This document provides an overview of insect biotypes and their management. It discusses key concepts such as the definition of a biotype as a group of insects with similar genetics. Biotypes can develop when insect pests evolve in response to selective pressures from insect-resistant crop varieties. Factors that can lead to biotype development include selection pressure from resistant crops and improper management practices. Studying biotypes is important for breeding resistant crop varieties and insect pest control. Several methods are described for detecting biotypes, and examples of biotypes in important pests like brown plant hopper, rice gall midge, and whitefly are provided. The document concludes with a discussion of management strategies to address biotype development such as gene pyramiding

2. Course Seminar
On
Development of insect biotypes and their
management
Narendra Deva University of Agriculture & Technology,
Kumarganj, Ayodhya – 224229 (U.P.)

3. Contents
Introduction
Concept of insect biotypes
Evalution of biotypes
Genetics of biotypes development
Factors leading to development of biotype
Importance Of Study Of Biotype
Occurrence of Biotypes
Methods of biotype detection
Biotypes of some important insect pests
Management Stratgies
Conclusion
References

4. INTRODUCTION
We all know this thing that plants and insects have
coexisted together for about 4 million years.
Insect have own defense mechanism which deters the
feeding of herbivores.
On the other hand, talking about insects, the selective
ability .
 In order to protect our crop plants from insect pests, what
immediately clicks our mind is to go for chemical pesticides.
The concept of using host plant resistance is of great
advantage which is an essential component of integrated pest
management.

5. ………..??

6. Concept of insect biotypes
Biotype:
A group of organisms having the same or nearly the same genotype,
such as a particular strain of an insect species.
A group of organism having an identical genetic constitution.
The continuous growing of insect resistant varieties may lead to
certain physiological and behavioural changes in insect pests so that
they are capable of feeding and developing on the resistant variety.
(Dhaliwal and Arora 2009. )

7. More specifically, biotype refers to the populations within a
species which can survive on and destroy varieties that have
genes for resistance.(Heinrichs et., al 1985).
Broadly speaking, the term biotype is an intraspecific
category referring to insect population of similar genetic
composition for a biological attribute. (Saxena and
Barrion,1987).

8. EVOLUTION OF BIOTYPES
The continuous growing of insect
resistant varieties.
Failure to recognize the existence
of insect biotypes.
Genetic factors

9. GENETICS OF BIOTYPE DEVELOPMENT
Genetics of biotype
development can be understood
with the help of Gene for Gene
hypothesis proposed by Flor
(1942). It is also known as
Matching Gene Theory.

10. Isolation mechanisms or barriers
pre mating isolating mechanisms Post mating isolation mechanisms
Differences in habitat
Seasonal differences
Ethological isolation
Mechanical isolation
Gametic mortality
Zygote mortality
Hybrid inviability
Hybrid sterility
Factors leading to development of biotype

11. Factors influencing Selection of Biotypes in
Insect pests:
 Selection pressure exerted by the resistant crop variety. E.g.
BPH, GM.
 Monogenic resistance
Combinations of antibiosis and antixenosis are less prone to
biotype than individual.
 Improper management practices.
Biotypes that possess an inherent genetic capability to
overcome plant resistance.
Some insect species with short life cycles, short generation
times and high fecundities
Conti…

12. Importance Of Study Of Biotype
Breeding for insect resistant varieties of crops
Better understanding of how to control manage by
resistant varieties.
Genetic control of insect pest population.
The Entomologists and plant breeders to combat
insect pest of crops and at same time maintain the
genetic diversity of crops.

13.  In 1970, biotypes were known to occur in eight
species of insect pests affecting agricultural crops.
 Twelve species of the phytophagous insects are
known to have biotypes of which seven come under
Aphididae as reported by Wilbert in 1980.
 Saxena and Barrion in 1987 reported that biotypes
reportedly occur in 36 arthropod species belonging to
7 families of 6 order.
Occurrence of Biotypes

14. Insect species Common name Crops Number of biotypes
Acyrthosiphon pisum
(Harris)
Pea aphid Pea
Alfalfa
4
Amphorophora idaei
(Born)
Raspberry aphid Raspberry 4
Eriosoma lanigerum
(Hausmann)
Apple woolly aphid Apple 3
Mayetiola destructor (Say) Hessian fly Wheat 16
Nephotettix virescens
(Distant)
Green leaf hopper Rice 3
Nilaparvata lugens (Stal) Brown plant hopper Rice 5
Orseolia oryzae (Wood-
Mason)
Gall midge Rice 6
Rhopalosiphum maidis
(Fitch)
Corn leaf aphid Corn 5
Schizaphis graminum
(Rondani)
Green bug Sorghum
Wheat
5
7
Therioaphis maculata
(Buckton)
Spotted alfalfa aphid Alfalfa 6
Some examples of insect biotypes involved in host plant resistance to insects

15. Methods of biotype detection
 Morphological differences:
Insects that exhibit measurably different traits with respect
to host range, host plant adaption, physiological character.
Figure: Three distinct biotypes of whitefly on the basis of morphological differences in cibarium.

16.  Behavioural differences:
Behavioral studies, especially mating behavior is used
for distinguishing biotypes.
Biotype – host association:
Understanding the interaction between host plant and
biotype will help to understand the mechanism of evolution
a virulent insect biotype.
Genetics of biotypes:
It helps to understand the mutation occurring single
allele and expressing changes behavioral and physiological
level.
Conti…

17. 1. Brown Plant hopper
Symptom of Damage
Hopper burn or yellowing, browning
and drying of plant.
Circular patches of drying and lodging
of matured plant.
Nymphs and adults congregate at the
base of the plant above the level.
Affected plant dries up and gives a
scorched appearance called hopper
burn.
 It is vector of grassy student ragged
stunt wilted stunt disease.
BIOTYPES OF SOME OF THE IMPORTANT INSECT PESTS
Symptom
Insect

18. Biotype Region Countries
Biotype 1 South East Asia Philippines, China, Japan,
Malaysia, Taiwan, Thailand
Biotype 2 South East Asia Philippines, Solomon
Islands, Vietnam
Biotype 3 South East Asia Philippines, Taiwan
Biotype 4 South Asia India, Bangladesh, Sri Lanka
Biotype 5 South East Asia Philippines
Brown plant hopper biotypes existing world wide
(Source: Dhaliwal and Ram Singh, 2005)

19. 2. Rice Gall Midge
 Symptom of damage
 Maggot feeds at the base of the
growing shoot.
 Causing formation of a tube like
gall that is similar to onion leaf or
Silver-shoot.
 Infested tillers produce no panicle.
Symptom
Insect

20. Germplasm Gene 1 2 3 4 5 6
W 1263 Gm 1 R S R S R R
Phalguna Gm 2 R R S S R S
RP 2068-18-
3-5
Gm 3 R S R R R S
Abhava Gm 4 R R R R R S
ARC 5984 Gm 5 R R S S S S
Dukong # 1 Gm 6 R S S S Not
tested
Not
tested
Reaction to biotypes for genes for resistance
(Source: Dhaliwal and Ram Singh, 2005)

21. White Fly
 Symptoms of Whitefly
Infestation and Affected Plants.
 Common noticeable symptoms are
an abundance of white, waxy material
covering leaves and fronds, a sugary
substance called "honeydew" produced
by the leaf-sucking insects,
and excessive dark sooty mold on
leaves or fronds that grows on the
honeydew.

22. BIOTYPES OF WHITEFLY
Sida race
Jetropha race

23. MANAGEMENT STRATEGIES TO OVERCOME DEVELOPMENT
OF INSECT BIOTYPES:
1. Systematic pest surveillance and monitoring:
Scheme for selection of new biotype of N. lugens on resistant rice varieties
Field population of N. lugens
Oviposition on TN1
Resistant
varieties
Mudgo, ASD 7
Adults oviposition
on TN1
First instar
nymphs
4 & 5 instar nymphs
New biotype
Rearing of insect on resistant varieties for 7 generations leads devept of biotype
Reared 12 years on TN1
First instar nymphs

24. 2. Sequential release of varieties with major genes:
When a variety with a major gene becomes susceptible due to selection for
a new biotype, another variety with new major genes for resistance should be
released.
3 .Gene pyramiding:
The incorporation of two or more major resistant genes in the same
variety to provide resistance to two or more biotypes is known as gene
pyramiding.
a) Bph 1 + Bph 3
b) bph 2 + Bph 3
c) Bph 1 + bph 4
d) bph 2 + bph 4
Conti…

25. 4. Horizontal resistance:
One of the effective practices to manage biotype selection is the use of
cultivar with a broad genetic base of resistance.
5. Gene rotation:
A strategy where varieties with different resistance genes are used in
different cropping season to minimize selection pressure on given resistant
gene.
7. Varietal mixture:
One should employ the use of varietal mixtures consisting of 80 – 90 %
resistant plants and 10 – 20 % susceptible plants of similar varietal
background.
Conti…

26. Conclusion
The threat of selection and spread of prolific insect biotypes cannot be
avoided and ignored.
 At the same time there is a need for better understanding of insect plant
interactions.
There is a need for developing several short and long term strategies in
breeding for insect resistance and the thrust should be to broaden the
genetic base of resistance both in terms of major and minor genes.
Also study the speciation of major factor responsible for speciation is
reproductive isolation, which may be due to various barriers, like
geographical isolation, reproductive incompatibility, differences in habitat,
seasonal occurrence and behaviour.
Presence of endosymbiont, like Wolbachia, present an all together
different perspective to look at the problem of biotypes.

27. REFERENCES
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Namrutha Publications, Chennai. pp. 296-301.
4. Dhaliwal, G.S. and Arora Ramesh. 2009. Integrated Pest Management: Concept
and Approaches. Kalyani Publishers, New Delhi. pp. 135-136.
5.Downie, D.A. 2010. Baubles, bangles and biotypes: A critical review of the use and
obuse of the biotype concept. Journal of Insect Science 10(6): 176-179.
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Learning Private Limited, New Delhi. pp. 470-471.
7. Rawat, N., Neeraja, C.N. and Jagadish, S.B. 2012. Differential gene expression in
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hybridization (SSH) c DNA libraries and microassay analysis. Rice. 5:8.

28. 8. Singh, B.D. 2005. Plant Breeding: Principles and Methods.Kalyani
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