The extent to which genetic gain achieved from selection programs under strictly controlled environments in the nucleus that can be expressed in commercial production systems is not well-documented in aquaculture species. The main aim of this paper was to assess the effects of genotype by environment interaction on genetic response and genetic parameters for four body traits (harvest weight, standard length, body depth, body width) and survival in Red tilapia (Oreochromis spp.). The growth and survival data were recorded on 19,916 individual fish from a pedigreed population undergoing three generations of selection for increased harvest weight in earthen ponds from 2010 to 2012 at the Aquaculture Extension Center, Department of Fisheries, Jitra in Kedah, Malaysia. The pedigree comprised a total of 224 sires and 262 dams, tracing back to the base population in 2009. A multivariate animal model was used to measure genetic response and estimate variance and covariance components. When the homologous body traits in freshwater pond and cage were treated as genetically distinct traits, the genetic correlations between the two environments were high (0.85-0.90) for harvest weight and square root of harvest weight but the estimates were of lower magnitudes for length, width and depth (0.63-0.79). The heritabilities estimated for the five traits studied differed between pond (0.02 to 0.22) and cage (0.07 to 0.68). The common full-sib effects were large, ranging from 0.23 to 0.59 in pond and 0.11 to 0.31 in cage across all traits. The direct and correlated responses for four body traits were generally greater in pond than in cage environments (0.011-1.561 vs. -0.033-0.567 genetic standard deviation units, respectively). Selection for increased harvest body weight resulted in positive genetic changes in survival rate in both pond and cage culture. In conclusion, the reduced selection response and the magnitude of the genetic parameter estimates in the production environment (i.e., cage) relative to those achieved in the nucleus (pond) were a result of the genotype by environment interaction and this effect should be taken into consideration in the future breeding program for Red tilapia.
The present study examines genetic variation and correlated changes in reproductive performance traits in a red tilapia (Oreochromis spp.) population selected over three generations for improved growth. A total of 328 breeding females (offspring of 111 sires and 118 dams) had measurements of body weight prior to spawning (WBS), number of fry at hatching (NFH), total fry weight (TFW) and number of dead fry (NDF) or mortality of fry including unhatched eggs at hatching (MFH). Restricted maximum likelihood (REML) analysis in a multi-trait model showed that there are heritable genetic components for all traits studied. The heritability for WBS was very high (0.80). The estimates for traits related to fecundity (NFH, TFW) and survival (NDF) were low and they were associated with high standard errors. Genetic correlations of WBS with other reproductive performance traits (NFH, TFW and NDF) were generally positive. However, NFH was negatively correlated genetically with TFW. As expected, body measurements during growth stage exhibited strong positive genetic correlations with WBS. The genetic correlations between body traits and reproductive performance (NFH, TFW, NDF) were not significant. Correlated responses in reproductive traits were measured as changes in least squares means between generations or spawning years. Except for WBS that increased with the selection programs, the phenotypic changes in other reproductive traits observed were not statistically significant (P>0.05). It is concluded that the selection program for red tilapia has resulted in very little changes in reproductive performance of the animals after three generations. However, periodic monitoring of genetic changes in fecundity and fitness related traits such as NDF or MFH should be made in selective breeding programs for red tilapia.
Quantitative genetic analysis was performed on 10,919 data records collected over three generations from the selection programme for increased body weight at harvest in red tilapia (Oreochromis spp.). They were offspring of 224 sires and 226 dams (50 sires and 60 dams per generation, on average). Linear mixed models were used to analyse body traits (weight, length, width and depth), whereas threshold generalised models assuming probit distribution were employed to examine genetic inheritance of survival rate, sexual maturity and body colour. The estimates of heritability for traits studied (body weight, standard length, body width, body depth, body colour, early sexual maturation and survival) across statistical models were moderate to high (0.13-0.45). Genetic correlations among body traits and survival were high and positive (0.68-0.96). Body length and width exhibited negative genetic correlations with body colour (- 0.47 to - 0.25). Sexual maturity was genetically correlated positively with measurements of body traits (weight and length). Direct and correlated genetic responses to selection were measured as estimated breeding values in each generation and expressed in genetic standard deviation units (σG). The cumulative improvement achieved for harvest body weight was 1.72 σG after three generations or 12.5% per generation when the gain was expressed as a percentage of the base population. Selection for improved body weight also resulted in correlated increase in other body traits (length, width and depth) and survival rate (ranging from 0.25 to 0.81 genetic standard deviation units). Avoidance of black spot parent matings also improved the overall red colour of the selected population. It is concluded that the selective breeding programme for red tilapia has succeeded in achieving significant genetic improvement for a range of commercially important traits in this species, and the large genetic variation in body colour and survival also shows that there are prospects for future improvement of these traits in this population of red tilapia.
To satisfy increasing demands for fish as food, progress must occur towards greater aquaculture productivity whilst retaining the wild and farmed genetic resources that underpin global fish production. We review the main selection methods that have been developed for genetic improvement in aquaculture, and discuss their virtues and shortcomings. Examples of the application of mass, cohort, within family, and combined between-family and within-family selection are given. In addition, we review the manner in which fish genetic resources can be lost at the intra-specific, species and ecosystem levels and discuss options to best prevent this. We illustrate that fundamental principles of genetic management are common in the implementation of both selective breeding and conservation programmes, and should be emphasized in capacity development efforts. We highlight the value of applied genetics approaches for increasing aquaculture productivity and the conservation of fish genetic resources.
Carbapenem-resistant Acinetobacter baumannii (A. baumannii, CRAb) is an emerging global threat for healthcare systems, particularly in Southeast Asia. Next-generation sequencing (NGS) technology was employed to map genes associated with antimicrobial resistance (AMR) and to identify multilocus sequence types (MLST). Eleven strains isolated from humans in Vietnam were sequenced, and their AMR genes and MLST were compared to published genomes of strains originating from Southeast Asia, i.e., Thailand (n = 49), Myanmar (n = 38), Malaysia (n = 11), Singapore (n = 4) and Taiwan (n = 1). Ten out of eleven Vietnamese strains were CRAb and were susceptible only to colistin. All strains harbored ant(3")-IIa, armA, aph(6)-Id and aph(3") genes conferring resistance to aminoglycosides, and blaOXA-51 variants and blaADC-25 conferring resistance to ß-lactams. More than half of the strains harbored genes that confer resistance to tetracyclines, sulfonamides and macrolides. The strains showed high diversity, where six were assigned to sequence type (ST)/2, and two were allocated to two new STs (ST/1411-1412). MLST analyses of 108 strains from Southeast Asia identified 19 sequence types (ST), and ST/2 was the most prevalent found in 62 strains. A broad range of AMR genes was identified mediating resistance to ß-lactams, including cephalosporins and carbapenems (e.g., blaOXA-51-like, blaOXA-23, blaADC-25, blaADC-73, blaTEM-1, blaNDM-1), aminoglycosides (e.g., ant(3")-IIa, aph(3")-Ib, aph(6)-Id, armA and aph(3')-Ia), phenicoles (e.g., catB8), tetracyclines (e.g., tet.B and tet.39), sulfonamides (e.g., sul.1 and sul.2), macrolides and lincosamide (e.g., mph.E, msr.E and abaF). MLST and core genome MLST (cgMLST) showed an extreme diversity among the strains. Several strains isolated from different countries clustered together by cgMLST; however, different clusters shared the same ST. Developing an action plan on AMR, increasing awareness and prohibiting the selling of antibiotics without prescription must be mandatory for this region. Such efforts are critical for enforcing targeted policies on the rational use of carbapenem compounds and controlling AMR dissemination and emergence in general.
For enhanced applications of solar cells, organic luminescence materials like long persistent luminescence (LPL) present one of the promising avenues for light enhancement. Currently, most existing luminescent materials are based on an inorganic system that requires rare elements such as europium and dysprosium, with a very high processing temperature. Adopting organic luminescence materials that are free from rare elements is necessary, considering the low-temperature fabrication and low material cost. In this work, we investigate the optical properties of an organic luminescence blend consisting of 2,8-bis(diphenylphosphoryl)dibenzo [b,d]thiophene (PPT) and N,N,N',N'-tetramethylbenzidine (TMB) through computational studies and experimental validations. Optical characteristics of the luminescence materials like optical absorption, photoluminescence, and time-resolved photoluminescence spectroscopy are characterized. To validate the functionality of the organic luminescence blend, the material is incorporated into the perovskite solar cell structure. Unfortunately, the blend is unable to emit sufficient illumination over extended periods due to its low intersystem crossing efficiency and weak spin-orbit coupling. Although the power conversion efficiency of the Luminescence/FTO/TiO2/Perovskite/Carbon structure is observed to be small under dark conditions, the application of organic luminescence materials can be further enhanced and explored.