Volume 4 Special Issue 1 2010
Plant science and biotechnology in South America: Focus on Argentina II

ISBN 978-4-903313-69-6

How to reference: Benedetto AD, Tognetti J, Galmarini CR (2010) Biomass Production in Ornamental Foliage Plants: Crop Productivity and Mechanisms Associated with Exogenous Cytokinin Supply. In: Di Benedetto A (Ed) Plant science and biotechnology in South America: Focus on Argentina 2. The Americas Journal of Plant Science and Biotechnology 4 (Special Issue 1), 1-22

Guest Editor

Adalberto Di Benedetto

Universidad de Buenos Aires and Facultad de Ciencias Agrarias

www.uba.ar

Universidad de Mar del Plata, Argentina

www.mdp.edu.ar/agrarias/

CONTENTS AND ABSTRACTS

Adalberto Di Benedetto, Jorge Tognetti, Claudio R. Galmarini (Argentina) Biomass Production in Ornamental Foliage Plants: Crop Productivity and Mechanisms Associated with Exogenous Cytokinin Supply (pp 1-22)

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ABSTRACT

Invited Review: An important mediator of shoot physiological processes associated with ornamental biomass production can be the supply of signal molecules (other than water and nutrients) from the root system. Root-to-shoot signaling is often considered to be important in regulating shoot growth when soil conditions determine a change in shoot water or nutrient status. There are strong indications that cytokinins are root factors which are transported via the xylem to the shoot where they exert a major regulatory influence on growth and photosynthesis. Cytokinins play a critical role in many aspects of plant growth and development, including the regulation of the apical dominance, root growth and plastid differentiation. Although it has long been known that the cytokinin signal transduction pathway actively interacts with other pathways, particularly with light and auxin pathways, details of these interactions remain poorly understood. The possible technological use of this information on cultivation of ornamental shade plants is still unclear because knowledge about cause-effect relationships between exogenous cytokinin supply and plant response is still scarce. Regulatory processes conditioned the balanced growth of roots and shoots and the conclusion that root cytokinins are part of the signaling pathway can be drawn.

Fernado H. Andrade, Pablo E. Abbate, María E. Otegui, Alfredo G. Cirilo, Anibal A. Cerrudo (Argentina) Ecophysiological Basis for Crop Management (pp 23-34)

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Invited Review: This review focuses on the effect of management practices on grain yield of maize, sunflower, soybean and wheat, the major extensive crops of the Argentine Pampas. We analyze and evaluate crop management practices in the light of the physiological determinants of growth and grain yield using basic information available for these crops. This approach also contributes to understand or explain the differential responses of crops to management practices observed among species or cultivars within species, or among different environmental conditions and production system. We focuse our discussion on the effect of sowing date, plant density, row spacing, plant distribution and emergence uniformity, and cultivar maturity group election on grain yield of maize, sunflower, soybean and wheat. The knowledge and quantification of the ecophysiological factors underlying crop growth and yield determination are critical for the design and selection of the most appropriate management practices for a specific genotype and environment combination. This approach constitutes a low cost technology that can contribute to (i) match crop demands to the particular environmental offer and (ii) an efficient use of environmental resources and inputs in a specific situation.

Silvia G. Assuero, Jorge Tognetti (Argentina) Tillering Regulation by Endogenous and Environmental Factors and its Agricultural Management (pp 35-48)

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Invited Review: The outgrowth of axillary buds in grasses, known as ‘tillering’, has been extensively studied over many decades because of its agronomic importance and biological interest as well. The control of tillering has proven to be multi-factorial and very complex. The physiological complexity of this process is demonstrated by the wide array of environmental, endogenous and biotic effects that, together with their interactions have been shown to modulate tillering. In this review we analyze current knowledge about the tillering process at both isolated plant and canopy levels, and discuss the opportunities for integrating experimental results into a unifying theory that can account for all effects and thus overcome the shortcomings of the previously proposed nutritional and hormonal hypotheses. We discuss recent advances on the control of tiller development by endogenous, environmental and biotic factors at the isolated plant level, while the empirical rules that had been developed to allow proper tiller management at a canopy level are presented in connection with available physiological basis. Attention is also given to the recent development of simulation models that provide a powerful tool for agronomic management of tiller dynamics, which in turn may facilitate, through their validation, new insights on the control of tillering by the plant.

Cecilia M. Creus, María A. Pereyra, Elda M. Casanovas, Rolando J. Sueldo, Carlos A. Barassi (Argentina) Plant Growth-Promoting Effects of Rhizobacteria on Abiotic Stressed Plants. Azospirillum-GrassesModel (pp 49-59)

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Invited Review: Plant growth-promoting rhizobacteria exert beneficial effects on plants when re-introduced by inoculation in a soil containing competitive micro flora. Amongst them Azospirillum is one of the most studied genera. Even though it colonizes different plant species in an ample variety of soils, it was first described in association with grass roots. In Argentina over 220,000 ha of wheat and corn were commercially inoculated with Azospirillum in 2008. In this review the management conditions leading to enhanced crop productivity are discussed. The beneficial effects of inoculation on abiotic stressed plants are also described. We present results showing how wheat and maize stress tolerance are enhanced due to Azospirillum brasilense Sp245 inoculation.

Marta Zulema Galván, Sebastián Alberto Stenglein, Pedro Alberto Balatti (Argentina) Common Bean Germplasm Molecular Analysis: A Biotechnological Approach for Breeding (pp 60-69)

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Invited Review: Argentina, which is a major producer of common bean (Phaseolus vulgaris L.), represents the southern most limit of the Andean diversification center of the species. The diverse environmental conditions of these places and human selection favored the development of a great variability of wild beans and landraces, which is endangered due to the destruction of habitats by forest exploitation and agriculture. Information on the variability of these resources is essential to set conservation strategies and design breeding programs aimed at enlarging the genetic base of commercial beans. This work is an overview of the marker-based studies on landraces and wild bean genetic diversity, with special emphasis on Argentinean beans, as a first step for the optimal exploitation of the naturally available bean genetic resources, to generate new traits and improve crop performance. The identification of diversity and hybridization between populations is enhanced by the application of the new tools and the information generated by bean genomic research. Gene flow, which appears to occur fairly frequently in bean, has to be studied in more detail in this region in order to facilitate the transfer of useful alleles from the unexploited germplasm to improved lines, broadening the genetic diversity available for breeding. Some resistance gene analogs (RGAs) have been described within the Andean gene pool and only a few have been functionally characterized or linked to a phenotype. Therefore, a strategy for the exploitation of bean germplasm variability based on the detection of RGAs is also mentioned, though more work should be devoted at identifying these sequences in Andean landraces and wild beans.

Ana María Castro, Daniel Gimenez, Erica Tocho, María Tacaliti, Mariana Barragán, Rubén Bottini (Argentina), John Snape (UK) Tolerance to Stress in Wheat (pp 70-78)

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Invited Review: Achieving tolerance to stress is one of the main objectives of wheat breeding, and genes or chromosomal regions with positive effects on tolerance to biotic and abiotic stresses need to be identified. The interaction between defence signaling pathways mediated by several phythormones is an important mechanism for regulating defence responses against various types of pathogens and herbivories. The response of bread wheat, Triticum aestivum (2n=6x=42) to greenbug attack or to exogenous application of the stress-induced hormones ethylene (E), jasmonic acid (JA), salicylic acid (SA) or ABA was analysed. In recent years, several components regulating the cross-talk between SA, JA and ET pathways have been identified. Treatment of plants with these hormones results in enhanced resistance to biotic challenge. However, the underlying physiological mechanisms are not well understood. Some of the main wheat physiological pathways affected by the cross-talk between biotic stress and stress-induced hormones are described below.

Sergio E. Feingold, Gabriela A. Massa, Natalia S. Norero (Argentina), Jim Lorenzen (USA/Uganda) Potato Functional Genetics (pp 79-89)

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Invited Review: Potato is the third most important food crop worldwide. The identification of genes or chromosome regions responsible for agronomic traits had been extensively attempt in the past 20 years, mainly for disease resistance and tuber traits. Despite the success of these studies, only few discoveries were incorporated to plant breeding programs or used in surveying germplasm. With the forthcoming complete genome sequence of potato we envisaged that gene identification and in vivo functionality will be dramatically increased, given the availability of genetic sequences of potato and tools to assess gene function. Assisted breeding based on markers derived from these genes will be in an ideal situation where cross-over cannot occur between the marker and the gene responsible for the trait. Moreover, genetic diversity of germplasm banks can be assessed in terms of allelic variability of important genes. In this review, we present some of the studies carried out for potato functional genetics, and our contribution in the development of tools for transient silencing. The lessons learned from functional studies can also be applied to other Solanaceae such as tomato, eggplant, petunia, tobacco and pepper, which present a high level of synteny with potato.

Paula Bey, Maria Binaghi, Alejandro Néstor Mentaberry, Alicia Mercedes Zelada (Argentina) Plant Viral Vectors as a Tool for Recombinant Vaccine Production (pp 90-97)

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Invited Review: Over the last few years the development of plant viral vectors for protein expression has made rapid and impressive progress. Plant viruses are versatile vectors for production of proteins since they are easy to manipulate, quick to evaluate and offer the possibility of great production yields. They are particularly powerful expression systems for the production of recombinant proteins and peptides for vaccination, since they are able to produce antigens alone or conjugated to viral capsid. Several viral vectors have been developed for vaccine production, mainly Tobacco mosaic virus (TMV) and Potato virus X (PVX). In this review, we will discuss the advantages of the use of plant viral vectors as expression vectors, the principal vectors that have been developed to date, and the different strategies used for expression, with emphasis on recent research conducted in Argentina.

Daniel S. Kirschbaum (Argentina), Kirk D. Larson, Steve A. Weinbaum, Theodore M. DeJong (USA) Relationships of Carbohydrate and Nitrogen Content with Strawberry Transplant Vigor and Fruiting Pattern in Annual Production Systems (pp 98-103)

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Invited Mini-Review: In strawberry (Fragaria x ananassa Duch.), fruit production systems based on leafless, bare-root transplants, successful plant establishment is dependent on crown/root reserves for the formation of new feeder roots and new leaves. Successful stand establishment, early fruiting, and sustained high productivity in strawberry have been correlated with total nonstructural carbohydrate (TNC) reserves. However, nitrogen (N) reserves have largely been overlooked. The importance of root carbon and N has been highlighted in studies focused on growth of perennial plants, where apparently growth and fruiting in spring are determined primarily by N reserves. In temperate fruit trees, protein would be the main form of N storage and the predominant storage amino acid would be arginine. This could be the case of strawberries, which share many of the general characteristics of temperate fruit trees. In this frame, the concept that confers a primary role to TNC over any other reserve nutrient in strawberry needs to be reconsidered. The N cycling process in strawberries remains largely unknown; however, emerging research lines suggest a key function of N in early fruit production of fresh-dug strawberry transplants, questioning the importance of TNC as the unique storage compounds involved in plant vigor.

Sandra García Lampasona, José Luis Burba (Argentina), Philipp W. Simon (USA) Molecular Markers: Are They Really Useful to Detect Genetic Variability in Local Garlic Collections? (pp 104-112)

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Invited Review: The cultivation of garlic (Allium sativum L.) is an important activity in economic and social terms in Argentina. The traditional techniques of improvement have allowed us to obtain monoclones with proven superiority, compared with to the populations of origin. Currently these materials have been registered in the INASE (Argentine National Institute of Seeds) as new cultivars. The aims of our studies have been to characterize the genetic diversity of selected garlic clones, to verify their identity and to propose a new tool to facilitate the legal protection of germplasm. To achieve these goals we have evaluated molecular markers such as RAPDs, AFLP and fAFLP. Their usefulness is discussed in this paper.

Marcelo Guerra Santos, Alphonse Kelecom, Selma Ribeiro Paiva, Moemy Gomes Moraes, Leandro Rocha, Rafael Garrett (Brazil) Phytochemical Studies in Pteridophytes Growing in Brazil: A Review (pp 113-125)

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Invited Review: Some 13,600 species of pteridophytes are known all around the world. Brazil, with about 1,300 species is considered as one of the centers of endemism and speciation of the South American continent. Notwithstanding this amazing biodiversity, very few phytochemical studies have been reported. The present study intends to review phytochemical investigations in pteridophytes growing in Brazil. We found 78 phytochemical studies carried out on 60 species and two varieties. Biological activity was the principal focus of published works (56 papers), the second most studied theme was molecular identification (with 21 publications) and then chemical ecology with 12 papers. The most addressed species was Pteridium arachnoideum (Kaulf.) Maxon (42 papers).