Cultivars Of Populus Research Articles

Transcriptome and association mapping revealed functional genes respond to drought stress in Populus

Drought frequency and severity are exacerbated by global climate change, which could compromise forest ecosystems. However, there have been minimal efforts to systematically investigate the genetic basis of the response to drought stress in perennial trees. Here, we implemented a systems genetics approach that combines co-expression analysis, association genetics, and expression quantitative trait nucleotide (eQTN) mapping to construct an allelic genetic regulatory network comprising four key regulators (PtoeIF-2B, PtoABF3, PtoPSB33, and PtoLHCA4) under drought stress conditions. Furthermore, Hap_01PtoeIF-2B, a superior haplotype associated with the net photosynthesis, was revealed through allelic frequency and haplotype analysis. In total, 75 candidate genes related to drought stress were identified through transcriptome analyses of five Populus cultivars (P. tremula × P. alba, P. nigra, P. simonii, P. trichocarpa, and P. tomentosa). Through association mapping, we detected 92 unique SNPs from 38 genes and 104 epistatic gene pairs that were associated with six drought-related traits by association mapping. eQTN mapping unravels drought stress-related gene loci that were significantly associated with the expression levels of candidate genes for drought stress. In summary, we have developed an integrated strategy for dissecting a complex genetic network, which facilitates an integrated population genomics approach that can assess the effects of environmental threats.

Evaluation of genetic diversity and germ plasm identification of 44 species, clones, and cultivars from 5 sections of the genusPopulus based on amplified fragment length polymorphism analysis

The genusPopulus L. (Salicaceae) can be divided into 5 sections with distribution throughout the world. Accurate identification ofPopulus clones and species is essential for effective selection, breeding, and management of genetic resources. In this study, amplified fragment length polymorphism (AFLP) analysis, which was reported as a reliable technique with high efficiency in detecting polymorphism, was used to conduct analyses of genetic diversity and variety identification of 44 species, clones, and cultivars ofPopulus that represent a wide range of breeding and commercially available germplasms. Cluster analysis of the 44 samples was carried out, and a dendrogram of genetic relatedness was developed on the basis of the AFLP data. DNA fingerprints of the 44 samples were developed from 12 selected bands amplified with 2 primer combinations (M-CAG/E-TA and M-CAG/E-TC). Each sample has its unique fingerprint pattern and can be distinguished from the others. Furthermore, 1 specific AFLP band of the cultivarPopulus canadensis cl. Guariento coming from fragments amplified by primer combination M-CTC/E-AG was successfully converted into a sequence-characterized amplified region (SCAR) marker. The results indicate that AFLP analysis should be considered as the preferred technique for the study of polymorphism inPopulus. This research is the first report concerning the use of AFLP analysis in genetic diversity and germplasm identification among all sections ofPopulus.

Physiologic specialisation in the hyperparasitism of races of Melampsora larici‐populina by isolates of Cladosporium tenuissimum

AbstractThree isolates of Cladosporium tenuissimum were prepared by culturing a field isolate of this organism separately on three races of Melampsora larici‐populina. In a subsequent experiment, the production of uredinia by these three races on three cultivars of Populus X euramericana was usually lowest in the presence of the isolate of C. tenuissimum which had been cultured on the particular race. This apparent adaptation of the isolates of the hyperparasite to particular races of the rust, i. et. “physiologic specialisation” in the relationship, is confirmed by the significant race x C. tenuissimum isolate term in the ANOVA.

Reaction of cultivars of populus spp. to radiation induced virulent mutants of melampsora medusae

Infection Type (IT) and Uredinial Number per Leaf Disk (ULD), induced on eleven cultivars of poplar in vitro, were employed to compare five radiation induced, mono-uredinial mutant lines of Melampsora medusaeThum. with the wild type race 5A from which they were derived. IT produced by the mutants was higher than (eight cultivars), similar to (two cultivars) and pronouncedly less than (IT from 4 to 1 in P. deltoides cv. 7–2) that of race 5A. Although the five mutants produced a uniform IT within a particular cultivar. ULD varied significantly between mutants on individual cultivars and there was a significant differential interaction of the mutant lines with cultivars. The ranking of mutant lines for aggressiveness on cultivars was not consistent while the differences among the mutants in mean ULD over all cultivars were not associated with the dosage level of irradiation from which they were isolated. The implications of the results in the interaction of leaf rust with poplar cultivars are discussed.

Effects of pre‐ and post‐inoculation photoperiod on the severity of Melampsora medusae leaf rust of Populus species

Disease severity, based on six parameters (time from inoculation to flecking, and eruption of uredinia, uredinial density and the amounts of urediniospoies produced), was assessed on leaf discs cut from four cultivars of Populus spp. raised with either a long (15 h) or a short (10 h) photoperiod. The discs were inoculated with race 4 of Melampsora medusae and subsequently incubated with either a long (15 h) or a short (10 h) photoperiod. While disease severity, based on most parameters, was lower in discs from the continuing long photoperiod (15 h pre‐ and 15 h post‐inoculation) than from the continuing short photoperiod (10 h pre‐ and 10 h post‐inoculation), maximum severity was developed by discs given a combination of a short pre‐ and a long post‐inoculation photoperiod. The relative contribution of the cultivar, the pre‐ and the post‐inoculation photoperiod and their second‐ and third‐order interactions to variation in disease severity depended on the parameter employed to assess severity. The parameters used are elements of disease monocycles and their possible significance in modelling epidemics is discussed.

Temperature-light effects on resistance of poplar cultivars to Melampsora medusae Thüm

The effects of combinations of post-inoculation temperature (15, 25°C) and light intensity (100, 500, 1000 μEm-2s-1) on disease severity (three parameters), induced by six races of Melampsora medusae in four cultivars of Populus were assessed in a factorial experiment. While all cultivars were immune when incubated at 25°C and 1000 μEm-2s-1, most were susceptible, to varying degrees at all other temperature/light intensity combinations. Although the relative rating for disease severity of cultivar/race combinations depended to a degree on the parameter used for assessment, the temperature of incubation, irrespective of the parameter, was the most important determinant of variation in severity. All the major variables, and their two-and three-way interactions, were significant determinants of variation in number of uredinia developed per unit leaf area. The ranking of cultivars for relative resistance, and of races for relative aggressiveness, depended on the temperature/light intensity treatment during incubation. The lability to environment, of the cultivar/race reactions in this pathosystem, could contribute to stability in resistance to leaf rust in plantations of poplar.

The effect of pre- and post-inoculation temperature on resistance in certain cultivars of poplar to races of Melampsora larici-populina kleb.

Four cultivars of Populus spp., compatible to varying degrees with four races of M. larici-populinaKleb., were raised in a controlled environment on a high (28°/20°C, day/night) and low (20°/10°C) temperature regime. Leaf discs cut from the plants were inoculated separately with four individual races of M. laricipopulina and subsequently incubated at either low (20°C) or high (25°C) temperature for 14 days when disease development on the discs was assessed using three parameters (Incubation period to flecking, uredia per leaf disc and uredospores per mm2). The degree of resistance in all cultivar/race combinations was high on cultivars cultured at a high temperature regime compared to those cultured on a low temperature regime. Analysis of variance demonstrated that the major components: pre-inoculation temperature regime, post-inoculation temperature regime, race and cultivar, and most second and third order interactions between these were highly significant (P<0.001) for most disease parameters. The variance of the temperature components and all interactions involving these were usually higher than those for the cultivar and race components and those interactions lacking temperature components.