eChapters

The response to selection is the change produced in the population mean through selection. This is achieved through selecting as parents of the next generation, individuals with highest genetic merit and whose progeny will, as a group, have the highest possible genetic merit for the trait in question. 

Selection is an important tool for changing gene frequencies to better fit individuals for a particular purpose. It may be defined as a process in which certain individuals in a population are preferred to others for the production of the next generation. Selection is of two kinds

In genetic studies it is necessary to distinguish two causes of correlation; is chiefly pleiotropy, though linkage is a cause of transient correlation, particularly in populations derived from crosses between divergent strains. Pleiotropy is simply the property of a gene whereby it affects two or more characters, so that if the gene is segregating it causes simultaneous variation in the characters as affects. For example, genes that increase growth rate increase both stature and weight, so that they tend to cause correlation between these two characters. The degree of correlation arising from pleiotropy expresses the extent to which two characters are influenced by the same genes. But the correlation resulting from pleiotropy is the overall, or net, effect of all the segregating genes that affect both characters. Some genes may increase both characters, while others increase one and reduce the other the former tend to cause a positive correlation the latter a negative one. So pleiotropy does not necessarily cause a detectable correlation. The correlation resulting from environmental causes is the overall effect of all the environmental factors that vary; some may tend to cause a positive correlation, others a negative one.

Estimates of heritability use statistical analyses to help to identify the causes of differences between individuals. Because heritability is concerned with variance, it is necessarily an account of the differences between individuals in a population. Heritability can be univariate–examining a single trait – or multivariate – examining the genetic and environmental associations between multiple traits at once. This allows a test of the genetic overlap between different phenotypes: for instance hair colour and eye colour. Environment and genetics may also interact, and heritability analyses can test for and examine these interactions (GxE models).

The concept of value, expressible in the metric units by which the character is  measured. The value observed when the character is measured on an individual is the phenotypic value of that individual. All observations of means, variance, or covariances, must clearly be based on measurements of phenotypic values. In order to analyse the genetic properties of the population we have to divide the phenotypic value into two componants. 
The first division of phenotypic value is into components attributable to the influence of genotypic and environment. The genotype is the particular assemblage of genes possessed by the individual, and the environment is all the non-genetic circumstances under the term ‘environment’ means that the genotype and the environment are by definition the only determinants of phenotypic value. The two components of value associated with genotypic value and the environmental deviation. 

The amount of variation is measured and expressed as the variance. When values are expressed as deviations from the population mean the variance is simple the mean of the squared values. For example, the genotypic variance is the variance of genotypic values and the environmental variance is the variance of environmental deviations. The total variance is the phenotypic variance of the variance of phenotypic values, and is the sum of the separate components. 

Gene Frequency

A population, in the genetic sense, is not just a group of individuals, but a breeding group and the genetics of a population is concerned not only with the genetic constitution of the individuals but also with the transmission of the genes from one generation to the next. In the transmission the genotypes of the parents are broken-down and a newest of genotypes is constituted in the progeny, from the genes transmitted in the gametes. The genes carried by the population thus have continuity from generation to generation, but the genotypes in which they appear do not. The genetic constitution of a population, referring to the genes it carries, is described by the array of gene frequencies, that is, by specification of the alleles present at every locus and the numbers of proportions of the different alleles at each locus. If for example, A1 is an allele at the A locus, then the frequency of A1, is the proportion or percentage of all genes at this locus that are the A1 allele. The frequencies of all the allele at any one locus must add up to unity, or 100 percent. 

Quantitative Versus Qualitative Inheritance

There is a continuum of traits being inherited as a Mendelian trait with simple inheritance and traits having quantitative inheritance without well separated classes and with many genes involved.
Classification of traits in relation to mode of inheritance and environmental tolerance are shown in Figure 1.2. First there are the well known traits with simple Mendelian mode of inheritance. The trait with quantitative genetic inheritance is caused by segregation of many gene pairs, each with small effect. At the same time the trait is influenced by a lot of minor environmental effects.
Diseases will often be ‘either/or traits’ as the simple Mendelian traits. Cases in which the severity of the disease has a normal distribution can also be found. In many production diseases the disease only occurs when a genetically prone individual is exposed to adverse environmental effects. Figure 1. Classification  of traits in relation to mode of inheritance  and environmental tolerance. 
 

Introduction
Statistics is a field of mathematics that pertains to data analysis. Statistical methods and equations can be applied to a data set in order to analyze and interpret results, explain variations in the data, or predict future data. A few examples of statistical information we can calculate are:
Average value (mean)

There are certain inherited traits (characters) in various species of livestock which are economically important. These traits have to be improved for increased production like milk, meat, egg, wool, etc.

Definition of Breed

A breed is a group of animal’s related similar characters like general appearance, size, features and configuration etc. A group of individual which have certain common characteristicsthat distinguish them from other groups of individuals is known as Species.

Domestication of Livestock

Domestication (from Latin domesticus) is the process whereby a  population  of  animals  or plants is changed at the genetic level through a process of selection, in order to accentuate traits that benefit humans. It differs from taming in that a change in the phenotypical expression and genotype of the animal occurs, whereas taming is simply the process by which animals become accustomed to human presence. In the Convention on Biological Diversity, a domesticated species is defined as a “species in which the evolutionary process has been influenced by humans to meet their needs.” Therefore, a defining characteristic of domestication is artificial selection by humans. Humans have brought these populations under their control and care for a wide range of reasons: to produce food or valuable commodities (such as wool, cotton, or silk), for types of work (such as transportation, protection, and warfare), scientific research, or simply to enjoy as companions or ornaments. Plants domesticated primarily for aesthetic enjoyment in and around the home are usually called house plants or ornamentals, while those domesticated for large-scale food production are generally called crops. A distinction can be made between those domesticated plants that have been deliberately altered or selected for special desirable characteristics and those plants that are used for human benefit, but are essentially no different from the wild populations of the species. Animals domesticated for home companionship are usually called pets while those domesticated for food or work are called livestock or farm animals.

Introduction

From the very early days human beings depend on animals and animal products for food and other requirements. In dairy and poultry farms high yielding animals are reared. These high yielding animals are produced by hybridization experiments. Previously the animals were developed basing on unscientific methods. Before the discovery of principles of heredity human beings have selected the animals with required characters and learned to develop the plants having the selected characters. This phenomenon is called Artificial selection. However, an increased knowledge of biology, especially genetics, has helped in improving the quality of animals and animal products as per the human requirements.

As mentioned above Bougainvillea is one of the most widely grown important perennial ornamental shrubs with numerous attractive plant colour (leaf) and shape, and bract colours and shape. It is very popular for its multipurpose use. Inspite of beautiful bract colour it can not be enjoyed as cut flower as its shelf-life is very limited. Bracts start drooping within few minutes after cut from the main plant. Dehydration techniques have been developed at CSIR-N.B.R.I., Lucknow, by which flowers and foliage retain their fresh look for several months or even years after dehydration. Their original shapes, colour and size remain as they were before dehydration and, thus, making them highly suitable raw materials for interior decoration and may be enjoyed for a long time and can be used for any occasion. NBRI has standardized two methods viz. Press Drying and Embedding (drying through embedding in sand and silica gel and drying using hot air oven, microwave oven and solar cooker). Bougainvillea leaves and bracts can be dehydrated beautifully by both the methods and the dried products are utilized for preparation of different types of commercial decorative items. 

There are different crop specific societies in different countries for registering new varieties. This does not provide any intellectual property right. It serves as a documental proof of new variety, author, mode of origin, place and date. For example, there is The American Rose Society which serves as the International Cultivar Registration Authority for Roses; The Royal Horticultural Society, International Registration Authority for the genus Dahlia; Indian Agricultural Research Institute, New Delhi -110 012, India for Bougainvillea. Each society either follows the rules set forth by the International Code of Nomenclature for Cultivated Plants or they are having their own rules and regulations for registration (Anonymous 1981, Choudhury 1973, Singh 1983, 1986, 1987, 1999, Singh et al., 1999, Sindhu 2015, Singh 2007). Newly evolved Bougainvilleas are being registered by the Division of Vegetable Crops and Floriculture, Indian Agricultural Research Institute, New Delhi, since 1966. A check list of all the existing important cultivars based on the available information from literature as well as from amateurs, professional traders and other sources from different countries are available.

New varieties of bougainvillea have been developed in India at different research institutions, nurseries, botanical societies and also by individual efforts. Details have been mentioned above. New varieties developed at CSIR-NBRI need special mention. 

CSIR-NBRI has developed a number of new varieties by using various available breeding tools viz. through spontaneous mutation, classical breeding, chromosome manipulation and induced mutation (Banerji 2007, 2008, Banerji and Datta 1986, 1988, 1993, 1996, Banerji et al., 1987, Data and Banerji 1990, 1994a,b, Datta 1992b, 2004, Nath et al., 1983, Ohri 1995, Sharma 1996, Zadoo et al., 1975b, Jayanti et al., 2007, Roy et al., 2015).

World trade of fresh cut flower is increasing day by day. Fresh flowers lose their freshness and quality both during travel and also during and after arrangements due to flower specific short vase life. Such deficiencies can be ameliorated through application of nutrient additives to vase water. Use of preservative solutions has been known for many years to increase the vase life of cut flowers. Different methods like use of holding, pulsing and bud opening solution, growth regulators, gamma irradiation, pre-cooling, cold storage, packaging etc. are already in practice in the flower trade to ensure the garden fresh quality of flowers to consumers (Singh et al., 2001). The floral business is expanding in a big way, nationwide.  Sales of cut flowers are rising faster through retailers as every state has entered into development of supermarket chains. Cut flower sale through retailers is  a booming business. Retail growers and Wholesale growers are the major players in our country for domestic market. Retail market suffers from logistic bottlenecks. Retailers do not have any background scientific knowledge to increase the vase life of cut flowers. Flower buyers are very choosy and prefer quality bloom with longer vase life.

Floriculture has become very important industry as a result of science based techniques and steady supply of improved plant materials. One of the major constraints of floriculture industry is non availability of large scale quality planting materials. Conventional methods of propagation can not meet the increasing demand of propagating materials. Micropropagation is perhaps the most widely used biotechnology tool for large scale propagation of floricultural crops. This economic proposition has led to intensive practical research to evolve tissue culture techniques for mass propagation and production of virus-free plant material.  Since most of the ornamental crops are highly heterozygous, their seed progeny is not true-to-type. Conventionally in these plants vegetative reproduction method is followed to produce genetically identical plants at commercial scale. But the main constrain of this method is that only a limited number of plants can be raised in a year from a single mother plant and often fail to meet the market demand. Therefore, most of the modern floriculturists follow the micropropagation technique for rapid multiplication of ornamental plants.

Considering the economic importance of chlorophyll variegation in floriculture trade attempt was made for cytological, anatomical and biochemical analysis of chlorophyll variegated mutants for better and clear understanding of origin of chlorophyll variegation (Kirk and Tilney-Bassett 1967, Datta et al. 1995). Following chlorophyll variegated mutants and their respective original varieties were analysed –

‘Los Banos Beauty’ (LBB) : Original double bracted Bougainvillea with green leaf.

For crop improvement and more specifically to develop new varieties a number of plant breeding methods are available. CSIR-NBRI from very beginning selected all available techniques and standardized their practical application for all ornamental crops. All crop specific basic information was collected/generated for successful application of techniques for development of new varieties by creating genetic variability. Ornamental plant species fall into two main categories. In the first group the plants that are capable of sexual reproduction, but are commercially propagated vegetatively. The second group of plant species are the apomicts. In obligate apomicts hybridization fails to generate any variability. For development of new variety creation of genetic variability is pre-requisite. Breeder should have all up-to-date knowledge about all the available techniques and their merits and demerits for improvement and development of new varieties.