Pyrus Betulaefolia Research Articles

Agrobacterium Rhizogenes and B12 Antioxidant Mediated Rooting Induction and Shoots Proliferation on Micro-Cuttings of Pyrus Betulaefolia Rootstock

Agrobacterium Rhizogenes and B12 Antioxidant Mediated Rooting Induction and Shoots Proliferation on Micro-Cuttings of Pyrus Betulaefolia Rootstock

Ferric reduction oxidase 2 gene from Pyrus betulifolia is regulated by iron deficiency and auxin

Pyrus betulifolia Bunge belongs to the woody plant family and is an ideal model for studying molecular strategies of iron acquisition and metabolism in strategy I plants. Using polymerase chain rea...

WITHDRAWN: Characterization and Expression Analysis of PbCS1 Gene Regulated by Iron Deficiency and Involved in Response to Auxin in Pyrus betulifolia

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://doi.org/10.1016/j.hpj.2016.11.002. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal

토양 과습처리에 의한 배 대목 Pyrus calleryana 와 Pyrus betulaefolia 집단의 유기물 함량 변화

토양 과습처리에 의한 배 대목 Pyrus calleryana 와 Pyrus betulaefolia 집단의 유기물 함량 변화

Characterization and Expression Analysis of PbCS1 Gene Regulated by Iron Deficiency and Involved in Response to Auxin in Pyrus betulifolia

Iron (Fe) is an essential micronutrient required by all fruit trees. To elucidate the regulatory mechanism of auxin to the long-distance transport of Fe, a gene encoding a putative CS protein was isolated from Pyrus betulifolia. This gene was designated as PbCS1 containing 1 422 bp in length with an open reading frame encoding a protein of 473 amino acids with a predicted molecular mass of 52.69 ku and a theoretical isoelectric point of 6.91. The deduced PbCS1 protein contained a conserved CS domain and WPNVDAHS sequence existing in the PWPN-box. Based on its conserved domain and phylogenetic status, the PbCS1 should be grouped into type-Ⅰ subfamily of plant CS. Quantitative real-time PCR results indicated that the PbCS1 expression was enriched in leaves, roots and phloem, but relatively weak in xylem. Using split root systems, Fe deficiency in one portion of the root system could induce dramatic up-regulation of the PbCS1 expression in the Fe-sufficient part, suggesting that the PbCS1 expression was activated by systemic signals. In addition, supplying with NAA and exogenous auxin to the de-topped shoots could recover the Fe deficiency-induced up-regulation of the PbCS1 expression in the Fe-sufficient part of the root system. In contrast, NPA (an auxin transport inhibitor) application to the shoot tips arrested up-regulation of the PbCS1 expression in the untreated portion. The results suggested that Fe-deficiency-induced alterations of the PbCS1 expression were mediated by auxin.

Isolation and characterization of PbCS2 gene regulated by iron deficiency and auxin-based systemic signals in Pyrus betulifolia

Iron (Fe) is an essential micronutrient for plants and citric acid acts as a chelate substance for the long-distance transmission of Fe. Citrate synthase (CS) protein is a key enzyme in the synthesis of citric acid. Using PCR amplification, a gene encoding a putative citrate synthase was isolated from Pyrus betulifolia, a widely-used rootstock native to China, and designated it as PbCS2. This gene was 1422bp in length with an open reading frame encoding a protein of 473 amino acids. The deduced PbCS2 protein contains a conserved citrate synthase domain and conservative WPNVDAHS sequence existing in the PWPN-box. Phylogenetic analyses clearly demonstrated that PbCS2 had the highest homology with rosaceous CS proteins. The expression of PbCS2 was enriched in roots, leaves and phloem, but relatively weak in xylem. Fe deficiency induced substantial up-regulation of the PbCS2 expression in the roots. The split-root experiments showed that Fe deprivation in one part of the root system caused dramatic up-regulation of the PbCS2 expression in the Fe-sufficient portion, indicating that the PbCS2 expression was triggered by systemic signals. Furthermore, supplying auxin to the de-topped shoot could recover the Fe deficiency-caused up-regulation of the PbCS2 expression in the Fe-supplied part of the root system. By contrast, NPA application (an auxin transport inhibitor) to the shoot apex blocked up-regulation of the PbCS2 expression in the untreated portion. These results strongly indicated that Fe deficiency-caused alterations of the PbCS2 expression were mediated by IAA.

Gene characterization and transcription analysis of two new ammonium transporters in pear rootstock (Pyrus betulaefolia)

Ammonium is the primarily nitrogen source for plant growth, but the molecular basis of ammonium acquisition in fruit species remains poorly understood. In this study, we report on the characterization of two new ammonium transporters (AMT) in the perennial tree Pyrus betulaefolia. In silico analyses and yeast complementation assays revealed that both PbAMT1;3 and PbAMT1;5 can be classified in the AMT1 sub-family. The specific expression of PbAMT1;3 in roots and of PbAMT1;5 in leaves indicates that they have diverse functions in ammonium uptake or transport in P. betulaefolia. Their expression was strongly influenced by ammonium availability. In addition, the transcript level of PbAMT1;5 was significantly affected by the diurnal cycle and senescence hormones. They conferred the ability to uptake nitrogen to the yeast strain 31019b; however, the (15)NH4 (+) uptake kinetics of PbAMT1;3 were different from those of PbAMT1;5. Indeed, PbAMT1;3 had a higher affinity for (15)NH4 (+), and pH changes were associated with this substrates' transport in yeast. The present study provides basic gene features and transcriptional information for the two new members of the AMT1 sub-family in P. betulaefolia and will aid in decoding the precise roles of AMTs in P. betulaefolia physiology.

Identification of Differentially Expressed Genes Related to Dehydration Resistance in a Highly Drought-Tolerant Pear, Pyrus betulaefolia, as through RNA-Seq.

Drought is a major abiotic stress that affects plant growth, development and productivity. Pear is one of the most important deciduous fruit trees in the world, but the mechanisms of drought tolerance in this plant are still unclear. To better understand the molecular basis regarding drought stress response, RNA-seq was performed on samples collected before and after dehydration in Pyrus betulaefolia. In total, 19,532 differentially expressed genes (DEGs) were identified. These genes were annotated into 144 Gene Ontology (GO) terms and 18 clusters of orthologous groups (COG) involved in 129 Kyoto Encyclopedia of Genes and Genomes (KEGG) defined pathways. These DEGs comprised 49 (26 up-regulated, 23 down-regulated), 248 (166 up-regulated, 82 down-regulated), 3483 (1295 up-regulated, 2188 down-regulated), 1455 (1065 up-regulated, 390 down-regulated) genes from the 1 h, 3 h and 6 h dehydration-treated samples and a 24 h recovery samples, respectively. RNA-seq was validated by analyzing the expresson patterns of randomly selected 16 DEGs by quantitative real-time PCR. Photosynthesis, signal transduction, innate immune response, protein phosphorylation, response to water, response to biotic stimulus, and plant hormone signal transduction were the most significantly enriched GO categories amongst the DEGs. A total of 637 transcription factors were shown to be dehydration responsive. In addition, a number of genes involved in the metabolism and signaling of hormones were significantly affected by the dehydration stress. This dataset provides valuable information regarding the Pyrus betulaefolia transcriptome changes in response to dehydration and may promote identification and functional analysis of potential genes that could be used for improving drought tolerance via genetic engineering of non-model, but economically-important, perennial species.

PbWoxT1 mRNA from pear (Pyrus betulaefolia) undergoes long-distance transport assisted by a polypyrimidine tract binding protein.

Little is known about the mechanisms by which mRNAs are transported over long distances in the phloem between the rootstock and the scion in grafted woody plants. We identified an mRNA in the pear variety 'Du Li' (Pyrus betulaefolia) that was shown to be transportable in the phloem. It contains a WUSCHEL-RELATED HOMEOBOX (WOX) domain and was therefore named Wox Transport 1 (PbWoxT1). A 548-bp fragment of PbWoxT1 is critical in long-distance transport. PbWoxT1 is rich in CUCU polypyrimidine domains and its mRNAs interact with a polypyrimidine tract binding protein, PbPTB3. Furthermore, the expression of PbWoxT1 significantly increased in the stems of wild-type (WT) tobacco grafted onto the rootstocks of PbWoxT1 or PbPTB3 co-overexpressing lines, but this was not the case in WT plants grafted onto PbWoxT1 overexpressing rootstocks, suggesting that PbPTB3 mediates PbWoxT1 mRNA long-distance transport. We provide novel information that adds a new mechanism with which to explain the noncell-autonomous manner of WOX gene function, which enriches our understanding of how WOX genes work in fruit trees and other species.

Two AMT2-Type Ammonium Transporters from Pyrus betulaefolia Demonstrate Distinct Expression Characteristics

Ammonium transporters (AMTs) play dominant roles in ammonium transport and distribution across cellular membranes. However, the AMT2-type AMTs from pear remain poorly understood. To characterize ammonium transport pathways in Pyrus betulaefolia Bunge, one popular rootstock for pear and two new genes with high homology to AMT2-type AMTs, PbAMT2 and PbAMT3, were isolated from its seedlings. The analysis of the PbAMT expression patterns in different organs of P. betulaefolia showed that expression of a given transporter could be very specific and their regulatory mechanisms were distinct. Both responded to various nitrogen regimes, PbAMT2 was detected in all organs, and the highest transcription was found in roots, whereas PbAMT3 was restricted to leaves. In addition, transcript level of PbAMT2 was strongly affected by the diurnal cycle, and PbAMT3 was exclusively expressed in leaves after treatment with two phytohormones: abscisic acid and methyl jasmonate. A complementation experiment using the yeast strain 31019b revealed that both PbAMT2 and PbAMT3 encoded functional, high-affinity AMTs. Furthermore, uptake studies indicated that these two AMTs possessed disparate affinities for ammonium and had opposite responses to external pH change. In summary, the present study provides basic genomic, transcript information and nitrogen transporter features for the pear AMT2 subfamily; indeed, PbAMT2 and PbAMT3 demonstrated distinct expression characteristics, which will pave the way for deciphering the high-affinity ammonium transport system in pear.

Effects of microtopography on spatial point pattern of forest stands on the semi-arid Loess Plateau, China

Microtopography may affect the distribution of forests through its effect on rain redistribution and soil water distribution on the semi-arid Loess Plateau, China. In this study, we investigated the characteristics of microtopography on two shady slopes (slope A, 5 hm2, uniform slope; slope B, 5 hm2, microtopography slope) and surveyed the height, the diameter at breast height and the location (x, y coordinates) of all selected individual trees (Robinia pseudoacacia Linn., Pyrus betulifolia Bunge, Populus hopeiensis Hu & Chow, Armeniaca sibirica Lam., Populus simonii Carr. and Ulmus pumila Linn.) on slope A and slope B in the watersheds of Wuqi county, Shaanxi province. Subsequently, the effects of microtopography on the spatial pattern of forest stands were analyzed using Ripley’s K(r) function. The results showed that: (1) The maximal aggregation radiuses of the tree species on the uniform slope (slope A) were larger than 40 m, whereas those of the tree species on the microtopography slope (slope B) were smaller than 30 m. (2) On slope B, the spatial association of R. pseudoacacia with P. betulifolia, A. sibirica, P. simonii and U. pumila varied from being strongly negative to positive at microtopography scales. The spatial association of Populus hopeiensis Hu & Chow with U. pumila also varied from being strongly negative to positive at microtopography scales. However, there was no spatial association between P. betulifolia and P. hopeiensis, P. betulifolia and A. sibirica, P. betulifolia and P. simonii, P. betulifolia and U. pumila, P. hopeiensis and A. sibirica, P. hopeiensis and P. simonii, A. sibirica and P. simonii, A. sibirica and U. pumila, and P. simonii and U. pumila. On slope A, the spatial association between tree species were strongly negative. The results suggest that microtopography may shape tree distribution patterns on the semi-arid Loess Plateau.

English

The present study characterized and identified pear cultivars growing in the southern region of Minas Gerais State, Brazil, using microsatellite markers. Nineteen (19) pear cultivars were collected from two sites of Southern Minas Gerais State: Ribeirao Vermelho and Lavras. DNA was extracted from newly formed leaves and amplified using 21 simple sequence repeat (SSR) markers (NH001c, NH002b, NH005b, NH007b, NH008b, NH009b, NH011b, NH013b, NH012a, NH014a, NH015a, NH017a, KA4b, KA5, KA14, KA16, KB16, KU10, BGA35, BGT23b and HGA8b). The data was analyzed by examining unweighted pair group method with arithmetic mean (UPGMA) clustering, principal coordinate analysis, the Shannon index, and the expected heterozygosity for each primer. The markers used were efficient in separating the Asian and European cultivars as well as hybrids. The primer KA16 was noteworthy in distinguishing the species Pyrus communis , Pyrus pyrifolia and Pyrus betulaefolia by its different banding patterns. Grouping by principal coordinates was similar to UPGMA clustering, forming two distinct groups among the Asian and European pears. The Shannon index and the expected heterozygosity had medium values of 0.440 and 0.300, respectively. The pear cultivars from Southern Minas Gerais usually show low productivity, mainly due to the lack of improved strains for less-demanding weather (warmer) conditions. The selection of the most suitable materials would contribute considerably to overcoming this problem, and the markers selected here can be used in separating cultivars - and presumably contribute to the selection of better matrices. Key words: Pyrus sp., Rosaceae, microsatellite, heterozygosity.

Effect of Irrigation Water pH on Some Soil Properties and Growth of Some Pear Rootstocks Grown on Sand and Calcareous Soils

To study effect of irrigation water pH and soil type on growth of some pear rootstocks and some soil properties, two rootstocks (Pyrus communis and Pyrus betulaefolia) were grown on two soils (sand and calcareous) during successive seasons of 2010 and 2011. pH values of irrigation water were 6.0, 6.5, 7.0, 7.5 and pH 8.0. The experiment was performed in Horticultural Research Institute farm, Giza, Egypt. The tested soil properties were chemical analysis of soil water past extract, pH, soil texture and available nutrients (P, K, Fe, Zn and Mn). The following growth parameters were recorded plant height leaves number/plant, new current shoots number, vegetative growth dry weight, roots number, roots length, roots diameter. Obtained data showed significant effects for pH Original Research Article Ahmed and Sherif; IJPSS, 4(5): 475-493, 2015; Article no.IJPSS.2015.047 476 irrigation water and soil type on some of studied plant growth parameters and some of tested soil measurements. Data showed the importance nature of pH source in irrigation water i.e. chemical analysis of irrigation water. Pyrus betulaefolia was more tolerant to pH value variations in irrigation water than Pyrus communis.

Isolation and characterization of Calcineurin B-like gene (PbCBL1) and its promoter in birch-leaf pear (Pyrus betulifolia Bunge).

Calcium plays a critical role in regulating abiotic stress responses in plants. Calcineurin B-like (CBL) proteins are calcium sensors in calcium signaling pathways. However, the molecular mechanisms underlying calcium signaling remain to be elucidated. In this study, the CBL1 gene, which codes for the CBL protein, was isolated from the birch-leaf pear. One 2,969-bp sequence was cloned using PCR, and using the cloned 2,027-bp sequence was isolated from pear genomic DNA via genome walking. Sequencing analysis revealed that the 4,996-bp sequence was a PbCBL1 gene consisting of eight exons and seven introns, and the 2,027-bp sequence was identified as the promoter of the PbCBL1 gene, which contains the basic promoter elements TATA and CAAT boxes. In addition, some other cis-acting elements including heat, cold, drought, and hormone responsive elements were also present. To further investigate the activity of this promoter, the sequence was used to drive a GUS fusion gene into leaf discs of tobacco (Nicotiana benthamiana) with Agrobacterium-mediated transformation method. GUS gene expression could be regulated by the PbCBL1 promoter following induction by GA, ABA, SA, and MeJA. Furthermore, the results of real-time RT-qPCR indicate that the PbCBL1 gene can respond to changes in the intracellular calcium concentration, and that it can be induced by cold, heat, drought, and stress by several hormones including GA, ABA, SA, and MeJA. PbCBL1 gene may be involved in several signal transduction pathways, and play an important role in the condition of adversity stress in pear.

KNOTTED1 mRNA undergoes long-distance transport and interacts with movement protein binding protein 2C in pear (Pyrus betulaefolia)

KNOTTED1 (KN1)-like homologous box is a homeodomain transcription factor that is transported intercellularly through plasmodesmata and over long distances via phloem transport in plants. In this study, we investigated KN1 long-distance transport and its regulation by the viral movement protein binding protein of ‘Du Li’ (Pyrus betulaefolia, PbMPB2C) in two species of fruit trees, ‘Du Li’ (rootstock) and ‘Ya Li’ (P. bretschneideri, scion), using grafting experiments. The results showed that PbKN1 mRNA was present in the phloem in both transport directions across the graft junctions of tissue-cultured grafted plants and orchard saplings. To investigate the relationship between PbKN1 and PbMPB2C, we conducted interaction assays to demonstrate their physical interaction. An RNA–protein pull-down assay revealed that PbKN1 mRNA interacted with PbMPB2C protein in vitro but not with PbKN1 and that PbKN1 repressed the binding of PbMPB2C to PbKN1 mRNA. Additionally, using p35S:GFP-PbKN1 transgenic tobacco grafted with wild-type plants, we found that the movement of PbKN1 was increased by the silencing of NtMPB2C. Based on the above findings, we first demonstrate evidence of the bidirectional transport of PbKN1 mRNA and propose that PbMPB2C could act as a negative regulator of the phloem-mediated long-distance transport of PbKN1 mRNA.

Molecular cloning and identification of an ammonium transporter gene from pear

The molecular basis of ammonium acquisition in fruit trees remains poorly understood. Here, a new ammonium transporter gene, PbAMT1;1, was isolated from Pyrus betulifolia. The full length of PbAMT1;1 was 1,693 bp, coding a protein of 505 amino acids. The deduced structure of the PbAMT1;1 protein revealed 11 membrane-spanning domains and an ammonium transporter signature motif ‘D204FAGSGMVHMVGGIAGLWGAFIESPR229’ located in the fifth predicted transmembrane region. PbAMT1;1 transcripts were detectable in all parts of the seedlings and predominantly located to the roots. In addition, a change of pH had little effect on its expression patterns. PbAMT1;1 expression levels in roots were strongly induced by ammonium depletion and suppressed by high ammonium. However, its transcription levels in leaves were reduced by free nitrogen and increased after high amounts of ammonium were supplying. Further, PbAMT1;1 exhibited diurnal rhythms with the highest expression at noon. When abscisic acid and methyl jasmonate existed, the mRNA abundance of PbAMT1;1 increased. The results of yeast complementation showed that the PbAMT1;1 gene could help yeast mutant stain 31019b to grow in a media with micromole ammonium concentrations. Furthermore, PbAMT1;1 mediated NH4 + uptake with high affinity producing K m values from 20.9 to 23.2 μM at different pH values. However, the net 15NH4 + uptake K m of PbAMT1;1 showed no significant differences at pH 4.8, 5.8 or 6.8. In conclusion, PbAMT1;1 is a functional AMT gene having the features of the AMT1 family. Its expression was regulated by ammonium concentration, diurnal rhythms and plant hormones, but not by external pH levels.

Chloroplast DNA-based genetic diversity and phylogeography of Pyrus betulaefolia (Rosaceae) in Northern China

Pyrus betulaefolia Bunge, considered as an intermediate between oriental and occidental pear groups, is one of the most important wild pear species. The number of its populations is decreasing because of habitat destruction, fragmentation, and continuous exploitation, so protection and conservation measures are urgently needed. Assessment of its genetic diversity and phylogeography are imperative for its efficient conservation. Two chloroplast DNA intergenic fragments were used to detect genetic diversity and phylogeography of 320 individuals from 18 wild P. betulaefolia populations. Haplotype variation, genetic differentiation, and historical events of the populations were estimated. The results showed that P. betulaefolia populations sampled in northern China contained a high level of genetic diversity (H T = 0.826). A significant isolation-by-distance value (r = 0.587, P < 0.001, 1,000 permutations) among all 18 populations indicated a correlation between genetic divergence and geographic distance. Four population groups were identified in a neighbor-joining tree based on the genetic distance. Analyses of molecular variation showed that the genetic variation mainly existed among population groups, representing 64.61 % of the total variation. Phylogeographic analyses indicated that the populations of P. betulaefolia experienced a scenario of rapid range expansion, which probably occurred between 608,000 and 204,580 years ago. Meanwhile, both the restricted gene flow with isolation by distance and allopatric fragmentation were crucial processes responsible for shaping the genetic patterns of P. betulaefolia. The occurrence of specific haplotypes might be ascribed to an ancestral introgression or joint retention of an ancestral polymorphism with other Pyrus species at the northern edge of the distribution of P. betulaefolia. Three populations displaying a high level of haplotype diversity and unique haplotypes were assumed to be relict populations of Quaternary glaciation and should have conservation priority. Three additional large populations should also be preferentially protected by building natural preservation zones.

灵空山油松-辽东栎林乔木树种群落学特征及空间分布格局研究

参照CTFS技术规范对灵空山自然保护区油松（<em>Pinus tabuliformis</em>）-辽东栎（<em>Quercus wutaishanica</em>）林的乔木进行每木调查的基础上分析了不同乔木树种的群落学特征及空间分布格局。结果表明，4hm²样地中共有乔木树种25种，总计8210株。隶属于12科18属，种的区系以东亚、温带亚洲及中国特有分布类型为主。油松、辽东栎是群落中的共优种，个体占总个体的86.81%，杜梨（<em>Pyrus betulifolia</em>）、白蜡树（<em>Fraxinus chinensis</em>）、漆树（<em>Toxicodendron vernicifluum</em>）为群落中主要的伴生种。优势种的径级结构与所有乔木个体的径级结构相似，近似于倒"J"形，以小径级个体居多，林下更新良好。主要树种的空间分布格局在小尺度上表现为聚集分布。油松小径级个体在20 m以内的尺度上呈聚集分布，当空间尺度超过60 m时表现为随机分布，大径级个体在所有尺度上均呈随机分布；辽东栎不同径级个体在小尺度范围内呈现聚集分布，随着尺度增大由随机分布趋于均匀分布。主要树种除漆树外在坡度较缓的生境下分布密度大。灵空山自然保护区油松-辽东栎林中油松种群优势地位更显著，各个乔木种群处于相对稳定状态。;The community characteristics and spatial distribution were analyzed for the Forms <em>Pinus tabuliformis</em>-<em>Quercus wutaishanica</em> in the Nature Reserve of Lingkong Mountain by following the CTFS protocols, in which all free-standing trees were mapped and identified. The results showed that a total of 25 tree species in 18 genera and 12 families were recorded among the 8210 individuals. Most species are commonly found in the Temperate Asia and East Asia including the Endemic to China. The dominant species of <em>P. tabuliformis</em> and <em>Q. wutaishanica </em>accounted for 86.81% in abundance. The mian companion species were also observed as the <em>Pyrus betulifolia</em>, <em>Fraxinus chinensis</em>, <em>Toxicodendron vernicifluum</em> in the community. The diameter-class structure of dominant species was found similar to that of the whole community, roughly in inversed J shape, in which most individuals were in small diameter-class, suggesting sound community renewal under wood. Meanwhile, the main species demonstrated the bottleneck phenomena to various degrees, most like due to the self-thinning effects of <em>P. tabuliformis</em> and <em>Q. wutaishanica</em>, especially among the young trees of 4 cm and 15 cm in <em>DBH</em> respectively. In comparison, <em>Pvrus betulifolia</em> showed a faultage phenomena among the trees of 2-5cm in <em>DBH</em>, probably due to the thinning effect by other species. The age structure of <em>Fraxinus chinensis</em> suggested the transition from growth to stable phase. The diameter-class structure of <em>Toxicodendron vernicifluum </em>was approximately in inversed J shape, showing active natural renewal as being indicated by the seedlings in high abundance. In small scale the clustered distribution was observed among the dominant species. In <em>P. tabuliformis</em> the individuals of small diameter-class demonstrated clustered distribution in the scale of less than 20m, but random distribution in scale of 60-100m that is the same as that of the individuals of big diameter-class in all scales. In comparison, the <em>Q. wutaishanica</em> showed the trend from clustered to even and random distribution along the scale gradient from small to large. The trees of<em> Pyrus betulifolia</em> of small diameter-class showed clustered distribution in the scale of less than 10m but random distribution in scale of 10-100m; and the trees of big diameter-class demonstrated random distribution in all scales. The small diameter-class individuals of <em>Fraxinus chinensis</em> showed clustered distribution in scale of 0-25m and even distribution in scale of 25-70m, demonstrating trend to random distribution with the increase of spatial scale. <em>Toxicodendron vernicifiuum </em>showed clustered distribution in scale of 0-20m and even distribution over of 20m. The main species showed high density in relatively flat habitats except for <em>Toxicodendron vernicifiuum</em>. The data indicated <em>P. tabuliformis</em> being dominant over <em>Q. wutaishanica</em> in the community and all tree populations being in relatively steady state in the Nature Reserve of Lingkong Mountain.

Lavi 1—A new Pyrus betulifolia rootstock for ‘Coscia’ pear (Pyrus communis) in the hot climate of Israel

The vegetative and reproductive performance of ‘Coscia’ pear (Pyrus communis L.) grown on eight rootstocks [OHF 217, OHF 333 and OHF 97 (USA breeding of P. communis); NY 095, NY 221, NY 36 and Lavi 1 (Israeli selections of Pyrus betulifolia) and a seedling (Davis A×B) of P. betulifolia] were compared over a 7-year period. The trial was conducted at the Experimental Orchard Farm Station in northern Israel on well-drained, pH 7.5 soil. Trees were planted in December 2005 at 4.0m×2.0m spacing and trained with a central axis. The most vigorous trees were on the local and clonal P. betulifolia rootstock Lavi 1, followed by the three OHF and NY rootstocks; the P. betulifolia seedling produced the weakest tree. Tree size was positively correlated to yield and fruit size. Thus, the highest cumulative yield and cumulative yield of large fruit (>55mm) per tree were harvested from trees on Lavi 1, followed by the two OHF rootstocks (217, 97) and NY 221. The lowest cumulative total and large-fruit yields were obtained on the P. betulifolia seedling rootstock. These results could be due to the excellent water status, e.g., the high midday stem water potential (SWP) values of ‘Coscia’ trees on Lavi 1 rootstocks in comparison with the other rootstocks. The positively high correlation between tree size (trunk cross-sectional area) and water status (SWP) and the similar correlation between SWP and cumulative total yield or yield of large fruit support this hypothesis. We conclude that in a warm climate, yield efficiency is not the only parameter to be taken into account; building a strong tree for a weak cultivar scion such as ‘Coscia’ is the first requirement for establishing an orchard. The experiments demonstrate the advantages of selecting a local clonal P. betulifolia rootstock compared to seedlings of the same species introduced from foreign countries with different climatic conditions. In addition, two genetic markers for Lavi 1 were identified based on its S-RNase alleles.

Epidemiological aspects of ‘CandidatusPhytoplasma pyri’ transmission

Studies were carried out on pear decline epidemic in an experimental field located in Pignataro Maggiore (Caserta, Italy) where ‘William’, ‘Comice’ and ‘Conference’, pear varieties were grafted on the rootstocks ‘Quince A’ (EMA), ‘Farold 333’, ‘Quince C’, Farold 282’, ‘Farold 40’, ‘Farold 87’, ‘BP1’, ‘Farold 51’ and assessed their different susceptibility to ‘Candidatus phytoplasma pyri’ infection. The research continued to study susceptibility of Pyrus betulaefolia and a selection of Cydonia oblonga, Quince BA29 rootstocks. Five plants for each of the same three varieties, grafted on the two rootstocks were used for graft and insect inoculation with ‘Ca. P. pyri’ and controlled for two years for symptom expression and pathogen presence. None of the combination studied showed differences in susceptibility to the pathogen.