Sem. VI, Paper XV METHODS OF PLANT BREEDING Asso. Prof. Seema Gaikwad Dept. of Botany Vidnyan Mahavidyalaya, Sangola

1. PLANT INTRODUCTION It is a process of introducing new plants with desirable characters from their area of origin to a new area is called plant introduction. Taking a genotype or a group of genotypes in to a new place or environment where they were not grown previously. This process is very fast and easy method of breeding. If the plant if brought from foreign country than it is called exotic plant and if it is from the same country then it is called as indigenous plant. Plant introduction are usually done by cuttings or seeds.

PLANT INTRODUCTION Plant introduction may be of two types. 1. Primary Introduction and 2. Secondary Introduction 1. Primary Introduction - When the introduced crop or variety is well suited to the new environment, it is directly grown or cultivated without any alteration in the original genotype. This is known as primary introduction. E.g. IR. 8, IR 20, IR 34, IR 50 rice varieties; oil palm varieties introduced from Malaysia and Mashuri rice from Malaysia. 2. Secondary Introduction- The introduced variety may be subjected to selection to isolate a superior variety or it may be used in hybridization programme to transfer some useful traits. This is known as secondary Introduction.E.g. In soybean EC 39821 introduced from Taiwan is subjected to selection and variety Co 1 was developed. In rice ASD 4 is crossed with IR 20 to get Co 44 which is suited for late planting.

Objectives of Plant Introduction To introduce new plant species there by creating ways to build up new industries. E.g. Oil palm To introduce high yielding varieties to increase food production. E.g. Rice and wheat. To enrich the germplasm collection. E.g. Sorghum, Groundnut. To get new sources of resistance against both biotic and abiotic stresses.

Merits of plant introduction It provides new crop varieties, which are high yielding and can be used directly It provides new plant species. Provides parent materials for genetic improvement of economic crops. Enriching the existing germplasm and increasing the variability. Introduction may protect certain plant species in to newer area will save them from diseases. E.g. Coffee and Rubber.

Demerits of plant introduction Introduction of new weed unknowingly.E.g. Argemone mexicana, Eichornia and Parthenium Introduction of new diseases: Late blight of potato from Europe and Bunchy top of banana from Sri Lanka. New pests: Potato tuber moth came from Italy Ornamentals becoming weeds: Lantana camara Introduction may cause ecological imbalance E.g. Eucalyptus.

2. ACCLIMATIZATION Adjustment of plants to new or changed environment is called acclimatization. When superior cultivars from neighboring or distant regions are introduced in a new area, they generally fail initially to produce a phenotypic expression similar to that in their place of origin. But later on they pickup and give optimal phenotypic performance, in other words they become acclimatized to the new ecological sphere. Thus acclimatization is the ability of crop variety to become adapted to new climatic and edaphic conditions. The process of acclimatization follows an increase in the frequency of those genotypes that are better adapted to the new environment. The success of acclimatization depends upon two factors i) Place effect ii) Selection of new genotypes.

3) SELECTION It is the oldest method of breeding process.It involves picking up of better ones from the entire crop plants. TYPES OF SELECTION: a) MASS SELECTION: It is the simplest method followed by the farmers to improve mainly local varieties of crops.Before harvesting the crops,best looking and healthy plants are selected from the mass.seeds of these plants are collected and sowed them to raise new generation. Mass selection is based on external character.

3) SELECTION b) PURELINE SELECTION: A pureline is progeny obtained from a single individual by self fertilisation. A group of plants obtained from a single self fertilized homologous plant is called pureline. It involves a desirable homologous individual from the mixed population and multiplying the same.Pureline selection is the only method of improvement of local varieties of self pollinated crops.The progeny of pureline selection are similar in phenotypical and genotypical character. c) CLONAL SELECTION: A clone is defined as a progeny of a single plant obtained by vegetative propagation.The clonal selection is concerned with the selection and propagation of best individual of clones from mixed population of vegatively propagated plant.

4) HYBRIDISATION The process of crossing two or more plants together to get offsprings of new desirable characters as result of genetic recombination is called Hybridisation. TYPES OF HYBRIDISATION: a) INTRASPECIFIC HYBRIDISATION; Crosses are made between two individuals of same species. This crosses are done to improve self pollinated crops producing homozygosity or pure offspring. b) INTERSPECIFIC HYBRIDISATION: Crosses are made between individual of different varieties of the same species. This crosses are made to improve self pollinated and certain cross pollinated crops.

TYPES OF HYBRIDISATION c) INTRAGENERIC HYBRIDISATION: Crosses are made between two individuals of different species belonging to same genera. It is used to produce resistance varieties from diseases ,frost or drought. d) INTERGENERIC HYBRIDISATION: Crosses are made between two individuals of different genera belonging to same family. It produces resistance varieties as well as desirable combination of all characters. Eg: Brassica X Raphanus=Raphanusbrassica

TECHNIQUES FOR HYBRIDISATION It is necessary for the breeder to have following information: a)Whether plants are self or cross pollinated. b) Whether plants are monoecious or dioecious. c) Whether the flowers are unisexual or Bisexual. d) Time of Anthesis.

PROCESS OF HYBRIDISATION a) SELECTION OF PARENTS: Male and female parents, with desirable characters are selected from the available materials. Both the parents should mature at the same time. b) EMASCULATION: Removal of anthers from bisexual flowers before they dehisces or shed their pollen is known as emasculation. It is done in order to prevent self fertilization. Emasculation is not necessary in the parents are monoecious.

PROCESS OF HYBRIDISATION c) BAGGING: After emasculation, flower buds are kept enclose in bags made up of cloths, plastic or polythene etc.It is done to prevent pollination through unknown pollen. d) CROSSING: it is an artificial pollination. Pollens are collected from the desirable male flowers. These collected pollens are then dusted on the stigmas of pistils. After crossing the female flowers are bagged again. e) LABELLING: The female parents are then labeled properly. The labeling should bear the following information. i) Serial number ii) Details of male parents and female parents. iii) Date of emasculation and crossing f) HARVESTING: At the end of the season, the fruits and seeds of each cross are separately collected. They are dried and preserved and then sowed to raise the F1 generation.

5) MUTATION BREEDING Mutation is define as a sudden change in hereditary of an organism. They may be due to changes in chromosome number(Polyploidy),changes in the structure of chromosome(chromosomal abbrevation) or changes in molecular level of DNA(gene mutation). Mutation may occur naturally or artificially, produced by exposing organism to mutagenic agents like X-rays, Gamma rays, ultraviolet rays, chemical like colchicines etc.

6) POLYPLOIDY BREEDING Polyploidy breeding involves use of polyploidy in crops improvement. In general the odd numbered polyploidy 3x,5x etc are sterile while even numbered polyploid are fertile. There are two main categories of polyploidy--- a) Autopolyploids (multiples of same genomes) b) Allopolyploids(multiples of different genome)

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