🧵 Botany of Cotton
Botanical description, floral biology, and breeding-relevant characters of cotton.
This lesson covers core principles and exam-focused points from this topic in plant breeding.
Cotton _ Gossypium _ sp. (2n=26, 52) Malvaceae
Cotton is the most ancient crop of the tropical and subtropical. It is one of the most
important items of export in the developing countries. Cotton fiber is unchallenged natural textile
fiber even today. The genus gossypium consists of diploid and tetraploid cultivated cotton.
Old world cotton or Desi cotton or diploid cotton 2n=26 are G. herbaceum
(uppam cotton) and G. arboreum (Karunkanni cotton)
New world cotton or American cotton or Tetraploid cotton 2n=52 are
G. hirsutum .(Combodia or upland cotton) and G. barbadense . (Sea Island cotton)
Cotton fiber is epidermal prolongation of seed coat cells. The longer out growth make
lint and the shorter one make fuzz. In diploid cotton and upland cotton both lint and fuzz are
present where as Sea island cotton ( G. barbadense ) only lint are present and such seeds are
called naked seed .
Structure of fiber
There are five different parts in a mature fiber. 1) The integument or outer layer is also
called cuticle or waxy layer . 2) Outer cellulose layer which is largely the original cell wall. 3)
Layers of secondary deposits. This is nearly pure cellulose. Numerous concentric layers in this
portion is recorded. 4) Walls of the lumen, a spiral structure surrounding the central cavity of the
fiber and more dense than any other part of the fiber. 5) Substance in lumen is structure less and
of a nitrogenous nature.
Jute - Corchorus capsularis, C. olitorius .(2n=14) Tiliaceae.
Jute is a leading crop among all bast fiber. (Stem fiber) plants. It is a typical plant of
humid tropics and subtropics. Jute is chiefly raised for the sake of its fiber, which develops in the
external part of the stem (in the bark). Individual fibrils are from 5 to 40 mm long. The surface of
the jute fiber is smooth and brown in color. Commercial jute fiber is obtained from two species
viz. Corchorus capsularis (white or bitter jute) and C. olitorius (Tossa jute). Mainly grown in W.
Bengal, Bangladesh.
Fiber extraction .
The ideal phase of harvest is when the plants are in small pods. Harvested plants are
bundled and staked for the withering of leaves. After 2 to 4 days the leaves shed and the bundles
are then steeped in water.
Steeping
It is a process of immersing the bundles in water. After 2 to 4 days the tissues and cells
rupture. This facilitates the entry of micro organism into stem.
Retting
It is a process by which harvested stems are steeped in water so that the fiber in the stem
get loosened and separated from the woody stalk due to the removal of protein, gums and other
mucilaginous substances by the micro organisms. Fiber yield is 6% of the fresh stem weight.
Fiber Quality
Jute fiber is fine and silky but less stronger then many other fiber.
Mesta Hibiscus cannabinus (2n = 36 ) Malvaceae
Mesta fiber is a valuable fiber probably next to jute. This crop is successfully grown
throughout tropics and subtropics. Bast fiber is obtained from the stem similar to jute.
Sun hemp. _ Crotalaria juncea _ . 2n=16 Fabaceae
Sunnhemp is another source of bast fiber, grown in tropical countries. It is also grown as
fodder and green manure. The fibers are stronger than jute but lighter in color and more enduring
than jute. They are long strands of fiber of about 4 to 5 feet in length and yellow to green in
color. Fiber is obtained by retting.
Sugars
(Sugar cane _ Saccharum officinarum _ (2n=80) Poaceae.)
Sugar cane is a perennial gigantic grassy plant of Poaceae family. It is extensively grown
in India, Cuba, Hawaii W.Indies.
There are 5 species of sugarcane of which three are cultivated and two are wild species.
- Saccharum officinarum . Noble cane (2n=80). Large barreled, low fiber, high sugar
content, susceptible to diseases and pests.
- S. barberi. Indian cane (2n=82-124) Intermediate between noble and wild canes.
Small barrel, internodes spindle shaped, high fiber content, resistant to diseases.
- S. sinense. Chinese cane (2n=118) Vigorous thin grassy form resistant to drought,
pest and diseases. Fair amount of sucrose content.
- S. spontaneum. Wild cane (2n=40-128). Vigorous than grassy form. Virtually no
sucrose, resistant to drought, pest and diseases.
- S. Robustum. Wild cane (2n=60-194) Thick stock low sugar content, disease
resistant.
The above 5 species are important for the improvement of sugar cane. They all inter cross
freely.
Inflorescense is panicle. It is also called Arrow.
Nobilization
Back crossing of F1 with S. officinarum ( noble cane)
Forage Crops
The term forages is used broadly to mean all the plant constituents that are eaten by
herbivores, including that are grazed ( pastures ) and those that are cut and fed such as fodder .
Crop residues such as straw and the foliage of trees and shrubs also fall within this broad
definition.
Fodders- Plants, which are, cultivated as forages crops and they are cut and fed to animals in
stalls.
Pastures- grasses and legumes are grown in pasture lands where the animals are led to graze.
Forages can broadly be classified into three groups. viz. grasses, legumes and non legumes.
Grasses. Annual grass – Maize, sorghum, and cumbu.
Perennial grass.— B.N. and N.B, hybrids.
Legumes Annual Cowpea, cluster bean.
Perennial Lucerne, Sirato, Desmanthus
Non legumes . – Fodder beet, Fodder radish.
Grasses
Napier grass - Pennisetum purpureum
It is a tall perennial grass forming very thick clumps, tillering is heavy. It comes up well
in both under tropical and temperate regions. It comes well in any soil condition and also
responds to sewage irrigation 6-8 harvests can be taken in a year. The grass withstands drought
for short spell and regenerate with rains.
Pearl millet Napier (Bajara - Napier)
They are very vigorous in their growth and adopted for varying climatic and soil
conditions. They give heavy yield higher than Napier. They are more nutritious, palatable,
succulent, juicy and less fibrous. They tiller profusely have luxuriant growth and responds to
higher level of nitrogen.
Guinea grass - Panicum maximum
It is the most popular grass with heavy tillering, forming big clumps with long
internodes, slender and glabrous. It comes up well in tropical condition with moist climates.
Under cultivation it can be grown in any soil. It requires sufficient moisture but cannot withstand
water logging. It responds to sewage irrigation. It can be harvested once in 25 to 30 days interval.
The crop can be allowed in the field for several years. Dry matter content is 15- 20% Protein 6
8% free from all toxic principles.
Buffel grass- Cenchrus ciliaris
It is an important perennial pasture grass and grows well in a great variety of soil and
climate. It is a perennial grass with underground rhizomes. They are hardy and drought resistant
and have quick regeneration capacity. It gives the highest forage yield among the grasses grown
under rainfed condition. Aerial branches tufted, leaf sheath compressed with hairs raceme of
spikes sessile spikelets, no lodicules.
Johnson grass- S. halapense
It is native of Africa. It was taken by colonel Johnson and hence named after him. In
South India it occurs both in 2n = 20 & 40 forms. Because of rhizomatous condition it will
spread easily. Co. 27 fodder cholam (Co 11 x S. halapense)
Legume Fodder
Lucerne / Alfalfa (Medicago sativa)
It is also called as queen of fodder or green gold . Lucerne is grown for pastuer, hay,
dehydrated meal and for medicinal purpose. It is an important leguminaceous fodder grown as a
perennial crop in drier regions and as an annual crop in hot humid regions. It is heat and drought
resistant.
Cow pea- Vigna unguiculata
It is the most important leguminous fodder crop during summer and rainy seasons
mainly due to its quick growing habit, high yielding ability and high protein content.
Desmodium- D. tortuosum / intortum is commonly known as green leaf desmodium, is a larges
trailing and climbing, perennial rooting at nods and having a deep tap root. It can be harvested 2
3 times . Shade tolerant green manure cum fodder produces profuse seeds.
Protein 22%. It is a tropical legume. It grows well in acid soils.
Stylosanthus guianensis
It is a summer growing perennial pasture fodder legumes. S.hamata found to thrive in
alkaline soils . S.fruiticosa is from India. It is an herb and small shrub. It thrives in light soils due
to its deep rooting system.
Tree fodder
Subabul- Leucaena leucocephala .
Among the browsing leguminous trees it lops the best. It provides economic nutritious
and highly palatable forage to livestock and poultry. It has an amino acid mimosin. Excess
feeding leads to fall of hairs, thyroids gland swelling and stunted growth. Pods can be fed to
cattle. Protein 29%.
Glyricidia sepium
It is a medium tall tree grown in tea coffee and coca plantation for shade. It is pruned for
green manure purpose.
Agathi / sithagathi - Sesbania gandiflora and S. sesban .
It is a fast growing and leaves are rich in protein and very much relished by all types of
livestock.
Erythin- Erythnina indica
Indian coral leaf is a nirogen fixing cumfodder green manure tree suited even to high acid
soil.
Green manure and green leaf manure
Green manure is generally a leguminous crop raised in a field and incorporated in situ.
E.g. Sunnhemp, daincha.
Green leaf manure
It is a practice of cutting and applying them to the fields and ploughing them e.g. Neem,
calotropis, glyricidia.
Sunnhemp . Crotalaria juncea. Erect herbaceous shrub. Cylindrical stem silky
appearance pods oblong inflated and hairy.
Sesbania speciosa. It was introduced from South Africa. It is a quick growing and attains
3-4m in about 4 months. The crop stands drought and to some extent salinity. The stem is
pithy but if allowed To grow for more than 4 or 5 months it becomes woody.
Daincha. ( Sesbania aculeata) It is aquick growing succulent crop which adpts itself to
varying conditions of soil amd clinmates. It can be grown even under adverse drought, water
logging condition and salinity.
Tephrosia pururea noctiflora . It is a perennial undershrub, growing wild in sandy or
gravellywaste places. It ia also grown as and annual crop for green manure
Neem . Azadirachta indica . Evergreen tree with plenty of foliage. Loppings once or twice
a year.
Pungam . Pongamia glabra . A leguminous ever green tree. Lopping is done once or twice a year.
Summary Cheat Sheet
Quick Recall Points
- This lesson focuses on key plant breeding concepts, terminology, and exam-relevant applications.
- Review major definitions, classifications, and method-wise distinctions from the sections above.
- Revise tables and examples from this lesson for fast pre-exam recall.
Exam Traps
- Do not confuse similarly named breeding methods without checking their core selection logic.
- Pay attention to crop-specific examples because the same principle can behave differently by species.
References
1 source • [1]
References
Standard Plant Breeding Class Notes (GPBR211)
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