Durum Wheat Chemistry and Technology

Michael Sissons

• Publisher: Woodhead Publishing and AACC International Press
• Year: 2016
• ISBN:
  9780128104323
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

The most extensive and comprehensive reference on durum wheat chemistry and technology ever available, this ambitious update to the first edition covers more diverse and interesting topics in a new expanded format. Forty-six contributors, each highly experienced and recognized as world authorities on durum wheat, provide the latest developments in scientific research and technology. All aspects of durum wheat are covered, from agronomy and the chemical composition of the grain, to the latest industrial approaches to processing durum wheat, as well as food safety and quality assurance issues. Expanded to include new topics like functional pasta, grain safety, and biotechnology, along with practical and applied information including a table of uses for specific carbohydrates, descriptions of improved laboratory techniques, and international comparisons of HACCP experiences, Durum Wheat: Chemistry and Technology, Second Edition is a must-have reference for professionals, students, and researchers inside and outside the field who want to learn about durum wheat technology and chemistry.

New and Revised Topics Include:

• Agronomy of durum wheat production
• Pasta made from non-traditional raw materials: technological and nutritional aspects
• Grain safety assurance, including impacts on durum wheat trading
• Origin and distribution of durum wheat genetic diversity in the world
• Genetics and breeding of durum wheat
• Insect and mite pests and diseases of durum wheat
• Kernel components of technological value
• Vitamins, minerals, and nutritional value of durum wheat
• Durum wheat milling
• Manufacture of pasta products
• Other traditional durum derived products
• Methods used to assess and predict quality of durum wheat, semolina, and pasta
• Grading factors impacting on durum wheat and processing quality
• Grain safety assurance including impacts on durum wheat trading
• Marketing perspectives in the durum wheat trade

Special Features:

• Detailed figures outlining the processes used to manufacture durum products
• International comparisons of HACCP experiences
• Table of uses for specific carbohydrates
• Descriptions of improved laboratory techniques
• Extensive bibliography

An Essential Reference For:

• Scientists and researchers in agriculture and plant biology
• Professionals in the food industry who are processing durum wheat (millers, pasta makers, grain handling companies, and grain buyers)
• Government regulators
• Food scientists and technologists developing products using durum wheat
• Plant breeders
• University lecturers in agricultural science and plant biology
• Professionals who market wheat
• Nutritionists and medical practitioners interested in the impacts of food ingredients on human healthStudents
• Scientific libraries and their patrons

CHAPTER 1

Origin and Distribution of Durum Wheat Genetic Diversity in the World

Alessandro Bozzini, (Retired), Food and Agriculture Organization of the United Nations Rome, Italy

Jacques David, Montpellier Supagro UMR Amelioration Génétique et Adaptation des Plantes Montpellier Cedex 2, France

Vincenzo Natoli, ISEA S.r.l. Corridonia, Macerata, Italy

EVOLUTION AND CLASSIFICATION OF WHEATS

A Common Ancestral Genome for Grasses

All the wheats belong to the genus Triticum, a member of the grass (Gramineae or Poaceae) family. Barley (Hordeum vulgare L.) and rye (Secale cereale L.) belong to the same Hordeae tribe, in which one or more flowered spikelets are sessile and alternate on opposite sides of a rachis (the main axis of the inflorescence), forming a true spike. They are also close relatives of some weeds like Agropyron and other wild grasses that can be crossed with wheat (Thinopyrum, Leymus, Aegilops). This related group of Gramineae is often referred as the Triticeae, defined by its relatedness to wheat. Triticeae species are adapted to the steppes or semiarid areas, characterized, in the Northern Hemisphere, by winter rains and dry summers, where they develop with available fall-winter moisture and, depending on the elevation of these areas, reach maturity in late spring or summer (Van Slageren 1994). They grow in different ecological niches, some species being more adapted to dry and warm conditions (barley) and others thriving in more moist areas (Aegilops tauschii Coss.) or mountainous regions (wild rye). Most wild Triticeae species thrive in the eastern Mediterranean, Near East, and southwestern Asia, but some species can also be found in Australia (e.g., Australopyrum spp.), in western Mediterranean Europe, and the Maghreb region (Aegilops spp.). Wild Aegilops species (referred to as wild Triticum in some classifications) are closely related to wheat. They can cross with wheat either spontaneously or via controlled crosses and sometimes give rise to fertile offspring.

The Triticeae diploid species share a common number (seven pairs) of chromosomes, inherited from a common ancestor. Thus, even if evolutionary processes such as translocations (changes in gene order or gene content) occur, the derived homoeologous chromosomes still share large similarities among the different Triticeae species. For instance, chromosome 1H of barley is homologous to the chromosome 1R of rye.

This ancestry takes even deeper root in the phylogeny of grasses, including rice, maize, sorghum, sugarcane, and millet, which are all important crops for human and animal nutrition. Recent genomic evidence supports the hypothesis that all grass genomes evolved from a common ancestor with a basic number of five chromosomes through a series of whole genome and segmental duplications, chromosome fusions, and translocations (Salse et al 2008). Conservation of gene order within the Triticeae, which includes sets of common genes involved in the expression of similar traits, has permitted the use of DNA sequence data from barley or rice to help researchers understand the genetics in wheat (Salse and Feuillet 2007).

Polyploidization: A Common Evolutionary Feature in Triticeae

The Triticum genus is complex and rich in species. A description of their characteristics and related genomes is presented in Morris and Sears (1967), Kimber and Sears (1987), and Bozzini (1988). However, for the purposes of this chapter, the taxonomic classification system of Van Slageren (1994) will be followed. A “Triticum Comparative Classification Table” appears at https://www.ksu.edu/wgrc/Taxonomy/taxintro.html.

When species grow in the same area, spontaneous hybrids may be observed; many examples are reported in the herbaria (Van Slageren 1994). Such interspecific hybrids are usually highly sterile; the homeologous chromosomes of the two differentiated genomes do not pair uniformly during meiosis and produce nonviable unbalanced gametes. In some cases, though, meiosis alterations generate the formation of unreduced gametes (gametes carrying 2n = 14 chromosomes instead of the usual set of n = 7 chromosomes). The mating of a 2n male gamete with a 2n female gamete may lead to a new stable and fertile polyploidy species (allotetraploid) that consists of 2n=4x=28 chromosomes (Kihara and Lilienfeld 1949, Xu and Dong 1992). This ability to generate unreduced gametes is genetically determined and also observed in cultivated wheats (Zhang et al 2007).

Spontaneous polyploidy is common in plants, and many combinations between diploid Triticeae genomes can be observed in nature (Van Slageren 1994). Interspecific allopolyploidization can also involve species with higher ploidy and can lead to hexaploidy. (Octoploidy and higher ploidy levels are rare in the Triticeae.)

In newly produced polyploids, the homeologous chromosomes might still pair (mimicking autopolyploidy), leading to abnormalities in gamete formation and subsequently reduced fitness. Pairing between the different genomes can lead to chromosome rearrangements. In T. turgidum subsp. dicoccoides, a wild allotetraploid wheat (Badaeva et al 2007), as in T. araraticum (T. timopheevi subsp. armeniacum) (Jiang and Gill 1994), high rates of diversity for chromosome rearrangements can be found between individuals, including reciprocal translocations and chromosome inversions. The further stabilization of allopolyploids requires a restriction of pairing between the homoeologous chromosomes (Cifuentes et al 2010). In polyploid wheats, mechanisms for repression of homeologous pairing are under genetic control (Okamoto 1957, Riley and Chapman 1958, Sears 1976). One of these genes with a major effect, Ph1 (pairing homeologous), has been recently identified at the molecular level (Griffiths et al 2006).

Polyploidy appears to have occurred spontaneously in the Triticeae tribe in different periods of history. Divergent diploid genomes have been combined to produce new polyploid species by spontaneous hybridization between diploid (or diploid with tetraploid) Triticum or Aegilops species. For example, out of the 22 Aegilops wild species classified according to Van Slageren (1994), only nine species, representing six divergent genomes, are diploid. Most of the remaining species are allotetraploid, and a few are allohexaploid (Van Slageren 1994). The fact that high ploidy levels are observed in Triticeae strongly supports the hypothesis that the introduction of genetic variability by multiple origins can increase the ecological amplitude and evolutionary success of allopolyploid species compared with their diploid progenitors, for adaptation both in the wild and in agriculture (Meimberg et al 2009).

Classification of Wheats Within a Polyploid Series

In 1753, in “Species Plantarum,” Carl Linneus proposed the first classification system of plants, including wheats, based on morphological and physiological differences. In the twentieth century, as a result of pioneering cytogenetic work, the number of chromosomes present in each morphologically recognized type became an objective key for classification of wheats. The cytogenetic and cytological analysis showed that wheats fall into three basic natural groups, each one characterized by having in each somatic cell 14 chromosomes (seven pairs) or a multiple of 14 chromosomes. The groups are diploid wheats (e.g., Triticum monococcum subsp. monococcum, or einkorn, having 14 chromosomes); tetraploids like T. turgidum subsp. durum, or durum wheat, having 28 chromosomes; and hexaploids like bread wheat (Triticum aestivum subsp. aestivum), having 42 chromosomes. Both Aegilops and Triticum species are distributed within a polyploid series from the basic diploid number to a hexaploid state.

As all component genomes appear to share a common Triticeae ancestor with seven chromosome pairs, the chromosomes of polyploid wheats can be grouped into seven homeologous groups. Homeology is the state of coancestry between chromosomes present in the same polyploid species. A chromosome of a constituent genome does not normally pair at meiosis with its homeologous counterpart even if it is, at l...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Preface to the Second Edition
• Preface to the First Edition
• Chapter 1: Origin and Distribution of Durum Wheat Genetic Diversity in the World
• Chapter 2: Genetics and Breeding of Durum Wheat
• Chapter 3: Agronomy of Durum Wheat Production
• Chapter 4: Diseases of Durum Wheat
• Chapter 5: Insect and Mite Pests of Durum Wheat
• Chapter 6: Kernel Components of Technological Value
• Chapter 7: Vitamins, Minerals, and Nutritional Value of Durum Wheat
• Chapter 8: Durum Wheat Milling
• Chapter 9: Manufacture of Pasta Products
• Chapter 10: Other Traditional Durum-Derived Products
• Chapter 11: Pasta Made from Nontraditional Raw Materials: Technological and Nutritional Aspects
• Chapter 12: Methods Used to Assess and Predict Quality of Durum Wheat, Semolina, and Pasta
• Chapter 13: Grading Factors Impacting Durum Wheat Processing Quality
• Chapter 14: Grain Safety Assurance, Including Impacts on Durum Wheat Trading
• Chapter 15: Marketing Perspectives in the Durum Wheat Trade
• Index