European Pear Trees Research Articles

Floral visitors of European pear trees ‘Clapp’s Favourite’ in southern Brazil

Floral visitors of European pear trees ‘Clapp’s Favourite’ in southern Brazil

Use of quince ‘Adams’ rootstock in European pear crop in southern Brazil

Pear is the main fresh fruit imported in volume and value in Brazil, making it an excellent target to the diversification of orchard operations in temperate climate of the subtropical region of Brazil. One of the obstacles to pear cultivation in Brazil are issues related to high vigor plants in southern Brazil conditions. Excess vegetative growth with little floral differentiation can result in a low productive plant, thus requiring the use of dwarfing rootstocks, such as quince (Cydonia oblonga Mill.), whose advantages are reduction in plant vigor, earliness in the bearing stage of production, increased production efficiency and fruit size. Accordingly, this study aimed to research the vegetative and productive aspects of different European pear cultivars grafted with quince ‘Adams’ under the conditions of the mountainous plateau - Santa Catarina state of Brazil. The experimental orchard where the studies were conducted is located in Centro de Ciencias Agroveterinarias - CAV, belonging to the State University of Santa Catarina - UDESC, located in the city of Lages, Santa Catarina, 937.73 m of altitude, 27°19’44” latitude and 50°19’44” longitude. The adopted training system was central leader, with planting spaced four meters between rows and one meter between plants, with a total of 2,500 plants ha-1 density. The treatments consisted of different combinations of cultivars of European pear trees with the rootstock quince ‘Adams’. The cultivars used in combination with the rootstock cited above were ‘Abbe Fetel’, ‘Rocha’, ‘Santa Maria’, ‘Packham’s Triumph’ and ‘William’s’. The cultivars did not differ in the trunk diameter and its increment. The cultivar ‘Santa Maria’ had the smallest canopy. Cultivars ‘Rocha’ and ‘Packham’s Triumph’ were the most productive with the highest production efficiency.

Redução de vigor em pereiras europeias utilizando métodos físicos e químicos

The various failed attempts to produce pears in Brazil are driven by high consumption, which presents a growing scenario of imports to attend to the consumers demand. In 2015, 179 thousand tons of pears were imported, most from Argentina and Portugal. The limitation of pear cultivation has not been due to lack of market, but due to several factors, such as low fruit set, insufficient formation of production structures and excessive vegetative growth. The objective of this work was to evaluate the vegetative growth and fruit set of European pear trees submitted to different growth control techniques. The experiment was conducted during 2012/2013 and 2013/2014 season in a commercial pear orchard located in Vacaria city, Rio Grande do Sul State, at 971 m altitude. Packham’s Triumph, William’s, Red Bartlett, Abate Fetel and Carrick, all grafted on Pyrus calleryana, were submitted to treatments of simple girdling, double girdling, single trunk cutting, double trunk cutting and application of the Trinexapac-ethyl plant growth regulator (1600 mg L-1). According to the results, it was possible to observe that there was a reduction of vegetative growth only in the Packham’s cultivar submitted to double girdling, single trunk cutting and Trinexapac-ethyl. The use of the trunk cutting and girdling technique increases the flowering return and also the productivity of ‘Abate Fetel’ and ‘Carrick’ pear trees, and the Trinexapac-ethyl decreases the return bloom of ‘Abate Fetel’ and ‘Carrick’ pear trees in the studied conditions.

VEGETATIVE DEVELOPMENT OF EUROPEAN PEAR WITH QUINCE AND DIFFERENT APPLICATION FORMS OF NUTRIENTS

ABSTRACT The pear consumption in Brazil is significant and the country is dependent on the import of this fruit to meet the internal market. The aim of this study was to evaluate the vegetative growth of European pear trees grafted on quince with two application forms of nutrients. The study was conducted during the 2012/13, 2013/14 and 2014/15 harvests, in the experimental area of the Universidade do Estado de Santa Catarina / UDESC, in Lages. The cultivars used were Rocha, Santa Maria and Abbé Fétel. The quinces were ‘Adams’ and ‘EMA’. The application forms of the nutrients were conventional and fertigation. The experiment was carried out in a randomized block design and the arrangement of treatments was sub subdivided plots. The application form of nutrients and rootstocks of quince little influenced on the vegetative growth of the plants, being more influenced by the scion in the soil conditions of this study.

Comprehensive elemental analysis of fruit flesh from European pear ‘La France’ and its giant fruit bud mutant indicates specific roles for B and Ca in fruit development

The concentrations of macro- and microelements in fruits from European pear trees (Pyrus communis ‘La France’) were analyzed at seven developmental stages, ranging from two weeks after flowering to ripe fruits. Additionally, wild-type fruits (WT) were compared to a giant fruit bud mutant (GLaF) which sets 1.5 times bigger fruits compared to WT. With proceeding fruit development element concentrations relative to the dry biomass decreased. Differences in the rate and the degree of element concentration reduction were detected. Concentrations of B, K and Na were found to decrease at a slower rate and to a lesser degree compared to other analyzed elements. In comparison to WT fruits, most elements were detected at a lower concentration in GLaF fruits in early stage samples. During GLaF fruit development most element concentrations recovered, with the exception of B and Ca. Our results highlight common and differential element accumulation patterns in developing pear fruits. We suggest that B, K and Ca play key roles in pear fruit development and propose specific homeostasis mechanisms for these elements. Since GLaF fruits are more susceptible to corky spot disorder and B and Ca are important for the proper formation of the cell wall, we suggest that local B and/or Ca deficiency is responsible for corky spot disorder found in GLaF fruits.

Erwinia uzenensis sp. nov., a novel pathogen that affects European pear trees (Pyrus communis L.)

Bacteria were isolated from black lesions on shoots of European pear trees (Pyrus communis L.) in an orchard in Japan. Previous characterization of this novel pathogen by phenotypic and genotypic methods suggested that it should belong to the genus Erwinia but might not correspond to either Erwinia amylovora or Erwinia pyrifoliae. Here, phylogenetic analyses of the 16S rRNA gene, gyrB, and rpoD gene sequences indicated that it could not be assigned to any recognized species of the genus Erwinia. DNA-DNA hybridization confirmed that the bacterial strains represented a novel species. The DNA G+C contents, the fatty acid profile and phenotypic characteristics resembled those previously reported for members of the genus Erwinia. On the basis of these and previous results, the pathogen represents a novel species of the genus Erwinia, for which the name Erwinia uzenensis sp. nov. (type strain: YPPS 951(T) = LMG 25843(T) = NCPPB 4475(T)) is proposed.

Occurrence of bacterial black shoot disease of European pear in Yamagata Prefecture

Black lesions on shoots of European pear trees observed in an orchard in Yamagata Prefecture in May 2007 were suspected to be caused by a bacterial pathogen. The surface of the colonies isolated on a high sucrose medium did not have the crater morphology that is characteristic of E. amylovora bvs. 1–3, and a specific DNA fragment was amplified from the isolates in the PCR using the EprpoD primer set. The partial sequences of the 16S rRNA gene placed the isolates in the genus Erwinia. The isolates differed serologically from E. amylovora biovars and E. pyrifoliae in an Ouchterlony double-diffusion test although their bacterial properties suggested that they are closely related to E. amylovora biovars and E. pyrifoliae. In a DNA–DNA hybridization test, the relatedness between the isolates and E. amylovora biovars or E. pyrifoliae did not exceed 70% level, indicating that they are independent species. Thus, the isolates belongs to the genus Erwnia but are not E. amylovra or E. pyrifoliae. After succulent pear shoots were injected with bacterial suspensions (109, 108, 107 and 106 cfu/ml) of the isolates, lesions formed with 109 and 108 cfu/ml, but the disease incidence with 108 cfu/ml was much lower than with E. amylovora and E. pyrifoliae. Virulence of the present isolates is thus thought to be very weak. On the basis of these results, we consider that this is a new shoot disease of European pear. In the 2007 season, all affected trees were pulled out after harvest. No symptoms have been observed in field surveys since the fruitlet season in 2007.

Asian pear tree breeding for subtropical areas of Brazil

Introduction . In Sao Paulo State in Brazil, there is a demand for pear tree varieties that present fruit complementary characteristics and high adaptation for a subtropical-tropical climate. Thus, our study aimed at evaluating variety selections with better fruit quality and mainly adapted to the different areas of the Sao Paulo State. Materials and methods . Crosses among Asian [Pyrus pyrifolia (Burm.f.) Nakai] and European (P. communis L.) pear cultivars were made in Brazil from 1992 to 1998 aiming at finding new pear types for subtropical areas of the country. The first interspecific hybrids of the IAC pear breeding program were planted in various regions of Sao Paulo State, at latitudes from 21° 11’ S to 24° 11’ S and (11 to 200) chilling units (CU). About 20 phenological characteristics were evaluated. The hybrids and their parents were genetically characterized through RAPD markers. Results and discussion . In the progeny of ‘Okusankichi’ × ‘D'agua’, the mean age for the first bearing and fruit development period (FDP) were 3.8 years and 137 days, respectively. The fruit characters early ripening, rounded shape, russet-brown skin and crisp flesh were dominant in all crosses of Asian × Asian and Asian × European pear trees. Twenty-six hybrids were selected, of which twelve are still being tested in a subtropical-tropical climate (0–80 CU). Their main characteristics are fruit with rounded, oblate, oblong or pyriform shapes, russet-brown or green skin, and crisp or soft flesh, and plants with medium-high vigor, an upright-spreading form and a fruit development period of from (110 to 160) days. Conclusion . The precocity of hybrids is highly dependent on the parental characteristics and the environmental conditions. A fruit development period close to that of the earliest parent was obtained. In F1 generations from crossings among Asian and European pears, certain characteristics were dominant. The RAPD analysis was efficient at identifying cultivar genotypes, selections and hybrids of pear from different botanical groups.

Single-Strand Conformation Polymorphism Analysis of Apple Stem Grooving Capillovirus Sequence Variants

ABSTRACT In an earlier study, we demonstrated that isolates of apple stem grooving capillovirus (ASGV) from fruit trees comprise at least two to four sequence variants that differ considerably from each other in nucleotide sequence. In order to characterize the population of sequence variants within a single tree, we applied a combination of an immunocapture reverse transcription-polymerase chain reaction (IC-RT-PCR) and a single-strand conformation polymorphism (SSCP) analysis of a nested asymmetric PCR product. In the SSCP analysis of the PCR products from ASGV-infected apple, Japanese pear, or European pear trees, two to four bands were detected in samples from all trees, indicating that ASGV exists as a mixture of sequence variants. The composition of sequence variants (the number of bands and their relative quantity) differed among leaf samples from different branches, showing that each sequence variant is distributed unevenly within an individual tree. The SSCP analysis of isolates after serial passage in Chenopodium quinoa plants indicated that passages changed the composition of sequence variants originally contained in ASGV isolates; i.e., some sequence variants dominated and others decreased to undetectable levels.

Viruses and phytoplasma in European pear trees in New Zealand and the role of these pathogens in the compatibility of pear with quince rootstocks

The history of European pear (Pyrus communis L.) cultivars, and pear and quince (Cydonia oblonga Mill.) rootstocks used in New Zealand during the present century was investigated in relation to their virus and phytoplasma disease status. Early attempts to control tree size and vigour using quince clonal rootstocks or seedlings of Oriental pear (P.pyrifolia Burm. Nak.) were unsuccessful, in part because of the presence of these diseases, and pear trees were grown for most of this century on European pear seedling rootstocks. Testing of 12 older pear cultivars commonly grown in commercial orchards at the present time showed that most were infected with several viruses, and also with the phytoplasma disease apple rubbery wood. All of the 12 cultivars were imported before, or at the beginning of this century, and were likely to have been infected in their country of origin before being introduced to New Zealand. When freed from infection by heat therapy, some were successfully grown on the virus‐free East Mailing rootstocks ‘Quince A’ and ‘C, and on the French rootstock ‘Quince BA 29’ without incompatibility problems, but others required an intermediate such as ‘Beurre Hardy’ to overcome non‐pathogen induced incompatibilities.

Water use by European pear trees growing in drainage lysimeters

SummaryResults are discussed of a four-year study on water use by European pear trees, of cvs Conference and Comice on slender spindle and V-trellis training systems, growing outdoors in drainage lysimeters. The study covered the period from planting until the end of the first cropping season. During the first half of each season, weekly water use increased in relation to estimated potential evapotranspiration, presumably as the evaporative leaf surface area increased. In the final year, when the tree leaf area was up to 2 m2 m−2 planting square area, weekly water use was always less than 40% of the potential evapotranspiration. Annual water use varied strongly with variety and training system. For non-fruiting trees however, annual water use per unit leaf area at the end of the season showed a consistent relationship for trees of all variety x training system combinations. In the final year, the presence of fruit generally increased water use, especially per unit leaf area or per unit root weight.