest of above‐ground biomass in 2016, irrigation was withheld in both environments for 2 months; plants were subsequently re‐watered and evaluated. Recurrent drought stress changed the relationships between different traits. Moreover, prolonged drought stress resulted in increased plant productivity (recovery aerial biomass; RABI) of S1 and OP populations in recurrent drought stress compared with normal environment. Mandatory selfing increased persistence of smooth bromegrass genotypes but did not affect recovery after prolonged drought stress. Results revealed that, selecting among S1 families would be more effective than OP ones.
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.
Inbreeding depression is the reduction in the fitness of inbred offspring relative to progeny from unrelated parents. In orchardgrass (Dactylis glomerata L.), limited efforts have been made to evaluate the effects of deliberate selfing on agro‐morphological traits and to estimate the genetic variation of traits. Twenty‐five genotypes of orchardgrass, along with 25 S1 (full‐sibs) and 25 families of half‐sibs, were created in 2012 and used to assess the consequences of the first generation of inbreeding and outcrossing for offspring fitness and to estimate heritabilities, genetic parameters and correlations of agro‐morphological traits during the period of 2013–2014 in the field. Different levels of inbreeding depression were observed for the traits, with higher values for plant height, days to inflorescence emergence and dry matter yield. The degree of inbreeding or outbreeding effects varied among the studied genotypes. This facilitates the development of inbred lines for further studies. The results showed that some of the studied genotypes were self‐fertile, thereby indicating the possibility of developing inbred lines from these genotypes. Heritabilities ranged from 0.10 for the number of stems per plant to 0.64 for spread among the studied populations. Spread had high heritability as well as high correlation with forage yield, thereby indicating that this trait could be used to improve forage yield indirectly.
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