Saturday, July 13, 2019

BOMBAY BLOOD GROUP


Bombay blood group is the rarest blood group and is reported in Bombay (Mumbai) in India.This blood group phenotype was first discovered by the Doctor YM Bhende in 1952. It is reported to occur in 1 out of every 250,000 people.In parts of India the incidence has been observed to be as much as 1 in every 7,600 people.
 Bombayblood group is also called the HH group. The special feature of this group is that they do not express the H antigen. H antigen act as a precursor to each of the ABO blood group antigens, apparently present in all people except those with the Bombay Blood phenotype. As a result they cannot form A antigens or B antigens on their red blood cells. Thus they can donate blood to anybody with ABO grouping but can receive blood only from Bombay blood group people.
In a person with blood group A, antigen of type 'A' and antibody of type 'B' is present in his/her blood. People with B have antigenB and antibody B in their blood. People with AB have both antigen A and B in their blood and no antibodies. People with O blood group have only antibodies A and B and no antigens.All these groups have an antigen H in the blood as well. There are very few people who do not have this antigen H in their blood. Instead they have antibody H because of which no other blood can be given to them
.

Blood Groups  (Antigens and Antibodies)
Blood Group           Antigens              Antibodies
A                                 A,H                        B

B                                  B,H                       A

AB                              A,B,H                    Nil

O                                   H                        A,B

Bombay Blood Group   Nil                    A,B,H


                        Antigens A and B of A, B and O blood phenotype are synthesized from a precursor mucopolysaccharide in the presence of the dominant allele of another pair designated as H and h. With genotypes HH or Hh the precursor is converted to an H antigen which, in turn, in the presence of IA and/or IB allele is partly converted to antigen A and/or antigen B. Gene h is termed amorph because it is producing no visible product. When the  genotype of a person is HH or Hh, A persons of group A produce antigens A andH, group B persons produce antigens B and H, and group AB persons produce antigens A, B and H. Group O persons produce only antigen H if they are of the genotype ii
The H gene appears to be necessary for the formation of A and B antigens It is very common 99.9% of all individuals have an HH or Hh genotype.The allele h is very rare and does not produce the L-Fucose transferase necessary for formation of the H-Structure.The genotype (hh) is extremely rare and is known as the Bombay Phenotype

Wednesday, June 12, 2019

Allelic and non-allelic gene interaction

The phenomenon of two or more genes affecting the expression of each other in different ways in the development of a single character of an organism is known as gene interaction.  In gene interaction, expression of one gene depends on the presence or absence of another gene.
Interaction of genes may be either allelic (interallelic or intragenic) or non-allelic (intergenic)
Allelic Interactions occur between the alleles of the same gene that are located in identical
loci on different homologous chromosomes. On the other hand, non-allelic interactions
take place between the alleles of different genes that are located at different loci on the same
or different chromosomes. Some common examples of gene interaction.
I. Allelic Interactions: Incomplete dominance, overdomi
nance, codominance, multiple allelism, lethal gene action, pleiotropy
II. Non-allelic interactlons: The action of complementary, supplementary, duplicate,
polymeric, masking, inhibitory and epistatic genes

Saturday, March 2, 2019

Pests of stored grains

1.Sitophilus oryzae
Commonly called the rice weevil. It is the commonest and the most destructive pest of stored grains, such as rice, maize, wheat, barley, bajara, etc. It enjoys worldwide distribution. Sitophilus oryzae is distinct from the allied species S.granarius. Both them are somewhat similar in appearance and size, and may be found together.
Adult weevils are somewhat cylindrical and reddish-brown or brownish-black, with prolonged thorax, head and snout or rostrum, chewing type of mouth-parts and ridged elytra.
Life cycle:
Their life span is 4-5 months. Most of the time they remain inside grains for feeding. But, mating usually takes place outside the grains. Soon after mating, female weevil makes pits or cavities in the kernel of the grain, deposits eggs in them at the rate of one egg in each cavity and seals their mouth with a plug of gelatinous secretion. A female may lay as many as 400eggs. In about 6 or 7 days, eggs hatch out into soft, white and legless grubs (larvae). They bore into Sitophilus the grains and actively feed on the interior of the grain, hollowing it out. After 3 or 4 weeks, larvae
change to pupae. Initially, pupae are dirty white. But, later on, they become dark-brow and curved. Pupal life lasts for 6-14 days. Adult weevils come out through irregular
holes made in the grain. The whole life cycle is completed inside the grain passing through a period of 4-7 weeks.
Damage caused
Sitophilus oryzae is  the most destructive of all grain pests. Its l adults and larvae feed on stored grains and damage the beyond use. Often, it causes almost complete destruction of grains in granaries, ships, storage bins, etc., especially during the mon- soon season. This accounts for considerable loss of food grains.
Control measures
1.Cleaning of godowns, store rooms, storage bins, bags, etc. to make them free from
2.Disinfection of stored grains by fumigation and also by dusting of BHC and other insecticides.
3. Periodic fumigation with methyl bromide, ethylene dibromide, ethylene dichloride.
4.Through drying  of grains before storage to reduce moisture contents.

2.Callasobruchus chinensis
Commonly called the pulse beetle, is a serious pest of grams, peas, sorghum, maize cotton seed. ete., both in field crops and stores.
Distribution
Enjoys wide distribution in India, Myanmar, China, Taiwan, Sri Lanka, Japan, Philippines and Indonesia.
Life cycle
Adult beetle is small and cylindrieal, with deflexed head and blunt anal end It is shining black or dark brown in colour Antennne are terminally club shaped
Breeding occurs from March to September Vemale lays as many as 300-400 cylindrical and glistening white eggs in 20-60 day after mating They are glued to the grains in batches, Larvae (grubs) hatch out in 5-9 days. Their body is long and constricted, and dirty white in colour. They crawl about and feed on the flour, or bore into slightly damaged grains and feed inside them. Larval life lasts for 22- 52 days Full-grown larvae are  and curved They pupate inside the grains, or in the grain flour Pupal stage lusts for neurly 7 days. Adults emerge from within the grains after makingrounded holes. There would be 5 or 6 generations in a year
Damage
Adults and larvne cause serious damages to pulses and grains
They bore into pulses and grains
and feed inside them making tunnels. This severely hollows out und damages pules and In heavy infestation, avconsiderable amount of frass is formed, which forms the food for the young larva- Often, the pest attacks leguminous pods in the field, before they are curied to storage godowns
Control measures
(i) Thoroughly dry grains and other food products before storage
(ii) Clean and disinfect godowns, flour mills, storage bins, bags, etc. before storing food products.
(iii) Destroy infested food products.
(iv) Treat food products with mild insecticides before storage
(v) Periodic fumigation with methyl bromide, ethylene dibromide, etc. to kill larva and adults.

Monday, February 25, 2019

Rhynchophorus ferrugineus

Rhynchophorus ferrugineus
The common red palm weevil. Adult weevil is reddish brown in colour. Its body is almost cylindrical, with long and slender snout, and six dark spots on the thorax.
Life cycle:
Life cycle is completed within the host plant itself. It involves indirect development and complete metamorphosis. Female lays eggs either in the scooped out pits, or in the holes, cuts and wounds in the palm. Within 2-5 Days yellow-coloured larvae (grubs)emerge. They feed on the soft tissues of the palm and grow in size. Larval life lasts for 40-80 days. Towards the end of it, larvae pupate within fibrous cocoons inside the palm.After 12-30 days of pupal life, pupae transform to adult weevils. Fully grown adults come out for mating
Damage
Rhynchophorus is a highly destructive and persistent pest of coconut palms. It infests the crown either by boring through the soft parts, or by entering through the holes and cuts already present. It infests the trunk by getting into the interior through holes cuts. Its larvae and adults feed on the palm tissues and make tunnels inside. In cases attack, the interior of the palm gets crowded with adults, larvae pupae of the weevil. This causes the drying of the central shoot leading to the and of severe and advanced and wilting and ultimate death of the palm. The presence of small holes in the stem from which chewed fibres protrude and a thick brown liquid oozes is a clear indication of infestation.
Control measures
(i)Injection of carbontetrachloride or the emulsion of pyrethrum, sevin, etc. through the holes into the interior of the palm to kill grubs, pupae and adults.
(ii) Fill the leaf axils of the crown with a mixture of BHC and sand.
(iii) Kill the grubs and pupae by stabbing with sharp iron spikes.
(iv) Burn off severely affected palms.
(v) Scoop out the infested portion and dress it with tar.
(vi) Restrict or avoid the practice of making cuts and injuries on palms.
(vii) Biological control by using the dipteran fly Cheliosoches mori which preys on the eggs and grubs of the palm weevil.

Rhynchophorus ferrugineus

Rhynchophorus ferrugineus
The common red palm weevil. Adult weevil is reddish brown in colour. Its body is almost cylindrical, with long and slender snout, and six dark spots on the thorax.
Life cycle:
Life cycle is completed within the host plant itself. It involves indirect development and complete metamorphosis. Female lays eggs either in the scooped out pits, or in the holes, cuts and wounds in the palm. Within 2-5 Days yellow-coloured larvae (grubs)emerge. They feed on the soft tissues of the palm and grow in size. Larval life lasts for 40-80 days. Towards the end of it, larvae pupate within fibrous cocoons inside the palm.After 12-30 days of pupal life, pupae transform to adult weevils. Fully grown adults come out for mating
Damage
Rhynchophorus is a highly destructive and persistent pest of coconut palms. It infests the crown either by boring through the soft parts, or by entering through the holes and cuts already present. It infests the trunk by getting into the interior through holes cuts. Its larvae and adults feed on the palm tissues and make tunnels inside. In cases attack, the interior of the palm gets crowded with adults, larvae pupae of the weevil. This causes the drying of the central shoot leading to the and of severe and advanced and wilting and ultimate death of the palm. The presence of small holes in the stem from which chewed fibres protrude and a thick brown liquid oozes is a clear indication of infestation.
Control measures
(i)Injection of carbontetrachloride or the emulsion of pyrethrum, sevin, etc. through the holes into the interior of the palm to kill grubs, pupae and adults.
(ii) Fill the leaf axils of the crown with a mixture of BHC and sand.
(iii) Kill the grubs and pupae by stabbing with sharp iron spikes.
(iv) Burn off severely affected palms.
(v) Scoop out the infested portion and dress it with tar.
(vi) Restrict or avoid the practice of making cuts and injuries on palms.
(vii) Biological control by using the dipteran fly Cheliosoches mori which preys on the eggs and grubs of the palm weevil.

Pulse beetle (Callosobruchus chinensis) 

Distribution
Taiwan, Sri Lanka, Japan, Philippines and Indonesia.
Adult beetle is small and cylindrieal, with deflexed head and blunt anal end It is shining black or dark brown in colour Antennne are terminally club shaped
Life cycle
Breeding occurs from March to September Vemale lays as many as 300-400 cylindrical and glistening white eggs in 20-60 day after mating They are glued to the grains in batches, Larvae (grubs) hatch out in 5-9 days. Their body is long and constricted, and dirty white in colour. They crawl about and feed on the flour, or bore into slightly damaged grains and feed inside them. Larval life lasts for 22- 52 days Full-grown larvae are  and curved They pupate inside the grains, or in the grain flour Pupal stage lusts for neurly 7 days. Adults emerge from within the grains after makingrounded holes. There would be 5 or 6 generations in a year
Damage
Adults and larvne cause serious damages to pulses and grains
They bore into pulses and grains
and feed inside them making tunnels. This severely hollows out und damages pules and In heavy infestation, avconsiderable amount of frass is formed, which forms the food for the young larva- Often, the pest attacks leguminous pods in the field, before they are curied to storage godowns
Control measures
(i) Thoroughly dry grains and other food products before storage
(ii) Clean and disinfect godowns, flour mills, storage bins, bags, etc. before storing food products.
(iii) Destroy infested food products.
(iv) Treat food products with mild insecticides before storage
(v) Periodic fumigation with methyl bromide, ethylene dibromide, etc. to kill larva and adults.

Oryctes rhinoceros

Oryctes rhinoceros
Commonly called the rhinoceros beetle or the coconutAdult beetle is deep-black or reddish-black and stout, with a prominent head process, called cephalic horn, long and pointed in male and short and stumpy in female. Fore wings are hard, thick and cuticular, and are not used in fight. They simply cover and protect the membranous hind-wings, and hence ure called elytra or tegmina (wing covers). Mouth-parts are of the biting and chewing type, specialised for feeding on the soft tissues of the host plant.
Life cycle:
Life cycle involves indirect development and complete metamorphosis. Female lays up to 140 oval and creamy white eggs in dung hills, manure pits, decaying vegetable matters, heaps of rubbish, etc. In about 8-20 days, soft, stout, sluggish and creamy white larvae (grubs) emerge. They feed on decaying organic matter and grow to full size. Larval life lasts for 3-6 months. Larvae construct earthern cells in deep soil and pupate inside them. Pupal life lasts up to one month or more. Then, pupae transform to adult beetles and come out of the soil and ly to coconut palms.
Damages
Oryctes is a persistent cocont pest (pest occurring all the ycar Eg round). Adult beetles cause heavy destruction to coconut palms. They live in between the leaf sheaths near the crown, bore deep into the unopened frond, feed on soft tissues and partially or completely de stroy the host palm. The damaged leaves show holes in the leaflets Frequent attack causes the stunting of the palm and the death of the growing point
Control measures
1.Remove decaying organic matter from coconut fields to prevent larval growth.
2.Kill eggs, grubs and pupae by periodic spraying of BHC, aldrin, chlordane, etc in manure pits, stored cattle dung, etc
3.Burn dead and decaying palms, which may serve as breeding places.
4. Take out and kill adult beetles using iron hooks and spike
5. Kill adult beetles by filling sand, mixed with curbaryl or BHC or aldrin or chlordane, in the leaf axils of the crown of coconut palms
6.Biological control by releasing the following enemies:
(a)Sarcophaga fiuscicauda and Pheropsophus hilaris which parasitise the grubs of Oryctes.
b. The beetles Santalus parallelus which preys upon the eggs and young larvae of Oryctes.
c. The bug Platyeris laevicollis is a predator of adult.

Monday, February 18, 2019

Rhynchophorus ferrugineus

Rhynchophorus ferrugineus
The common red palm weevil. Adult weevil is reddish
brown in colour. Its body is almost cylindrical, with long and slender snout, and sixdark spots on the thorax.
Life cycle is completed within the host plant itself. It involves indirect developmentand complete metamorphosis. Female lays eggs either in the scooped out pits, or in theholes, cuts and wounds in the palm. Within 2-5 days, yellow-coloured larvae (grubs)
emerge. They feed on the soft tissues of the palm and grow in size. Larval life lasts for40-80 days. Towards the end of it, larvae pupate within fibrous cocoons inside the palm.After 12-30 days of pupal life, pupae transform to adult weevils. Fully grown adults come out for mating
Damage
Rhynchophorus is a highly destructive and persistent pest of coconut palms. It infests the crown either by boring through the soft parts, or by entering through the holes and cuts already present. It infests the trunk by getting into the interior through holes
cuts. Its larvae and adults feed on the palm tissues and make tunnels inside. In cases attack, the interior of the palm gets crowded with adults, larvae pupae of the weevil. This causes the drying of the central shoot leading to thea nd of severe and advanced
and wilting and ultimate death of the palm. The presence of small holes in the stem from which chewed fibres protrude and a thick brown liquid oozes is a clear indication of
infestation.
Control measures
(i)Injection of carbontetrachloride or the emulsion of pyrethrum, sevin, etc. throught he holes into the interior of the palm to kill grubs, pupae and adults.
(ii) Fill the leaf axils of the crown with a mixture of BHC and sand.
(iii) Kill the grubs and pupae by stabbing with sharp iron spikes.
(iv) Burn off severely affected palms.
(v) Scoop out the infested portion and dress it with tar.
(vi) Restrict or avoid the practice of making cuts and injuries on palms.
(vii) Biological control by using the dipteran fly Cheliosoches mori which preys on thee ggs and grubs of the palm weevil.

Monday, October 15, 2018

CLASSIFICATION OF INSECTICIDES


CLASSIFICATION BASED ON MODE OF ENTRY: The way in which insecticides penetrate into an insect
From out side vary with the chemical nature of the insecticide.  Four major routes of entry in to an insect body have been recognized and accordingly insecticides are grouped under four major categories as follows.
1) CONTACT INSECTICIDES: These are highly toxic insecticides which have the ability to penetrate the body surface of insects on contact with it. After getting into the body of insects they interfere with its nervous system and kill it.
Eg:- DDT, HCH, Aldrin, Parathion, Nicotine.
2)STOMACH POISON:  These are chemicals which become toxic and fatal to the insect only when the insect ingests/eat them. From the gut they are absorbed to the tissues, interfere with the normal metabolism and kill the insect. They are basically compounds of Arsenic or fluorine.
3) FUMIGANTS: These are highly volatile insecticides, whose gases can produce a toxic cover around the insect. Fumigants are gases at normal temperature and pressure and hence they are stored in pressurized containers. They get into the insect body through spiracles. Fumigants are usually used to protect stored grains and other materials.
Eg:- Hydrogen cyanide, Methyl bromide, Ethylene dichloride, Ethylene dibromide, Lindane, Dichlorvos.
4) SYSTEMIC INSECTICIDES:  Systemic insecticide is a compound which can get absorbed to the sap stream of plants from stem, leaves, fruits and roots, generally it is through roots.  They move along the vascular system in an apical direction from the area of application. This may poison the insects that feed on the sap of these plants.
Eg:- Parathion,  Malathion, Diazinon, Lindane, Nicotine.   
The advantage of systemic insecticides are that (1) They need not be applied all over the plant body, (2)Action persists for long time,(3) No harmful effect on non-sap feeders and beneficial insects (4)They can be applied as direct foliar sprays or can be injected to the shoot system.         
CLASSIFICATION BASED ON APPLICATION: Based on the nature of their application, chemical pesticides can be grouped as the following categories.
1)ATTRACTANTS:  These are substances which can attract insects without contact. Synthetic chemical attractants are important in pest control. Both male and female insects will respond to them for feeding purpose, while only mature female insect will be attracted for egg-laying purpose.
2) REPELLENTS:  These are not successful in controlling plant pests, because a continuous emission is essential for effective protection. But chemical repellents are effective for personal protection from blood- sucking insects.
3)FEEDING DETERRENTS: These are chemicals which suppress the feeding instinct of insect pests. They influence the pests only after contacting them.
4) AUXILIARY SUBSTANCES:   These are substances that are mixed with insecticides to boost up its action.
CLASSIFICATION BASED ON CHEMICAL NATURE:
INORGANIC INSECTICIDES:  These are mainly made up of sulphur and mineral compounds. The common mineral compounds are the compounds of arsenic, copper, lead, mercury and fluorine. They are broad- spectrum poisons, which are highly toxic and essentially non-degradable. They can remain in the soil for log time and can cause permanent damage to most of the organisms.
Arsenic Compounds:- Lead arsenate, Calcium arsenate, White arsenic, Paris green.
Fluorine compounds:- These are primarily stomach poisons, and is soluble in the digestive juice of insects.               Eg:-Sodium fluoride, Sodium floroalumintate, Sodium fluorosilicate.
Sulphur:- Sulphur is mixed with

Insect Pest Management


PESTS: Pests are harmful species, whose population size or population density goes beyond the damage threshold level, either throughout the year or during specific seasons, adversely affecting the availability, quality and value of human resources.
NATURAL PEST CONTROL: This involves the operation of natural factors, without much human influence. Includes Climatic, Topographic and Biological Factors.
Climatic Factors:
a)  Temperature:  Temperature is the most effective and most important factor in insect control. Each insect requires an optimum range of temperature for each stage of its life cycle. If the temperature goes above or below the optimum range, it will have a damaging effect on insect population and even kill the insects.
b) Rain: Too much or too little rain fall can control the growth of insects. Eg:- Red hairy caterpillar of Cut worms has to burrow in to the soft soil for pupation and moderate rain enables this. Absence of rain makes the soil hard and caterpillar find it difficult to enter in to the soil for pupation.
c) Humidity:  High humidity helps the developments of certain fungi which attacks the insects and thereby control insect population.  Eg:- In Nilgiri area, during October to January,  when  humidity goes high, resulting  in the growth of a fungi, Cephalosporium lecanii  on Green Scale Insect of Coffee and controls it.
Topographic Factors:
Geographical barriers like large mountain ranges, large water bodies, vast deserts, dense forests etc limits or restrict the dispersal of insects. The nature of lakes and rivers like the larva of some insects survive only in stagnant or slow moving waters, while the larva of black flies and caddis flies live only in swift flowing streams.
Biological Factors:
For any insect there are natural enemies. They may be parasites or predators. Predators include other insects, mites, spiders, birds, reptiles, fishes and mammals. Parasites include insects, mites and disease causing viruses, bacteria and fungi. These keep the insect population in an optimal size. Birds are very effective in controlling insect population as they feed on grass hoppers, caterpillars, wood-boring insects and scale insects. Many larvivorous fishes feed on the larvae of insects.

CULTURAL  PEST CONTROL:
     Cultural pest control is the deliberate modification of agricultural practices so as to destroy the insect pests or to prevent them from destroying the crop. Pests are either locally eliminated or are reduced to well below the damage threshold level. This method is the cheapest of all control measures, has no toxicity and minimal harm to non targeted organisms. This include
a)  Crop Rotation: This is the practice of growing a different crop in a field every year in a 2-6 year cycle. It keeps the pest population from building up. This is most effective to control soil- inhabiting pests. If the same crop is grown continuously for many years, the pest of that crop will get a regular and continuous source of food and breeding sites, which will result in an uncontrolled increase of that pest. Eg:- A soya bean  Corn crop rotation is effective and economical against some weevils because the host plant  of the insect will be altered and  is deprived of food supply.
b) Trap Cropping or Companion Cropping:  In this method, small ‘trap plots (Plots where more susceptible or preferred crops are grown) are maintained near the major crop. Trap crop act as a trap’ and attracts the pest. After the pest had established on the host in the trap plot, the plot is either ploughed or treated with pesticide. Eg:- Castor plants are often planted near chilly cultivation and Tomatoes in Citrus orchards.
c) Mixed Cropping: In this method 2 or more crops are grown simultaneously in the same plot. Even if one crop suffers from pest attack, the others grow up well.
d) Tillage Operation:- Thorough ploughing helps to burry and kill soil  inhabiting insects and their eggs, larvae and pupae. This is also helpful in exposing hiding and hibernating stages of pests to hot sun, desiccation and bird predation.

MECHANICAL PEST CONTROL:
These are procedures by which pest species are trapped or killed by mechanical means, or are prevented from gaining access to the host plants by making barriers. It is very effective in the initial stages of infestation of some insect pests, such as aphids, jassids, scale insects etc. The commonly used mechanical pest control procedures are the following.
1) Killing of the eggs, Larvae and other inactive stages of pests by hand picking, net collection etc.
2) Collection and destruction of pests using Traps and Trenches like Cricket-traps, Light-traps, Suction- traps, Electric traps etc.
3) Sieving and winnowing for stored products.
4) Mechanical exclusion using barriers, which will prevent the pests from reaching the crop.
5) Destruction of affected plants and plant parts together with the pest.
6) Spiking of stem- borers in their bore holes.
7) Banding of fruit trees with grease or other banding materials to stop or entangle & kill crawling pests.
8) Shaking of trees & shrubs to dislodge and kill pests.
9) Flooding of the infested fields after harvest to kill the soil- inhabiting larvae, pupae, and adult pests.
10) Pest- proof packing of stored products.
11) Covering of fruits and vegetables.

PHYSICAL PEST CONTROL:
This involves the deliberate modification of some physical factors to slow down the growth or minimise or prevent pest infestation. They include,
a) Use of Drie- die:   Drie die is a material formed of highly porous silica gel. Its application causes the excessive loss of moisture from the body of insects, result in their death. This method is effectively used against the pests of stored grains in USA.
b) Use of high and low lethal temperatures:  High frequency radio waves generate a temperature of about 80*C and is used to kill granary weevils and flour beetles.
c) Use of ionizing radiations to kill insect pests or to induce sterility; male insects can be made sterile by exposing them to gamma radiation.
d) Blowing of refrigerated air through stored grains to maintain a very low temperature and to kill the pests.
e) Use of light traps to attract, catch and kill nocturnal insects.
f) Use of colour traps to attract, catch and kill some diurnal insects.

LEGAL OR REGULATORY PEST CONTROL:
Legal or legislative pest control is the control of pests through the enactment of laws and regulations. This prevents the entry of pest species from one country to another so that living things could not be freely imported or exported between countries. The legal measures, now in force in different countries are
1) Legislation for foreign quarantine to prevent the introduction of new pests, diseases and weeds from foreign countries.
2) Legislation for domestic quarantine to prevent the spread of established pests, diseases and weeds from one part of the country to another.
3) Legislation to ensure the application of effective control measures to prevent the damage by established pests, diseases and weeds.
4) Legislation to fix the permissible level of pesticide residues in food stuffs and also to prevent the adulteration and misbranding of pesticides.
5) Legislation to regulate pest- control activities and operations and also to regulate the applications of hazardous pesticides.
In India presently there are 2 kinds of regulatory measures for pest control. They are
1) Legislative measures through plant quarantine - This deals with the prevention of introduction of exotic pests and diseases in to the country and their spread from one state or union territory to another.
2) Legislative measures through State Agricultural Pests and Diseases Act.  This deals with the prevention of spread of pests and diseases in areas within a state or union territory.
CHEMCALCONTROL:
ORGANIC INSECTICIDES:  Organic insecticides are different types and are widely used in modern agricultural practices. The major categories are 1) Hydrocarbon oils, 2) Organic compounds of animal origin, 3) Organic compounds of plant origin, 4) Synthetic organic insecticides.
HYDROCARBON OILS:- These are the insecticides, formed of Hydrogen and Carbon. Mineral (petroleum) oils and coal tar are example. The insecticidal property of these oils is due to the presence of a heterogeneous mixture of cyclic and saturated as well as unsaturated hydrocarbons in them.
Hydrocarbon oils are widely used as insecticides mainly because they are cheap, have good spreading capacity, are less toxic to animals, are easy to mix, and insect develop no resistance against them. The disadvantages of hydrocarbon oils include, they are more toxic to plants and less toxic to insects, and are unstable to store. Often they damage the rubber parts of the spraying instruments.
ORGANIC INSECTICIDES OF ANIMAL ORIGIN:- There are only very few insecticides of animal origin. The most important of this type is the toxic substance extracted from the marine Annelids Lumbrineris heteropoda and Lumbrineris brevicirra. This extract is called Neristoxin (Dimethylamino dithiolane) and is very effective.
ORGANIC INSECTICIDES OF PLANT ORIGIN:- These are generally called botanicals . They are extracted from plants. The following are examples.
Nicotine :- Nicotine is the main alkaloid present in tobacco, is well known for its insecticidal property.  It is present in the leaves of Nicotiana tabacum. Nicotine is neurotoxic and it can enter into the body of insect pests through cuticle, spiracles and ingested food. It can be sprayed as a solution with soap, lime or ammonium hydroxide. The solution can be prepared by boiling 1 kg of tobacco waste in 10 litres of water for 30 minutes and then by diluting it into 30 litres and adding 90 gm of soap. This solution is an effective insecticide.
Pyrethroids:- Pyrethroids are extracts of the plant Chrysanthemum coccineum. The insecticidal property of pyrethroids is due to the presence of esters. The flowers of Chrysanthemum are powdered and a mixture of this power and talc or clay is used as an insecticidal dust. This is a contact poison. When this powder is dusted on a pest, it knocks down the pest immediately. Usage of increased concentration of this pesticide ensures the death of the pest and prevents recovery of the pest due to enzymatic degradation of pyrethroids. They have broad insecticidal property and low mammalian toxicity.
Rotenoids:-  Rotenone is a  compound present in the roots of plants Derris and Lonchocarpus. It was first extracted in 1848, and used against leaf-eating caterpillars.  Insects, poisoned with rotenone , show a decline in oxygen consumption, leading paralysis and death. On exposure to light and air, rotenone may get oxidized to a non-insecticidal compound.
Neem products:- The comounds extracted from Neem plant, Azadirachta indica are of high inscecticidal usage. From neem tree compounds such as Nimbecidine and from the kernels of neem tree Azadirachtin is extracted.
SYNTHETIC ORGANIC INSECTICIDES:-
These include organochlorines, organophosphorus compounds, carbamates, synthetic pyrethroids, insect growth regulators, organic thiocyanates and dinitrophenols.
Organochlorines :- They are also called Chlorinated hydrocarbons. They consists of an aliphatic or aromatic hydrocarbon nucleus and varying number of chlorine atoms attached to it. DDT, BHC (more correctly termed HCH- Hexachlorocyclic hexane.), Chlordane, Lindane, Heptachlor, Toxaphene, Aldrin, Dieldrin,Endrin, Endosulfan  are some of the examples.
Organochlorines are hard or persistent pesticides, because they are not easily bio-degradable. They persist in the soil up to 15 years, get biologically magnified and are stored in the fatty tissues of a variety of organisms. This causes severe problems with environmental contamination and residues in soil and harvested food products.
Chlorinated hydrocarbons are quick acting and highly toxic to most of the organisms. They are neurotoxins, which inhibit iron transport across nerve membrane and interfere with the transmission of nerve impulses. Some of them have hormone-like growth regulating properties. Most organochlorines act by contact, some by ingestion and others by vapour action. The toxicity to human beings varies with their kind and there is no effective remedy for mammalian poisoning.
DDT (dichloro diphenyl trichloro ethane) is the most important organochlorine compound. In India, the use of DDT in agriculture is banned. It was first synthesized by Othnar Zeidlar in 1874 and insecticidal properties were discovered by Paul Muller in 1934. DDT is a stomach poison and a contact insecticide of high persistence. It affects sense organs and nervous system. Many insects developed resistance to DDT due to irrational use.
Endosulfan is a chlorinated hydrocarbon and an organic sulphate. It was using since 1956 as an insecticide. It acts as a contact poison and also a stomach poison. It is effective against insects which sucks plant juice. Endosulfan is discussed widely now a days because of the toxicity caused to human beings and other organisms due to the over and irrational usage in the cashew plantations of Kasaragod District. Thousands of people are affected due to environmental contamination in soil, water and air and residues in soil and harvested food.
ORGANOPHOSPHORUS COMPOUNDS:- These are organic pesticides, with a invariable phosphorus- containing central core and variable remaining part. This group includes some of the most toxic insecticides such as parathion, malathion, diacinon, trithion, ethion, fenthion, dichlorvos, etc.
These are nerve poisons, extremely toxic to not only insects, but also to fishes, birds and mammals including human beings. They inhibit the action of choline esterase enzyme, which degrades the excess of the neurotransmitter and thereby prevents persistent post-synaptic depolarization. They are bio-degradable and hence are not persistent, which remain in the atmosphere only for few hours or days. Most of them are contact poisons, while demeton-S-methyl is systemic poison and dichlorvos is a fumigant.
CARBAMATES or URETHANES:- They are derivatives of carbamic acid and have a carbamic acid nucleus. They are inhibitors of choline esterase. Carbaryl (sevin), isolan, pyrolan, aldicarb (temik), aminocab (zeneb), carbosulfan, carbofuran (baygon), etc are examples.  Carbaates like carbaryl are less toxic , mostly used for horticultural purposes, while others are highly poisonous.
SYNTHETIC PYRETHROIDS:-   Synthetic pyrethriods can over come the draw backs of natural pyrethrum since they are more stable and more toxic and are effective against a wide range of insect pests. Eg:- Permethrin, Cypermethrin, Allethrin, Cyfluthrin, Fenvalerate.
INSECT GROWTH REGULATORS (IGRs) :-  These are chemicals with the properties of moulting and growth hormones of insects, and also with the potentiality to kill insects. They interfere with the action of insect growth hormone systems and thereby inhibit moulting and growth , eventually killing the insects. Eg:- Dimilin, Penfluron, Juvabione, Methoprene, Ecdysoid etc.

Wednesday, November 8, 2017

Properties of the genetic material

Genetic material is the substance that carries the biological information regarding the  structural, functional, developmental and behavioural properties of organisms. It also serves  as the agent that transfers or transmits biological information from parent to progeny. In most organisms, DNA is the genetic material. But, in some viruses, RNA serves as the  genetic material.
Properties of the genetic material                       
Some of properties are the following:
(i)Genetic material should be present in every cell.
(ii) Ability to store and transmit biological information in a stable form.
(iii) Ability to replicate with high fidelity to produce identical functional copies.
(iv) Ability to distribute its copies equally from parent cells to daughter cells with extreme  accuracy and minimal error.
(v) High physical and chemical stability to prevent the loss of information and also to  ensure genetic constancy in organisms.
(vi) Potentiality to generate variations (through mutation, recombination and minor errors in replication and distribution) in order to promote genetic diversity.
(vii) Ability to act and express itself for controlling the inheritance of characters specified by it.

Sunday, November 5, 2017

Experiments of Avery MacLeod and McCarthy

Griffith could not understand the cause of bacterial transformation and that is first of all identified by Oswald Avery, Colin MacLeod and Maclyn McCarty (1944). They partially purified the transforming principle from the cell extract (i.e., cell free extract of S-III bacteria) and demonstrated that it was DNA. These workers modified the known schemes for isolating DNA and prepared samples of DNA from S-III bacteria. They added this DNA to a live R bacterial culture; after a period of time they placed a sample of S-III containing R-II bacterial culture on an agar surface and allowed it to grow to form colonies. Some of the colonies (about 1 in 104) that grew were S-III typeTo show that this was a permanent genetic change, they dispersed many of the newly formed S-III colonies and placed them on a second agar surface. The resulting colonies were again S-III type. If an R-II colony arising from the original mixture was dispersed, only R-II bacteria grew in subsequent generations. Hence, the R-II colonies retained the R-II character, whereas the transformed S-III colonies bred true as S-III.Further, because S-III and R-II colonies differed by a polysaccharide coat around each S-III
bacterium, the ability of purified polysaccharide to transform was also tested, but no transformation
was observed.
Avery, MacLeod and McCarthy repeated Griffith's expts in vitro in a much refined way. Culture of live IIR cells produced typical IIR cell colonies, while a culture of heat-killed III s cell or a a culture of the DNA isolated from IIIS cells produced no colony. At the same time. of IIR cells, mixed either with heat-killed IIIS cells or with the DNA isolated from lllS on a medium containing antibodies for IIR cells (Ab IIR), produced some colonies of III s cells. AbIlR was used for inactivating some llR cells so that the number of IIR cells may not exceed the number of IIIS cells. These findings reveal that DNA can be the transforming Since DNA preparations often contain traces of RNA and proteins. this conclusion is not beyond doubt. In order to establish beyond doubt that DNA alone is the transforming principle, Avery and associates conducted two separate experiments, using the DNA isolated from lllS cells.In one of them, the DNA isolated from lllS cells was treated with the enzyme RNAse (to digest RNA if any), and in the other with the enzyme protease (to digest protein), before it was mixed with live llR cells. ln both these expts, some IllS cell colonies were fomied. This clearly shows  that RNA and Proteins are not responsible for the transformation of III R cells to lllS cells.In another expt DNA was treated with the enzyme DNAase before it was mixed with live IIR cells.This did not yield a III S colony.This confirms that DNA is the transforming principle.