(i) The process is referred as bagging in plant hybridization.
(ii) It is done after emasculation to protect the contact of the stigma of the flower against any other pollen grain.

Plant breeding is a proposal manipulation of plant species in order to develop improved crop varieties with a higher yield, better quality, resistance to disease and quick maturation.

Green manuring helps to increase the content of nitrogen soil and also improves the structure and physical property of soil

(i) Bio pesticide - E.g. Trichoderma species
(ii) Green manure - E.g. Crotalaria juncea
(iv) Bio fertilizer - E.g. Azolla

(a) Anabaena azolla (blue green alga)
(b) Rhizobium
(c) Angiosperm roots

When chromosome number is doubled by itself in the same plant, is called Autopolyploidy. Example: A triploid condition in sugar beets, apples and pear has resulted in the increase in vigour and fruit size, large root size, large leaves, flower, more seeds and sugar content in them. It also resulted in seedless tomato, apple, watermelon and orange

In asexually propagated crop, progenies derived from a plant resemble in genetic constitution with the parent plant as they are mitotically divided. Based on their phenotypic appearance, clonal selection is employed to select improved variety from a mixed population (clones). The selected plants are multiplied through vegetative propagation to give rise to a clone. The genotype of a clone remains unchanged for a long period of time.

i) To increase yield, vigour, and fertility of the crop.
ii) To increase tolerance to environmental condition, salinity, temperature, and drought.
iii) To prevent the premature falling of buds and fruits, etc.
iv) To improve synchronous maturity.
v) To develop resistance to pathogens and pests.
vi) To develop photosensitive and thermos-sensitive varieties.

Green manuring is defined as the growing of green manure crops and use of these crops directly in the field by ploughing. One of the main objectives of the green manuring is to increase the content of nitrogen in the soil. Also, it helps in improving the structure and physical properties of the soil. The most important green manure crops are Crotalaria juncea, Tephrosia purpurea, and Indigofera tinctoria.

Trichoderma species are free-living fungi that are common in soil and root ecosystem. They have been recognized as bio-control agent for
(1) the control of plant disease
(2) ability to enhance root growth development
(3) crop productivity
(4) resistance to abiotic stress and
(5) uptake and use of nutrients.

i) Arbuscular mycorrhizae have the ability to dissolve the phosphate found in soil.
ii) Provides resistance against diseases, germs, and unfavorable weather conditions.
iii) It assures water availability.

Azolla is a free-floating water fern that fixes the atmospheric nitrogen in association with nitrogen fixing blue green alga Anabaena azolla. It is used as a bio-fertilizer for wetland rice cultivation and is known to contribute 40 - 60 kg/ha/crop. The agronomic potential of azolla is quite significant particularly for increasing the yield of rice crop, as it quickly decompose in soil.

Bio-fertilizers containing rhizobium bacteria are called rhizobium bio-fertilizer culture. Symbiotic bacteria that reside inside the root nodules convert the atmospheric nitrogen into a bio available form to the plants. This nitrogen-fixing bacterium when applied to the soil undergoes multiplication in billions and fixes the atmospheric nitrogen in the soil. Rhizobium is best suited for the paddy fields which increase the yield by 15 - 40%.

(a) Dr. M.S. Swaminathan
(b) C.T. Patel
(c) Dr. B.P. Pal

China, India, South America, Mediterranean, Mesoamerica and South East Asia.