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Loblolly pine (Pinus taeda L.) is the most widely planted forest tree species in the United States. Most of the seedlings used to establish these plantations come from seed collected in open-pollinated seed orchards, but an increasing number are coming from controlled crosses, about 15%–20% of the loblolly pine seedling crops in the last five years. To produce this seed, millions of pollination bags are installed each spring in orchards throughout the southeastern United States; over 2.6 million bags were installed in 2022. This study evaluated 13 pollination bag types available for use in the mass production of control-cross seed. Using cone analysis, significant differences were found among bag types for the proportion of ovules resulting in filled seed, empty seed, and first-year aborts. Due to differences in the efficacy of orchard management, study trees varied greatly in their proportion of ovules resulting in filled seed and first-year aborts. Under good orchard management, open-pollinated cones had 72% of their ovules as filled seed and 12% in first-year aborted ovules. The best pollination bag type had 62% of its ovules as filled seed with 22% in first-year aborted ovules. These differences are apparently due to the quality of pollen used in the controlled crosses. Study Implications : Compared with open-pollinated families, full-sibling crosses among elite parents of loblolly pine produce more market value to landowners due to greater productivity, increased disease resistance, and enhanced stem form. Specific crosses of loblolly pine have occupied about 15%–20% of the recent seedling market because the seed are costly and difficult to produce. This study tested pollination bag types to determine their effectiveness in producing control-cross seed. Some bag types were superior in increasing seed yield, but seed yields for open-pollinated cones tended to be higher, suggesting problems in the control-cross process. Cone analysis is a useful tool for seed orchard managers to diagnose problems in seed production. Understanding and correcting these problems will help managers increase their production of full-sibling seed and lead to the establishment of new plantations with increased forest productivity. [ABSTRACT FROM AUTHOR]

Optimal deployment of improved loblolly pine (Pinus taeda L.) planting stock in the southeastern United States requires knowing how diverse seed sources and families perform over time across the wide range of sites used for plantations. This study tests if the relative growth performance of provenances and families is the same at the individual-tree and stand levels for family block plantings and determines what type of adjustment may be required to account for genetic differences when modeling growth and yield. Ten open-pollinated families from two very different provenances, Atlantic Coastal Plain and 'Lost Pines' Texas, were grown in single-family block plots to test for growth differences between provenances and among families under severely deficient and optimal nutrition regimes on a nutrient-deficient, dry site. The three-parameter Chapman- Richards function was fit to plot means over time by provenance, family, and nutrition treatments. Models with provenance- or family- specific parameters of the Chapman-Richards function were tested for significant improvement over global parameters. At age 14 years, family, provenance, and nutrition treatments all significantly affected individual-tree growth traits of height, diameter, and volume. Significant nutrition by provenance interactions were found for stand-level traits of basal area per hectare and volume per hectare. Family differences were also significant for these traits. Provenance- or family-specific asymptotic parameters accounted for differences in growth over time. Several traits required the use of local asymptotic and rate parameters in the fertilized treatment only. For modeling growth, a multiplier would be sufficient to account for genetic effects on the majority of traits. Key words: loblolly pine, Chapman-Richards function, genotype x environment interaction, growth and yield, fertilization. Le deploiement optimal des plants ameliores de pin a encens (Pinus taeda L.) dans le sud-est des Etats-Unis demande des connaissances sur le rendement des plantations dans le temps en fonction de l'origine des graines et des familles pour toute la gamme de stations utilisees. Cette etude verifie la similitude de croissance relative entre les provenances et les familles aux echelles de l'arbre et du peuplement pour des familles plantees en bloc. On veut aussi verifier quel type d'ajustement peut etre necessaire pour tenir compte des differences genetiques lors de la modelisation de la croissance et du rendement. Dix familles a pollinisation libre de deux provenances tres differentes, la plaine cotiere de l'Atlantique et' Lost Pines ' au Texas, ont ete plantees dans des parcelles composees de blocs a famille unique pour verifier les differences de croissance entre les provenances et les familles sous des regimes nutritifs optimal et fortement carence sur une station seche et pauvre en nutriments. La fonction de Chapman-Richards a trois parametres a ete ajustee aux moyennes des parcelles en fonction du temps, de la provenance, de la famille et du traitement nutritionnel. Nous avons teste si les modeles avec des parametres de Chapman-Richards specifiques a la provenance ou a la famille etaient significativement meilleurs qu'un modele avec des parametres globaux. A l'age de 14 ans, la famille, la provenance et le traitement nutritionnel ont tous eu un effet significatif sur les traits de hauteur, de diametre et de volume a l'echelle de l'arbre. Une interaction significative entre la nutrition et la provenance a ete decelee a l'echelle du peuplement dans le cas des traits de surface terriere et de volume a l'hectare. Des differences significatives entre les familles ont aussi ete decelees pour les memes caracteristiques. Les differences temporelles de croissance etaient prises en compte par des parametres asymptotiques specifiques a la provenance ou a la famille. Plusieurs traits ont necessite l'utilisation de parametres locaux d'asymptote et de taux seulement dans le cas du traitement de fertilisation. Pour modeliser la croissance, un multiplicateur serait suffisant pour tenir compte des effets genetiques sur la majorite des traits. [Traduit par la Redaction] Mots-cles: pin a encens, fonction de Chapman-Richards, interaction entre le genotype et l'environnement, croissance et rendement, fertilisation., Introduction Loblolly pine (Pinus taeda L.) tree improvement programs have been actively selecting and breeding a wide range of genotypes in the southeastern United States for over 50 years. Virtually [...]

Controlled inoculations with 10 bulk inocula of Cronartium quercuum (Berk) Miyabe ex Shirai f.sp. fusiforme were carried out on open-pollinated progeny of 25 fast-growing Pinus taeda L. parents. The parents had a range of breeding values for resistance to fusiform rust in progeny field trials. There were highly significant differences among the halfsib families in response to inoculations, and these differences were very reproducible; the half-sib family-mean heritability of resistance to controlled inoculation was 0.97. All of the families that were susceptible in the field were susceptible in controlled inoculations, and most (12 of 17) of the field-resistant families were resistant in response to controlled inoculations. Significant pathogenic variability was observed among the different bulk inocula, although this accounted for only 1.9% of the total variation. Genetic differences among families within field-resistant or field-susceptible groups accounted for 13.7% of the total variation. The family by inocula interaction was highly significant, but a single field-resistant family contributed 44% of the total family by inocula interaction variance, and two other field-resistant families also showed significant interactions. Des tests d'inoculation controlee avec 10 sources d'inoculum de Cronartium quercuum (Berk) Miyabe ex Shirai f. sp. fusiforme ont ete effectues sur des descendances issues de pollinisation libre et provenant de 25 parents de Pinus taeda L. a croissance rapide. Les parents representaient une gamme de valeurs genetiques pour la resistance a la rouille fusiforme dans des tests de descendance sur le terrain. Il y avait des differences significatives parmi les descendances uniparentales en reaction aux inoculations et ces differences etaient tres reproductibles; l'heritabilite moyenne des descendances uniparentales pour la resistance aux inoculations controlees etait de 0,97. Toutes les familles qui etaient sensibles sur le terrain etaient egalement sensibles dans les essais d'inoculation controlee et la plupart (12 sur 17) de celles qui etaient resistantes sur le terrain etaient egalement resistantes dans les essais d'inoculation controlee. Une variation significative de la pathogenicite a ete observee parmi les sources d'inoculum bien que cela ne representait que 1,9 % de la variation totale. Les differences genetiques entre les familles parmi les groupes de familles resistantes ou sensibles sur le terrain representaient 13,6 % de la variation totale. L'interaction famille x source d'inoculum etait tres significative mais une famille contribuait a elle seule 44 % de la variation de l'interaction famille x source d'inoculum qui etait egalement significative chez deux autres familles resistantes sur le terrain. [Traduit par la Redaction], Introduction Fusiform rust disease, caused by Cronartium quercuum (Berk) Miyabe ex Shirai f.sp. fusiforme (Cqf), is manifested by swollen regions called galls on stems or branches of pines, and is [...]

The economic consequence of continuing or increasing the tree improvement efforts for loblolly pine (Pinus taeda L.) in the southern United States is immense. For the more than one million acres planted each year with germplasm from the North Carolina State University Cooperative Tree Improvement Program, the present value of continuing current tree breeding efforts and deploying the genetic gains to landowners is estimated to be more than $1.7 billion at current prices. The present value of increasing the rate of genetic gain from 1% per year to 1.1% per year is $211 million. These analyses can be used to justify maintaining and even increasing efforts in tree improvement. With the aggressive fourth-cycle breeding program underway and plans for fifth-cycle breeding and deployment strategies being developed, we have every reason to believe that this trend for at least 1% gain per year will continue for decades, provided the resources to continue tree improvement efforts remain available. Even a modest increase in genetic gain per year would be justification for stakeholders to invest more than $12 million per year to realize this gain. [ABSTRACT FROM AUTHOR]

Abstract Background The plastic response of fine roots to a changing environment is suggested to affect the growth and form of a plant. Here we show that the plasticity of fine root growth may increase plant productivity based on an experiment using young seedlings (14-week old) of loblolly pine. We use two contrasting pine ecotypes, "mesic" and "xeric", to investigate the adaptive significance of such a plastic response. Results The partitioning of biomass to fine roots is observed to reduce with increased nutrient availability. For the "mesic" ecotype, increased stem biomass as a consequence of more nutrients may be primarily due to reduced fine-root biomass partitioning. For the "xeric" ecotype, the favorable influence of the plasticity of fine root growth on stem growth results from increased allocation of biomass to foliage and decreased allocation to fine roots. An evolutionary genetic analysis indicates that the plasticity of fine root growth is inducible, whereas the plasticity of foliage is constitutive. Conclusions Results promise to enhance a fundamental understanding of evolutionary changes of tree architecture under domestication and to design sound silvicultural and breeding measures for improving plant productivity.

Recently published hazard maps for fusiform rust (Cronartium quercuum f. sp. fusiforme) using US Department of Agriculture Forest Service Forest Inventory and Analysis data appear to be biased because of incorrect assumptions about genetic improvement in rust resistance for loblolly pine (Pinus taeda) plantations in the southeastern United States. We used progeny tests to estimate the regional hazard and genetic gain in resistance based on rust incidence in local nonimproved trees. The largest genetic gains occurred in regions having higher hazard. The Coastal Georgia/Florida region had the greatest gains, with 11% lower mean incidence for second-cycle families when compared with the local nonimproved trees. In northern regions of Tennessee and Virginia, where rust incidence was low, no significant gains in resistance were realized. The recently published rust hazard maps overestimate hazard, especially for regions with low incidence, because those maps ignored plantations with low incidence and assumed that they were planted with resistant genotypes. [ABSTRACT FROM AUTHOR]