培养抗性植物的细胞/组织培养途径

抗性育种在作物品种改良中已日益显得重要。近10多年来,随着细胞/组织培养、遗传操作等生物技术的迅速发展,以及由于植物具有全能性,在人工培养条件下,从单细胞原生质体可以再生成一个完整的个体成功以来,人们试图利用细胞/组织培养等生物技术将野生种的抗性基因引入到作物中来,或是人工诱发抗性变异,从而筛选出抗性愈     

Fertility interactions in Drosophila: Theoretical model and experimental tests

The results of 11 experiments with Drosophila species show that fertility is not a reducible property: the fertility of a mating pair cannot be predicted from the average fertility of the two genotypes involved. We propose a model of fertility selection that does not assume additivity (or multiplicativity) but assumes random mating and that the genotypic frequencies are in Hardy-Weinberg equilibrium. Numerical simulations show that removal of the assumption of Hardy-Weinberg frequencies does not significantly change the equilibrium frequencies predicted by the model.     

Analysis of variations of handling-time inTrichogramma maidis

Variation in handling-time is studied in the association betweenTrichogramma maidis Pintureau & Vœgelé [Hym.: Trichogrammatidae] and one of its factitious hosts: the eggs of the Mediterranean flour mothEphestia kuehniella Zeller [Lep.: Pyralidae]. It is shown that the duration of egg laying behaviour decreases exponentially from the first host egg encountered onwards. This decreasing kinetic, which corresponds to a learning ability, shows a high variability between females, but a mother-daughter regression analysis fails to demonstrate any genetic transmissibility of this learning ability over 2 successive generations. Once the learning is over, there remains a residual variability which is, in part, under genetic control. The possible consequences of these results on the stability of host-parasite associations are discussed.      

混合家系遗传参数估计方法研究

针对混合家系遗传参数估计,本文在假定公畜方差组分和母畜方差组分相等这一理论基础上,通过对方差分析的期望均方组成分析,提出了新的遗传力估计方法,以及某些特殊情况下的近似估计方法。通过一个估测实例比较了几种遗传力估计方法,结果表明,本文方法与全同胞组分估计最为接近,而且遗传力标准误最小,本文近似估计方法的效果也较好。对各种方法而言,资料越不平衡其差异越大。本文方法可以在一定程度上弥补全同胞分析时,因实际资料的公母畜方差组分差异过大的缺陷,具有实际可行性。此外,由于本文方法是用单因方差分析解决二因方差分析问题,计算更为简便,并可免于计算混合家系平均亲缘相关系数。     

嗜热脂肪芽孢杆菌质粒的分离

从堆肥和污泥中分离到一批抗药性高温细菌,经电泳检查,发现6株高温细菌细胞中有质粒存在。其中,嗜热脂肪芽孢杆菌T653的细胞DNA提取液电泳图谱上,有三条非染色体DNA条带,用电镜直接观察,证明它们是T653细胞中的三个质粒。测得两个较小质粒的分子量分别为3.6×10~6和45×10~6道尔顿。研究了嗜热脂肪芽孢杆的T653的温度生长条件与其细胞中质粒的关系。T653细胞中三个质粒的明确功能有待进一步探讨。     

Analysis of founder representation in pedigrees: Founder equivalents and founder genome equivalents

The concepts of “founder equivalent” and “founder genome equivalent” are introduced to facilitate analysis of the founding stocks of captive or other populations for which pedigrees are available. The founder equivalents of a population are the number of equally contributing founders that would be expected to produce the same genetic diversity as in the population under study. Unequal genetic contributions by founders decrease the founder equivalents, portend greater inbreeding in future generations than would be necessary, and reflect a greater loss of the genetic diversity initially present in the founders. The number of founder genome equivalents of a population is that number of equally contributing founders with no random loss of founder alleles in descendants that would be expected to produce the same genetic diversity as in the population under study. The number of founder genome equivalents is approximately that number of wild-caught animals that would be needed to obtain the same amount of genetic diversity as is in the descendant captive population. Founder equivalents and founder genome equivalents allow comparison of the genetic merits of adding new wild-caught stock vs. further equalizing founder representations in a captive population.     

GENETIC RELATEDNESS OF TWO POPULATIONS OF THE SOUTHERN ELEPHANT SEAL, MIROUNGA LEONINA

Blood samples from southern elephant seals ( Mirounga leonina ) from Heard and Macquarie Islands were surveyed electrophoretically for protein variation. Thirty proteins encoded by a minimum of 35 loci were screened, four of which were found to be polymorphic. Statistically significant differences in allele frequencies were found between the two populations at three loci. Heterozygosity estimates for the Heard and Macquarie island populations were 0.034 ± 0.020 (mean ± standard error) and O.029 ± 0.017 respectively, with a Nei distance of 0.007. The findings suggest that the two populations may have diverged genetically and very limited gene flow exists between the islands, a finding consistent with limited information from mark-recapture studies.     

A comparison of within-plant karyological heterogeneity between agamospermous and sexualTaraxacum (Compositae) as assessed by the nucleolar organiser chromosome

Morphological variation for the NOR chromosome was studied for four half-siblings of a sexual outbreedingTaraxacum, for three siblings of the obligate agamospermT. pseudohamatum, and for two individuals of the agamospermT. brachyglossum. No rearrangement was detected for the 113 chromosomes of sexuals, or for 41 chromosomes of two agamospermous individuals. In the other three agamospermous individuals, 3/16, 5/50, and 5/20 chromosomes showed evidence of chromosomal rearrangement. The majority of rearrangement events (10/13) occurred to the satellite rather than to the body of the NOR-chromosome. It is considered that such high levels of somatic chromosomal rearrangement in agamospermousTaraxacum may be the result of activity by transposable genetic elements. This recombination may be of selective advantage to asexual plants which cannot generate genetic variability through the sexual process.     

Genetic variation and population structure of cod, Gadus morhua L., in some fjords in northern Norway

Biochemical genetic polymorphism in cod from several fjords in Troms, northern Norway was analysed. Gene frequencies at several polymorphic loci ( Hb, Pgi, Ldh, Pgm, Gpd and Idh ) are given. Significant variation was found both within and between fjords, and even between samples from the same locality sampled in different years, indicating a mosaic structure of the cod population in the area studied. The results of the haemoglobin variation are compared to similar results obtained more than 20 years ago in the same and adjacent areas. The biochemical genetic variation is discussed in relation to stability of gene frequencies, isolation mechanisms and migration patterns.