Improvement in Food Production:
Food is one of the basic need which gives us energy for everything. It keeps us alive, strong and healthy.
Food can be defined as, “anything solid or liquid, which when swallowed, digested and assimilated in the body, keeping us well. It is organic, energy rich, non-poisonous, edible and nourishing substance.”
Green plants synthesize their own food through photosynthesis. But animals including humans cannot synthesize their food on their own, hence are directly dependent on plants.
The drought (famine) is responsible for shortage (dearth) of food, besides the rapid increase in world population over the time. To meet the increasing demand for food, there is need for improvement of food production, both quantity wise and quality wise (nutritive).
Plant breeding and animal breeding help us to increase the food production.
Plant breeding:
“The improvement in the heredity of crops and the production of new superior varieties of existing crop plants, constitute what is called plant breeding.”
1. Plant breeding is an applied branch of botany, in fact it is an art and the science of changing and improving the heredity of plants.
2. Plant breeding can be carried out by using the applications of principles of genetics, taxonomy, physiology, pathology, agriculture, rDNA technology, etc.
3. Plant breeding is a method of changing the genome of plants to increase their value and utility for human welfare.
4. The plant breeding is done to increase crop yield, improve quality, increase tolerance to environmental stresses, make the plants resistant to pathogens and increase tolerance to insect pest.
5. Green Revolution was the result of a sequence of scientific improvement and developmental activities that successfully drought hunger by increasing food production.
6. Seeds with superior quality, use of chemicals - pesticides and fertilizers, and multiple cropping system supported by the use of modern farm machinery and proper irrigation system, helped for the development of high-yielding and disease resistant varieties in wheat, rice, maize, etc.
7. The present-day crops are the result of domestication and acclimatization.
Aim of plant breeding-
1. Primary aim of plant breeding is to obtain a new crop variety superior to the existing type, in all characters.
2. This purposeful manipulation incorporates various objectives. which differ from plant to plant depending upon its type and the use.
3. Some objectives are common like yield, quality, resistance, life cycle span, etc.,
Hybridization and its technique:
1. It is the chief method with greater possibilities in the crop improvement than other methods.
2. The use of this method is the only effective means of combining together the desirable characters of two or more varieties.
3. By this method, one can create new genetic combinations of already existing characters and new genetic variations with hybrid-vigour.
4. “Hybridization can be intravarietal, intervarietal (between two varieties of the same species), interspecific (between two species of the same genus) and intergeneric (between two genera of the same family).”
5. As parental plants are distantly related, such crosses are also called wide/ distant crosses. Interspecific and intergeneric hybrids are seldom to occur in the nature.
6. The main steps of the plant breeding program (Hybridization) are as follows:
1. Collection of Variability:
a. Wild species and relatives of the cultivated species having desired traits, should be collected and preserved.
b. The entire collection having all the diverse alleles (i.e. variations) for all genes in a given crop, is called germplasm collection.
c. Variations are useful in the selection.
d. Germplasm conservation can be done in following ways-
i) In situ conservation: It can be done with the help of forests and Natural Reserves.
ii) Ex situ conservation: It is done through botanical gardens, seed banks, etc.
2. Evaluation and Selection of Parents:
a) The collected germplasm is evaluated (screened) to identify plants with desirable characters.
b) The selected parents must be healthy, vigorous and should show desirable but complementary features.
c) The selected parents are selfed for three to four generations to make them pure or homozygous.
d) It is made sure that only pure lines are selected, multiplied and used in the hybridization.
3. Hybridization:
a) The variety showing maximum desirable features is selected as female (recurrent) parent and the other one as male parent (donor) which lacks good characters found.
b) The pollen grains from anthers of male parent are collected and then artificially dusted over stigmas of emasculated flowers of female parent.
c) Pollination is followed by seed and fruit formation in due course.
d) The seed, thus obtained represents the hybrid generation.
e) The hybrid F1 progeny is selected and evaluated for the desired combinations of characters.
4. Selection and Testing of Superior Recombinants:
a) The F1 hybrid plants showing superiority over both the parents and having high hybrid-vigour, are selected.
b) Such hybrids are then selfed for few generations to make them homozygous for the said desirable characters till there is a state of uniformity, so that the characters will not segregate further.
5. Testing, Release and Commercialization of New Cultivars:
a) The newly selected lines are evaluated for the productivity and other features like disease resistance, pest resistance, quality, etc.
b) Initially, these plants are grown under controlled conditions of water, fertilizers, etc. and their performance is recorded.
c) The selected lines are then grown for three generations at least in natural field, in different agro-climatic zones.
d) Finally, variety is released as new variety for use by the farmers.
e) Many high yielding, hybrid varieties of rice, wheat, sugarcane, millets, developed through hybridization, have helped farmer community to attain record agricultural production in India since 1961. This is called green revolution.
