Preference for Some Nursery-grown Hybrid \u3ci\u3ePopulus\u3c/i\u3e Trees by the Spotted Poplar Aphid and Its Suppression by Insecticidal Soaps (Homoptera: Aphididae)

Susceptibility ranking of more than 50 clones of hybrid Populus whips showed a wide range of attack ranging from none to very heavy. Clones with P. x jackii parentage were the most susceptible, whereas Carolina poplar was unscathed. Growth loss differed little between very heavily aphid-attacked whips and unattacked whips. Two insecticidal soaps adequately controlled the aphid but one caused some phytotoxicity to Populus

Laboratory and field evaluation for the resistance of commonly used woods against _Coptotermes heimi_ (Wasmann).

The current study was conducted to evaluate the resistance of four wood species (_Azadirachta indica_, _Pinus roxberghii_, _Dalbergia sissoo_ and _Populus deltoides_) against subterranean termite species _Coptotermes heimi_ by choice and no choice field and laboratory trials. Of these four wood species _P. roxberghii_ and _D. sissoo_ proved to be most resistant to termite attack. Taken together these results we can conclude that _D. sissoo_ is the least preferred and _P. deltoides_ is the most preferred wood by the _C. heimi_. The data obtained from the field choice and no-choice the woods are arranged in order of preference DS>PR>AI>PD whereas in laboratory choice and no-choice trials the order of preference was PD>AI>PR>DS

Ecophysiological responses of two poplar species to intraspecific and interspecific competition under different nitrogen levels

Aims Populus deltoides and P. euramericana are widely used in China as major forestry species. At present, little is known about their responses to nitrogen (N) deficiency when grown in monocultures or mixed plantations. The aim of this investigation was to analyze the growth, and morphological and physiological responses of P. deltoides and P. euramericana to different N levels under competition conditions. Methods We employed two Populus species (P. deltoides and P. euramericana) to discover how N deficiency affects plant traits under different competition types (P. deltoides x P. deltoides, intraspecific competition; P. euramericana x P. euramericana, intraspecific competition; P. deltoides x P. euramericana, interspecific competition). Potted seedlings were exposed to two N levels (normal N, N deficiency), and nitrogen- and competition-driven differences in growth, morphology and physiology were examined. Important Findings Under normal N conditions, interspecific competition significantly decreased the total root weight, root mass fraction (RMF), root-shoot ratio (R/S) and carbon/nitrogen ratio (C/N), and increased the leaf dry weight, leaf mass fraction and total leaf area of P. euramericana compared with intraspecific competition. The same conditions significantly affected the growth and morphological variables of P. deltoides, except for the dry weight of fine roots, R/S, specific leaf area, RMF, total nitrogen content and C/N compared with intraspecific competition. In addition, chlorophyll a (Chla), total chlorophyll (Tchl), carotenoid contents (Caro) and the carbon isotope composition (delta C-13) of P. deltoides were significantly lower in interspecific competition than in intraspecific competition, but no difference was detected in P. euramericana. The effects of N deficiency on P. deltoides under intraspecific competition were stronger than under interspecific competition. In contrast, the effects of N deficiency on P. euramericana between intraspecific and interspecific competition were not significantly different. These results suggest that under normal N condition, P. deltoides is expected to gain an advantage in monocultures rather than in mixtures with P. euramericana. Under N deficiency, the growth performance of P. euramericana was more stable than that of P. deltoides under both cultivation modes.Peer reviewe

Susceptibilidad de híbridos de Populus spp. al ataque de áfidos y roya en tres localidades de Chile

Ramirez, CC (reprint author), Univ Talca, Inst Biol Vegetal & Biotecnol, Talca, Chile.In the last few years an increasing interest on species and hybrids of the genus Populus has occurred in Chile. However, such plantations are strongly affected by pest and diseases. With the aim to identify potentially resistant (or less susceptible) hybrids of the genus Populus, the susceptibility of some poplar hybrids growing in experimental nurseries in Southern-Center Chile to the aphid Chaitophorus leucomelas Koch and to the rust Melampsora spp. was assessed. Results showed that aphid abundance was higher in the month of March, particularly in Coinco (O'Higgins Region) and lower in Pillanlelbun (Los Rios Regions) and Yumbel (Biobio Region). In Pillanlelbun the most susceptible hybrid to aphids was TDxTD [(P. trichocarpa x P. deltoides) x (P. trichocarpa x P. deltoides)], and the less susceptible ones were TDxD [(P. trichocarpa x P. deltoides) x P. deltoides], TxN (P. trichocarpa x P. nigra), TMxTM [(P. trichocarpa x P. maximowitzii) x (P. trichocarpa x P. maximowitzii)] and TDxT [(P. trichocarpa x P. deltoides) x P. trichocarpa]. Hybrid TxN (P. trichocarpa x P. nigra) was the most susceptible to rust in all testing sites, while the less susceptible hybrids were TDxT [(P. trichocarpa x P. deltoides) x P. trichocarpa], TDxD [(P. trichocarpa x P. deltoides) x P. trichocarpa] and TDxT [(P. trichocarpa x P. deltoides) x P. trichocarpa]. These susceptibilities varied among localities, particularly on aphids. Genetic and environmental factors accounting for by these results are discussed

End-use related physical and mechanical properties of selected fast-growing poplar hybrids (Populus trichocarpa x P-deltoides)

This study focused on physical and mechanical properties of fast-growing poplar clones in relation to potential end uses with high added value. A total of 14 trees from three different clones, all P. trichocarpa x deltoides (T x D) hybrids, were felled in a poplar plantation in Lille (Belgium): six 'Beaupre', four 'Hazendans' and four 'Hoogvorst'. Growth rate was found to have no significant influence on the physical mechanical properties. Although the investigated clones are genetically closely related, important variations in physical and mechanical properties were observed. Specific features such as spatial distribution of tension wood and dimensional stability are the main quality factors. It was concluded that 'Beaupre' is suitable for a wide range of high value added applications, such as plywood or construction wood. 'Hazendans' and 'Hoogvorst' will need adapted technology in processing. Further research is needed to characterize clonally induced variation in properties and to assess adequate processing strategies for multiclonal poplar stands

Overexpression of a Prefoldin β subunit gene reduces biomass recalcitrance in the bioenergy crop Populus.

Prefoldin (PFD) is a group II chaperonin that is ubiquitously present in the eukaryotic kingdom. Six subunits (PFD1-6) form a jellyfish-like heterohexameric PFD complex and function in protein folding and cytoskeleton organization. However, little is known about its function in plant cell wall-related processes. Here, we report the functional characterization of a PFD gene from Populus deltoides, designated as PdPFD2.2. There are two copies of PFD2 in Populus, and PdPFD2.2 was ubiquitously expressed with high transcript abundance in the cambial region. PdPFD2.2 can physically interact with DELLA protein RGA1_8g, and its subcellular localization is affected by the interaction. In P. deltoides transgenic plants overexpressing PdPFD2.2, the lignin syringyl/guaiacyl ratio was increased, but cellulose content and crystallinity index were unchanged. In addition, the total released sugar (glucose and xylose) amounts were increased by 7.6% and 6.1%, respectively, in two transgenic lines. Transcriptomic and metabolomic analyses revealed that secondary metabolic pathways, including lignin and flavonoid biosynthesis, were affected by overexpressing PdPFD2.2. A total of eight hub transcription factors (TFs) were identified based on TF binding sites of differentially expressed genes in Populus transgenic plants overexpressing PdPFD2.2. In addition, several known cell wall-related TFs, such as MYB3, MYB4, MYB7, TT8 and XND1, were affected by overexpression of PdPFD2.2. These results suggest that overexpression of PdPFD2.2 can reduce biomass recalcitrance and PdPFD2.2 is a promising target for genetic engineering to improve feedstock characteristics to enhance biofuel conversion and reduce the cost of lignocellulosic biofuel production

Resource and non-resource root competition among trees of different successional status

1. This study assessed the effects of resource (i.e. nutrients) and non-resource (i.e. interference for space) competition from fine roots of competing grasses on the growth, morphology and architecture of fine roots of four tree species of varying successional status: Populus deltoides × P. balsamifera (a\ud hybrid), Betula papyrifera, Acer saccharum and Fraxinus americana. We tested the general hypothesis that tree fine-roots are affected by both below-ground resource and non-resource competition from non-self plants, and the more specific hypothesis that this effect is stronger in early- successional tree species.\ud 2. The experiment was conducted in split-containers where half of the roots of tree seedlings experienced either below-ground resource competition or non-resource competition, or both, by grasses while the other half experienced no competition.\ud 3. The late-successional tree species A. saccharum and\ud F. americana were mostly affected by resource competition, whereas the early-successional P. deltoides × balsamifera\ud and B. papyrifera were strongly affected by both resource and non-resource competition. Non-resource competition reduced fine-root growth, root branching over root length (a measure of root architecture) and specific root length (a measure of root morphology) of both early-successional species.\ud 4. Synthesis. This study suggests that early-successional tree species have been selected for root avoidance or segregation and late-successional tree species for root tolerance of competition as mechanisms to improve below-ground resource uptake in their particular environments. It also\ud contradicts recent studies showing perennial and annual grasses tend to overproduce roots in the presence of non-self conspecific plants. Woody plants, required to grow and develop for long periods in the presence of other plants, may react differently to non-self root competition than perennial or\ud annual grasses that have much shorter lives