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Domestication of Plant

APPLICATION OF PLANTLETS PRODUCED BY PLANT TISSUE CULTURE

(I) Rapid clonal propagation of superior lines Þ e.g. oil palm 

•  Clone : Group of individuals or cells derived from a single individual or cell by asexual reproduction.

•  Multiplication of genetically identical copies of a cultivar by asexual reproduction is called clonal propagation or cloning or micro propagation. 

•  All the cells in culture are derived from a single explant by mitotic division, so all plantlets regenerate from a culture generally, have the same genotype and constitute a clone. These plantlets can be used for rapid clonal propagation of superior lines like oil palm.

Two common types of micropropagation are :-

(a) Multiple shootlet production : 

(b) Somatic embryogenesis :-

(II) Somaclonal variation :-

•  Genetic variation presents among plants regenerated from tissue culture have been termed as somaclonal variation. 

•  These variations originated by minor chromosomal aberration, by gene mutation.

•  The variation which are stable and have agronomic characters like resistance to diseases and pests, stress to tolerance, early maturation, better yields are useful only.

•  By somaclonal variations many useful varieties are developed.

•  Rusts resistance in wheat.

•  Resistance for Tungro virus and leaf hopper in rice.

•  Resistance for late blight in potato.

•  High protein content in potato.

•  Shortening of harvest duration in sugarcane.

(III) To produce transgenic plants :

CYBRID

Cybrids possess a nuclear genome from only one parent but cytoplasmic genes from both parents. The process of protoplast fusion resulting in the development of cybrid is known as cybridisation/cytoplasmic hybrids.

Formation of cybrids :– 2 methods

(i) By fusion of nucleated protoplast of one parent to nucleated protoplast of another protoplast.

(ii) By elimination of one nucleus from heterokaryon.

Use of Cybrids :– In plant cell some genetic factors are also present in cytoplasm. During cybridisation these factors fused together and perform cytoplasmic inheritance. eg.:- 

(i) Streptomycin resistant gene is transfer from Nicotiana tabacum to N. silvestrise.

(ii) Gene of male sterility is transferred in Nicotiana, Brassica and Petunia from one–another

PLANT DISEASE & THEIR CONTROL

Disease :– 

•  An abnormal development of plant caused by either an abiotic or a biotic factor of the environment.

•  The development of disease and perpetuation of pathogens occurs through a series of events–

(i) Pathogen comes in contact with its host.

(ii) Now it enters into the host tissue by wounds, natural openings or by direct penetration.

(iii) The pathogen multiplies and spreads in the host tissues.

(iv) Pathogen then reproduces and the new individuals so produced spread to new host plants.

(v) At last the pathogen must survive by some mechanism through that period of year when the host plants are absent, so that it is able to infect the host plant again during the next crop season.

Plant pathology :– The branch which deals with study of plant diseases.

Pathogen :– The causal agent of a disease.

PLANT DISEASE CAUSED BY FUNGI

Obligate parasite fungi :– Fungi which can grow and multiply only in association with their specific host plant.

Facultative parasite fungi – Which can grow and multiply on dead organic matter as well as on living host plants.

Spreading – In form of spores by air, water, bird, insects, other animals and humans. Fungal pathogens enter their hosts by direct penetration or through natural opening or through wounds.

Symptoms – Necrosis, stunting, pustules, wilting 

Control – Use of resistant varieties, destruction of infected plants parts and crop residues, use of chemicals and bio-pesticides.

Eg. –– Ascochyta leaf blight of chickpea by Ascochyta rabiei.

Fusarium wilt of pigeon pea by Fusarium Udum (arhar) PLANT DISEASE CAUSED BY BACTERIA

Pathogen –Plant pathogenic bacteria develop mostly in host tissues. Number of some pathogenic bacteria decline only gradually when they are released in soil, but some bacteria can survive as saprophytes only in the dead host tissue for a long time.

Spreading – By water, insects, animals and humans some bacteria persist in insects and depend on them for their spreading.

Bacteria enter plants mainly through wounds and sometimes through natural opening.

Symptoms –Necrosis, stunting, wilting excessive growth of tissues.

Control – Use of resistant varieties, use of pathogen free seeds, chemicals, pesticides etc.

Eg. –– Bacterial blight of chickpea by Xanthomonas species.

PLANT DISEASE CAUSED BY VIRUSES

Pathogen –Mostly plant virus contain single stranded RNA.

Spreading – Viruses enter plant cells only through wounds either made mechanically or by vectors (in most cases). Normally virus finally reach phloem and transported to long distances within the plant.

Spreading of virus from one plant to another plant occurs as follows :–

(i) Through vegetative propagules

(ii) Mechanically through sap of infected plant

(iii) Through seeds, pollens

(vi) By insect vectors, birds, nematodes and fungi

Symptoms –Stunting, light–green, yellow or white spots (mosaics) on leaves, flowers, fruits and stem.

Control – 

•  Use of resistant varieties

•  Use of pathogen free plant

•  Control of insect vectors

•  No chemical control is available for viral diseases.

Eg. – Increased proliferation in chickpea by cucumber mosaic virus.

PLANT DISEASE CAUSED BY NEMATODES

Pathogen –Nematodes are worm like pathogen. All plant pathogenic nematodes spend some part of their life in soil.

Spreading – By water, animal feet, farm equipment, birds, human, dust storms, soil.

Symptoms –Firstly the punctured cell wall inject saliva into the cell and withdraw part of cell contents. Mostly damage seems to be caused by the saliva injected into the cells. Main symptoms of nematode disease are root knots or root galls, root lesions, excessive root branching, reduced growth of shoot, yellowing.

Control 

•  Use of resistant varieties

• Use of pathogen free plant

• Control of insect vectors

• No chemical control is available for viral diseases.

Eg. – Increased proliferation in chickpea by cucumber mosaic virus.

PLANT DISEASE CAUSED BY NEMATODES
Pathogen –Nematodes are worm like pathogen. All plant pathogenic nematodes spend some part of their life in soil.
Spreading – By water, animal feet, farm equipment, birds, human, dust storms, soil.
Symptoms –Firstly the punctured cell wall inject saliva into the cell and withdraw part of cell contents. Mostly damage seems to be caused by the saliva injected into the cells. Main symptoms of nematode disease are root knots or root galls, root lesions, excessive root branching, reduced growth of shoot, yellowing.
Control –Use of resistant varieties, disease free seeds, chemical, flooding of the field.
Eg. – Root knot of brinjal by Meloidogyne incognita.

SPECIAL POINT
Necrosis –Necrosis means death of cells, tissue and organs has occurred as a result of the parasitic activity.
Stunting – Dwarfing of a plant/plant part due to infection of pathogen.
Mosaic – Light green or yellow spots on infected plant organ.
Wilting – Drying or wilting of the entire plant. The leaves and other green or succulent parts lose their turgidity, become flaccid and dropped.
Galls –Long, round/irregular shaped malformations. Small galls are called wart or tubercle large galls are called knot or excrescences.
Canker –It is a dead area in the bark or cortex of the stem, specially in woody plants. It is a type of necrosis.
Blight –This term means the burnt appearance. The dead organ turns brown or black. It is a type of necrosis.

• Recorded evidence of plant breeding dates back to 9000 – 11000 years ago.

• Agriculture accounts for approximately 33% of India's GDP and employs nearly 62 percent of the population.

• The conventional method of breeding for disease resistance is that of hybridization and selection.

• In mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutation.

• Resistance to yellow mosaic virus in bhindi (Abelmoschus esculentus) was transferred from a variety of "Parbhani Kranti".

• High aspartic acid, low nitrogen and sugar content in maize leads to resistance to "Maize stem borers"

• Biofortification : Breeding crops with higher levels of vitamin, minerals, protein and healthier fats for improving public health.

• Rice has maximum genetic diversity in India (approximately – 20000 varieties)

• Sustainable agriculture : Any type of farming practice that helps protect the environment by conserving water and energy and by limiting the use of synthetic pesticides and fertilizer.

• Monoculture farming : The continuous growing of a single species of an agriculture crop of commercial value.

ECONOMIC BOTANY
The primary needs of human life are food, clothing and shelter, which are supplied by nature particularly plants. Plants yield drugs, wood, fibres, oils, latex, spices, masticatories, beverages, gums, tannins, dyesetc. Such plants may be classified as follows -
 

CEREALS
These are the members of family Gramineae and grown for their edible seeds. They are characterised by the presence of caryopsis a type of fruit in, which seed wall becomes fused with the ovary to form the husk. The true cereals are the following –

(1) Wheat(Triticum aestivum) :- Wheat is the chief cereal used by man as food from ancient times. It is an annual grass and the inflorescence is a terminal spike consisting of 15-20 spikelets. In India its cultivation is confined to north-west regions. The important varieties of wheat, grown in India are Sonalika, Sharbati Sonara, Lerma Roja, Sonara 64 etc.; Triticale hexaploides a man made variety is also cultivated; wheat is used mostly for human consumption; the flour is chiefly used for making bread, biscuits etc.: wheat straw is used in packing and as fodder.

(2) Maize(Zea mays) :-  It is the second important cereal crop. Maize is a tall annual grass with height of 4 to 10 feet; plants are monoecious. In India common varieties grown are Sona, Vijay, Jawahar, Amber etc. The maize grains are very nutritious; they contain high percentage of easily digestible carbohydrates, proteins and fats; the grains are also used in the manufacture of corn starch, glucose and alcohol; also used as a chief food for livestock; the fibre from stem and spathe is used in paper industry.

(3) Rice(Oryza sativa)- Rice is the principal food crop of millions of peoples of the world. The rice plant is an annual grass having a height of 2-4 feet and produces a panicle, an inflorescence consisting of a number of fine branches; it grows best on damp soils, where it can be flooded. The rice grains are used as a food after cooking; stem, husk etc. are used as fodder; grain is also used in the manufacture of alcoholic beverages.

(4) Sorghum(Sorghum vulgare) :- Sorghum is staple food for millions of peoples in Asia and Africa. It is a tall annual plant with a height of 6-12 feet; the stem is stout and the panicle much-branched. The grains are made into flour often mixed with wheat, forming a nutritious food. The plants are used as fodder, in the manufacture of brushes, syrup and also in the paper industry.

(5) Barley(Hordeum vulgare) :- Barley is an annual plant with a height of 3 feet. The inflorescence is a spike; the grains may be white, purple of red and are covered with husk. Barley is used in the preparation of bread, cakes after mixing it with wheat flour; straw is used as a livestock feed; also used as a source of malt, used in the manufacture of beer, whisky, alcohol etc.

(6) Pearl millet or Bajra(Pennisetum typhoides) :- It is cultivated almost throughout India. The plants attains a height from 6-12 feet and the dark-brown spikes, 15-25 cm in length occur in clusters. It is an important food for poor people in our country; the flour is used for making chapatis; the plants are also used as fodder.

PULSES
These are the members of family Leguminosae which is characterised by a type of fruit i.e. legume. Legumes or pulses are highly proteinaceous; they form excellent green manures as they are having root- nodules for nitrogen fixation. Some of the important pulses are as follows :-

(1) Pea(Pisum sativum) :- It is grown all over India during winter months. The plant is an annual herb climbing by means of tendrils. The seeds are eaten after cooking as vegetable; plants are used as valuable fodder.

(2) Gram(Chana)(Cicer arietinum) :- It is cultivated all over India as an important pulse. The plant is a bushy annual and matures in about three months. The seeds are eaten as dal and the flour which is commonly called as besan is used in the preparation of sweets and other foodstuffs; the plants and seeds are also used as cattle feed.

(3) Pigeon pea or red gram(Arhar)(Cajanus cajan) :- It is widely cultivated in India and is grown as a pure crop or mixed crop. The plant is a perennial shrub. Dry grains are used as dal; leaves form a valuable fodder; branches are used for making baskets.

(4) Ground nut (Moongphali) (Arachis hypogea) :- The plant is a bushy annual with underground fruits.
Groundnuts are very nutritious as they are rich is proteins. Seeds are used after roasting for preparation of peanut butter;groundnut oil is largely used as cooking oil.

(5) Black gram(Urd)(Phaseolus mungo) :- It is the one of the best pulses grown all over India. The plant is a trailing annual. It is used as Dal; flour is used in the preparation of papads and biscuits; seeds and straw form a valuable cattle feed.

(6) Soya-bean(Glycine max) :- The seeds of this plant are the protein richest, natural vegetable food known.
It is cultivated all over India. The plant is a small, bushy, erect of prostrate annual. It has 30-60% protein content. Seeds are used green or dry; soya milk, soya cheese etc. are prepared from the seeds; soyabean flour is used in bakery, icecream etc.

(7) Green gram (Moong) (Phaseolus aureus) :- It is cultivated as an important pulse crop in Uttar Pradesh, Madhya Pradesh, Rajasthan, Bihar and Bengal. The green pods are eaten as vegetable and seeds are used as dal. The entire plant is used as cattle feed.