Biomedical subjects

Bailian Li

Publications and source records attributed to Bailian Li.

7 recordsLinked to original sources

PubMed2006

Major gene detection for fusiform rust resistance using Bayesian complex segregation analysis in loblolly pine.

The presence of major genes affecting rust resistance of loblolly pine was investigated in a progeny population that was generated with a half-diallel mating of six parents. A Bayesian complex segregation analysis was used to make inference about a mixed inheritance model (MIM) that included polygenic effects and a single major gene effect. Marginalizations were achieved by using Gibbs sampler. A parent block sampling by which genotypes of a parent and its offspring were sampled jointly was implemented to improve mixing. The MIM was compared with a pure polygenic model (PM) using Bayes factor. Results showed that the MIM was a better model to explain the inheritance of rust resistance than the pure PM in the diallel population. A large major gene variance component estimate (> 50% of total variance), indicated the existence of major genes for rust resistance in the studied loblolly pine population. Based on estimations of parental genotypes, it appears that there may be two or more major genes affecting disease phenotypes in this diallel population.

Basidiomycota↗

PubMed2006

Additive genetic variation and the distribution of QTN effects among sites.

Early quantitative genetic theories emphasize the distribution of gene effects at individual loci or the distribution of mutant effects in maintaining quantitative genetic variation, but infrequently stress the distribution of gene effects among loci. In this study, we analyse the effects of the distribution of quantitative trait nucleotides (QTN) effects among sites under artificial and stabilizing selection. Wright's formula is applied to describing the density distribution of allele frequencies of multiple diallelic QTN at the equilibrium of mutation-drift-selection. Our results demonstrate that the distribution of QTN effects among sites can affect additive genetic variation in terms of total additive variance, average gene diversity, per-class contribution of QTN effects and per-QTN contribution. When the distribution of QTN effects among sites is changed from L-shaped to bell-shaped or to be a flatter, both the total additive variance and the average gene diversity are changed. Per-class and per-QTN contributions exhibit different distribution patterns. The L-shaped distribution indicates the predominant role of the aggregative effects from the QTN of small finite effects. The bell-shaped or flatter distributions indicate the predominance of the QTN of intermediate and large effects. These predictions highlight the significance of the distribution of QTN effects among sites in interpreting the maintenance of quantitative genetic variation at the fine genome scale.

Animals↗

PubMed2005

The distribution of genetic parameter estimates and confidence intervals from small disconnected diallels.

The distributions of genetic variance components and their ratios (heritability and type-B genetic correlation) from 105 pairs of six-parent disconnected half-diallels of a breeding population of loblolly pine (Pinus taeda L.) were examined. A series of simulations based on these estimates were carried out to study the coverage accuracy of confidence intervals based on the usual t-method and several other alternative methods. Genetic variance estimates fluctuated greatly from one experiment to another. Both general combining ability variance (sigma(2) (g)) and specific combining ability variance (sigma(2) (s)) had a large positive skewness. For sigma(2) (g) and sigma(2) (s), a skewness-adjusted t-method proposed by Boos and Hughes-Oliver (Am Stat 54:121-128, 2000) provided better upper endpoint confidence intervals than t-intervals, whereas they were similar for the lower endpoint. Bootstrap BCa-intervals (Efron and Tibshirani, An introduction to the bootstrap. Chapman & Hall, London 436 p, 1993) and Hall's transformation methods (Zhou and Gao, Am Stat 54:100-104, 2000) had poor coverages. Coverage accuracy of Fieller's interval endpoint(J R Stat Soc Ser B 16:175-185, 1954) and t-interval endpoint were similar for both h(2) and r(B) for sample sizes n</=10, but for n=30 the Fieller's method is much better.

Analysis of Variance↗

PubMed2004

A blocking Gibbs sampling method to detect major genes with phenotypic data from a diallel mating.

Diallel mating is a frequently used design for estimating the additive and dominance genetic (polygenic) effects involved in quantitative traits observed in the half- and full-sib progenies generated in plant breeding programmes. Gibbs sampling has been used for making statistical inferences for a mixed-inheritance model (MIM) that includes both major genes and polygenes. However, using this approach it has not been possible to incorporate the genetic properties of major genes with the additive and dominance polygenic effects in a diallel mating population. A parent block Gibbs sampling method was developed in this study to make statistical inferences about the major gene and polygenic effects on quantitative traits for progenies derived from a half-diallel mating design. Using simulated data sets with different major and polygenic effects, the proposed method accurately estimated the major and polygenic effects of quantitative traits, and possible genotypes of parents and progenies. The impact of specifying different prior distributions was examined and was found to have little effect on inference on the posterior distribution. This approach was applied to an experimental data set of Loblolly pine (Pinus taeda L.) derived from a 6-parent half-diallel mating. The result indicated that there might be a recessive major gene affecting height growth in this diallel population.

Chromosome Mapping↗

PubMed2003

On migration load of seeds and pollen grains in a local population.

We have extended Wright's model of migration load to hermaphrodite plants showing variation at a single locus with two alleles. The model incorporates independent migration of seeds and pollen grains, the selection at both the haploid gametophyte and the diploid sporophyte stages, and a mixed mating system. The analytical relations between migration load and migration rate of seeds and pollen grains are explicitly formulated. The results show that under certain conditions, seed flow can have a more effect on migration load than pollen flow. Pollen selection at the gametophyte stage cannot substantially affect the migration load at the sporophyte stage. Selection at the diploid sporophyte stage is critical in determining the migration load of pollen grains. The relative migration loads of pollen versus seeds can be approximately estimated in predominantly outcrossing populations by the ratio of pollen flow to twice the seed flow, when the selection coefficient (s(T)) is greater than, or approximately equal to, the migration rate (m).

Models, Genetic↗

PubMed2002

Annual shoot growth components related to growth of Pinus brutia.

Shoot elongation patterns of Pinus brutia Ten. were studied in six natural populations and 10 open-pollinated families within each population. The data were collected from a provenance-progeny trial that was thinned at Ages 13 and 17 years. Annual height increment was partitioned into first flush (spring shoot) and subsequent flushes (summer shoots) and the contribution of each to annual height increment was measured from Ages 7 to 17. Spring shoot elongation patterns were similar in all populations and families for 9 out of 10 years. In contrast, at all ages, populations differed significantly in total summer shoot growth and number of summer flushes. Families within populations differed in number of summer flushes in 7 out of 10 years. Summer shoot growth was the major cause of the differences in annual height growth among the six populations. Significant and high correlations were observed between summer shoot growth at Ages 7 to 12 and height at Age 13. A population from near the middle of the species' altitudinal range had more summer flushes than populations from higher or lower elevations, indicating an opportunistic growth pattern. Compared with mid-elevation populations, low- and high-elevation populations had more conservative growth patterns that depended mainly on growth of spring shoots. We conclude that summer shoot growth can serve as an explanatory variable to predict height growth of populations. Differences in shoot elongation patterns among Pinus brutia populations may be useful for selecting seed sources and for gene conservation programs.

Analysis of Variance↗

PubMed1998

Developmental factors responsible for heterosis in aspen hybrids (Populus tremuloides x P. tremula.

Juvenile growth and bud set phenology were analyzed to study the biological basis of heterosis (hybrid vigor) in interspecific hybrids of Populus tremuloides Michx. (T) and P. tremula L. (Ta). Growth, measured as seedling volume index, was significantly higher for each of the two reciprocal interspecific crosses, T x Ta and Ta x T, than for the T x T intraspecific cross. Broad-sense heritabilities were 2-6 times larger than narrow-sense heritabilities for growth and shoot components in the T x T intraspecific cross, suggesting an important role for dominance or overdominance in aspen growth. Previous genetic analyses have indicated that hybrid vigor may be the result of overdominance at several key loci each with an allele inherited from each of parental species. Internode length and leaf number contributed substantially to the heterosis of stem volume, but their effects on heterosis differed between the T x Ta and Ta x T hybrids. In T x Ta seedlings, heterosis of stem volume was attributed to a high diameter growth rate, whereas in Ta x T seedlings heterosis of stem volume was probably the result of delayed bud set resulting in a longer duration of height growth. In addition to internode number and length and leaf number, other morphological or physiological components might affect heterosis, for example, extended leaf retention.

Journal Article↗