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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5569_Библиотеки_им_академика_М_И_Перельмана
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S. Zafar etal.
17.4.5 Starter Fertilizers
The onion seedlings showed slow growth. It’s roots branch little and seldomly
develop root hairs. This makes it difcult to supply adequate amount of nutrients to
the seedling at it’s early growth stages for proper growth of onion. Mostly the fertilizers are applied in granular form as base dressing before sowing onions. But it’s not
benecial as N fertilizers or the N content of the soil leaches out before the onion
roots are able to reach out. So, an effective method to use fertilizer is in the form of
liquid rather granules, in a zone close to or below the root zone of onion. This is
starter fertilizer concept. In many areas, these starters help to accelerates the growth
of shoot and yield of the onion plants. Increase in the bulb development takes place
with the application of starters as compared to the without these starters. Starters
conrms the adequate supply of nutrients to the roots, mostly of P.Ammonium
Phosphate improved early growth and yield as compared to ammonium nitrate.
Experiments were performed on spring sown onions in nitrogen depleted soil. Also,
the use of starter helps to prevent the water contamination and leaching of nitrogen
from the soil, so that the roots have better access to the nitrogen [2, 32].
17.4.6 Onion Propagation
The application of biotechnology in the onion production is more attractive due to
high cost of seed production and long generation time of onion. These things are
improving with the passage of time and will give signicant valuable verities of
onion in the coming future.
Following are the methods used by the early scientist upto near past, for the
propagation of onion verities, in the labortary.
17.4.6.1 In Vitro Propagation
Firstly, the onion were produced using callus culture and micro-propagation. These
were considered as the signicant usage of tools for onion production. The use of
this technology depends upon the cost of propagating male sterile plants in relating
to the increased revenue for the hybrid seed. For reducing the occurrence of viruses,
meristem culture is used for plants [34].
17.4.6.2 Molecular Based Selection
For the identication of molecular markers in onion, gel electrophoresis and recombinant technologies are being used. Polymorphism were identied using the following
methods, like amplied fragment length polymorphisms AFLPs; [35], isozymes [32],
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randomly amplied polymorphic DNA [36] and RFLPs [37]. These marker classes
helped in the identication of onion populations. For obtaining desirable traits, these
genetic markers are of great benet. The characters of plants are identied at an early
stage of development by these genetic markers. It helps in crossing of the desire plants
with signicant characteristics. Markers linked to the genes conditioning traits with
relatively high evaluation costs, such as male-sterility res-toration and avor proles,
would reduce the number of phenotypic evaluations that must be completed for each
plant or family. For obtaining desired genotypic plants, eventual sequencing of the
onion plants are done followed by the resequencing of the key population. This method
reveals large number of DNA polymorphism for the identication desire genes. It
automatically gives desire phenotypes. Large numbers of DNA markers will also
enable the genomic estimation of breeding values, allowing the performance of
hybrids from crosses of male-sterile lines with various male parents to be predicted.
17.4.6.3 Doubled Haploid
To reduce the time commitment and cost of the inbrebs lines, haploid plants are subjected to chromosome doubling. The method is performed by extracting the haploid
plants from the gametophyte and then the doubling of chromosome is performed.
The doubled haploid produce by this way carry out similar sexual behavior as of the
normal lines [38]. Male gametophyte of the onion does not produce successful haploid. Whereas the gynogenic production of haploid is successful when ower buds
are grown on simple media [39–44]. Haploid plants develop from the egg and another
cell of the female gametophyte [39]. Flow cytometry is used to check this haploidy.
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17.4.7 Challenges toUse Double Haploid
One of the main challenge to use double haploid is that no male sterile is available
for the developed double haploids. If a sterile male is used for double haploid, then
it will automatically produce male sterile and will be propagating asexually.
17.4.8 Transformation andGene Editing
Though, onion is a monocotyledonous plant, still it’s transformation is being
reported by Agrobacterium [45, 46] Onion can be transformed stably the following
methods, like herbicide-resistance genes, anti-sense construct which helps in the
removal of lachymatory (tearing) factor [45]. Many gene editing technologies are
being used for the production of desired lines of onion like CRISPR/Cas system. It
also helps to reduce the long generation time involved in the selection and commercialization of new onion varieties.
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17.5 Pests andDiseases
Onion plants show susceptibility to root diseases. When the onions are grown as
monocultures or the same eld is being used by the farmers to produce onions, then
there are chances of onions to become more susceptible to pathogenic fungi [2,
37, 46].
17.5.1 Onion Maggots
Delia antiqua are the onion maggots are the severe pests of onion. These are basically the descendants of houseies. The larva infects the young plants. These plants
do not cause plant mortality. These mostly grow on decaying plant material. These
also effects the plants after their damage by the frost formation. For avoiding these
pests, the soil should be free from high quantity of organic matter or proper insecticides should be used [28, 47].
17.5.2 Aster Leaf Hopper (Mycrosteles Fascifrons)
This insect is basically vector of the phytoplasma which results in the Aster yellows
disease in onion plants. Nymphs does not feed on onion plants whereas the adult
show low preferences. Symptoms caused by the leafhopper are stunting, twisting of
leaves and stem and chlorosis of leaves [47].
17.5.3 Cutworms
Cutworms are the larval stage of the most of the species of moths. These mostly
feeds at night and hide during day time. The damage occurs, when the plant cut off
near the soil line. For their nocturnal habit, these plants are detected only during
early or late day time [27, 28].
17.5.4 Wireworms
These are the larval stage of the click beetles. These mostly feed on the ground portions of the plants. Some of the species produce multiple generation in a single year,
whereas some have the ability to produce adults after a period of 1–2years [27].
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17.5.5 Thrisp
These are the primary insect pest of onions [47, 48]. These mostly damage the
leaves. These leaves are then easily attacked by other disease as well and lost the
ability of photosynthesis. With the increase in temperature their number also
increase. The pests mostly congregate in the leaf folds and down the plant portions.
17.5.6 Gout andMetabolic Syndrome
Gout and metabolic syndrome are characterized by the abnormal xanthine oxidase
(OX) and high serum uric acid concentrations. These are common health problems
in many diseases. These are the common symptoms of gout and metabolic disease.
These make the base of precipitation of gout. Therefore, the concentration of serum
uric acid and XO should be normal. In this regard, potential effects of active ingredients of onion proves to be benecial. Onion has inhibitory effect on these oxidants
and xanthine oxidase. The onion active compounds like are the potential source of
anti-gout and anti-oxidants [48, 49].
17.6 Classication ofOnion
Onion plants can be classied by day length sensitivity into long-day plants (LD), very
long-day plants (VLD), short-day plants (SD), intermediate-day plants (ID). These
lengths of days effect the following paratmeters rmness, skin, scale colors, shape,
size, sweetness, juciness, storage potential and pungency. Following scale colors were
observed like bronze, light yellow, dark yellow, pink, dark purplish, red and white [2].
17.6.1 Important Chemical Constituents
In onion, water is about 80–90% of the fresh weight of the onion. Almost 65% of
the dry weight of onion is composed of non-structural carbohydrates, in the form of
fructose based polymer, called fructan. In onions, in which the fructan is in lower
amount as a constituent of dry matter, there, the fructose, sucrose and glucose
dominates.
The two main and important component found in the onions are Alkyl cysteine
sulphoxides and avonoids. Two of the avonoids sub-groups are also found in the
onion like avanos e.g. quercetin which impart yellow and brown color to the onion
varieties And anthocyanins, which impart red or purple color to the onion. The
ACSOs are the main avor precursors, which when broken down by the enzyme
allinase, gives the characteristics odor and taste of the onion.
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A volatile oil is present in the onion bulb which contains Sulphur containing
compounds like allin [50], allicin, avonoids, sterols, phenolic acids and
allypropyldisulphide.
Onion gypoglycaemic activity due to the presence of allicin and allylpropyldisulphide. Antihyperglycaemic activity is also shown by onion due to the presence of
Diphenylamine in the mature bulbs. Allicin and alliin both involves in the inhibition
of the platlet aggregation. Onion juice contains thiosulphinates, which are involved
in anti-asthmatic activity [51–56].
Some of the other chemicals found in the onions are sugars like fructans, and no
starch, many decomposed products of cysteine sulphoxides [2]. Phenolic hydroxyl
compounds include polyphenols. These are the class of natural onion content.
S. Zafar etal.
17.6.2 Medicinal Uses
It is used against headache, vomiting, malaria, constipation, blood pressure, antiseptic, diuretic, cold, rheumatism etc.[3, 54]. Some of the additional uses of onions are
antibiotic, antibacterial, antisclerotic, anticoagulant, anti-inammatory, antiasthmatic, expectorant, carminative, antispasmodic, hypotensive, antidiabetic. In China,
Allium macrostemon, is found. It is used for treating dysponea, dysentery, angina
pectoris and cough [4].
17.6.3 Insulin Requirement
The regular use of onion of about 50g/day, decrease the insulin requirement of a
diabetic patient from almost 20–40 per day [4].
17.7 Onion Stem Diseases
17.7.1 Sour Skin andBacterial Canker
The disease is caused by Burkholderia cepacia (Pseudomonas cepacia) which
causes sour smell of onion bulbs due to the which the name is given. In this disease,
extensive tissue maceration occurs which releases with the water. In some cases,
this bacterium cause disease in the leaf axil, from which the name bacterial canker
is develop. This result in the death of the infected leaves and infection spread to the
bulb and also neck tissue of the plant. The onions infected with the neck-wound
disease, result in the sour skin disease of the onion while in storage. Environmental
conditions effect the severity of disease, as the humidity promotes the disease while
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the disease vanishes when the dry conditions exceed. Also, in low humidity, canker
lesion dried up and the infected leaf sloughed off [2].
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17.7.2 Bacterial Streak andBulb Rot
The disease Bacterial streak and bulb rot of onion is caused by Pseudomonas viridiava (Burkholder) Dowson. The disease effects the foliage leaves and bulb both in
eld and in storage. In this disease, lesions develop as water soaked, dark color
streak which spread to the entire length of the leaf. In severe conditions, lesions
blightened entire plant. These lesions are small, oval, olive green to tan in color and
are surrounded by chlorotic area. These lesions go downward to the bulb [2].
Symptoms mostly develop in a circular pattern due to the restriction of the rot by
scales [49].
17.7.3 Centre Rot
The disease is caused by Pantoea ananatis (Serrano). In this disease, the center of
the leaves is mostly affected. The infected leaves become soft, bleached white and
water soaked when the disease progresses. Tissues turn tan to brown. In severe condition, wilting and bleaching of leaves occur. Bulb also get infected, it become
water, have foul smell and soft. It also leads to the loss of seeds heads [2].
17.7.4 Bacterial Soft Rot
This disease is caused by Erwinia pathogens belonging to the soft-rot ‘carotovora’
group. In this disease, tissues become infected with pale yellow to light brown rot
and water-soaked condition occur. Bulb disintegrates. In severe condition, wilting
and whitening of onion foliage occur. Flower stalks, pedicle also get infected with
lesions [2, 32].
17.7.5 Pink Root
The disease is caused by Phoma terrestris, a fungus. It is the most damaging disease
of the fungus. This disease is greatly increased due to stresses like cold, heat, ooding, drought and nutrient deciencies/toxicities. The fungus survives and reproduces in the soil, so continuous production of onions in the same led result in the
increased in the disease occurrence. Roots in this case turn pink or purplish. In
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severe cases, the roots become brown and deteriorate. Disease at early stage result
in the production of unusable bulbs while in the later stages, the plants become
stunted or produce small bulbs. Crop rotation, balancing temperature and fertilizers
help to reduce the disease [24, 27].
S. Zafar etal.
17.7.6 Fusarium Basal Rot
The disease is caused by the fungus Fusarium oxysporum f. sp. cepae. This disease
also effects the onion roots both in led and in storage. The disease increased by the
repetition of the onions in the eld. The symptoms include yellowing of leaf tips,
necrotic areas, curling or curving of leaves, infected and decaying of basal plate and
white and uffy mycelium. The control includes the use of healthy transplants, controlling insects and avoiding fertilizer injury [27, 28, 56, 57].
17.7.7 Onion Smut
Onion sumt is caused by Urocytis cepulae. Temperature is most effecting in controlling this disease as low temperature and damp places increase its occurrence while
high temperature and dry weather decrease its growth. The disease mostly effects
seedlings while the adult plants are somehow resistance to this disease [58].
17.7.8 Botrytis Neck Rot
The is the most damaging disease of the fungus on onions. The fungus survives in
the form of sclerotia. Conidia arise from the sclerotia and spread by wind to spread
the disease. The symptoms include stunted growth, splitting of leaves and leaf distortion around the neck area. A greyish sporulation appears near the neck area.
Harvesting healthy mature onions, temperature balance and avoiding over usage of
fertilizers are some of the management practices [27, 28].
17.7.9 Purple Blotch
The disease is caused by Alternaria porri, one of the commonest diseases of the
onion. Older plants are more susceptible to disease then younger ones. The fungus
overwinters in leaf debris of onion. The symptoms appear as elliptical, small and tan
lesions which later turn purplish brown. Concentric rings appear as they enlarge.
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Use of fertilizers, deep soil turning, long rotations and destruction of cull piles are
some of the management practices [27, 28].
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17.7.10 Downy Mildew
Downy mildew is caused by Peronospora sp. It is detected in early morning as vel-
vety, violet sporulation. Later on, these lesions become yellow. Use of fungicides,
destroying the cull piles and avoiding infected onions planting are some of the recommendations for controlling disease [27, 28, 59].
17.7.11 Iris Yellow Spot Virus (IYSV) andTomato Spotted Wilt
Virus (TSWV)
IYSV is spread by onion thrips (Thrips tabaci). This virus has also been found in
Tobacco thrips (Frankliniella fusca). In this disease small necrotic spots with green
tissues develop in the center of the leaves. Controlling thrips, proper fertilization is
some of the recommendations for controlling this disease [2, 38].
17.8 Control ofDiseases
The most effective treatment in the control of diseases is the rotation which also
helps to reduce the pesticide and herbicide application and minimize nitrate leaching. The order of rotation must be kept in mind while doing rotation. As Lucerne
reappear as weeds while maize is a high-volume residue crop which in turn effect
the onion emergence. Some of the best proceeding crops are melon, cauliower,
beans, peas, pepper, cucumber, aubergine and tomato can be used as proceedings
crops. The rotation sequence was experimented for 3years to be cauliower as the
early crop, followed by onion cv. ‘Babosa’, chufa (Cyperus esculentus), early potatoes, lettuce, artichoke and melon, for the central-eastern coast of Spain. In Spain,
onions–maize–wheat/lucerne–wheat rotation sequence is mostly followed. In
Switzerland, rotation of onion along with carrots, cabbage, tomato and celery is
used [2].
Environmental condition also plays important part while performing crop rotation. Following shallow rooted onions, sugarbeet is used to scavenge the nitrate of
soil. Beet uses the soil nitrates and in turn protect the soil from nitrate pollution of
groundwater. Onion growing as intercrop helps to decrease the pest damage. Beans
as intercrop, reduce the attack of leaf aphids, red spider mite (Tetranychus urticae)
etc. [2].
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17.8.1 Insecticides forOnion Control
Some of the insecticides used to control insect’s pests of onions are,
1. Bacillus thuringiensis (Xentari): These can control beet armyworms and
hornworms.
2. Lambda-Cyhalothrin (Karate Zeon): These control leaf miners, aphids, beet
armyworms, thrips, leaf hoppers.
3. Abamectin (Newmectin): These are used for broad spectrum of insect control
like leaf miners, aphids, thrips and mites.
4. Indoxacarb (Avaunt 30 WG): These are used against thrips, aphids and beet
armyworms [26].
17.8.2 Fungicides
1. Copper products are effective for the bacterial and fungal disease control.
2. Menab products control fungi.
3. Sulphur products effective against insect and fungal disease.
4. Chlorothalonil control fungi.
5. Copper sulphate pentahydrate and Azoxystrobin (Amistar) are effective against
purple bloctch, botrytis leaf blight and Downy mildews.
6. Mefenoxam (Ridomil) products control some of the systemic diseases [26].
17.8.3 Biological Control ofOnion Pests
Onion pests can also be controlled biologically.
Leaf miner can be controlled using lacewings, parasitic wasps and Eulophidae.
Soldier bug can control beet army bug. Braconid control onion maggot. And onion
thrips are controlled by predatory mites, lacewing and ower bug [2, 26].
17.9 Health Benets ofOnion
17.9.1 Antibacterial Effects
Onion extracts and oils have great antibiotic properties. Onion have the chemicals
to be used as a remedy for diarrhea, worms, inammatory and other infectious diseases. All these controllable effects of onions are due to the presence of saponins,
phenolic compounds, proteins and organo sulphur etc. These mostly act against
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gram positive bacteria rather gram-negative bacteria. Onion extract is effective for
oral bacterial inhibition [2, 50, 60].
In some of the experiments, an antimicrobial protein is isolated from the onion
seeds, which are highly effective against plant pathogenic fungi with the concentration below 10 micrograms per milliliter. The protein isolated was Ace-AMP1 which
interacts with the phospholipid membranes [2].
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17.9.2 Cardiovascular Effect
Onion plant extract is used for the antiplatelet activity which in turn decrease the
number of the platelet aggregation and provide a preventive effect for cardiovascular disorders, like atherosclerosis. Also, onion extract has some lipid-lowering
effects. It’s extract also shows some of the antithrombotic potential. In experiments,
higher concentration of onion extract was used intraperitoneally and orally to rats.
Boiling of extract results in decrease in it’s activity. Therefore, cooking decreases
the antithrombotic activity in alliums. Almost 90mgml- is found to cause platelet
aggregation in rabbits. Human plasma also shows the same result. Heating also
effects the inhibition capability. Onions with high Sulphur contents show greater
antiplatelet activity as compared to the lower concentration of the Sulphur. Extract
prepared from the owering umbel show greater antiplatelet activity as compared to
the same amount of the extract obtained from bulbs. Typical organo Sulphur compounds found in the onion species are (+)-S-methyl-L-cysteine sulphoxide which
show antidiabetic and hypolipidaemic activity [2].
17.9.3 Effects onRespiratory System
One of the best activities shown by onion is it’s antiasthmatic activity. This activity
is shown by the synthesized or isolated organo Sulphur compounds found in the
onion extracts, which are potentially used as medicinal drugs. Cepaenes and
Thiosuphinates effects also observed invitro. In upcoming studies, experiments are
expected to perform on guinea-pigs for observing the effects of organo sulphur
compounds on platelet activating factor. A single dose of onion extract of almost
100mgkg−1 body weight inhibit PAF-induced bronchial hyperactivity to histamine
for over 12h. Experiments performed on the persons suffering from allergic bronchial asthma, indicated that there was remarkable reduction in the immediate and
late bronchial reactions of the patients just with the use of 100ml of 5% ethanol
extract. The extract was prepared from 100g sliced onions and was used for allergen inhalation test [2].
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