This document discusses nematode resistance in crop varieties, including types of resistance, modes of inheritance, breeding methods, and sources of resistance identified in various crops. It describes immunity, resistance, tolerance, susceptibility and escape as types of resistance to nematodes. Resistance can be controlled by single genes (monogenic), a few genes (oligogenic), or many genes (polygenic). Breeding methods discussed include mass selection, line breeding, hybridization, and backcrossing. Sources of resistance identified for various nematodes include varieties of potato, tomato, brinjal, rice, bottle gourd, bitter gourd, chilli, pulses, and oilseeds.

1. NEMATODE RESISTANT
CROP VARIETIES – SUCCESS
AND FAILURE
Vikas Bamel

2. Importance of resistance in
nematodes.

3. Types of resistance and their
relative significance
 Immunity : A pathogen cannot cause disease even
under favourable conditions, meaning absolute
freedom from disease
 Resistant : A pathogen’s development, either
completely or to some degree, is hindered in a plant
 Tolerance : Cultivars produce a good yield despite
infection by pathogen
 Susceptible : Plants greatly damaged or killed by
pathogen
 Escape : Occurs when inherently susceptible plants
do not become infected because of phenology,
absence of inoculum, or conditions unfavourable to
infection.

4. Crop resistance in plants against
nematode is expressed the following
modifications
 Thickening of cell wall, which interfere with
feeding.
 Proliferation of wounded tissue.
 Formation of trichomes i.e. unicellular or
multicellular outgrowth from the epidermis of
leaves, shoot and root, these trichomes
besides performing water consevation, affect
feeding, digestion, locomotion and attachment
and may contains allelochemicals which are
toxic.
 Accumulation of surface wax which affect
colonisation and oviposition
 Incorporation of silica, which result in
inhibition of feeding.

5. Chemical resistance
 Due to inorganic substances and
also due to primary (citric acid and
amino acids) and secondary
metabolites (isoprenoides and
alkaloids in cucurbits against pests and
L-terthienyle), Glycosides (phenols),
Coumarins, IAA, peroxidase and
polyphenol oxidase, L -Phenylalamine
ammonia lyase (PAL)

6. Resistance - mode of inheritance
 monogenic (single gene),
– controlled by single gene
– Differences between resistant and susceptible plants are
clear-cut
– segregation for resistance occurs in simple ratio
– race specific
 oligogenic (a few genes)
– controlled by a small number of major genes or a few
genes
 polygenic (many genes).
– Many genes govern polygenic resistance
– only few examples of polygenically controlled resistance
– usually durable and non-race specific
– difficult to exploit it in a breeding programme

7. major genes and minor genes
 According to the amount of the
phenotypic effect they express,
being either major genes (large
effects) or minor genes (small
effects) for phenotypic expression

8. Vertical resistance and
Horizontal resistance
 Vertical resistance
– race-specific or qualitative
– controlled by one to as many as three genes
and is identified with the gene-for-gene type of
plant-pathogen interaction
 Horizontal resistance
– race-non-specific or quantitative, effective
against all variants of the pathogen
– polygenically inherited as several minor genes,
often with additive effects that confer a
quantitative level of resistance
– more durable

9. Inheritance of resistance
 The mode of inheritance of resistance to a
disease/pest will largely determine as to which
method of breeding is to be used.
 It is, therefore of great importance for a plant
breeder to discover at the start of a breeding
programme whether the resistance is controlled
by a few or many genes and whether influence of
cytoplasm is likely to be significant or not.
 It is also important to know whether resistance is
governed by dominant or recessive genes.

10. Breeding for resistance
Conventional methods
 Main objective of screening for resistance is to differentiate
between resistant and susceptible plants
 Differentiation between highly resistant and highly
susceptible plants should be easy, provided that the
inoculation has been carried out correctly and that the
environmental conditions are suitable for disease/pest
development
 Easy to distinguish between susceptible and resistant
individuals in a segregating population of inoculated plants
in which resistance is controlled by one or a few major
genes
 Resistance is often controlled by many genes and in such
cases there is no clear cut distinction between resistant
and susceptible plants
 In case of nematode pests, generally the degree of
resistance is indicative of the ability of nematode to
reproduce on a host plant

11. Methods of breeding for resistance
Cross-pollinated Crops
Common methods
 Mass selection
– individual plants are selected for resistance
from a heterogenous population of plants and
these selections are then allowed to
interpollinate to produce seed for the next
generation
 Line breeding
– selected plants are either selfed or
interpollinated and the resulting progenies are
individually tested for resistance

12.  Resistant lines resulting from line breeding or
recurrent selection programme can be used to
produce hybrid or synthetic varieties.
 synthetic variety is produced by intercrossing
a number of selected phenotypes or lines which
have been found to have good general combining
ability.
 A hybrid variety is produced by controlled
pollination between lines and male sterility is
often employed to achieve this

13. Self-pollinated Crops
(mass selection, pure line selection or hybridization)
 Mass selection,
– several plants of a similar phenotype are
selected for resistance from a self-pollinating
population and the progenies are bulked to
form the basis of a variety.
 Pure line
– varieties are derived from the progeny of a
selfed homozygous plant selected from a line or
variety.
 Hybridization
– involves the crossing of two pure line varieties
to combine desirable characters from each
parent. Hybridization , followed either by the
pedigree or bulk selection methods or by a
backcross method

14. Back cross method
 is a form of recurrent hybridization
by which a superior characteristic
may be added to an otherwise
desirable variety.
 Very useful for transferring one gene
or a few genes (monogenic or
oligogenic resistance) from one
genetic background to another.

15. Resistance against major
nematodes
 Meloidogyne spp
 Heterodera spp
 Globodera spp
 Rotylenchulus reniformis

16. Identification of source of resistance
against major nematodes in economically
important crops
 Source of resistance
– (locally adopted, high yielding varieties, exotic varieties,
indigenous varieties , closely related species or even in
different genera )
 Simple inherited resistance to several diseases
has been successfully transferred by crossing
susceptible varieties with resistant plants of
another species
 Interspecific crosses –
– wild relatives of some species sometimes present great
difficulties -large number of undesirable characteristics
of the wild parent ,- resistance to a disease/pest is
controlled by several genes so that much of the
resistance would probably be lost in the backcross
generations

17. Screening varieties for
resistance to Heterodera sp.

18. Screening varieties for resistance
to Heterodera sp.
 Sow 1-2 seeds/pot (500g soil)
 Inoculate one week old seedling with 500
larvae / seedling
 For inoculation remove top 1 cm of soil
and pour nematode suspension and cover
with soil
 Uproot plants after 20 days of inoculation
 Count the no. of cysts on root system and
also from washing on 60 mesh sieve

19. Observations
 Rating on 1-5 scale based on mean no.
of white females/cysts per plant
 No cyst Immnue
 1-5 cysts/plant Resistant
 6-25 cysts/plant Moderately Resistant
 26-50 cysts/plant Susceptible

20. Cereal cyst nematode, Heterodera
avenae on barley/wheat
 Resistance in barley to H. avenae was
characterized on the basis of production of more
males than females and inhibition of development
beyond third stage larvae.
 Resistance in barley is controlled by single
dominant gene.
 At least six genes controlled the resistance of H.
avenae in barley, three of these are Ha1, Ha2 and
Ha3 located on long arm of chromosome-2,
 Pankaj et al. (1995) studied the inheritance of
resistance in barley against Indian population of
H. avenae and reported that single dominant
gene (monogenic) was responsible for imparting
resistance in barley against pathotype 1

21. Potato cyst nematode, Globodera rostochiensis
and G. pallida on potato

22. Potato cyst nematode, Globodera
rostochiensis and G. pallida on potato
 Solanum species to G. rostochiensis
decided on the basis of fewer cysts
development revealed that S. vernei
and a few clones of Andigena potato
were highly resistant
 S. oplacense, S. spegazzinii, S.
famatlinae etc. were resistant

23. Methodology for screening for
resistance (Root-Knot
Nematode)

24. Methodology for screening for
resistance (Root-Knot Nematode)
Experimental Design
 Green House and also microplot testing- Replication 4
Methods
 Transplant one seedling/ sow 4 seeds/pot on ½ kg sterilized
soil (thin to one seedling)
 Always keep susceptible check and also resistant one
 Inoculate 15 days old seedling with Inf.J2/pot removing top
1 cm soil, pour nematode suspension, cover with soil
 Conduct screening in appropriate season
 Record temperature from the day of inoculation
 Remove plant 40 days after inoculation and record gall
index and egg masses.

25. OBSERVATIONS
 No gall, no egg masses – HR
 1-10 galls/egg masses – R
 11-30 galls/egg masses - MR
 31-100 galls/egg masses - S
 101& above galls/egg masses – HS
* A variety showing susceptibility even in
one replication may be considered
susceptible

26. Root-knot nematodes, Meloidogyne spp.
in crops
 Potato
– Crossed Kufri Red with (clandstone x Toborky) to obtain
H-294 selection was resistant to M. incognita in India
 Tomato
– Tiny tim X NTDR-1; and reported complete resistance due
to single dominant gene.
– The varieties of tomato showing resistance to root-knot
nematode, Meloidogyne incognita are Hisar N-1, Hisar N-2,
Hisar N-3, PAU-6, PAU-9, PAU-11, PAU-12, PAU-13, PAU-
15, Hisar Lalit, Mangala hybrid, NT-3x, NT-12x, Columbia,
LX-12x, NF-318, B-12, PAU-8, PAU-10, PNR-7, PC-119, PC-
120, HT-8, HS-10, Homeset, SB-6, HENZ-2, HS-110, Market
King, Kalyan Selection-2, Kalyan Selection-3, LA-125, EC-
113 and NF-31.
– Resistant varieties identified as M. javanica are NF-31, Hoe-
616, PT-203, TH-212, NA-501, NDT-9, Century-12,
Dhanshree, Mangala hybrid, P-120, Hisar Lalit, PNR-7, NT-
12, NT-3, HS-101, NF-3188-8 and NT-3188.

27. Hisar Lalit

28.  Brinjal
– S. torvum, S. sisymbrifolium, S. werceweixii.
– The resistance of S. sisymbrifolium a wild
cultivar were also reported by Ahuja and
Chadha (1984) and it is still not incorporated
in commercial varieties.
– Resistant at some AICRP (Nematodes) centres are as
under :
– Rajendra baigan, Pant Rituraj, KS-224, IC-
127040, Rajendra Annapurna, Rajendra baigan-
II Long, KS-224, IC-127029, IC-122076 and IC-
90903
Root-knot nematodes,
Meloidogyne spp. in crops

29. Source of resistance in other crops
 Rice (M. graminicola)
– OR-621-20-1, RNR-87877, RP-2541-172-293, WGL-3910,
WGL-47969, RP-2334-148-47-11, RP-2081-322-145-48,
Bhanja badami, Neela, OR-776-SSD-26 and KAU-28-1-1.
 Bottlegourd (M. incognita)
– PSPL, Hoe-505, Samrat and Bogh-2.
 Bittergourd (M. incognita)
– Hybrid lines 3, 42, 46, 57 and 58.
 Chilli (M. incognita )
– PSL-3, Surajmukhi, Hoe-818, Guchhedar, Pusa Jwala,
Pusa Sadabahar, BSS-138, LCA-304, LCA-305.

30. Methodology for screening for
resistance (Reniform Nematode)

31. Methodology for screening for
resistance (Reniform Nematode)
 Green House and also microplot testing Replication 4
Methods
 Recover nematodes egg masses from culture in glass house –
incubate 7 days in water at laboratory temperature
 Sow 2 seeds/pot on ½ kg sterilized soil (thin to one seedling)
 Always keep susceptible check
 Inoculate one week old seedling with 500 infective females/pot
removing top 1 inch soil, pour nematode suspension, cover
with soil
 Conduct screening in appropriate season
 Record temperature from the day of inoculation
 Remove plant one month after inoculation and record gall index
and egg masses.

32. OBSERVATIONS
 Record the number of parasitic females
and egg masses attached to the roots.
 No of dislodged females/egg masses also
estimated by washing soil and examining
the 60 mesh catch.

33. Index for reniform nematode
 No females, no egg masses – Immune
 1-10 females /egg masses – Resistant
 11-20 females /egg masses - MR
 21-30 females /egg masses - S
 31& above galls/egg masses – HS
* A variety showing susceptibility even in
one replication may be considered
susceptible

34. Source of resistance in other crops
Pulses
 Blackgram (M. incognita)
 AKU-7, AVT-2SZ, KU-305, UV-218
 Blackgram (H. cajani)
 UG-218
 Cowpea (M. incognita)
 EC-241018, EC-29254, C-152, 82-1b
 Cowpea (H. cajani )
 VRT-11937, EC-11910, VL-16, V-322, V-604 and HC-94-2
 Mung (M. incognita )
 HUM-6, HUM-7, KU-308, KU-309, Pusa-9331, Pusa-9632, Pusa-9871,
ML-131
 Mung (H. cajani)
 PM-96-1, PMB-24
 Pigeonpea (M. incognita)
 PPH-4, T-92, AF-293, MRG-66, Pant-A-104, ICPH-8 F-2

35. Source of resistance in other crops
Oilseeds
Groundnut (M. arenaria )
 Virginia Runner, Group, AH-18, Valencia Group NCAC-465,
Spanish, Bunch Group, AH-688, ICG-7883, JB-104, JB-182,
BS-59
Groundnut (M. javanica)
 ICG-3208, ICG-7294, ICG-7895, ICG-8827, ICG-8828, ICG-1288
Sesamum (H. cajani)
 G Til-1, G Til-2, AVTS-13, AVTS-12, TNAU-119
Castor (R. reniformis )
 SKI-152, SKI-112, SHB-172, SKI-176, RG-125
Soyabean (M. incognita)
 ACPS-157, EC-4247, Pusa-20, IS-2, IS-21, PK-416. Shilajeet,
Shivalink, Kalitur and Durya.

36. New approaches
 Split root system
– the ability of Pseudomonas fluorescens (Pf1
isolate) and Bacillus subtilis (isolate Bst) to
induce systemic resistance in tomato against
R. reniformis was achieved.
– Reduction in nematode penetration by 42.0%
into split root in which one half received the
nematode one-week after bacterial inoculation
(1010 cells/ml) on the corresponding half
through soil drenching.
– The nematode penetration into unsplit root
was decreased by 46.5%. These findings
revealed that the bacterium could induce
systemic resistance in tomato against R.
reniformis.

37. Proteinase Inhibitors (PIs)
 Urwin et al., (2000) reported the level of
resistance to the reniform nematode R. reniformis
conferred on Arabidopsis thaliana by transgenic
expression of proteinase inhibitors (PI) over 40
days of infection
 Cloning of proteinases from targeted nematodes
is useful for defining the relative importance of
distinct proteinases for different developmental
stages of a cyst-nematode.
 It also aids protein engineering of PIs to enhance
their efficacy against targeted proteinases.
Efficacy in both di- and monocotyledonous plants
against M. incognita and R. reniformis suggests a
broadly effective approach to nematode control.

38. Problems in breeding nematode resistant
varieties - Failures
 Abiotic factors play an important role in
genetic expression of resistance
– temperature is important which reduce the level of
resistance with the increase or decrease of
temperature
– Resistance of a plant is also related to its age,
– Resistance expression basically increase with
maturity.
– Existence of pathotype or races in nematode species
is other factor contributing significantly in failure of
resistant varieties which have been developed after
incorporating resistance source of that particular
variety resistant to that particular pathotype or
race.

39.  Though large number of source of resistance in
different crops are available for incorporating
these in the breeding programmes to develop
commercially acceptable cultivars which has not
been carried out except few crops like tomato,
cowpea against Meloidgyne incognita.
 Possibility of break down of resistance due to
several abiotic factors and also reporting of
resistance without proper and confirm testing by
scientists
 Now hybrids has come up at large scale which
have been very well accepted by farmers. These
hybrids is yet to be tested against major nematode
pests to level their reaction and performance in the
nematode infested fields

40. Conclusion
 Host resistance is a management tactic that has
much potential and needs to be utilized more
effectively. Many of the available germplasm
resources remain to be characterized with
respect to resistance to nematodes
 Even after the resistant phenotypes have been
identified, further research will be required to
determine the number of unique genes for
resistance that may be present in different
accessions.
 Genetic transformation of plants with cloned
resistance genes is an exciting part of the future
for resistance to nematodes. The recently cloned
Mi-1 from tomato and HS pro-1 from sugarbeet
represent an essential first step towards the goal.

41.  Studies on nature of resistance both genetic as well as
biochemical are encouraging, though limited, and further
concentration in this area may reveal exciting possibilities
of reniform nematode management through resistance.
 Host resistance will not be the solution to all problems
caused by R. reniformis or other nematodes. But the
resistance could play a bigger role in many nematode
management systems.
 The era of nematicides is approaching an end and we must
develop alternative management strategies. Clearly the use
of host plant resistance must be one of these alternatives,
and it will play a priority role in many crop production
systems, both directly and as a component of an integrated
approach to nematode management