336 Chapters
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19: Auxin Biosynthesis

D'Mello, J.P.F. CABI PDF

19 

Auxin Biosynthesis

J.W. Chandler*

Institute of Developmental Biology, Cologne Biocenter,

Cologne University, Cologne, Germany

19.1  Abstract

Auxin is arguably one of the most important plant hormones and is implicated in almost every aspect of development, including the specification of the apical–basal body axis, lateral organ formation, organogenesis, tropisms and environmental responses. Although the majority of the auxin in plants is produced from l-tryptophan (Trp), tryptophan-independent biosynthesis might also occur. Auxin biology has enjoyed a renaissance in recent years, with the recognition and elucidation of its role in gene regulation, and an understanding at the cell biology level of how gradients and concentration maxima are created in tissues via polar transport. However, many questions remain open, especially concerning the function of auxin as a morphogen and how auxin self-regulates aspects of its own transport.

The major auxin in plants is indole-3-acetic acid (IAA), though other active forms exist as well, including

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Medium 9781780644837

2: Genetics and Breeding

CABI PDF

2 

Genetics and Breeding

Shashi Banga,1* P.R. Kumar,2 Ram Bhajan,3 Dhiraj Singh4 and S.S. Banga1

1

Punjab Agricultural University, Ludhiana, Punjab; 2Indian Council of

Agricultural Research, Krishi Bhawan, New Delhi; 3Department of Plant

Breeding & Genetics, College of Agriculture, G.B. Pant University of

Agriculture & Technology, Pantnagar, Uttrakhand; 4(ICAR), Directorate of

Rapeseed-Mustard Research, Sewar, Bharatpur, Rajasthan, India

Introduction

Oilseed brassicas are critical for the edible oilseeds economy of the world. Therefore, these crops have received much attention from cytogeneticists, taxonomists, evolutionary biologists, crop breeders and biotechnologists.

Notwithstanding unsolved problems of susceptibility to pests and diseases, significant progress has been made towards enhanced productivity and seed quality modifications.

A great deal is also understood about the origin and diversification of the genus. Modern molecular technologies have helped to answer many critical questions about the origin of the polyploid brassicas, the relationships among species and species groups, and the genesis of the domesticated forms from their wild progenitors. Also well characterized are wild crucifers and their relatedness with cultivated species. Investigators also focused on introgressing alien genetic resources in crop brassicas. Hybrids are now available in otherwise self-­pollinated di-genomic species, Brassica jun­ cea (mustard) and Brassica napus (rapeseed), thanks to alloplasmic male sterility systems. Genome sequencing has been completed in all three monogenomics and B. napus. Complete genome sequences of B. juncea and Brassica ­carinata,

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15 RNA Interference Strategy for Crop Protection Against Insect Pests

Soberon, M.; Gao, Y.; Bravo, A. CABI PDF

15

RNA Interference Strategy for

Crop Protection Against Insect

Pests

Sneha Yogindran and Manchikatla V. Rajam*

Department of Genetics, University of Delhi South Campus,

New Delhi, India

Summary

RNA interference (RNAi) has significantly accelerated functional genomic research on insects. Since its discovery, numerous reports have reported efforts to apply RNAi approaches to insect species lacking characterized genomes. The technique also has substantial potential for use in the control of insect pests that cause severe loss of crop yield and quality. Several approaches have been exploited to control these pests, including the application of different agrochemicals and the development of resistant crops by breeding and transgenic approaches.

However, there are certain limitations with these strategies, and therefore novel alternative strategies are required for the development of stress-tolerant plants. RNAi strategies have proven to be such a novel and potential alternative for disease and pest control. This technique essentially involves the production of hairpin double-stranded

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19 Acetogenesis as an Alternative to Methanogenesis in the Rumen

Malik, P.K CABI PDF

19

Acetogenesis as an Alternative to Methanogenesis in the Rumen

Emma J. Gagen, Stuart E. Denman and

Christopher S. McSweeney*

CSIRO Agriculture, St Lucia, Queensland, Australia

Abstract

Bacteria capable of producing acetate from

H2 and CO2 using the acetyl-CoA pathway

(4H2 + 2CO2 Æ CH3COOH + 2H2O) are known as acetogens. They have been found in a variety of anaerobic ecosystems, including sediments, wastewater treatment systems, soils and animal gut systems. In recent years, acetogens have received attention as a hydrogenotrophic population that may play a role in reducing methane

(CH4) emissions from ruminant animals.

During ruminal fermentation, methanogenic archaea reduce CO2 (4H2 + CO2 Æ CH4 +

2H2O) or methylated compounds to CH4.

Ruminal methanogenesis represents a loss of 2–12% of gross energy of ingested feed and contributes significantly to global greenhouse gas emissions. If methanogenesis could be suppressed in the rumen, acetogenesis may serve as an effective alternative hydrogen sink, resulting in an energy gain for the ruminant through the production of acetate. Acetogenesis is the dominating hydrogenotrophic pathway in other gut systems such as those of humans, pigs, termites and potentially some native Australian marsupials. The latter are of particular interest as they exhibit foregut fermentation analogous to that of ruminants, though resulting in significantly less CH4 production, suggesting the

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10: The Future of Animal Trade

Phillips, C.J.C. CABI PDF

The Future of Animal Trade

10

10.1  Introduction

The past has seen some dramatic changes in world trade in animals. This chapter considers what will shape the future of the animal trade and what changes in the trade are likely. Continuation of current trends does not seem to be an option. Worldwide meat and milk production have been growing, as outlined in

Chapters 4 and 5, respectively. Even taking into account increasing population, meat availability per capita has been increasing steadily over the last 50 years to approximately double what it was at the beginning of the 1960s; milk availability per capita has increased by about 20% over the last 10 years (Fig. 10.1). The increasing livestock production requires prodigious quantities of feed grain and there is still potential for meat consumption to increase in many developing regions of the world, e.g. sub-Saharan Africa. The steadily increasing trajectory for meat availability per capita has been consistent over the last 50 years (Fig. 10.1), and it will therefore take extreme measures if this is to be changed.

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