不同品种鸡肌纤维的发育规律及杂种优势研究

选用北京油鸡、隐性白鸡及杂交鸡(北京油鸡♂×隐性白鸡♀)为试验材料,相同条件下饲养14周,自出生起每2周采集1次腿肌和胸肌的肌肉样本,做常规石蜡切片,测定肌纤维的直径和密度。结果表明:随着鸡的生长,肌纤维直径越来越粗,密度越来越小,直径和密度负相关极显著(P<0.000 1);并且不同品种肌纤维的生长速度差异较大。14周龄时,北京油鸡的腿肌肌纤维直径为42.89μm,杂交鸡是49.29μm,隐性白鸡的达56.93μm;而14周龄的腿肌肌纤维密度,北京油鸡达581.80根/mm2,杂交鸡是447.53根/mm2,隐性白鸡为349.87根/mm2;4周龄到14周龄,北京油鸡和隐性白鸡肌纤维直径差异极显著(P<0.01)。同一周龄同一品种的鸡,腿肌肌纤维直径大于胸肌,密度则小于胸肌;6周龄的隐性白鸡,腿肌和胸肌肌纤维直径分别是27.96μm和24.61μm,密度分别是1 557.50根/mm2和1 809.30根/mm2。在杂种优势率上,肌纤维直径和密度没有随周龄而呈现递增或递减的规律性变化,且波动比较大;总体来看,杂交后代没表现出杂种优势,而偏向其隐性白鸡母本,表现出一定的母体效应。     

论梅娘小说的永恒追求视界

梅娘的小说带有自传性色彩,她从自己的身世出发,从思念生母之情和生为人母之心,并进一步从自身延伸出去,关注、同情身处沦陷区女性,为思考女性的命运而呐喊。并试图为女性找寻挣脱不幸命运的出路。     

Environmental maternal effects on seed morphology and germination in Sinapis arvensis (Cruciferae)

Pioneer plants are adapted to grow in unpredictable environments. These plants have evolved several traits related to seed morphology and germination to cope with this unpredictability. The main aim of this study was to investigate the effect of plant identity and maternal environment on seed mass and germination of Sinapis arvensis. This study was undertaken with S. arvensis plants grown in four experimentally manipulated resource availability scenarios: (i) nitrogen addition, (ii) water addition, (iii) nitrogen and water simultaneously added, and (iv) control. Plants grew under field conditions in an emerging plant community. Germination response was mainly affected by maternal plant identity. This reflects not only genotype quality but also phenotypic plasticity, which allows adaptation to habitat conditions. Seed coat colour together with mean seed mass per plant explained significant fractions of the variability in germination rate. Changes in the germination response because of maternal environmental effects were also detected. Germination rate decreased in seeds from nitrogen‐enriched conditions; this may be due to the induction of dormancy caused by high concentration of nitrogen in the seeds. Addition of water to maternal environment caused a decrease in total germination percentage and germination rate of seeds. Thus, our results provide evidence for maternal environmental effects on germination under field conditions. Furthermore, changes in germination timing, as detected in our study, may determine plant development and fitness in unpredictable conditions.     

Quantitative Genetic Analysis of Traits in Avocado Cultivars *

This research is aimed at quantitative genetic analysis of several avocado traits and cultivars. The experimental material consists of our avocado breeding project in which data were collected from several crosses as well as selfings of cultivars. Parenthood was determined by isozymes and the seedling progenies were assessed for eight traits. A biometrical genetic approach for analysis of this breeding project is presented. Genetic profiles of the traits and cultivars were detailed by several characteristics: level of heterozygosity and dominance deviation, dominance of alleles, dominance direction, general evaluation of additive and non-additive genetic variance, maternal inheritance, and allelic differences among the various cultivars in major genes controlling the same quantitative trait. Five avocado cultivars: ‘Fuerte’, ‘Hass’, ‘Ettinger’, ‘Tova’, and ‘Rosh-Hanikra’, were characterized separately for each trait. Practical conclusions for the breeder regarding economically important quantitative traits are discussed.     

Maternal origins,population structure and demographic history of ten Chinese indigenous goat breeds from Yunnan

Yunnan as a frontier zone that connects China with South and Southeast Asia, has 11 well‐recognized goat breeds. However, the knowledge about maternal origins, population structure and demographic history of Chinese indigenous goats from Yunnan is limited. In this study, we analysed a 481‐bp fragment of first hypervariable segment (HVSI) of the mitochondrial DNA (mtDNA) control region sequences of 749 individuals from 10 Yunnan indigenous goat breeds, of which 556 sequences were newly determined. There were 110 polymorphic sites that defined 158 haplotypes among all sequences. The haplotype and nucleotide diversity of these breeds ranged from 0.782 ± 0.079 to 0.982 ± 0.015 and from 0.028 ± 0.003 to 0.043 ± 0.005, respectively. Phylogenetic analysis identified two lineages A and B, of which the lineage A had higher frequency (68.1%) and distributed in all Yunnan breeds. We combined previously reported sequences with our sequences belonging to the lineage B and detected two subclades B1 and B2, in which the B1 subclade shared individuals from Eastern Asia, Southeast Asia and Southern Asia. Given higher level of diversity and more unique haplotypes, the B2 subclade probably originated from Southwestern China. The haplotype network, analysis of molecular variance (AMOVA) and a Mantel test revealed no significant phylogeographic structuring among Yunnan goat breeds. This can be explained by high gene flow and genetic admixture among these breeds from different geographic regions in Yunnan. Additionally, both the lineages A and B reflected different demographic histories. This study will provide a scientific basis for the conservation and utilization of Yunnan indigenous goats.     

Tolerance of Maize(Zea mays L. )to Chlorsulfuron

Fourteen inbreds of maize were tested for the tolerance to chlorsulfuron with the method of seedling wa- ter culter. Significant difference existed in the tolerance of different type maize when tested with 1 and 2 μg/ kg of chlorsulfuron. The tolerance in different type maize wa dent＞flint＞sugar＞midiem＞super sugar pop. The tolerance of different inbred maize was negative correlated with the concentration concentration of chorsulfuron. The tolerance of hybrids might have some relation with their parent lines because in this test the hybrids response to chlorsulfuron showed significant positive correlation with that of tits female parent which suggented some maternal in inheritance and was not controlled by nuclear. It was possible that toler- ance of maize to chlorsulfuron was cytoplasm inheritance.     

苹果主要经济性状遗传动态的研究

对９个苹果杂交组合和１个国光天然实生苗群体的童期，果实大小及颜色，成熟期和抗病性等经济性状的遗传特性进行了分析研究，结果认为，苹果遗传组成比较复杂，以上性状均属微效多基因控制，呈连续分布的数量性遗传。杂种性状明显表现母性遗传优势，杂种群体结果的早晚，果实大小及颜色均有倾向母本的现象。     

甘蔗亲本正反交对经济性状的相对效应

以甘蔗6个亲本选配8个正反交组合的F_1代为试验材料,研究了亲本品种作母本或作父本对后代7个主要经济性状表现的相对效应.结果表明母性效应对后代多数性状的表达起了重要作用.高产品种Co419作母本的后代,产量性状普遍优于其作父本的后代.高糖品种CP65-357、CP70-1133和CP72-1312作母本的组合,后代分离出高糖个体的频率明显高于作父本的组合.以综合性状好的粤农73-204作母本。后代出现的综合性状好的单株也较多.本研究结果有助于甘蔗高产高糖育种中亲本的选择和组合的选配.     

Maternal periconceptual nutrition,early pregnancy,and developmental outcomes in beef cattle

The focus of this review is maternal nutrition during the periconceptual period and offspring developmental outcomes in beef cattle, with an emphasis on the first 50 d of gestation, which represents the embryonic period. Animal agriculture in general, and specifically the beef cattle industry, currently faces immense challenges. The world needs to significantly increase its output of animal food products by 2050 and beyond to meet the food security and agricultural sustainability needs of the rapidly growing human population. Consequently, efficient and sustainable approaches to livestock production are essential. Maternal nutritional status is a major factor that leads to developmental programming of offspring outcomes. Developmental programming refers to the influence of pre-and postnatal factors, such as inappropriate maternal nutrition, that affect growth and development and result in long-term consequences for health and productivity of the offspring. In this review, we discuss recent studies in which we and others have addressed the questions, “Is development programmed periconceptually?” and, if so, “Does it matter practically to the offspring in production settings?” The reviewed studies have demonstrated that the periconceptual period is important not only for pregnancy establishment but also may be a critical period during which fetal, placental, and potentially postnatal development and function are programmed. The evidence for fetal and placental programming during the periconceptual period is strong and implies that research efforts to mitigate the negative and foster the positive benefits of developmental programming need to include robust investigative efforts during the periconceptual period to better understand the implications for life-long health and productivity.