Genetic parameters for strongyle and Nematodirus faecal egg counts in lambs and their relationships with performance traits

Genetic resistance to the gastro-intestinal parasites of lambs can contribute to sustainable systems of parasite control with associated benefits for health and welfare. This study reports estimates of the genetic parameters of strongyle egg counts (FEC), Nematodirus egg counts (NEM), faecal consistency scores (FCS) and their associations with growth and ultrasonic measurements of muscle (UMD) and fat (UFD) depths in lambs. The lambs were the progeny of 45 Bluefaced Leicester sires from Scottish Blackface and Hardy Speckled Face dams. Faecal samples were taken from lambs at 10, 14, 18, 22 and 26 weeks of age, giving 1024 to 3055 records per trait. Live weight was recorded for all lambs at 16 weeks and live weight, UMD and UFD were recorded in female lambs at 28 weeks. Mean FEC and NEM were significantly higher for twin versus single reared lambs, for male castrate versus female lambs and for the offspring of Scottish Blackface versus Hardy Speckled Face ewes. Heritability estimates for FEC were low (0.04 ± 0.02 to 0.20 ± 0.08) and showed a non-significant trend to increase with age. The phenotypic correlations between measures of FEC at different ages were low (0.06 to 0.34) but genetic correlations were not significantly different from one in most cases. Heritability estimates of NEM ranged from 0.05 ± 0.03 to 0.09 ± 0.05 and genetic correlations among counts at different ages were not significantly different from zero. FEC and NEM were strongly correlated genetically (0.62 to 0.93) and estimates of the genetic correlations between FEC and NEM with live weights (− 0.36 to 0.23), UMD (− 0.35 to 0.25) and UFD (0.08 to 0.55) were variable in sign, though not significantly different from zero. Heritability estimates for faecal consistency scores (FCS) were 0.06 ±0.03 to 0.11 ± 0.04, with strong genetic correlations between successive measures. FCS was not significantly correlated with FEC or lamb performance traits. It is concluded that selection for reduced strongyle egg counts in lambs at around 5–6 months of age will give favourable correlated responses in NEM in lambs, with limited correlated response in lamb performance or faecal consistency scores.     

Genetic parameter estimates for prenatal and postnatal mortality in Nellore cattle

The aim of this study was to estimate genetic parameters for prenatal (PRE) and postnatal (POS) mortality in Nellore cattle. A total of 13 141 (PRE) and 17 818 (POS) records from Nellore females were used. PRE and POS were recorded using binary scale scores: a score of ‘1’ was given to calves that were born alive (PRE) and those that were alive at weaning (POS), and a score of ‘0’ was given to calves that were not alive at or around birth (PRE), as well as to those weighed at birth but not at weaning (POS). The relationship matrix included 698 sires, 107 paternal grandsires and 69 maternal grandsires. Data were analysed using Bayesian inference and a sire–maternal grandsire threshold model, including contemporary groups as random effects, and the classes of dam age at the beginning of mating season (for PRE), and dam age at calving and birthweight (linear covariable) (for POS), as fixed effects. For both traits, the covariance between direct and maternal effects (r_D,M) was estimated (r_D,M≠ 0) or fixed at zero (r_D,M = 0). PRE and POS rates were 3.00 and 4.04%, respectively. Estimates of direct and maternal heritability were 0.07 and 0.17, respectively, for PRE, and 0.02 and 0.07, respectively, for POS, assuming r_D,M = 0. For r_D,M ≠ 0, these estimates were 0.07 and 0.12, respectively, for PRE, and 0.03 and 0.07, respectively, for POS. The correlation estimates between direct and maternal effects were ?0.71 (PRE) and ?0.33 (POS). PRE and POS show low genetic variability, indicating that these traits probably suffer major environmental influences. Additionally, our study shows that the maternal genetic component affects preweaning calf mortality twice as much (or more) as the direct genetic component. A large number of offspring per sire is necessary in progeny tests to genetically decrease calf mortality.     

Within‐population variation in autumn frost hardiness and its relationship to bud‐set and height growth in Picea abies

Artificial freezing tests were performed with two sets of 12 full‐sib families of Picea abies. Each set was selected from a complete diallel cross performed within a natural population. Significant differences in autumn frost hardiness were observed between the two populations, which originate from the same altitude and longitude approximately 60 km apart. Substantial variation in frost hardiness was observed within both populations. Significant pheno‐typic correlations at the individual level were found between freezing injury and the two traits terminal bud‐set and height growth year one. However, no significant relationships were present between freezing injury and bud‐set at the family level, indicating that bud‐set cannot be used to predict autumn frost hardiness for families.     

Environmental correlations among grain yield and other important traits of wheat in drylands

Summary Environmental correlation coefficients were computed among all pairs of five traits, namely grain yield, heading date, number of tillers per m², plant height and 1000-grain weight (grain size) using 30 Triticum durum and 30 Triticum aestivum varieties grown in 18 environments. Grain yield was significantly correlated with the other four traits in almost all of the varieties. The mean correlation coefficient over all varieties ranged from 0.58 to –0.83 for durum wheat and 0.66 to 0.88 for aestivum wheat. The correlation coefficients between heading date and the other traits were also significant, ranging from –0.45 to –0.79 in durum wheat and –0.61 to –0.85 in aestivum wheat. The correlation coefficient between number of tillers with plant height and 1000-grain weight were the smallest, 0.19–0.32 in durum wheat and 0.39–0.60 in aestivum wheat. It was concluded that agronomic practices favouring early and good stand establishment in the dry regions will favour the yield components and important adaptive traits, which contribute towards larger yields. Significant differences were found among genotypes in the environmental correlation coefficients and the associated changes in one trait as a result of changes in other traits.     

Genotypic Variation in Maize Shoot Biomass at Different Stages of Development

A diallel cross from nine early-maturing lines of maize was grown in northern Germany during 1981 and 1982 in order to study the genotypic variation of shoot biomass at early and late stages of development. Inbred lines had been chosen from breeding programmes for early and medium early cultivars. Nevertheless, the date of maturity varied between them which can have some influence on the correlation between plant parameters. Plants were harvested at the fourth and sixth leaf stages, at anthesis and at maturity. S.c.a. effects were highly significant for traits during the vegetative stage. G.c.a. effects were highly significant for traits of the mature plant including grain yield components. The ratio of g.c.a. to s.c.a. effects for shoot biomass was dominated throughout the growing season by s.c.a. effects. Hybrids from the diallel cross had a superior growth rate until the fourth leaf stage; thereafter, relative growth rates of lines and hybrids were similar for the average of both groups until maturity. The correlation of g.c.a. effects and s.c.a. effects between shoot biomass throughout the season revealed that no significant relationship existed between early and late stages. G.c.a. and s.c.a. effects for grain yield components, with the exception of hundred kernel weight, were negatively correlated with shoot biomass at an early stage while correlation was positive at maturity. This would probably make it a difficult task to improve shoot growth and grain yield components simultaneously through the season.     

Genetic analysis for oil and protein contents of rapeseed (<Emphasis Type="Italic">Brassica napus</Emphasis> L.) at different developmental times

The dynamic expression of genes for oil and protein contents of rapeseed (Brassica napus L.) was carried out with time-dependent measures by using the developmental genetic models for quantitative traits in diploid plant. The unconditional and conditional analysis showed that the accumulated genetic effects or net genetic effects from diploid embryo nuclear genes, cytoplasmic genes and diploid maternal plant nuclear genes were all important for the performance of both nutrient quality traits at most developmental times/stages. Results from the conditional analysis further revealed that the activation of quantitative genes was gradually carried through the developmental process with maternal genes playing more active role at most developmental stages. Additive effects from embryo and maternal plant were found more important than the dominant effects at most developmental times/stages for both traits, and especially for protein content of rapeseed. Heritability analysis confirmed that the maternal heritability for protein contents were considerably stronger throughout developmental period except for the developmental time at 22 days, while for oil content the heritability components were dynamic and time dependent. The differences of genetic relationships from various genetic systems were found for oil and protein contents among the developmental times or between the two quality traits. M. T. Variath and J. G. Wu are contributed equally to this paper.     

Heritability of resistance to brown spot and root rot of narrow-leafed lupins caused by Pleiochaeta setosa (Kirchn.) Hughes in field experiments

Resistance to brown spot (BS) and Pleiochaeta root rot (PRR) in narrow-leafed lupin (Lupinus angustifolius L.) was assessed on a broad range of breeding lines and cultivars in field trials in Western Australia in 1985 and 1986. Both diseases are caused by Pleiochaeta setosa (Kirchn.) Hughes. Lines were grown in 5m × 1m plots in randomized complete block experiments with various disease pressures associated with cropping history — first, second and third successive lupin crops after cereals at one site in 1985, and first and second lupin crops at two sites in 1986. Best linear unbiased predictors (BLUPs) of defoliation caused by BS across experiments ranged from 64% to 123% of ‘Gungurru’, and BLUPs for PRR lesion severity ranged from 82% to 118% of ‘Gungurru’. For both diseases, genotypic variance was several times greater than genotype × environment variance, but error variance was relatively low for BS and high for PRR. Consequently, broad sense heritability (h²) for BS resistance was high in the seven experiments (range 0.89–0.94) but low for PRR resistance (range 0.00–0.53). There was a moderate correlation between BLUPs for resistance to BS and PRR across experiments (r = 0.36, P < 0.05). Genotypic correlations between resistance to BS and PRR were estimated at 0.57 ± 0.20 and 0.75 ± 0.31 in two experiments in 1985. Breeding progress is likely to be high for BS resistance and there may be slight improvements in PRR resistance associated with BS resistance. However, this field technique is not suitable for rapid breeding progress for PRR resistance.     

面向大规模农田生境监测的无线传感器网络节能优化策略

针对大规模农田生境监测场景中无线传感器网络节点在部分作物生长期内呈现节点空间冗余,以及传感器节点采集到的数据之间通常具有很强的时间关联性的特点,本研究提出一种基于矩阵补全的两步节能优化策略来同时降低传感器网络的数据采集和传输能耗,以实现延长网络寿命的目的。该算法首先通过对节点数据信息量的衡量来寻找出空间上的非冗余节点,剩余的冗余节点关闭其采集功能,只作为中继节点传输数据;其次,利用矩阵补全算法的部分采样原理在采样阶段进一步减少时间上的数据冗余量,达到同时降低采集和传输模块能耗的目的。试验结果表明,所提出的算法可减少网络中83%的工作节点数目,有效降低了网络能耗。     

Multivariate analysis of morphological characters in Setaria leiantha Hackel

Summary Continuous characters related to plant morphology and seed production were measured in eight populations of Setaria leiantha. Phenotypic variation for 12 traits was analyzed by multivariate methods. A canonical variate analysis provided a preliminary criteria for distinguishing the populations. The first three canonical components account for 93% of the total variance. Seed weight per ear was the most important character to discriminate among populations. The preliminari groups formed will serve as centers of diversity for future collections.