Cotton Fiber: Physics, Chemistry and Biology PDF by David D. Fang

Contents

Preface
Cotton fiber is the most important natural fiber used in the textile industry. The physical structure and chemical compositions of cotton fibers have been extensively studied. Newer high-speed spinning instruments are being deployed around the world that demand longer, stronger, and finer fibers. Consequently, genetic improvement in fiber quality has been stressed. With improvement in fiber quality has come the realization that further fiber improvement will require a better understanding of fiber development and biology. As a consequence, cotton fiber developmental biology, genetics, and genomics have become focal points in the cotton research community. As the longest single-celled plant hair, cotton fiber has been used as an experiment model to study trichome initiation and elongation in plants. This book provides a comprehensive update on cotton fiber physics, chemistry, and biology that naturally separate the book into three sections. In the physics section, the physical structure of cotton fiber is first illustrated in great detail. Then a suite of fiber properties and their measuring methods are described. The pros and cons of each method are outlined. New methods to measure physical properties of single fiber and young developing fibers are included. In the chemistry section, the chemical compositions of cotton fibers are described in detail. This knowledge is necessary for efficient modification of cotton fibers for better and broader utilization. The advancement in cotton fiber modification using chemical and enzymatic methods opened new ways to utilize cotton fibers. In the biology section, the book first introduces the utilization of naturally occurring color cottons. Color cottons possess unique attributes such as better fire retardant ability. Advancement in understanding fiber color genetics and biochemical pathways and new utilization of color cottons are discussed. Recent technological advancements in molecular biology and genomics have enabled us to study fiber development in great depth. Many genes and quantitative trait loci related to fiber quality attributes have been identified and genetically mapped. Some of these genes and QTLs are being used in breeding.

Progresses in cotton fiber improvement using breeding and biotechnology are discussed in the last chapter. This book serves as a reference for researchers, students, processors, and regulators who either conduct research in cotton fiber improvement or utilize cotton fibers.

I greatly appreciate all the authors who contributed excellent work to this book. I also thank my employer, USDA-ARS Southern Regional Research Center (SRRC), where most contributors are employed. Cotton fiber research and utilization has been a major research component at SRRC since its establishment in 1939. Many research results described in this book are from SRRC.

Chapter 1
General Description of Cotton
David D. Fang

Throughout the world, cotton fiber is the most widely used plant-produced fiber for apparel, home furnishings, and industrial products. In 2016, about 106.5 million bales (218 kg or 480 pounds per bale) of cotton fiber were produced from more than 50 countries around the world. The economic value of the worldwide raw cotton fiber is estimated at $35 billion annually. India, China, the United States, Pakistan, and Brazil account for over 75% of world cotton production (www.cottoninc.com). Of the entire world production, about 36 million bales were destined to the export market with the United States being the largest exporter and Vietnam as the largest importer in 2016.

Naturally, a cotton plant grows as a perennial in tropical and subtropical regions, often reaching the size of a small tree. However, for commercial production of raw fibers, most if not all cotton cultivars are grown as annuals, i.e., the crop is harvested in the same year of planting. An “annual” cotton is not a true annual because the death of a plant is not a natural consequence of seed ripening, rather due to application of chemicals or mechanical destruction. A cotton plant can be maintained indefinitely under a warm environment such as a glasshouse. Indeed, cotton germplasm repositories in several countries use glasshouses to maintain live cotton plants (Percy et al. 2014).

Cotton belongs to the family Malvaceae, the tribe Gossypieae, and the genus Gossypium (Wendel and Grover 2015). The cotton genus (Gossypium L.) consists of about 45 diploid species (2n = 2x = 26) classified as 8 genome groups (A–G and K) and 6 allotetraploid (AD) species (2n = 4x = 52) (Fryxell 1992; Wendel and Grover 2015). The haploid genome size of diploid species ranges from 885 Mbp of a D-genome species to 2570 Mbp of a K-genome species. A tetraploid species has a genome size of about 2400 Mbp (Hendrix and Stewart 2005; Zhang et al. 2015).

A preponderance of evidence has demonstrated that the six tetraploid cotton species (G. barbadense, G. darwinii, G. ekmanianum, G. hirsutum, G. mustelinum, and G. tomentosum), which are entirely New World distribution, originated from a single hybridization event between an A-genome species (either G. herbaceum or G. arboreum) and a D-genome species (possibly G. raimondii) 1–2 million years ago (Endrizzi et al. 1985; Paterson et al. 2012; Wendel and Cronn 2003; Wendel and Grover 2015; Zhang et al. 2015). Four species, i.e., G. arboreum, G. barbadense, G. herbaceum, and G. hirsutum, are cultivated for their ability to produce high fiber yield.

G. hirsutum (Fig. 1.1), native to Mexico and Central America, was introduced into the United States as early as the sixteenth century shortly after Columbus’ discovery of the Americas (Beckert 2014). Tremendous efforts in introduction, selection, and breeding significantly improved G. hirsutum plants to better adapt to commercial production under new environments in subsequent centuries (Fig. 1.2). Eli Whitney’s invention of a saw gin to mechanically separate cotton fiber from seeds in 1793 greatly helped the expansion of cotton production in the United States and the spread of American cotton varieties to other countries (Lee and Fang 2015). Of the four commercially cultivated species, G. hirsutum commonly known as upland cotton or American upland cotton is grown on the most acres and accounts for over 90% of the world’s raw cotton fiber production. In general, upland cottons have fiber length ranging from 20 to 32 mm, micronaire value falling between 3.5 and 5.5, and bundle fiber strength between 27 and 32 g/tex.