Raphael A. Stern

Bio: Raphael A. Stern is an academic researcher from Tel-Hai Academic College. The author has contributed to research in topics: Pyrus communis & PEAR. The author has an hindex of 24, co-authored 81 publications receiving 1546 citations.

`Jonathan' apple is a lower-potency pollenizer of `Topred' than `Golden Delicious' due to partial S-allele incompatibility

Abstract: Summary`Topred' is one of the main apple cultivars in Israel. Since `Topred' exhibits full self incompatibility, its fruit production is totally dependent on cross pollination. The two commercial pollenizers of `Topred' in Israel are `Golden Delicious' and `Jonathan'. In the study presented here, the potential of these two pollenizers was determined. In two consecutive seasons, it was found that the rate of fruit-set and fruit yield were significantly higher in the rows of `Topred' adjacent to the `Golden Delicious' as compared with the rows adjacent to the `Jonathan'. PCR analysis of the S-alleles, a polymorphic gene locus, determining the outcome of pollination, revealed that `Jonathan' and `Topred' share allele S9. PCR-S-allele analysis of progeny seedlings revealed that in `Jonathan' only S7, the unshared allele, took part in fertilization, whereas both alleles of `Golden Delicious' (S2,S3) participated at equal rates. Thus, the lower potency of `Jonathan' as a pollenizer of `Topred' is due, at least ...

The Appropriate Management of Honey Bee Colonies for Pollination of Rosaceae Fruit Trees in Warm Climates

Abstract: Most of the Rosaceae fruit trees, such as apple, pear, plum, almond and cherry, exhibit full self-incompatibility. Therefore, their fruit production completely depends on cross pollination. The ultimate pollen carrier in Rosaceae is the honey bee. In the present review, different bee-hive management techniques for improving fruit set and yield are discussed. The main manipulations are of colony density and the timing and number of colony introductions. In pear, it was found that increasing the density from 2.5 colonies ha -1 to 5 colonies ha -1 in one introduction at 10% full bloom (FB), did not increase bee activity on the trees and did not improve fruit set and yield. However, introducing the colonies sequentially (1.25 colonies ha -1 at 10% FB and 1.25 colonies ha -1 at FB) increased bee activity and consequently improved fruit set and yield. In apple, the combination of both treatments: increasing the density to 2.5 colonies ha -1 at 10% FB and a second introduction of 2.5 colonies ha -1 at FB, for a total of 5 colonies ha -1 , increased the number of bees tree -1 , their mobility between the rows and the proportion of “topworkers” compared with “sideworkers”. As a result, fruit set and yield were enhanced. In Japanese plum, highest bee activity, fruit set and yield, were achieved when colonies were introduced at four different times (multiple introductions). Each introduction was of a density of 1.25 colonies ha -1 at 10% FB, 50% FB, FB and FB+3 days (total of 5 colonies ha -1 ). For all three species, there was a positive and statistically significant correlation between the average number of bees tree -1 and fruit set or yield. The optimum number of bees tree -1 min -1 at FB was 6-7 for pear, 7-8 for Japanese plum and 12-14 for apple.

The relationship between floral structure and honeybee pollination eficiency in ‘Jonathan’ and ‘Topred’ apple cultivars

Abstract: Apple (Malus domestica) has a gametophytically determined self-incompatibility (SI) system, which limits inbreeding. As a result, apple fruit-set is dependent on effective cross-pollination, which may be enhanced by honeybees (Apis mellifera) Excess pollination results in over-cropping, leading to many small fruit, regarded as of low quality. On the other hand insufficient pollination is also possible, and is manifested by low crop production. In the present work, characteristics of nectar reward and floral morphology revealed that 'Jonathan' and 'Topred' flowers had similar nectar constitutions. However, honeybee behaviour was totally different in the two cultivars. 'Jonathan' flowers attracted fewer honeybees but, due to their anther arrangement, more of the flowers were approached from the top by honeybees collecting nectar than in 'Topred'. This finding demonstrates the importance of determining the pollination efficiency to achieve optimum honeybee management, in terms of the number of honeybee colonies required for sufficient pollination and minimum fruit thinning.

Light-induced expression of a MYB gene regulates anthocyanin biosynthesis in red apples.

Abstract: Anthocyanins are secondary metabolites found in higher plants that contribute to the colors of flowers and fruits. In apples (Malus domestica Borkh.), several steps of the anthocyanin pathway are coordinately regulated, suggesting control by common transcription factors. A gene encoding an R2R3 MYB transcription factor was isolated from apple (cv Cripps' Pink) and designated MdMYB1. Analysis of the deduced amino acid sequence suggests that this gene encodes an ortholog of anthocyanin regulators in other plants. The expression of MdMYB1 in both Arabidopsis (Arabidopsis thaliana) plants and cultured grape cells induced the ectopic synthesis of anthocyanin. In the grape (Vitis vinifera) cells MdMYB1 stimulated transcription from the promoters of two apple genes encoding anthocyanin biosynthetic enzymes. In ripening apple fruit the transcription of MdMYB1 was correlated with anthocyanin synthesis in red skin sectors of fruit. When dark-grown fruit were exposed to sunlight, MdMYB1 transcript levels increased over several days, correlating with anthocyanin synthesis in the skin. MdMYB1 gene transcripts were more abundant in red skin apple cultivars compared to non-red skin cultivars. Several polymorphisms were identified in the promoter of MdMYB1. A derived cleaved amplified polymorphic sequence marker designed to one of these polymorphisms segregated with the inheritance of skin color in progeny from a cross of an unnamed red skin selection (a sibling of Cripps' Pink) and the non-red skin cultivar Golden Delicious. We conclude that MdMYB1 coordinately regulates genes in the anthocyanin pathway and the expression level of this regulator is the genetic basis for apple skin color.

Biodiversity, Ecosystem Functioning, and Human Wellbeing: An Ecological and Economic Perspective

Abstract: In an age of accelerating biodiversity loss, this timely and critical volume summarizes recent advances in biodiversity-ecosystem functioning research and explores the economics of biodiversity and ecosystem services. The book starts by summarizing the development of the basic science and provides a meta-analysis that quantitatively tests several biodiversity and ecosystem functioning hypotheses. It then describes the natural science foundations of biodiversity and ecosystem functioning research including: quantifying functional diversity, the development of the field into a predictive science, the effects of stability and complexity, methods to quantify mechanisms by which diversity affects functioning, the importance of trophic structure, microbial ecology, and spatial dynamics. Finally, the book takes research on biodiversity and ecosystem functioning further than it has ever gone into the human dimension, describing the most pressing environmental challenges that face humanity and the effects of diversity on: climate change mitigation, restoration of degraded habitats, managed ecosystems, pollination, disease, and biological invasions.However, what makes this volume truly unique are the chapters that consider the economic perspective. These include a synthesis of the economics of ecosystem services and biodiversity, and the options open to policy-makers to address the failure of markets to account for the loss of ecosystem services; an examination of the challenges of valuing ecosystem services and, hence, to understanding the human consequences of decisions that neglect these services; and an examination of the ways in which economists are currently incorporating biodiversity and ecosystem functioning research into decision models for the conservation and management of biodiversity. A final section describes new advances in ecoinformatics that will help transform this field into a globally predictive science, and summarizes the advancements and future directions of the field. The ultimate conclusion is that biodiversity is an essential element of any strategy for sustainable development.

In Posidonia oceanica cadmium induces changes in DNA methylation and chromatin patterning

Abstract: In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.

Regulation of floral initiation in horticultural trees

Abstract: The intention of this review is to discuss floral initiation of horticultural trees. Floral initiation is best understood for herbaceous species, especially at the molecular level, so a brief overview of the control of floral initiation of Arabidopsis (Arabidopsis thaliana (L.) Heynh.) precedes the discussion of trees. Four major pathways to flowering have been characterized in Arabidopsis, including environmental induction through photoperiod and temperature, autonomous floral initiation, and regulation by gibberellins. Tropical trees are generally induced to flower through environmental cues, whereas floral initiation of temperate deciduous trees is often autonomous. In the tropical evergreen tree mango, Mangifera indica L., cool temperature is the only factor known to induce flowering, but does not ensure floral initiation will occur because there are important interactions with vegetative growth. The temperate deciduous tree apple, Malus domestica Borkh., flowers autonomously, with floral initiation dependent on aspects of vegetative development in the growing season before anthesis, although with respect to the floral initiation of trees in general: the effect of the environment, interactions with vegetative growth, the roles of plant growth regulators and carbohydrates, and recent advances in molecular biology, are discussed.