Resistance to Streptococcus iniae and its genetic associations with traits of economic importance in Asian seabass (Lates calcarifer)

Streptococcus iniae is one of the most serious aquatic pathogens, causing significant economic losses in marine and freshwater species, including Asian seabass (Lates calcarifer). Controlling this gram‐positive bacterial pathogen has been an issue in aquaculture systems, due to the combined effects of aquaculture intensification and climatic impacts. To date, there have not been any genetic parameter estimates for S. iniae resistance in Asian seabass. The main aim of this study was to examine genetic variation in S. iniae resistance and its genetic correlations with growth and cannibalism in Asian seabass families produced from a breeding programme for high growth in 2016 and 2017. The study included a total of 5,835 individual fish that were offspring of 41 sires and 60 dams (31 half‐sib and 34 full‐sib families). The experimental fish were challenged by intraperitoneal injection with a volume containing 10⁵ CFU (colony‐forming unit)/fish. Resistance to S. iniae was measured as survival rate at 6 hr, 3, 5, 7, 10 and 15 days post‐challenge test. There were significant variations in S. iniae resistance among families at different observation periods (ranging from 24.4% to 80%). Restricted maximum‐likelihood method and mixed model analysis were applied to estimate heritability for S. iniae resistance. The heritability for S. iniae resistance ranged from 7% to 18% across different statistical models used. The common full‐sib effects accounted for 0.1%–2% of the total variation in resistance to S. iniae. Genetic correlations of the S. iniae resistance at 6 hr and 3 days with later post‐challenge test periods were low to moderate. However, these estimates for S. iniae resistance between successive measurement times (5, 7, 10 and 15 days) were high and close to 1. The genetic correlations of resistance with body weights at 180, 270 and 360 days post‐hatch were not significant as well with cannibalism. It is concluded that there is substantial additive genetic variation in resistance to S. iniae, suggesting there is potential for genetic improvement of Asian seabass for resistance to S. iniae through selective breeding.     

Quantitative taurine requirement for juvenile Florida pompano (Trachinotus carolinus) fed soy‐based practical diets

Florida pompano Trachinotus carolinus is an important species in which the essentiality of taurine has been demonstrated, yet a quantitative requirement has not been estimated. Two experiments were conducted where a combined twelve diets were formulated with graded levels of taurine (ranging 1.6–41.6 g/kg dry matter) and fed to juvenile pompano (initial weight 7.73 and 4.37 g in trial 1 and 2, respectively). Dose responses were observed in terms of growth, feed efficiency and whole‐body taurine content, but there was no effect on survival. Several regression models were evaluated to determine the most appropriate one to draw conclusions from. A 4‐parameter saturation kinetic model was selected to model feed efficiency, while a 5‐parameter saturation kinetic model fitted the growth data (as thermal‐unit growth coefficient, TGC). A broken‐quadratic model served to estimate a breaking point in the whole‐body taurine content, although it also showed that whole‐body taurine kept increasing even at dietary levels in far excess of the requirement. The dietary taurine requirement was estimated at 2.5 g/kg (2.0–3.3 g/kg, 95% CI, dry matter basis) based on feed efficiency, while TGC was maximized at levels between 4.9 and 31.4 g/kg dietary taurine.     

Intra‐cohort cannibalism in early life stages of pikeperch

Cannibalism has been described in 390 teleost fish species belonging to 104 families. In rearing conditions, intra‐cohort cannibalism is one of the major bottlenecks during the early life stages of pikeperch (Sander lucioperca). This study aims to describe precisely the occurrence and the onset of cannibalism of this species during the first two post‐hatching months. In a first step, the cannibalistic behaviour was analysed through observations in three experiments. In each experiment, the number of cannibalistic cases was similar. From 14 to 48 days post‐hatching (dph), more than 60 % of prey ingestions were realized by tail‐first, but after 48 dph, the number of prey ingestions by head‐first increased. In a second step, the behavioural sequence exhibited to attack and to capture a conspecific was analysed, taking into account the size ratio between the cannibal and its prey. The behavioural sequence to capture was always the same, similar to a predatory sequence and it seems that the cannibal chose its prey about 10 s before attacking. Moreover, prey choice by a cannibal was based more on the size ratio between the cannibal and its prey than the previous activity of the potential prey. These new results could lead to solutions to decrease cannibalism in pikeperch rearing.     

尾叶桉二代测定林家系的综合评选

对49个家系的尾叶桉测定林各年度生长性状进行分析与遗传评估,结果表明：各年度树高、胸径和材积生长量在家系间存在极显著差异;分枝、干形和保存率在家系间存在显著差异;树高、胸径、单株材积、保存率的累积贡献率达95．45％,此4因子是综合评定家系时采用的;以家系群体平均选择指数I0为基准,两种选择标准下的家系材积增益,3年生时为7．63％～15．80％,4年生时为3．92％～10．39％,5年生时为6．08％～23．53％;以选择指数为指标,5年生时人选的5个优良家系是：109,113,66,81和100号。     

Genotypic variation in water relations and gas exchange of urban trees in Detroit,Michigan, USA

Increasing tree species diversity has become a key underpinning for communities to improve resilience of urban and community forests. Increasingly, urban forestry researchers are examining physiological traits to aid in selecting trees for urban sites. Knowledge of physiological responses also has implications for understanding species’ resilience to increased stresses associated with climate change. Here, we compare growth, leaf SPAD chlorophyll index, water relations, and gas exchange of seven genotypes of shade trees planted in two locations in downtown Detroit, MI, USA. Genotypes included Redpointe® maple (Acer rubrum ‘Frank Jr.’), Flashfire® maple (Acer saccharum ‘JFS-Caddo2′), Pacific Sunset® maple (Acer truncatum x platanoides ‘Warrenred’), Emerald City® tulip tree (Liriodendron tulipifera ‘JFS-Oz’), Chanticleer® pear (Pyrus calleryana ‘Glen’s Form’), swamp white oak (Quercus bicolor), and Emerald Sunshine® elm (Ulmus propinqua ‘JFS-Bieberich’). Trees were planted in either Lafayette Plaisance Park (Park), a large urban greenspace, or on the median of St. Aubin Avenue (Median), a nearby major thoroughfare. Tree height growth and leaf SPAD index were higher for trees planted in the Park location than on the Median. However, genotypic variation was larger than the effects of location or the interaction of Genotype × Location for most traits. Across measurement dates, midday leaf water potential was lowest for Pyrus trees and highest for Ulmus and Liriodendron trees. Pyrus and Quercus trees had relatively high rates of net photosynthesis (A) and stomatal conductance (g_s) while Liriodendron, Acer saccharum, and Ulmus trees had low rates of A and g_s. Liriodendron trees closed their stomata rapidly as leaf water potential (Ψ_w) declined (isohydric response), while Pyrus and Quercus trees maintained g_s across a range of leaf Ψ_w (anisohydric response). Liriodendron trees also had the highest relative growth rates, suggesting that drought stress avoidance through isohydry is a viable drought tolerance mechanism in urban trees.     

Urban density does not impact tree growth and canopy cover in native species in Melbourne,Australia

Trees provide multiple ecosystem services in urban centers and increases in tree canopy cover is a key strategy for many municipalities. However, urban trees also experience multiple stresses and tree growth can be impacted by urban density and impervious surfaces. We investigated the impact of differences in urban form on tree growth in the City of Merri-bek, a local government area in metropolitan Melbourne, which is the temperate climate zone. Merri-bek has a gradient in population density and urban greenness from north to south, and we hypothesized that tree growth in the southern areas would be lower because trees were more likely to have less access to water with high levels of impervious surfaces. We selected three common native evergreen species, Eucalyptus leucoxylon, Melaleuca linariifolia, and Lophostemon confertus that exhibit differences in climate vulnerability and assessed the tree canopy expansion in four urban density zones in Merri-bek between 2009 and 2020 using aerial image analysis. The differences in urban form did not significantly influence tree canopy growth and all species showed similar canopy expansion rates. However, smaller trees showed a greater relative canopy increase in the ten years, whereas larger trees had a greater absolute canopy growth. Thus, older and larger trees should be protected and maintained to achieve the canopy expansion. Our study indicated that differences in urban form are unlikely to have major impacts on the growth and canopy expansion of well adapted native tree species in open, suburban centers.     

Designing optimal training sets for genomic prediction using adversarial validation with probit regression

Genomic selection (GS) is a disruptive methodology that is revolutionizing animal and plant breeding. However, its practical implementation is challenging since many times there is a mismatch in the distribution of the training and testing sets. Adversarial validation is an approach popular in machine learning to detect and address the difference between the training and testing distributions. For this reason, the adversarial validation method in this research was implemented using probit regression to detect the mismatch in distributions and also to select an optimal training set. We evaluated the proposed method with 14 datasets, and the results were benchmarked regarding of using the whole reference population and simple random samples. We found that the proposed method is effective for detecting the mismatch in distributions and outperformed in prediction accuracy by 11.67% (in terms of mean square error) and by 5.35% (in terms of normalized mean square error) when the whole reference population was used as training sets. Also, in general, this outperformed some existing methods for optimal training designs in the context of GS.     

松浦镜鲤与德国镜鲤选育系（F4）的可量性状、鳞片数比较

对松浦镜鲤（SP）和德国镜鲤选育系（F4）（DJ）的可量性状及体表鳞片数进行比较,SP与DJ的可量性状与体表鳞被存在差异。SP的体长／体高（2．44±0．15）、头长／眼间距（2．24±0．08）明显小于DJ,体长／头长（3．86±0.20）、头长／吻长（2．99±0．23）明显大于DJ,SP体表的鳞片数明显少于DJ。结果表明,从DJ到SP遗传选育过程中,体型和鳞片的变化已达到了选育目的。     

基于序相关的作物育种评价性状特征选择方法

将育种家对作物性状表现的综合评价融入作物育种评价中,提出了一种基于序相关的作物育种评价性状特征选择方法。首先,从育种数据中筛选训练样本集及候选性状特征集合,计算候选性状特征集合中各性状与育种材料评价结果的相关性和作物在性状特征间表现的相似性,然后,利用计算的相关系数同时综合考虑性状表现的相似性系数,以期望选择的性状特征的相关性最大、相似性最小为目标,建立基于序相关的作物育种评价性状特征选择模型。该模型可为不同育种目标提供重点关注的性状特征集合,为数据化育种提供支持及依据。利用该方法对2013年大豆品系鉴定试验中早熟、中熟、毛豆3类育种材料进行了性状特征选择试验,结果验证了方法的有效性。该方法可以作为育种评价方法的前置步骤,与现有的综合评价、模糊综合评价等方法结合作为性状特征权重的确定手段,提高权重确定的科学性。     

长白落叶松纸浆材优良家系多性状联合选择研究

采用胸径木芯与伐倒木取样方法,对24年生长白落叶松优树子代测定林14个处理的生长性状、木芯材质性状、解析木材质性状及其制浆造纸特性进行了研究,结果表明:生长性状、木芯基本密度、木芯管胞性状均存在丰富的变异;家系间生长性状差异极显著;木芯基本密度、木芯管胞性状差异显著,家系遗传力在0.56 0.80之间;解析木基本密度、早材微纤丝角、管胞长度、早材壁腔比、木质素、阿拉伯糖含量、抗张强度、撕裂度等差异极显著,家系遗传力在0.64 0.86之间;晚材率、管胞长宽比、综纤维素含量等差异显著,家系遗传力在0.51 0.61,家系水平的材性改良潜力较大。生长性状与木芯管胞长度呈极显著正相关,与木芯基本密度、管胞长宽比相关不显著;木芯基本密度、管胞长度、管胞宽度以及管胞长宽比与解析木相应性状呈极显著正相关关系,且回归模型较为理想,可以利用胸径木芯各性状值预测其单株值,间接选择和评价纸浆材优良家系。通过生长性状、木芯基本密度和木芯管胞长宽比综合分析选出166、169为优良家系,根据解析木生长、材质以及纸张物理性状选出的优良家系与其结果一致。优良家系材积、木芯基本密度和木芯管胞长宽比的遗传增益(超过对照)分别为48.34%(38.80%)、14.01%(3.63%)和19.89%(6.42%)。