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Jack bearing the largest edible fruit in the world, is a tropical evergreen tree belonging to the family Moraceae. Previously, it was known as Artocarpus integrifolia.It is an indigenous fruit crop, probably originated in Western Ghats of India (Santapau, 1966) and is widely cultivated in South Asia, East Indies and other warm areas of both the hemispheres. Jack tree is commonly grown in Burma, Malaysia and Brazil. It is hardly recognized as a commercial fruit crop in India even though it is widely distributed in Southern states viz,. Kerala, Tamil Nadu, Karnataka and Andra Pradesh. It is also cultivated in other states like Assam, Bihar, Orissa, Maharashtra and West Bengal. It is an invariable component of Kerala’s homesteads and also grown as a shade crop in coffee, arecanut and cardamom plantations. It is also grown as a standard crop in pepper plantations. The crop has got a rare distinction of being used as the staple food of Kerala tribals and also in some African countries like Uganda.

The mango is one of the choicest fruit crops of tropical and sub-tropical regions of the world. Its popularity and importance can easily be realized by the fact that it is referred as ‘King of fruits’ in the tropical world. India ranks first, both in area (2.51 million hectares) and production (15.02 million tonnes) of mango and it contributes to 42.1 per cent of world’s mango production. Presently, India is home to more than 1000 mango cultivars differing in taste, aroma, size, fibre content and pulp characteristics.

Though more than 1000 mango cultivars are reported, only 25-30 are of commercial importance. Most of the important cultivars are not amendable to hi-tech cultivation practices and do not meet the requirements of modern horticultural production systems like precocity in bearing, dwarfing, regularity in bearing with high yield, resistant to diseases, pests, physiological disorders and good keeping quality. Hence, breeding attempts to develop an ideal mango variety would be dwarf, regular bearer with medium size fruits (250-300g). Additionally, it should be highly tolerant to various fungal and bacterial diseases. A variety suitable for pickling is also gaining the attention of the breeders. An ideal pickling type should have high acidity, high fibre, good texture and characteristic raw mango flavour.

The first and foremost step in developing an ideotype is to explore the vast diversity and systematic characterization for utilization in the breeding programme.

Considering the importance of conserving the available gene pool, systematic exploration works are being carried out by National Institute like Indian Institutes of Horticultural Research (IIHR, Bangalore), National Bureau of Plant Genetic Resources (NBPGR, New Delhi) and others to collect and conserve the germplasm in Field Gene Banks. Recently, in addition to the traditional germplasm conservation methods, cryopreservation is also gaining importance especially in the conservation of nuclear gene (pollen parent) diversity for future breeding.

Utilizing the conserved germplasm in the breeding programme requires precise information on the genetic relationships within such germplasm. Information on the genetic distance among the germplasm accessions will also help to avoid the duplicates, widen the genetic base of the core collections and ultimately help in preserving the valuable diversity.

Pomegranate is one of the popular fruit crops of tropical and sub tropical in India and enjoys high reputation for its dietetic and medicinal properties. The fruit is native of Iran and is extensively cultivated in Mediterranean countries like Spain, Morocco, Egypt, Iran, Afghanistan. It is also grown to a lesser extent in Myanmar, China, Japan, India and U.S.A.

The area under pomegranate cultivation has increased several folds in the recent past after the introduction of soft seeded varieties. Out of 30,000 hectares under this crop in India, Maharashtra state alone grows over eighty per cent of area with an average production of 8000 kg ha^-1 (Mote et al.,1992). The export of pomegranate fruits was 1790.3 tonnes in 1991-92 valued at rupees 215.3 lakhs which was more than two fold over the previous year’s export earnings (Chadha, 1994). The utility of the crop is gaining importance and at present new orchards of pomegranate are being planted on large acreage. Because of its versatile adaptability, hard nature, low maintenance cost, steady and high yields, fine table and therapeutic values, better keeping quality and very good export potential, there is greater scope for extending its area and increasing the production especially in the hot and semi arid regions of India.

In pomegranate, market preference is for the attractiveness of the fruit which are exhibited through better size, colour with bold and deep coloured arils besides possessing high juice-content. However consumers prefers the softness of the arils with low acidity. While, there are number of cultivated types available with these desirable characters, there are hardly cultivar having a combination of all or atleast a majority of them. Pomegranate improvement work, therefore has to be oriented towards the production of soft seeded type with other desirable characters (Phadnis, 1974).

Rice (2n = 24) is an annual grass (family: Graminae) with terminal panicles bearing the grains. It originated in Asia between the fourth and fifth millennia B.C. A substantial portion of the people in south and Southeast Asia and the southern part of China are depending on rice as staple food (Chang, 1976). Rice is planted in the most diverse environmental conditions of any major food crop, from sea level to around 3000 m altitude and from 30°S to 49°N. Temperature and day lengths are therefore quite diverse in the rice growing areas. Rice is also grown under water regimes ranging from dry land to deepwater fields where water may reach 5 m depth. The wide geographical distribution of rice and its early history of cultivation have resulted in the development of a great diversity of varietal types (Vergara, 1985).

Rice has been used as food by man for over 10,000 years and has fed a great number of people for a longer period than has any other crop. “Rice is life” for almost four billion people of the world contributing over 20 per cent of the total caloric intake of human population (Chaudhary and Tran, 2001). Rice is cultivated in 113 countries and on all continents except Antarctica and it is the staple food for 17 countries in Asia and the pacific, eight countries in Africa, seven countries, in Latin America and the Caribbean and one in the near east (IRC, 2003).

Globally rice is grown in around 155 million ha occupying one tenth of arable land, with an annual production of 579 million tonnes of rough rice (Iiyas Ahmed, 2003). The average productivity of 3.89 t ha^-1 of rice provides a per capita. Consumption of 100 to 240 kg per year across the globe. Over 90 per cent of the world’s rice is produced and consumed in Asia and more than half of it from India and China exploiting maximum arable land. More than two billion people obtain their 80 per cent calorie from rice and its derived products from 90 per cent of world’s rice area (FAO, 1999). Rice based on production systems and their associated post harvest operations employ nearly a billion people in rural areas in developing countries (IRC, 2003).

In recent years, we are just experiencing marginal surplus production in cereals leading to self-sufficiency through green revolution. However, the shortage of production in edible oils has drawn the attention for the increased cultivation of oil seeds, and increased productivity per unit area to provide sustainable food and nutrition security (Swaminathan, 1989).

The importance of oil seeds cannot be over emphasized in the Indian economy. Oilseed occupied nearly 19 million hectares, next only to food grains, in 1986-1987. Yet, the domestic production in the country has lagged far behind the increasing demand for edible oils, necessitating a massive import of edible oils which lead to the drain of the valuable foreign exchange. The total import bill on edible oil has increased from 1.41 per cent in 1970-71 to 3.05 per cent in 1986-87. Even then, the annual per capita availability of edible oils registered only a nominal increased from 3.5 kg to 5.9 kg during the same period, against the nutritional norm of 14 kg (Suresh Pal, 1989). Due to the concerted efforts made through the ‘Technology Mission on Oilseeds’, oil seeds production reached a peak of 178.9 lakh tonnes during 1988-’89 in India (GOI, 1990a). This is an impressive achievement in Indian Agriculture, to reduce the bill on the import of edible oils from 4.11 per cent (1987-’88) to 2.58 per cent (1988-’89) (Gill, 1990). Further efforts in increasing oilseeds production definitely will go a long way in drastically reducing the present import bill.

Among the oilseed crop, sesame (Sesamum indicum L.), “The Queen of Oil Seeds”, is one of the important ancient and traditional crops occupying third position in terms of acreage on the oilseeds map of the country. It is commonly known as Gingelly, Til, Benniseed and Simsim. It is an important source of edible oil for the nutritional refugees of most part of the world, especially for India. The oil is rich in oleic and linoleic acid. In addition, it serves as a good source of proteins, vitamins and minerals (Nagaraj, 1990). Its high keeping quality deserves special mention.

Preternatural development of recombinant DNA technology has established genetic engineering in animals the most important field in application of biology for human benefit, from production of genetically modified animals to providing crucial technologies to medical science sector. On the basis of the nature of the target tissues, genetic engineering may target single cell line, particular tissue sectors or the organism as a whole. The purpose of transformation may be basic research involving elucidation of gene function, study effect of directed mutations, examination of physiological and developmental processes in animals or may be target oriented, such as production of proteins or metabolites in large quantities in a cell line, incorporating rDNA in the germline cells, gene therapy, use of rDNA in disease diagnostics, or production of transgenic animals for specific purposes.

The polymerase chain reaction (PCR) is a rapid way of amplifying (duplicating) specific DNA sequences

Method was devised by Kary Mullis of Cetus Corporation, Emeryville He recieved a $20,000 bonus and later a Nobel Prize

DNA heated to high temperature is not destroyed; separates into single strands, but reforms helix when cooled

PCR Method:

DNA to be amplified is put into solution containing:

Advances in molecular biology have sharpened the tools of the breeders, and brighten the prospects of confidence to serve the humanity. The application of biotechnology to field crop has already led to the field testing of genetically modified crop plants. Genetically engineered Rice, Maize, Soybean, Cotton, Oilseeds like Rape seed, Sugar Beet and Alfalfa cultivars are expected to be commercialized in the late of 20^th century. Genes from varied organisms may be expected to boost the performance of crops especially with regard to their resistance to biotic and abiotic stresses

Genetic engineering involves isolation of DNA fragments within a cell recombining them outside. The basic technique is quite simple. Two DNA molecules are isolated and cut into fragments by one or more specialized enzymes, the fragments joined together in a desired combination, then restored to a cell from replication and reproduction. This method also referred to as recombinant DNA technology. Genetic engineering developed in the mid 1970 when it becomes possible to cut DNA and to transfer particular pieces of DNA containing specific bits of information, from one type of organism into other.

Introduction

It refers to all activities designed to identify materials that cannot be used directly in breeding programmes, and further to transfer these traits to an intermediate set of materials that breeders can use further in producing new varieties for farmers. It is a bridge between Genetic Resources and Crop Improvement. That is collaboration between germplasm curator and plant breeder.

Crosses between adapted and exotic materials, where different proportions of introgression are obtained and evaluated, have been denominated as semi exotic materials. That should be readily used in regular breeding programme for cultivar development.

Objectives of pre-breeding 8-10 Years • Improved germplasm and associated genetic knowledge that enhance resistance expression and diversity.

• Reduce genetic uniformity in crops through the use of a wider pool of genetic material to increase yield, resistance to pests and diseases, and other quality traits.

• Identification of desirable traits/genes and their subsequent transfer into a suitable set of parents for further selection.

• Improved parental stocks which can be readily utilized within breeding programs and improved selection methodologies.

• Identify potentially useful genes in a well-organized and documented gene bank Designing strategies that lead to development of an improved germplasm that are ready to use in varietal development.

Phenotype is a result of gene products brought to expression in a given environment. Genes specify the structure of proteins. All known enzymes are proteins. Enzymes perform catalytic function, causing the splitting or union of various molecules. All of the chemical reactions which occur in the cell constitute the subject of intermediary metabolism. These reactions occur as stepwise conversions of one substance into another, each group being mediated by a specific enzyme. All of the steps which transform a precursor substance to its end product constitute a biosynthetic pathway. Several genes are usually required to specify the enzymes involved in even the simplest pathways. Before gene-enzyme relationship could be postulated, soon after rediscovery of Mendelian principles of inheritance, it was discovered that genes were not merely separate elements producing distinct individual effects, but they could interact with each other to produce completely novel phenotypes. The simplest example of gene interaction could be the fact that allele A could be characterized by phenotype A, and the allele B by the phenotype B and an organism having both alleles A and B at the same time might show phenotype C. The occurrence of such interactions means that the phenotype we observe is not present in the genes themselves but arises from a complicated developmental process resulting from a biosynthetic pathway as illustrated below (Stansfield, 1969)

Linkage and Crossing Over

Crossing over may produce recombinant phenotypes.

Bateson and Punnett discovered two traits that did not assort independently.

Morgan provided evidence for the linkage of several X-linked genes and proposed that crossing over between X chromosomes can occur.

A chi square analysis can be used to distinguish between linkage and independent assortment.

Creighton and McClintock correlated crossing over that produced new combinations of alleles with the exchange of homologous chromosomes.

Crossing over occasionally occurs during mitosis. Genetic Mapping in Plants and Animals

The frequency of recombination between two genes can be correlated with their map distance along a chromosome

Alfred Sturtevant used the frequency of crossing over in dihybrid crosses to produce the first genetic map.

Trihybrid crosses can be used to determine the order and distance between linked genes.

Interference can influence the number of double crossovers that occur in a short region.

Genetic Transfer and Mapping in Bacteria

Bacteria can transfer genetic material during conjugation

Hfr strains contain an f factor integrated into the bacterial chromosome

Conjugation experiments can be used to map genes along the E. coli chromosome

A detailed genetic map of the E. coli chromosome has been obtained from many conjugation studies

Bacteriophages can also transfer genetic material from one bacterial cell to another in the process of transduction

Cotransduction can be used to map genes that are within 2 minutes of each other

Bacteria can also transfer genetic material by transformation

Horizontal gene transfer is the transfer of genes among different species

International Board for Plant Genetic Resources (IBPGR) now known as International Plant Genetic Resources Institute (IPGRI) uses the following items in genetic resources documentation. 
    i)    Passport (accession identifiers and information recorded by collectors) 
    ii)    Characterization (consists of recording those characters which are highly heritable, can be easily seen by the eye and are expressed in all environments) 
    iii)    Preliminary evaluation (consists of recording a limited number of additional traits thought to be desirable by a consensus) of users of the particular crop
Characterization and preliminary evaluation will be the responsibility of the curators while further characterization and evaluation should be carried out by the plant breeders. The data from further evaluation should be fed to the curators who will maintain a data file.

Genetic Transfer and Mapping in Bacteria a

Bacteria can transfer genetic material during conjugation

Hfr strains contain an F factor integrated into the bacterial chromosome

Hfr strains can transfer a portion of the bacterial chromosome to recipient cells

Conjugation experiments can map genes along the E. coli chromosome

A genetic map of the E. coli chromosome has been obtained from many conjugation studies

Bacteria may contain different types of plasmids

Bacteriophages transfer genetic material from one bacterial cell to another via transduction

Cotransduction can be used to map genes that are within 2 minutes of each other

Bacteria can also transfer genetic material by transformation

Bacteria may acquire new genes by horizontal gene transfer

Any crop improvement programme primarily depends on the amount of genetic variability available and the extent to which the economic traits are heritable. A wide survey of genetic variability and a thorough understanding of the genetic makeup of the crop with the biometrial tools is very much indispensable for initiating an effective breeding programme.

Effectiveness in breeding programme depends upon three main factors viz., (i) the extent of genetic variation available, (ii) heritabiity of the variation and (iii) intensity of the selection pressure that can be applied. As most of the characters of economic importance and related characters which influence the performance of the economic character in a given set of environment are highly influenced by the environmental conditions, the heritable (genotypic) variation usually masked by non-heritable (environmental) variation and thereby creates difficulty in exercising the selection. Hence, it becomes necessary to partition the overall variability into heritable and non-heritable components to enable the breeders to plan for proper breeding programme.

The estimates of mean, variance and standard error are worked out by adopting the standard methods of Panse and Sukhatme (1961). Usually, randomized block design is the choice of the statistical design. Various genetic parameters are worked out from the mean squares. Assessment of genetic variation is usually made through the computation of genotypic variance and genotypic coefficient of variation. The proportion of the total genetic variance expressed as percentage of total phenotypic variance has been used as a measure of genetic variability of heritability in broad sense.

MENDEL’S RULES OF GENETICS DO NOT ALWAYS WORK

Mendel’s rules:

Segregation of alleles

Independent assortment of genes for different characters

Hold for characters:

Which have dominant & recessive traits

Determined by single genes

Genes are on separate chromosomes

Different types of chromosomes, or

Different homologues of same type of chromosome

These conditions are not always met, so there are many complications

A. Define / Explain the following

1. Mitosis: The multiplication of a body cell into two daughter cells of equal size and containing the same number of chromosomes as in the parent cell is called mitosis or somatic division.

2. Meiosis: Meiosis occurs only in gonads (in germ mother cells) during the formation of gametes like sperm and ovum. Meiosis is a process by means of which double number or 2N or diploid chromosomes is reduced to its half number or n or haploid. It is also called reduction process.

Genetics and Gene

Genetics is defined as the branch of biology dealing with heredity and variation. The hereditary units which are transmitted from one generation to the next are called genes. Genes have been defined in various ways. These are units of inheritance located in linear order on chromosomes. The genes are considered as hereditary determinants of a specific biological function located in a fixed place on the chromosome. Chemically, gene is a segment of DNA (deoxyribonucleic acid) encoding one polypeptide and defined operationally by the cis-trans or complementation test. Gene is the functional unit of inheritance (a sequence of DNA) which is located on a certain position (locus, plural loci) on a chromosome. The locus is sometimes used interchangeably for gene. DNA, in conjunction with a protein matrix, forms nucleoprotein and becomes organized into structures with distinctive staining properties which are known as chromosomes. The chromosomes are located in the nucleus of the cell. Since genes are located on the chromosomes, in many ways behavior of genes is parallel to the behavior of the chromosomes. Two or more alternative forms of a gene are called as alleles. All genes on a chromosome are said to be linked and they all belong to the same linkage group.

BACTERIA HAVE SMALL, COMPACT GENOMES

We now know the complete DNA sequences for about a dozen bacteria

Bacteria seem to need about 500 to 5000 genes to conduct their lives

Because they are small, bacterial genomes are highly organized

Most of the time there are only a few bases between the end of one gene and the beginning of the next

Few introns are found in bacteria

Bacteria contain accessory “chromosomes” called plasmids; each has only a few genes

Genetic Analysis of Diseases

A genetic basis for a human diseases may be suggested from a variety of observations

Inheritance patterns of human diseases may be determined via pedigree analysis

Many genetic disorders are heterogeneous

Genetic testing can identify many inherited human diseases

Prions are infectious particles that alter protein function posttranslationally