猪冻精推广应用的思考

随着蓝耳病及非洲猪瘟等生猪病毒性疾病的暴发,猪场如何进行批次化生产和闭群繁殖成为首要解决的问题,猪冻精的出现正是解决这一问题的希望。就猪冻精生产推广的意义、配种优势、操作规程及应用前景进行了思考。

Analysis of Heterosis, Combining Ability and Heritability of Cadmium Content in Brown Rice of Three-line Indica Hybrid Rice

Five cytoplasmic male sterile （CMS） lines were used as parents in an incomplete diallet cross and six restorer lines of rice design （Nc II design）. Thirty hybrid combinations with the same growth period were selected as experimental ma- terials to investigate the heterosis, combined ability and heredity of Cd content in brown rice of indica hybrid rice. According to the results, Cd content in brown rice showed a significantly negative heterosis; the general combining ability and specific combination ability of Cd content in CMS and restorer lines both reached extremely significant level （P〈0.01）, indicating that both genetic improvement of parents and e- valuation of combinations are important to the breeding of hybrid combinations with low accumulation of Cd; the broad-sense heritabitity and narrow-sense heritability of Cd content were both relatively high with slight differences, which respectively reached 97.73% and 80.10%, indicating that Cd content in brown rice mainly de- pends on the additive action of genes; in addition, parent improvement showed bet- ter effect on the selection of early generation.

Parentage Analysis of Dongfang No.2, a Hybrid of a Female Gametophyte Clone of Laminaria japonica (Laminariales, Phaeophyta) and a Male Clone of L. longissima

The cultivation of the first filial generation of monoploid gametophyte clones of different Laminaria species (hybrid Laminaria) is an effective way of utilizing heterozygous vigor (heterosis). A female gametophyte clone of L. japonica and a male gametophyte clone of L. longissima were hybridized, generating Dongfang No.2 hybrid Laminaria. The parentage of this hybrid Laminaria was determined using AFLP of total DNA, SNP of the ITS region of ribosomal RNA transcription unit and microsatellite DNA variation at two loci. In addition to 167 AFLP bands shared by Dongfang No.2, L. japonica and L. longissima, Dongfang No.2 hybrid Laminaria shared another 70 and 55 bands with L. japonica and L. longissima, respectively, which were obviously more than 11 bands shared by L. japonica and L. longissima. Dongfang No.2 held both ‘T’ and ‘C’ at position 847 of the ITS region, while ‘T’ at this position was specific for L. japonica and ‘C’ for L. longissima, respectively. Dongfang No.2 also held the microsatellite DNA alleles of two parents together at two microsatellite DNA marker loci. These observations clearly proved that Dongfang No.2 is a true hybrid of L. japonica and L. longissiuma. Unfortunately, the origin of the chloroplast of Dongfang No.2 was not determined based on the variation of RuBisCo spacer. More sequence variants of both ITS region and RuBisCo spacer were identified in Dongfang No.2 and most of them did not exist in either L. japonica or L. longissima. The unexpected variants may be due to the mutation of ga- metophyte clones occurring during their vegetative amplification.

Heterosis and combining ability:a diallel cross of three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino

We conducted a complete diallel cross among three geographically isolated populations of Pacific abalone Haliotis discus hannai Ino to determine the heterosis and the combining ability of growth traits at the spat stage.The three populations were collected from Qingdao(Q) and Dalian(D) in China,and Miyagi(M) in Japan.We measured the shell length,shell width,and total weight.The magnitude of the general combining ability(GCA) variance was more pronounced than the specific combining ability(SCA) variance,which is evidenced by both the ratio of the genetic component in total variation and the GCA/SCA values.The component variances of GCA and SCA were significant for all three traits(P<0.05),indicating the importance of additive and non-additive genetic effects in determining the expression of these traits.The reciprocal maternal effects(RE) were also significant for these traits(P<0.05).Our results suggest that population D was the best general combiner in breeding programs to improve growth traits.The DM cross had the highest heterosis values for all three traits.

Estimate of Genetic Parameters of Grain Yield and Some Agronomic Traits in Durum Wheat Using Diallel Crosses

Five varieties of durum wheat were crossed in full diallel fashion through 2010/2011 growing season. The five parents and their 20 F1 progenies were grown in 2011/2012 at the farm of faculty of agricultural and forestry, Duhok university, Iraq, using randomize complete block design with three replications to estimate heterosis, heritability and some genetic parameters for yield and its components. The results showed highly significant difference among genotypes for all studied traits. The parent Um Raby-5 had a positive general combining ability effect for most traits including grain yield. The crosses （Kokorete71× LD - 357E）, （Crezo × Um Rahy-5）, （Cimeto×Um Raby-5）, （Cimeto×crezo） and （Cimeto × Kokorete 71） exhibited significant desirable specific combining ability effect for most traits. The dominance was greater than additive almost traits. Heritability inbroad sense was high but heritability in narrow sense was low. The expected genetic advance as percent of traits mean was low for all traits. Most crosses showed significant positive heterosis for most traits and two crosses, （Crezo Cimeto） and （Cimeto Urn Raby-5） had the highest positive heterosis for the most studied traits including grain yield.

Large males have a mating advantage in a species of darter with smaller,allopaternal males Etheostoma olmstedi

Theory suggests that males that are larger than their competitors may have increased mating success, due to both greater competitive ability and increased attractiveness to females. We examined how male mating suceess varies with male size in the tessellated darter Etheostoma olmstedi. Previous work has shown that large males tend to move around and breed in vacant breeding sites, and consequently provide less care for their eggs, while smaller individuals can be allopaternal, caring for the eggs of other males as well as for their own. We studied female egg deposition in a natural breeding population using artificial breeding sites and in the laboratory, where female choice of spawning site was restricted to two breeding sites tended by two males of different sizes. In both the field and the laboratory, nests tended by larger males were more likely to receive new eggs. Additionally, the mean size of males associated with a nest was positively correlated with both the maximum coverage of eggs at the nest and the number of times new eggs were deposited. We discuss how the increased mating success of larger males, despite their decreased parental care, may help explain aUopaternal care in this species [Current Zoology 56 （1）： 1-5, 2010].

A Study on Combining Ability and Heritability of Agronomic Trait of Indica Hybrid Rice

In present study, under North Carolina design Ⅱ, 5 sterile lines and 2 restorer lines were analyzed by crossing test so as to study the combining ability, habitability and correlation of each major agronomic characters. The results showed that plant height, panicle length, filled grains per plant, grains per plant, 1 000-grain weight, yield per day, yield per plant by parent gene additive effect, seed set of parent gene additive and the additive effect work together, additive effect played a relatively important role, effective tillers per plant by additive genes of the parents and the additive effect had more consistent effects on offspring traits. General combining ability effect analysis showed that the better parents were P1A and R102. The special combining ability of plant height and panicle length in hybrid rice combination was mainly correlated with the general combining ability of restorer line, whereas not with the general combining ability of parent. For the other 7 traits, if the general combining ability of both parents was higher, the special combining ability of hybrid F1 combinations was also higher. The best combination of special combining ability of 9 traits in hybrid rice was P2 A/R102, followed by P1 A/R102.