Plants have evolved various constitutive and induced defense strategies against herbivores. Constitutive defenses include physical defenses like thorns and trichomes as well as chemical defenses like alkaloids, terpenes, and glucosinolates. Induced defenses are activated in response to herbivore attack and can be direct like proteinase inhibitors or indirect like releasing volatile signals to attract natural enemies of herbivores. Key phytohormones like jasmonic acid and salicylic acid mediate induced defense responses by activating genes related to toxins, repellents, and signal production. Understanding these plant defense mechanisms could help develop new ecofriendly pest management approaches for agriculture.
Genetic Engineering in Insect Pest management Mohd Irshad
gene incorporation is gaining attention across the globe with the aim of improving plant health, crop protection, and sustainable crop production. This versatile method of Scientific cultivation should be adopted by the growers as it has been investigated and assessed by experts and environmentalists. There is not any kind of toxic effect on mammalian.
Hi there,
This was topic on which I presented a talk in our department. As we know Insecticide such as pyrethroids are being most widely used for controlling insect pest in agriculture because of their safe, cheap, effective and long-lasting nature (Bulter et al. 2011). However, the widespread development of insecticide resistance, especially resistance to pyrethroid and the fact that resistance to an insecticide generally confers cross-resistance to other insecticides has become a serious problem challenging the control of agriculturally, economically, and medically important insect pests and resulting in increase of insect vector-borne diseases in many parts of the world (Zaim 2002; Bulter 2011). Three major mechanisms are involved in insecticide resistance: (1) increased metabolic detoxification of insecticides; (2) decreased sensitivity of the target proteins on which an insecticide acts, known as target site insensitivity; and (3) decreased cuticular penetration/or increased sequestration/storage.
Bacillus thuringiensis(Bt)Cry protein is one of the most effective biopesticides that can act against a large group of insect orders like Lepidoptera, Coleoptera, Diptera etc. But through the course of evolution insects have developed resistance so that they can combat against Bt. Mutation(s) in the target site; reduced protease activity; sequestration of toxin molecules; mutations in the ABCC2 transporter protein are few mechanisms which govern resistance in insects against Cry protein. Therefore, it has become prime importance to understand the molecular basis of insect resistance and what could be the strategies by which the efficacy of the Cry protein can be enhanced. The strategies for improving the efficacy of Cry toxin are (i) Expression of chitinase gene along with Cry toxins; (ii) Expression of hybrid toxin; (iii) Introduction of intramolecular cleavage sites. The insects have developed resistance against different groups of Cry proteins such as Cry2Aa, Cry1Ac, Cry2Ab etc. But the relative fitness (such as larval and pupal weight, pupal duration, and survival rate, etc.) in resistant larvae is much lower than the susceptible larvae because of genetic changes in insects. One of such genes that affects the relative fitness in Helicoverpa armigera is death associated LIM only protein (Ha-DALP) which is basically involved in cell signalling, cell fate determination, transcriptional regulation of gene expression etc.
Role of secondary metabolites in insect pest managementMohd Irshad
SECONDARY METABOLITES ARE THOSE COMPOUNDS WHICH ARE DIRECTLY INVOLVED IN PLANT DIFFENCE MECHANISM SO HERE I ADDED SOME SLIDES WITH KNOWLEDGABLE INFORMATION AND CITED SOME CLEAR CUT EXAMPLES.
Genetic Engineering in Insect Pest management Mohd Irshad
gene incorporation is gaining attention across the globe with the aim of improving plant health, crop protection, and sustainable crop production. This versatile method of Scientific cultivation should be adopted by the growers as it has been investigated and assessed by experts and environmentalists. There is not any kind of toxic effect on mammalian.
Hi there,
This was topic on which I presented a talk in our department. As we know Insecticide such as pyrethroids are being most widely used for controlling insect pest in agriculture because of their safe, cheap, effective and long-lasting nature (Bulter et al. 2011). However, the widespread development of insecticide resistance, especially resistance to pyrethroid and the fact that resistance to an insecticide generally confers cross-resistance to other insecticides has become a serious problem challenging the control of agriculturally, economically, and medically important insect pests and resulting in increase of insect vector-borne diseases in many parts of the world (Zaim 2002; Bulter 2011). Three major mechanisms are involved in insecticide resistance: (1) increased metabolic detoxification of insecticides; (2) decreased sensitivity of the target proteins on which an insecticide acts, known as target site insensitivity; and (3) decreased cuticular penetration/or increased sequestration/storage.
Bacillus thuringiensis(Bt)Cry protein is one of the most effective biopesticides that can act against a large group of insect orders like Lepidoptera, Coleoptera, Diptera etc. But through the course of evolution insects have developed resistance so that they can combat against Bt. Mutation(s) in the target site; reduced protease activity; sequestration of toxin molecules; mutations in the ABCC2 transporter protein are few mechanisms which govern resistance in insects against Cry protein. Therefore, it has become prime importance to understand the molecular basis of insect resistance and what could be the strategies by which the efficacy of the Cry protein can be enhanced. The strategies for improving the efficacy of Cry toxin are (i) Expression of chitinase gene along with Cry toxins; (ii) Expression of hybrid toxin; (iii) Introduction of intramolecular cleavage sites. The insects have developed resistance against different groups of Cry proteins such as Cry2Aa, Cry1Ac, Cry2Ab etc. But the relative fitness (such as larval and pupal weight, pupal duration, and survival rate, etc.) in resistant larvae is much lower than the susceptible larvae because of genetic changes in insects. One of such genes that affects the relative fitness in Helicoverpa armigera is death associated LIM only protein (Ha-DALP) which is basically involved in cell signalling, cell fate determination, transcriptional regulation of gene expression etc.
Role of secondary metabolites in insect pest managementMohd Irshad
SECONDARY METABOLITES ARE THOSE COMPOUNDS WHICH ARE DIRECTLY INVOLVED IN PLANT DIFFENCE MECHANISM SO HERE I ADDED SOME SLIDES WITH KNOWLEDGABLE INFORMATION AND CITED SOME CLEAR CUT EXAMPLES.
Pathogenesis-related proteins (initially named “b” proteins) were discovered in tobacco leaves
hypersensitively reacting to TMV by two independently working groups (Van Loon and Van Kammen,
1970; Gianinazzi et al., 1970)
what is Antixenosis, Antibiosis, and Tolerance.pptxRamshaShaikh11
what are the mechanism resistance in plants(Antixenosis, Antibiosis and Tolerance), their adaptation resistances like morphological, anatomical and biochemical basis etc.
Pathogenesis-related proteins (initially named “b” proteins) were discovered in tobacco leaves
hypersensitively reacting to TMV by two independently working groups (Van Loon and Van Kammen,
1970; Gianinazzi et al., 1970)
what is Antixenosis, Antibiosis, and Tolerance.pptxRamshaShaikh11
what are the mechanism resistance in plants(Antixenosis, Antibiosis and Tolerance), their adaptation resistances like morphological, anatomical and biochemical basis etc.
Content:
Introduction
Importance of Host Plant Resistance
Historical perspectives
Advantages and Disadvantages of HPR
Mechanisms of Resistance
Adaptation of Resistance in Plant to Insect
Morphological
Anatomical
Biochemical
Assembly of plant species - Gene Pool
Behavior in Relation to Host Plant Factor
Trichoderma is a filamentous fungus that is widely distributed in the soil, plant material, decaying vegetation, and wood. It belongs to the family Hypocreaceae. They have high potential for colonizing their habitats and have various applications in food industry, agriculture, as a biocontrol agent with mechanism involving antibiosis, competition, mycoparasitism, promotion of plant growth, solubilization and sequestration of inorganic plant nutrients, inducing resistance and inactivating pathogen’s enzymes and also as a source of transgene. The major driving force for investigation of biocontrol with Trichoderma is sustainability. As a plant symbiont and effective mycoparasites, numerous species of this genus have the potential to become biofungicides. the extensive studies on Trichoderma, including its diverse physiological traits available, is still progressing and making these fungi versatile model organisms for research on both industrial fermentations as well as natural phenomena. Jasmine Chughasrani | Abhishikta Dasgupta | Rutuja Das "Applications of Trichoderma- A Review" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-2 , February 2021, URL: https://www.ijtsrd.com/papers/ijtsrd38341.pdf Paper Url: https://www.ijtsrd.com/biological-science/botany/38341/applications-of-trichoderma-a-review/jasmine-chughasrani
In the following slides, I have discussed the need for developing insect-resistant transgenic plants, the sources of transgenes, and methods for development
Functional Genomics of Plant Pathogen interactions in Wheat Rust PathosystemSenthil Natesan
Cereal rust fungi are pathogens of major importance to agriculture, threatening cereal production worldwide. Targeted breeding for resistance, based on information from fungal surveys and population structure analyses of virulence, has been effective. Nevertheless, breakdown of resistance occurs frequently and continued efforts are needed to understand how these fungi overcome resistance and to determine the range of available resistance genes. The development of genomic resources for these fungi and their comparison has released a torrent of new ideas and approaches to use this information to assist pathologists and agriculture in general. The sequencing of gene transcripts and the analysis of proteins from haustoria has yielded candidate virulence factors among which could be defence-triggering avirulence genes. Genome-wide computational analyses, including genetic mapping and transcript analyses by RNA sequencing of many fungal isolates, will predict many more candidates (Bakkeren et al., 2012)
Dissecting the mechanisms of host-pathogen systems like wheat-rust, including pathogen counter-defenses will ensure a step ahead towards understanding current outcomes of interactions from a co-evolutionary point of view, and eventually move a step forward in building more durable strategies for management of diseases caused by fungi (Hadrami et al.,2012)
Mechanism of insect resistance in plants (non preference, antibiosis, tolerance and avoidance) – nature of insect resistance – genetics of insect resistance – horizontal and vertical – genetics of resistance – sources of insect resistance – breeding methods for insect resistance – problems in breeding for insect resistance – achievements.
Predators are one of the most important aspects of biologial control of crop pests. The predators may be insects or mites or nematodes or any other living organisms. Like the parasitoids, predators also follow a typical prey selection strategy. It includes Prey Habitat Selection, Prey Finding, Prey Acceptance and Prey Suitability. Prey Habitat Selection can be obtained by different plant odors or prey odors (like- honeydew, prey frass etc) or herbivore induced plant volatiles (HIPV). The HIPV is the most of important and reliable one to select the prey species by the predators. Actually when a plant is attacked by the pest species, the defense system is activated and it includes production of de novo or phytoalexins or secondary plant metabolites of various odors which actually attract the predators. Like- the bean plants attacked by Tetranychid mites, are attracted by the predatory Phytoseiid mites. Besides plants attacked under pests, release Methyl Salicylate like molecules which also attracts predators like Chrysopa spp. After habitat finding, the predators forage for suitable prey and if initial inspection of the habitat leads to evidence of prey in the local area, the predator is likely to engage in Intensified Local Search (ILS). ILS includes frequent turning, sinous search paths and slower walking. Theere are a number of factors which influence the efficiency of ILS. These include- Host Plant Architecture, Surface Texture of Plants, Hunger Status of Predators, Visual Cues, Patch Quality and Prey Products. Like- Larvae of some ladybirds foage less frequently for aphids on highly branched varieties than on normal branched varieties of crops. Similarly waxy surfaces can reduce their foragig efficiency and some of the predators are entrapped and died within the trichomes. Native adults of Harmonia axyridis are more attracted to yellow colour as compared to green colour. They are also attracted to the surface treated with prey products like honeydew to search for the preys while there are lots of exceptions regarding this. After a prey has been contacted, the age and experience of the predator, size of the prey and prey's defensive actions can influence the success of attack. The acceptance of prey depends on certain features like- food habit of the prey, chemical composition of prey cuticle, warning colourations and gregarious nature of prey species. After the acceptance, the suitability of prey is important to determine. This depends on- whether it supports both developement and reproduction or only developement or unpalatable. Suitability of prey for immature stages of predators depends on the survivorship of them, developemental time and adult body weight. Indexing prey suitability for mature adults depends mainly on the reproductive capability, high fecundity and viability. If predators feed on diseased or paralyzed hosts, it may induce low body weight, low immunity and survivorship. This understanding helps in successful IPM bio-control
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
2. Introduction
As autotrophs, plants require effective
defense mechanisms to survive in the world
of heterotrophs.
A range of adaptations evolved
by plants which improve their survival and
reproduction by reducing the impact
of herbivores.
Plans face challenges from various
herbivores and microbes at all stage and in
all organs.
3. DEFENCE STRATEGIES OF PLANTS AGAINST INSECTS
• Tolerance
• Avoidance
• Defence (Physical or
chemical)
• Association with other
spp.
Plants have 4
basic strategies
by which they
reduce the
impact of
herbivory-
4. Constitutive or Direct
• Physical characters
• Biochemicals
Induced
• Induced direct
• Induced indirect
Defence
5.
6. Constitutive defence
Always present in the plant.
Multitude of structures and chemicals incorporated into their tissues.
They can deter, repel and interfere with the development and reproduction
of herbivores.
It may depend on the texture and composition of the plant surface.
Presence of anatomical structures such as :-
Veins, thorns, silica, trichomes and resin ducts etc.
Absence of nutrients.
Presence of hormones that affect the development.
10. Induced defence
Involves the production of chemicals or physiological structures, or removal of
nutrients essential to herbivore, in response to attack.
May take several forms :-
(a) Nutrient removal
(b) Cell lignification
(c) Controlled chemical biosynthesis
(d) Uncontrolled chemical biosynthesis
11. Biochemistry of induced resistance
Environmental conditions can increase, or decrease, the level of a plant`s intrinsic
chemical defence.
Insect feeding on plant tissues could elicit defensive metabolism in the plant (Akazawa
et al., 1960).
1. Highly volatiles, which elicit negative insect orientation with regard to source, and may
negatively affect the insect before physical contact.
2. Less volatiles, which prevent or reduce feeding if the insect contacts the plant.
3. Chemicals which are non volatile variously affects the herbivore`s nutritional and
developmental physiology after feeding.
12. INDUCED DIRECT DEFENCE
Affects the attackers directly through toxins, repellents, digestibility reducers,
spines and thorns(Koiwa et al.,1997)
Defence induced by mechanical wounding in a plant results in induction of
proteinase inhibitors in tomato and potato, leading to a reduction of the
digestibility of plant tissues(Green and Ryan,1971).
Wounding by Manduca sexta, tobacco hornworm caterpillar induce the
production of nicotine(Green and Ryan, 1971).
Caterpillars, Helicoverpa zea and leafminer flies, Liriomyza trifoli induce
different combinations of polyphenol oxidase, peroxidase, lipoxygenase and
proteinase inhibitors in tomato plants(Stout, et al., 1994).
13. Proteinase inhibitors
Inhibit proteinase activities of herbivores.
PIs bind to the digestive enzymes in the insect gut and inhibit their activity.
Thereby reduce protein digestion resulting in the shortage of amino acids.
Slow development and starvation of the insects.
PI in plants species Against Insect species
Sorghum bicolor Schizaphis graminum
Tomato Manduca sexta
Helicoverpa armigera
Solanum nigrum Spodoptera littoralis
Spodoptera exigua
Transgenic Arabidopsis/ tobacco Spodoptera littoralis
14. Herbivore-induced plant volatiles
Attracts the natural enemies of the herbivores
Act as feeding and/or oviposition deterrent.
HIPVs are the lipophilic compounds with higher vapor pressure which are released
from the leaves, flowers, and fruits into the atmosphere, and into the soil from the roots
by plants in response herbivore attack (Arimura G, Matsui K, Takabayashi J,2009).
Plant volatiles such as methyl salicylates and the C16- Homoterpene 4, 8, 12-
Trimethyl-1, 3(E), 7(E), 11- Tridecatetraene [(E, E)-TMTT] have been found to attract
the predatory mites (de Boer JG et al., 2004).
15. Cont…
Most frequent component of the HIPVs is methyl salicylate (MeSA) reported in the
headspace of many insect-infested plants including lima bean, and Arabidopsis (Chen F. et
al., 2003).
MeSA is a component of many leaf and floral blends and MeSA baited sticky cards attract
many insect predators including the big- eyed bug, Geocoris pallens Stal., ladybird
beetle, Stethorus punctum picipes (Casey), green lacewing Chrysopa nigricornis and other
natural enemies (James DG, 2003)
16. Cont…
Inhibition of oviposition of cabbage moths Mamestra brassicae by MeSA released during
infestation (Ulland et al., 1960).
MeBA (methylate benzoic acid) has also been detected from insect-infested plants.
S. frugiperda infestation in rice induces emission of about 30 volatiles, including MeSA and
MeBA, which are highly attractant to the natural enemies such as, Cotesia marginiventris.
HIPVs has the potential of attracting crop pests. For example, Colorado potato
beetles, Leptinotarsa decemlineata (Say) is attracted to a blend of volatiles consisting of cis-
3-hexenyl acetate, linalool, and MeSA
17. Cont…
In black mustard, trichomes density and glucosinolates levels were elevated after feeding
by Pieris rapae (Traw MB, 2002).
Trichome density increased in plant, Alnus incana as a result of damage by beetles (Baur
R; Binder S; Benz G., 1991).
Increase in trichome density in response to herbivory between 25 to 100%.
Positive correlation has been observed between natural enemies abundance and trichome
density.
Trichome exudates also serve as extra floral nectar (EFN) for scelonid egg parasitoid, of
squash bugs, Gryon pennsylvanicum (Olson DL; Nechols JR., 1995).
20. Induced indirect defence
It promotes the effectiveness of natural enemies of herbivores through the provision of
shelter, food and the production of signals that enable carnivorous arthropods to locate
the herbivores (Kessler and Baldwin, 1997).
Emission of volatiles after damage that attract carnivorous enemies of herbivores.
Eg. Parasitoid Aphidius ervi, its aphid host Acyrthosiphon pisum and
Its host plant Vicia faba- shown that feeding by aphid alters the composition of
volatiles released by the plant (Wadhams et al., 1999).
21. 1. A volatile signal
is released as
the caterpillar
eats a leaf.
2. Female wasp is attracted
by the volatile signal,
finds caterpillar, and lays
eggs.
3. Wasp larvae
feed on the
caterpillar and
then emerge.
Volatile signal
Larvae
4.Larvae continue to feed on
the caterpillar after it dies,
but not the plant. The larvae
then spin cocoons to pupate.
22. Applications
Soyabean var. “Davis” attractive to Mexican bean beetle, Epilachna varivestis, but
larvae emerged from eggs can`t survive further or died.
Feeding on foliage of this var. “Davis” by attracted adult female caused a premature
termination in their egg laying.
Volatiles of G. max breeding introduction PI 227687 strongly repellent to adult of this
beetle (Burden and Norris, 1994).
Microplitis demolitor attracted by the volatile 3-octanone in G. max, Soybean
looper, Pseudoplusia includens and more arrested by quaiacol, found in its host`s frass.
Quaiacol was only detected in Pseudoplusia includens frass when this herbivore fed on
this plant and was never detected in volatiles from intact host plants (Ramachandran et
al., 1991)
23. Role of phytohormones in induced resistance
Many signal transduction pathways mediated by a network of phytohormones.
Regulating plant growth, development, and defense mechanisms.
A number of plant hormones have been implicated in intra– and inter- plant
communication in plants, damaged by herbivores.
Most of the plant defense responses against insects are activated by signal-transduction
pathways mediated by JA, SA, and ethylene.
Specific sets of defense related genes are activated by these pathways upon wounding
or by insect feeding.
These hormones may act individually, synergistically or antagonistically, depending
upon the attacker.
24. Jasmonic acid
Naturally occurring, non-toxic compound.
Function of JAs in defence proposed by Farmer & Ryan,1992.
Wounding caused release of linolenic acid(LA), precursor of JAs from membrane lipids.
Important role in plant’s defence in response to wounding.
JA plays a role in insect and disease resistance: many genes during plant defence are
induced by JA, and ethylene may act together in defence responses.
25.
26. Applications
JA seed treatment stimulates the natural anti-pest defenses of the plants that germinate
from the treated seeds, without harming plant growth.
Exogenous application of JA on rice plants elicits the production of proteinase inhibitors,
phytoalexins, PRs, and salt-induced proteins (Tamogamia et al., 1997; Rakwal and
Komatsu, 2000; Rakwal et al., 2001; Kim et al., 2003) and it may increase the emission
of volatiles.
JA application to rice plants on the host-searching behavior of the rice brown
planthopper Nilaparvata lugens and its mymarid egg parasitoid Anagrus nilaparvatae.
27. Cont..
Exogenous application of MeJA increases the release of volatile organic
compounds (Halitschke et al., 2000), which enhances the mortality rates of
the herbivores by attracting the natural enemies of herbivores (Kessler and
Baldwin, 2001).
Appl. of jasmonates affects trichome formation, glucosinolate biosynthesis
and terpenoid emission.
JA-treatment reduces larval mass of S. exigua and induces the attraction
of Cotesia rubecula parasitoids.
28. Complexity of volatile blend and large numbers of different herbivore enemies
suggests that many of these defenses remain to be characterized.
Application of these defense strategies in an agricultural setting might offer new
ecofriendly approaches to increase insect resistance in crops.
CONCLUSION