Search

Abstract: Better knowledge of aerobiological properties of pollen clouds is needed for pines and other woody perennials because these properties shape the predictive accuracy of spatially explicit pollen dispersal models. [...]

Abstract: Outcrossing, wind-pollinated members of the Pinaceae have high self-pollination rates yet produce few selfed seedlings. How are selfs selectively eliminated? Barriers to selfing have long been considered to be [...]

Abstract: The question of how to estimate a founder's proportion of a single descendant's genome has renewed relevance for outbred pedigrees, given the abundant DNA sequence data for model and [...]

Prefertilization mechanisms influencing selfing rates are thought to be absent in conifers. Outcrossing in conifers is promoted via an embryo-lethal system, but the genetic mechanism is poorly understood. This study is the first experimental profile of the genetic mechanism promoting outcrossing in conifers. Molecular dissection of a Pinus taeda L. selfed pedigree detected a chromosomal region identified as PtTX3020-RPtest9. Within this region, a semilethal factor was tightly linked (r = 0.0076) to a polymorphic expressed sequence tag (EST). The linkage group flanking the lethal factor showed strong heterozygote advantage. Using genotypic frequencies for the linkage group, three hypotheses about the semilethal factor could be tested: (1) the presence of a balanced lethal system, i.e., a lethal factor present in each of the two marker intervals; (2) gametic selection operative prior to fertilization; and (3) a stage-specific lethal factor. Selection acted via the embryo-lethal system. No support for a genetic mechanism operating prior to fertilization was found. The semilethal factor exerted no effect after embryo maturity. The genetic mechanism promoting outcrossing in P. taeda L. appears to have a balancing selection system due to either pseudo-overdominance or true overdominance.

A study to determine whether Pinus taeda introductions into Zimbabwe came from one US region or whether the population is mixed, having introductions from east and west of the Mississippi River Valley has been carried out. The study shows it to be an admixture with five novel alleles in the population not represented in indigenous US populations, perhaps because of de novo mutation or introgression with other introduced North American pines or sampling error.

A study was conducted to compare recombination distances and linkage heterogeneity among a wide range of maize inbreds, wide crosses and maize crossed with teosinte hybrids. The results showed a higher recombination fraction for exotic germplasm than for either US maize or maize crossed with teosinte crosses.