Genetic and site effects on stem breakage in Pinus tecunumanii     

W. S. Dvorak  C. C. Lambeth  Bailian Li 《New Forests》1993,7(3):237-253

Fifteen provenance/progeny tests of Pinus tecunumanii (Schw.) Eguiluz et Perry were assessed for upper-crown stem breakage at 5 to 8 years of age in Brazil, Colombia and South Africa. Five year results indicated that the mean percent stem breakage was moderate in Colombia (14% to 21%), low in South Africa (2% to 6%) and very low in Brazil (<1%). In the Colombian tests, trees from provenances of Mexican origin were more susceptible to wind damage than those from Central America, 20% versus 14%. Provenance order of percent stem breakage at 5 years of age in Colombia was Montebello (27%), La Soledad (25%), San Jose (20%), Chempil (20%), Jitotol (18%), Las Piedrecitas (18%), Celaque (17%), Km 47 (16%), San Vicente (13%), San Jeronimo (13%), San Lorenzo (12%) and Las Trancas (7%). Two half-sib progeny tests assessed at 8 years of age in Colombia with trees from the Mountain Pine Ridge source of P. tecunumanii exhibited 13% stem breakage. Family variation in stem breakage ranged from 0 to 44% in Colombia and 0 to 33% in South Africa at 5 years of age and were highly significant. The Spearman rank correlations in stem breakage of 36 half-sib families common to tests in Colombia and South Africa were r=0.13 and not significant. Family heritabilities for stem breakage at 5 and 8 years of age ranged from 0.17 to 0.63. Results indicate that stem breakage was more common on trees with branches of large diameter and was not strongly related to growth rate.  相似文献   

Variation in pitch canker resistance among provenances of <Emphasis Type="Italic">Pinus patula</Emphasis> and <Emphasis Type="Italic">Pinus tecunumanii</Emphasis> from Mexico and Central America     

G. R. Hodge  W. S. Dvorak 《New Forests》2007,33(2):193-206

Pinus patula and high-elevation (HE) sources of P. tecunumanii exhibit intermediate levels of resistance to pitch canker (Fusarium circinatum), compared to extremely resistant species such as P. oocarpa, and extremely susceptible species such as P. radiata. Seedlings from 20 P. patula provenances and 15 HE P. tecunumanii provenances were artificially inoculated with the pitch canker fungus at 21 and 12 weeks of age, respectively, and assessed for resistance 12–20 weeks later. There was important provenance variation in pitch canker resistance for both species. The 20-week LiveStem percentage ranged from 70.3% to 43.6% among the P. patula provenances and 59.6% to 11.7% among HE P. tecunumanii provenances. There was a geographic pattern to the provenance variation, and in both species, low altitude sources demonstrated more resistance than those from high elevation. Provenance variation in pitch canker resistance could be useful when making selection and breeding decisions with these species.  相似文献   

Assessing evolutionary relationships of pines in the Oocarpae and Australes subsections using RAPD markers     

Dvorak  W.S.  Jordon  A.P.  Hodge  G.P.  Romero  J.L. 《New Forests》2000,20(2):163-192

RAPD marker technology was used to assessevolutionary relationships among species classified inthe Oocarpae and Australes subsections. A total of 127 RAPD markers was assessed across 10taxa in Oocarpae and 8 taxa in Australes. A phylogenetic tree was constructed byneighbor-joining analysis of a p-distance matrixgenerated from the marker data. Results indicate thattaxa in the California Oocarpae are distinctfrom Mesoamerican Oocarpae and Australes.The Mesoamerican Oocarpae and Australesare closely aligned and apparently are derivatives ofa common progenitor, most likely ancestral Pinusoocarpa. The Mesoamerican Oocarpae subsectionis polyphyletic, sharing ancestry with taxa from theTeocote subsection. We propose anevolutionary scenario that suggests that an ancestorof Oocarpae migrated south through Mexico andCentral America, as well as east across the southernUS, with the two paths converging in Florida or theCaribbean. Pinus caribaea var. hondurensisis intermediate between the Mesoamerican Oocarpae and Australes, and its ancestorsformed the species line that migrated to the US fromCentral America. Pinus palustris is the oldestof the Australes species studied, havingdiverged from ancestral Oocarpae as thissubsection moved east. Subsequent divergences withinAustrales produced P. echinata and P. taeda.  相似文献   

Financial feasibility of participating in an international seed cooperative for tropical pines     

Jan G. Laarman  William S. Dvorak 《New Forests》1988,2(3):161-172

A break-even analysis indicates the level of annual tree planting that covers the costs of participating in an international seed cooperative for tropical pines. The financial framework is estimated for CAMCORE, the Central America and Mexico Coniferous Resources Cooperative. The present value of financial returns is compared with the present value of expenditures of participating in the Cooperative.Results suggest that membership is feasible for organizations planting 100–500 ha annually if the opportunity cost of capital is 8%. Break-even levels rise dramatically for higher costs of capital. A number of difficult valuation issues are necessarily omitted from the framework. The strictly financial analysis likely understates benefits.  相似文献   

Allozyme variation and recent evolutionary history of eastern hemlock (<Emphasis Type="Italic">Tsuga canadensis</Emphasis>) in the southeastern United States     

K.?M.?PotterEmail author  W.?S.?Dvorak  B.?S.?Crane  V.?D.?Hipkins  R.?M.?Jetton  W.?A.?Whittier  R.?Rhea 《New Forests》2008,35(2):131-145

Eastern hemlock (Tsuga canadensis [L.] Carr.) is a widespread and ecologically important conifer species of eastern North America that is threatened by the hemlock woolly adelgid (Adelges tsugae Annand), a pest introduced into the United States from Asia in the 1920s. Information about the genetic composition of eastern hemlock is necessary to guide ex situ conservation efforts in the southeastern United States, where the species is expected to harbor relatively high amounts of genetic variation in areas of Pleistocene glacial refuge. Nineteen allozyme markers were used to quantify the genetic variation present in 20 eastern hemlock populations in the southeastern United States. Results indicate that the species has low levels of genetic diversity in the region compared to most other conifers, but greater population differentiation (F _ST = 0.126). Populations along the eastern periphery and in the Appalachian interior exhibited higher levels of diversity than those along the western periphery of its geographic range. The results suggest that the glacial refuge area for eastern hemlock was likely located east of the southern Appalachian Mountains, and indicate that ex situ conservation seed collections should be concentrated in these areas of higher diversity.  相似文献   

Use of recombinant substitution lines for gene mapping and QTL analysis of bread making quality in wheat   总被引：7，自引：0，他引：7  

M. Rousset  P. Brabant  R.S. Kota  J. Dubcovsky  J. Dvorak 《Euphytica》2001,119(1-2):81-87

Three populations of 41 to 74 homozygous recombinant substitutionlines (RSLs) were used for RFLP mapping and quantitative trait analysis ofthe following parameters: total proteins (%prot), SDS-sedimentationvolume (SDSsed), bread mixing time (Bmxt) and loaf volume (Blvol). TheRSLs were developed from crosses between disomic substitution linesinvolving chromosomes 1A, 1B, and 1D of the high-quality wheat cv.`Cheyenne' (Cnn) substituted into the genetic background of the poorquality cv. `Chinese Spring' (CS). The QTL analysis indicated regions in thethree chromosomes responsible for the differences between CS and thethree disomic substitution lines. The major effect detected on chromosome1A of Cnn was high SDSsed, Bmxt and Blvol associated with the H-M-WGlutenin subunit locus Glu-A1. In addition a QTL was identifieddistally on the long arm of chromosome 1A for Bmxt and Blvol. Ahigh %prot QTL was mapped on the long arm of chromosome 1B of CSand a high Bmxt QTL was mapped on the long arm of chromosome 1B ofCnn. Additionally, this chromosome enhanced SDSsed, Bmxt and Blvol,which were associated with the region of the gliadin and L-M-W Gluteninsubunit locus Gli-B1/Glu-B3. A second more proximal region on theshort arm of chromosome 1B could be involved in loaf volume. QTLanalyses for% prot, showed a strong clear QTL mapped in the centromericregion (XTri/Centromere linkage group) of chromosome 1D with anapparent positive effect brought by CS. For Blvol we revealed two QTLs inopposite phase: one in the Xtri/Centromere region with a positive effect ofCS allele, one in the Glu-D1 region with a positive effect of Cnnallele. This organization `in repulsion' in the parental lines could explain thesmall difference between them for Blvol and the significant transgressionobserved among the RSLs. No clear candidate gene explained the positiveeffect of the centromeric region of CS on %prot and Blvol. Contrary to thecurrent belief that wheat bread-making quality is determined primarily byvariation at the Glu-1 locus, present results showed that the trait isunder a complex control and the Glu-1 loci was only a component ofthe genetic control of the trait.  相似文献   

Genome plasticity a key factor in the success of polyploid wheat under domestication     

Dubcovsky J  Dvorak J 《Science (New York, N.Y.)》2007,316(5833):1862-1866

Wheat was domesticated about 10,000 years ago and has since spread worldwide to become one of the major crops. Its adaptability to diverse environments and end uses is surprising given the diversity bottlenecks expected from recent domestication and polyploid speciation events. Wheat compensates for these bottlenecks by capturing part of the genetic diversity of its progenitors and by generating new diversity at a relatively fast pace. Frequent gene deletions and disruptions generated by a fast replacement rate of repetitive sequences are buffered by the polyploid nature of wheat, resulting in subtle dosage effects on which selection can operate.  相似文献