Cell wall is the most important physical barrier in protoplast fusion experiments. This can be overcome by treatment with enzymes like cellulase and pectinase which have the ability to digest the cell wall and liberate the naked protoplast surrounded only by the cell membrane.

Maize, wheat, rice, bathua, spinach, pulses have biofortified varieties. Maize hybrids have twice the amount of amino acids, fortified wheat variety has high protein content, fortified rice has high quantity of iron.

Consumption of such biofortified foods will enrich the nutritive value of our common foods and will vastly improve public health.

Instead of consuming different food items for obtaining different nutrients, if 2 or 3 nutrients can be incorporated into a single crop, it would offer enormous benefits to human beings and may even help to overcome several nutrient deficiency disorders latent in our country.

Plant breeding programmes are carried out in a systematic way world wide-in government institutions and commercial companies.

The main steps in breeding a new genetic variety of a crop are

(i) Collection of Variability Genetic variability is the root of any breeding programme. In many crops pre-existing genetic variability is available from wild relatives of the crop.

Collection and preservation of all the different wild varieties, species and relatives of the cultivated species (followed by their evaluation for their characteristics) is a pre-requisite for effective exploitation of natural genes available in the populations.

The entire collection (of plants/seeds) having all the diverse alleles for all genes in a given crop is called germplasm collection.

(ii) Evaluation and Selection of Parents The germplasm is evaluated so as to identify plants with desirable combination of 'characters. The selected plants are multiplied and used in the process of hybridisation. Purelines are created wherever desirable and possible.

(iii) Cross Hybridisation Among the Selected Parents The desired characters have very often to be combined from two different plants (parents), e.g., high protein quality of one parent may need to be combined with disease resistance from another parent.

This is possible by cross hybridising the two parents to produce hybrids that genetically combine the desired characters in one plant. This is a very time-consuming and tedious process since the pollen grains from the desirable plant chosen as male parent have to be collected and placed on the stigma of the flowers selected as female parent.

Also, it is not necessary that the hybrids do combine the desirable characters, usually only one in few hundred to a thousand crosses shows the desirable combination.

(iv) Selection and Testing of Superior Recombinants This step consists of selecting, among the progeny of the hybrids, those plants that have the desired character combination. The selection process is crucial to the success of the breeding objective and requires careful scientific evaluation of the progeny.

This step yields plants that are superior to both of the parents (very often more than one superior progeny plant may become available). These are self-pollinated for several generations till they reach a state of uniformity (homozygosity), so that the characters will not segregate in the progeny.

(v) Testing, Release and Commercialisation of New Cultivars The newly selected lines are evaluated for their yield and other agronomic traits of quality, disease resistance, etc.

This evaluation is done by growing these in the research fields and recording their performance under ideal fertiliser application, irrigation and other crop management practices.

The evaluation in research fields is followed by testing the materials in farmers' fields, for at least three growing seasons at several locations in the country, representing all the agroclimatic zones when the crop is usually grown.

The material is evaluated in comparison to the best available local crop. After evaluation the variety can be relased for the farmers.

(a) The shift from grain to meat diets creates more demand for cereals as it takes $3-10 \mathrm{~kg}$ of grain to produce 1 kg of meat by animal farming.

(b) This research is related to single cell protein.

Microbes are being grown on an industrial scale as a source of good protein. Microbes like Spirulina can be grown easily on materials like wastewater from potato processing plants (containing starch), straw, molasses, animal manure and even sewage, to produce large quantities and can serve as food rich in protein, minerals, fats, carbohydrate and vitamins.

Such utilisation also reduces the environmental pollution.

As traditional (conventional) breeding methods failed to keep pace with demand and to sufficiently provide fast and efficient systems for crop improvement, another technology called tissue culture developed.

The advantages of tissue culture over conventional breeding are as follows

(i) It can be used to produce large number of plantlets within a short period by micropropagation.

(ii) All cells in the culture are derived from a single explant by mitotic division, therefore all have the similar genotype and constitute a clone.

(iii) Tolerance to stress can be obtained by providing pollutants, toxins, salts, etc., in culture medium in increasing dosage. The surviving healthy cells are selected for raising resistant plants.

(iv) Virus free plantlets can be obtained by meristem culture.

(v) Embryos which do not survive inside seeds can be grown by tissue culture to form new plants.