Morphological and genetic comparison between naturally produced smolts of Atlantic salmon,brown trout and their hybrids

Morphological characters were compared between smolts (standard length 110–220 mm) of Atlantic salmon Salmo salar L., anadromous brown trout Salmo trutta L. and their hybrids captured in River Driva, western Norway. Morphological discrimination between S. salar, S. trutta and their hybrids was correct for 93% of the individuals (correct form was determined genetically). Morphological discrimination of hybrids was incorrect with 9.1% (n = 7) classified as S. salar and 1.3% (n = 1) as S. trutta, suggesting that the hybrids were morphologically more similar to S. salar than S. trutta despite a bias towards S. trutta mothers (7 of 8 cases). The largest morphological differences were found in head (notably maxilla length) and caudal peduncle morphology. Hybrids between S. salar and S. trutta had the longest pectoral and pelvic fins. This indicates that precise discrimination based on morphological traits can be made between S. salar, S. trutta and their hybrids.     

Incidence of spinal injuries in migratory Yellowstone cutthroat trout captured at electric and waterfall‐velocity weirs

The South Fork Snake River (Idaho, USA) supports a native Yellowstone cutthroat trout (YCT) population Oncorhynchus clarkii bouvieri (Richardson) threatened by non‐native rainbow trout O. mykiss (Walbaum). Electric weirs prevent rainbow trout passage into YCT spawning tributaries but may cause spinal injuries. YCT captured at electric weirs on Palisades and Pine Creeks and a control waterfall‐velocity weir on Burns Creek were X‐rayed in 2012 and 2013 to estimate spinal injury rates. Electrical pulse frequency was increased from 2012 to 2013 at the Palisades (from 11.5 to 20 Hz) and Pine weirs (13–20 Hz), and spinal injury rates were found to increase from 11.3 to 21.3% at Palisades and from 6.5 to 14.7% at Pine, while Burns injury rates remained constant (4.5% in 2012 and 6.0% in 2013), suggesting the electric weirs caused spinal injuries in YCT. Lower pulse frequencies may minimise YCT spinal injury but still prevent rainbow trout from accessing YCT spawning tributaries.     

Gibberellic Acid + 2,4-D Improves Seed Quality in Hordeum vulgare L. ×H. bulbosum L. Crosses

Doubled haploid production from crosses between barley (Hordeum vulgare L.) and H. bulbosum L. is a well established technique for inducing homozygosity. One problem which occurs using certain barley cultivars is premature seed degeneration. In this paper, a post-pollination spray of gibberellic acid and 2,4-dichlorophenoxyacetic acid that delays the onset of senescence is described. The technique improved the number of high quality seeds to more than 75% of the seed set. This improvement should result in increased survival of embryos for culture and subsequent plant regeneration.     

Failure in an interspecific cross between Solanum khasianum Clarke and Solanum mammosum L.

Summary Attempts to obtain a successful interspecific cross between Solanum khasianum Clarke and Solanum mammosum L. were unsuccessful, and the probable reasons for this failure were investigated. A reduced number of viable pollen grains and low receptivity of the stigmas of S. mammosum L. and heterostyly in both species are the probable reasons for the failure of the attempted interspecific crosses between S. khasianum Clarke and S. mammosum L.     

Plant regeneration from protoplasts of Nicotiana alata ‘Crimson Bedder’ for somatic hybridisation studies

Protoplasts could be isolated readily from mesophyll and suspension cells of Nicotiana alata cultivar ‘Crimson Bedder’ and could be cultured in liquid media to yield small colonies. Suspension culture protoplasts exhibited a higher plating efficiency, and colonies regenerated from mesophyll protoplasts possessed enhanced plant regeneration capacity. These protoplast systems could be used for somatic hybridisation assessment with Petunia using a simple procedure for manual isolation and culture of heterokaryons.     

Protoplast technology in relation to crop plants: Progress and problems

Summary The ready availability of isolated plant protoplasts, and the ability of these naked plant cells to fuse together, has greatly stimulated interest in the production of plant somatic hybrids. This new protoplast technology may enable interspecies hybrids to be obtained which are otherwise not possible. Many such interspecies hybrids are required amongst the crop plants, but application of this new technology to these species in presently prevented by our inability to culture cells of many of these species in vitro, and to regenerate plants reproducibly from cultured tissue.Agricultural Research Council Group, Department of Botany, University of Nottingham, U.K.     

Temporal segregation in spawning between native Yellowstone cutthroat trout and introduced rainbow trout

Hybridisation with introduced taxa poses a threat to native fish populations. Mechanisms of reproductive isolation can limit or prevent hybridisation between closely related species. Understanding how these mechanisms interact between the same species across geographically distinct occurrences of secondary contact, and how regional factors influence them, can inform our understanding of hybridisation as a threat and management actions to mitigate this threat. We used data collected on adult fish migration timing and approximate emergence timing of subsequent juvenile fish paired with genomic data to assess whether temporal isolation in the timing of spawning exists between Yellowstone cutthroat trout, rainbow trout and hybrids in the North Fork Shoshone River drainage in northwest Wyoming. We found evidence that Yellowstone cutthroat trout spawn, on average, two to four weeks later than rainbow trout and hybrids and two environmental covariates related to water temperature and discharge were associated with differences in spawning migration timing. Despite statistical support for Yellowstone cutthroat trout spawning later, disproportionately high numbers of rainbow trout and hybrids, paired with extended spawning seasons, lead to substantial overlap between all genotypes. Our results provide further evidence of temporal segregation in the timing of spawning as a mechanism of reproductive isolation between closely related species, but substantial spawning overlap suggests temporal segregation alone will not be enough to curtail hybridisation in conservation populations.