Vol.4, No.6, 292-301 (2013) Agricultural Sciences
Status and strategies in breeding for rust resistance
in wheat
Mudasir Hafiz Khan*, Asifa Bukhari, Zahoor Ahmad Dar, Syed Mudasir Rizvi
Division of Plant Breeding and Genetics, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Srinagar,
India; *Corresponding Author: drmhkhan8@gmail.com
Received 4 September 2012; revised 1 February 2013; accepted 6 March 2013
Copyright © 2013 Mudasir Hafiz Khan et al. This is an open access article distributed under the Creative Commons Attribution Li-
cense, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Wheat along with rice and maize is fulfilling half
of the calories demands of the world. Global
Wheat production has increased tremendously
since green revolution in 1960’s and helped in
minimizing hunger and malnutrition. Developing
countries, which consume 60% of the global
wheat production, have shown a higher yield
increase than the developed countries in the
past [1]. It was driven by the hunger prevalence
in these countries and was attributable to the
introduction of high yielding and rusted resis-
tant semi dwarf varieties developed under the
collaborative efforts of International and Na-
tional research sy stems during the last 50 y ears.
Whereas, climate change and the emergence of
new pests and diseases are thr eateni ng th e food
sustainability. The evolution of new races of
disease pathogens like stem rust (Ug 99) is of
serious concern. In order to feed the ever in-
creasing population we have to increase wheat
production at the rate 1.6% which can be
achieved by developing high yielding varieties
having a good tolerance level for biotic and
abiotic stresses.
Keywords: Leaf Rust; Strip Rust; Stem Rust;
Resistance ; Wheat
Among the most important diseases in wheat that sig-
nificantly reduce wheat production are those caused by
the rusts (leaf, stem, and stripe). The rusts of wheat are
among the most important plant widespread pathogens
that can be found in most areas of the world where wheat
is grown. Wheat leaf rust is caused by Puccinia triticina
Eriks, wheat stem rust by Puccinia graminis f. sp. tritici,
and wheat stripe rust by Puccinia striiformis f. sp. tritici.
Leaf rust occurs more regularly and in more world-wide
regions than stem rust or stripe rust of wheat. Yield
losses in wheat from P. triticina infection s are u sually th e
result of decreased nu mber of kernels per head and lower
kernel weight and it may reach 40% in susceptible culti-
vars [2]. Yield losses caused by the stem rust pathogens
in the mid of the 20th century reached 20% - 30% in
Eastern and Central Europe and many other countries
including Australia, China and India [3]. The yield losses
caused by the most virulent stem rust race Ug99 emerged
first in Uganda and after that in Kenya, Ethiopia, Yemen,
in the Middle East and South Asia and losses were esti-
mated to be approximately USD $3 billions
The disease-causing wheat rust fungi are spread in the
form of clonally produced dikaryotic urediniospores,
which can be dispersed by wind for thousands of kilo-
meters from initial infection sites across different conti-
nents and oceans. Epidemics of wheat rusts can occur on
a continental scale due to the widespread dispersal of
urediniospores [4]. Wheat rust fungi are highly specific
obligate parasites. Their avirulent genes interact with
resistance genes in wheat in a gene-for-gene manner.
Rust populations can be characterized by distribution of
races and the frequencies of virulence against specific
rust resistance genes on a defined set of wheat differen-
tial hosts. The avirulence genes that are present reflect
only a small proportion of the total genetic variation
found in rust populations, but this variation is subject to
intense selection by the resistance genes in commonly
grown wheat cultivars. Selectively neutral markers such
as isozymes or more recently developed molecular mark-
ers, such as random amplified polymorphic DNA ( RAP D) ,
simple sequence repeat (SSR) and amplified fragment
length polymorphism (AFLP) can also be used to char-
acterize and compare rust populations. As the wheat rust
fungi are spread easily within and between continents, it
is essential to document the genetic changes in rust
Copyright © 2013 SciRes. OPEN ACCESS
M. H. Khan et al. / Agricultural Sciences 4 (2013) 292-301 293
populations over large geographic areas in order to fa-
cilitate the development of rational strategies or durable
The semi dwarf and dwarf varieties developed at
CIMMYT, Mexico in the early days of green revolution
(Penjamo 62, Pitic 62, Lerma Rojo 64, Sanora 64 and
Siete Cerros etc.) had been responsible for yield break-
through in India, Pakistan, Turkey, Afghanistan and
many other parts of the world. The life time of most of
these Mexican varieties was short as appearance of new
stem rust race has terminated their useful life time how-
ever, there were some exceptions also. The variety Lerma
Rojo 64 had life time of eleven year, while others like
Yaqui 50, Champingo 52 and Champingo 53 retained
their resistance until they were displaced from commer-
cial cultivation by new high yielding varieties [5]. The
long life of these varieties is attributable to their genetic
background. They h ad co mbinatio n of Hop e and Th acher
type and Kenya type resistance. During the period
1965-1985, the CMMYT breeding program has incorpo-
rated diversity of genes. Most of the material distributed
during this period contains Sr2 and two to four addition al
genes for stem rust resistant. These additional genes in-
clude Sr5, Sr6, Sr7a, Sr7b, Sr8a, Sr9b, Sr9d, Sr9e, Sr9g,
Sr10, Sr11, Sr12, Sr17, Sr24, Sr26, Sr30, Sr31, Sr36 [6].
The parallel strategy was also adopted by many national
The importance of Lr13 gene for leaf rust (Puccinia
triticina) resistance was recognized in the early 1970’s
when it was transferred along with other genes in to
many wheat varieties. Some varieties containing Lr13 in
combination with other genes developed in Mexico, In-
dia and Pakistan are given in Table 1. The gene, Lr13
itself does not provide desired level of resistance but
when present in combination with other genes it provides
a degree of resistance of high probability of being dura-
ble. The mode of action of Lr13 complex in CIMMYT
program is non specific type of resistance. Its presence in
combination with Lr34 in some members of Bluebird
series gave them long life. Another example of this com-
bination is a Pakistani variety Lyalpur 73 which although
replaced in the farmers field by the introduction of new
high yielding varieties b ut even after 36 years of release,
it still have very good resistance for leaf rust (20 M) in
screening nurseries. The varieties like Genero81 and
Torim 73 which remained resistance to leaf rust in Mex-
ico for long time also have Lr34 gene in combination
with other genes.
The adult plant resistance to leaf rust of the Brazilian
wheat cultivar “Frontana” was first described as due to
the gene Lr13 (effective in the adult plant stage) and one
or two modifiers [7].
Subsequent studies by [8] indicated the presence of
Lr34 and LrT3 in “Frontana”. Reference [9] showed that
Table 1. Leaf rust resistance genes in old wheat varieties.
S No Varieties Ye ar Country/Region Genes
1 Lerma Rojo 1964 Mexico Lr13, Lr17
2 Champingo 53 1953 Mexico Lr34
3 Penjamo 62 1962 Mexico Lr14a, Lr34
4 Pitic 62 1962 Mexico Lr14a
5 Sonora 64 1964 Mexico Lr1
6 Mexipak 65, Kalyansona 1965 India, Pakistan Lr14a
7 Sonalika, Bluesilver 1967, 1971 India, Pakistan Lr13, Lr14a
8 Lyalpur 73 1973 Pakistan Lr1, Lr13, Lr34
9 Bluebird, Yecora 70 1970,s Mexico, Pakistan Lr1, Lr13, Lr34
10 Ciano 79 1979 Mexico Lr16
11 Arz 1973 Lebnon Lr17
12 Pavon F 76, Dollarbird 1983, 1987 Mexico, Australia Lr1, Lr10, Lr13, Lr46+
13 Parula 1981 CIMMYT Lr34 & Lr46+
14 Punjab 81 1981 Pakistan Lr10, Lr13, Lr34
15 Era 1970 North America Lr10, Lr13, Lr34
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M. H. Khan et al. / Agricultural Sciences 4 (2013) 292-301
Lr13 could confer low seedling reaction at elevated
temperature. The gene Lr13 appears to be common in
cultivars from Australia (Hawthorn 1984); India [10];
and Brazil, Argentina and Unites States [4]; and in
cultivars derived from CIMMYT germplasm [11]. Gene
Lr13 has been shown to interact with other genes such as
Lr16 and Lr34 [12]. Durable resistance to leaf rust in
various cultivars has been thought to be due to the
interaction of Lr13 with other Lr genes [4]. Reference
[13] investigated the inheritance of adult plant resistance
in “Frontana” and 3 globally leaf rust resistant CIMMYT
spring bread wheat varieties, the genetic test for the
presence of Lr34, the postulation of the other known Lr
genes, and the role of Lr13 and other known Lr genes in
conferring adult plant resistance. They concluded that
resistance w as independent of ma jo r g en e s.
The material developed during mid 1960’s had ac-
quired resistance for yellow rust from Andean region
varieties which possessed high level of resistance. The
Anza was derived from cross LR/N10B//3*ANE and
released in North Africa, Sudan, South Africa and New
Zealand. It was regarded as durable resistant for yellow
rust by reference [14] and may have derived durable re-
sistance from Anderson [15]. Durable resistance of Anza
is widely deployed in spring wheat and in some winter
wheat varieties. This durable resistance was attributed to
the presence of gene Yr18 by reference [16]. The gene,
Yr7 is also present in a range of spring wheat and winter
wheat varieties and it is frequently associated with Sr9g.
It is reported in number of varieties such as Barani 83,
PBW12, WL2265, Ser i 82 (Yr2, Yr7, Yr9), Pavon76 (Yr6,
Yr7, Yr29), Pak.81 (Yr7, Yr9) [17]. Veery and Pavon
containing Yr7 have been released in 31 and 16 countries,
repectively with different names which show the wide
use of Yr7 ge ne.
Reference [18] produced several lines having a trans-
location between a segment of hairy neck chromosome
of rye 5R and different wheat chromosome segments.
Due to genetic relationship between rye chromosome 5R
and wheat chromosome of homeology group 1, the des-
ignation 1R was proposed for this chromosome [19]. The
rye chromosome 1R was reported to be containing pow-
dery mildew and stripe rust resistance genes in its short
arm. It was found that these genes were linked with stem
rust and leaf rust resistant genes and cultivars Salzmun-
der, Baertweizen and Weique have identical genes [20].
A sister line of these “Neuzutch” was used for breeding
in Soviet Union and gave rise to Russian cultivars
Kavkaz, Aurora, Besostaya 2, Skorospelka and many
others. Neuzutch possesses a complete 1R chromosome,
whereas Kavkaz and Aroura have an interchange chro-
mosome having 1B segment and a rye chromosome 1R
segment. Kavkaz was introduced in to CIMMYT germ-
plasm where a high yielding spring wheat cultivar
“Veery” was released. This segment was also transferred
to several Europian cultivars. These cultivars were found
possessing resistance to wheat streak mosaic virus and its
vector wheat curl mites. There was good compensation
of Rye chromosome 1R for the elimination of wheat
chromosome 1B. The 1B.1R translocation appears to be
more stable and superior in agronomic properties. It was
easy for the breeders to work with this translocation as
there was no cytological problem associated with it [21].
Therefore, this translocation became widespread in
wheat cultivars released in China and USA, India, Paki-
stan and several other countries during the mid-1980s
and later. The Veery derivatives due to their superior ag-
ronomic feature and disease resistance were widely cul-
tivated in different parts of the world. This germplasm
showed significant gr ain yield advantage and wide adap-
tation with superior disease resistance attributes due to
the presence of the 1B.1R translocation. The higher
yielding ability of 1B-1R germplasm was attributed to
post anthesis stress tolerance of this material resulting in
higher Kernal weight [22]. The frequency of 1B.1R
translocation went up to approximately 70% at one stage
in CIMMYT’s spring wheat germplasm but has declined
to about 30% in more recent advanced lines [23]. This
translocation, derived from imperial Rye carries genes
Sr31, Lr26, Yr9 and Pm8 [24], when used initially it pro-
vided resistance to stem rust, leaf rust and yellow rust but
with the development of new virulent races, these genes
are in effective now [23]. Despite, its successful use it
was not widely deployed in Australia due to sticky dough,
poor mixing characteristics resulting poor bread making
qualities [24].
The wide spread global popularity of the germplasm
with 1B-1R translocation created monoculture situation.
This lead to the evolution of some new devastating rust
races results a serious threat to global wheat production.
A race of P. striiformis, Yr9 was 1st observed in East
Africa in 1986 and subsequently migrated to North Af-
rica and South Asia. Once it appeared in Yemen in 1991
it took just four years to reach wheat fields of south Asia
[25]. On its way it caused major yield losses in Egypt,
Syria, Turkey, Iran, Iraq, Afghanistan and Pakistan ex-
ceeding USD 1 billion. Similarly, Yr27 emergence and its
movement following the same pathway posed major
threat to wheat production in India and Pakistan, where
mega cultivars PBW343 and Inqilab 91 were having
Yr27 gene based resistance. In 2005, the wheat crop in
Nothern Pakistan was severely hit by this race of yel-
Copyright © 2013 SciRes. OPEN ACCESS
M. H. Khan et al. / Agricultural Sciences 4 (2013) 292-301 295
low rust where most of the area was under Inqilab-91.
Stem rust resistance in wheat cultivars with Sr31 re-
mained effective for more than 30 years. In 1990’s, most
of the wheat varieties were having 1B-1R translocation
which created a monoculture situation in Africa, Asia and
other parts of the world. Isolates of Puccinia graminis
tritici (pgt), which were virulent on Sr31 were collected
for the 1st time in Uganda during 1999 and then spread
throughout East Africa [26]. It subsequently spread to
Kenya and Ethiopia in 2005 [27]. The race, named as
TTKS (Ug99), is virulent on majority of mega wheat
varieties and can cause 100% yield losses whereas, up to
80% yield losses have been reported in Kenya. A new
variant of this stem rust race has been found in Kenya
since 2006, which is virulent on Sr24 [28,29]. Now a day
fungicides are being used to control stem rust in Kenya
[30]. It ultimately jumped the red sea and its presence
has been reported in Yemen since 2006 and was also
found in Sudan in the same year. In March 2007, isolates
of pgt were collected from different locations in Iran and
the collections from Borujerd and Hamadan were identi-
fied as TTKSK [31]. The race identified, produced high
IT’s of 3 to 4 on wheat genotypes carrying 1BL-1Rs
translocation (Falat and PBW343). Subsequently, FAO
announced its existence in Iran and alarmed a threat for,
the breadbasket zone of the world, South Asia and other
neighboring regions. A new race of stem rust virulent on
Sr25 gene, have been detected in India [32]. This isolate
collected from Karnataka, has shown IT’s 3+ to 4 on
primary leaves of differential types with Sr25 gene. This
race is named as PKTSC according to North American
system. The detection of Sr25 virulent race alarmed the
breeders that they should breed for adult plant resistance
or pyramid 2 or 3 major genes to enhance the field life of
wheat cultivars.
The problem of newly emerged races of pathogens has
led to the adoption of alternative forms of resistance by
the breeders that are more durable such as slow rusting
or partial resistance [33]. It has been indicated that dura-
ble rust resistance is more likely to be of adult plant type
rather than seedling type and is not associated with the
genes conferring hypersensitive reaction [34]. Durable
rust resistance is a mechanism conferring resistance to a
cultivar for long period of time during its widespread
cultivation in a favorable env ironment for a disease [35].
This type of resistance is mainly associated with the mi-
nor genes which are also known as slow rusting genes.
The concept of slow rusting in wheat was proposed by
reference [36], similar to partial resistance to late blight
of potato put forth by reference [37]. Various workers
have stressed the need to recognize and exploit longer-
lasting resistance. Reference [35] defined durable resis-
tance as a resistance source that remained effective after
widespread deployment over a considerable period. A
general concept of a durable resistance (a race non-spe-
cific) resistance source for a cereal rusts is as follow:
1) It may be controlled by more than a single gene;
2) It is more likely to operate at the adult-plant stage
rather than at both the juvenile and adult stage;
3) It confers non-hypersensitive response to infection.
Example of durable resistance include resistance to stem
rust transferred from tetraploid emmer to bread wheat
Hope and H-44 [38], resistance to leaf rust in the South
American wheat cultivar Frontana and related sources
The durable resistance is based on additive effect of
partial resistant minor genes, usually polygenic in nature
and active in adu lt plant stage. Genetic studies conducted
at CIMMYT, Mexico has shown that at least 10 - 12 dif-
ferent genes are involved in group of CIMMYT germ-
plasm, and by accumulating 4 - 5 minor genes resistance
level near to immunity can be achieved. However 2 - 3
genes in a line provide moderate level of resistance [39].
Most of these genes are undesignated only the genes
Lr34/Yr18, Lr46/Yr29 and Sr2/Yr30 have been given
names and designated to specific chromosomes. Each of
these genes pairs are tightly linked or pleotropic. The
varieties possessing minor gene based resistance show
almost same level of resistance over space and time. For
example Lyalpur 73 which was among major varieties of
Pakistan in 1970’s still show very good level of resis-
tance in screening nurseries. Whereas, the varieties hav-
ing major gene based race specific resistance did not
have long life and collapsed usually after 4 - 5 years.
Varieties having durable type of resistance show almost
same level of reaction against different races and their
resistance remained effective in different climatic condi-
tions. The leaf rust and yellow rust reaction of some va-
rieties having durable rust resistance are same at CIM-
MYT, El Batan, Mexico and Faisalabad, Pakistan. The
variety Frontana being released about half century ago
still have effective rust resistance almost every where.
There are very rare examples that resistance based on
major genes had been effective for a longer period of
time. Reference [40] identified 6 independent loci, con-
tributing to adult plant resistance (APR) or slow rusting
contributing to two rusts in a population derived from
cross of Avocet S and Pavon. The putative loci identified
on chromosomes 1BL, 4BL and 6AL influenced resis-
tance to both stripe and yellow rust. The loci on chro-
Copyright © 2013 SciRes. OPEN ACCESS
M. H. Khan et al. / Agricultural Sciences 4 (2013) 292-301
mosome 3BS and 6BL had significant effect on stripe
rust. The locus on the distal region of chromosome 1BL
with highly significant effects had also detected in other
mapping populations [34,41]. The distortion associated
with chromosome 4B linkage map has also been ob-
served in some other research reports [41]. Even Mo-
rocco and Avocet S have some genetic factors that con-
tain some slow rusting resistance which results in sig-
nificant delay in becoming completely susceptible [40].
The material having minor gene based resistance near to
immunity for leaf and yellow rust was developed and
distribute d w or ldwide in 1990’s by CIMMYT [33].
7. Sr2/Yr30 GENE
The gene, Sr2 was transferred to hexaploid wheat from
tetraploid emmer wheat cultivar Yaroslav in 1920. It is
present on chromosome 3BS and is also reported to be
associated with Lr27 [42]. It is completely linked with
pseudo black chaff (Pbc), which is used as morphologi-
cal marker for identification of lines carrying this gene.
The genotypes with Pbc show varying levels of stem rust
infection. The maxi mum severity lev el of 60% - 70 % ha s
been noted as compared to 100% severity of susceptible
check in disease screening nursaries in Kenya. When
present alone it does not provide sufficient level of resis-
tance but in combinatio n with other genes d esirable level
of resistance can be achieved. Much information is not
available about the interaction of Sr2 and other genes in
Sr2 complex. The adequate resistance level can be
achieved by accumulating 4 - 5 minor genes. Sr2 was
detected in several highly resistant old, tall Kenyan cul-
tivars like Kenya plume and semidwarf CIMMYT, culti-
vars Pavon F 76, Parula, Kingbird, Dollarbird etc. These
cultivars show maximum disease severity of 10% - 15%
with moderately resistant reactions. The gene Sr2 is
tightly linked with Yr30 or has pleotropic effects [43]. A
microsatellite (SSR) marker gwm533 is tightly linked
and associated with the presence of this gene, which can
be used to facilitate selection of this difficult to score
gene [44].
8. Lr34/Yr18
Numerous genes conferring resistance to wheat rusts
have been identified and used in wheat (T. aestivum L.)
breeding. However, several of these genes have been
rendered ineffective due to emergence of new virulent
races. Cultivars with the rust resistance gene Lr34 such
as Frontana had effective durable rust resistance to leaf
rust (P. triticina). Although Lr34 has been used exten-
sively in spring wheat grown in US, isolates of P.
tiriticina with complete virulence to this gene had not
been detected [45]. It has been found that soft red winter
wheats having Lr34 in combination with seedling resis-
tant Lr2a, Lr9, Lr26 were highly resistant while in com-
bination with Lr10, Lr11, Lr18 were moderately to low
resistant in USA [46].
Gene Lr34 first described by reference [8] has been
shown to enhance leaf rust resistance in combination
with other genes [47]. Another feature of Lr34 resistance
is that it remained genetically inseparable from Yr18
gene, which confers APR. This gene co-segregates with
leaf tip necrosis (Ltn1), powdery mildew resistance (Pm8),
Barley yellow dwarf virus (Bydv1) genes [48,49]. These
multipathogen resistance traits have made the Lr34/Yr18
locus one of the highly valuable regions for disease re-
sistance in wheat [45]. If Lr34/Yr18 complex is present
alone the disease level may go high but in combination
with other genes it could give effective control [50]. At
low temperature the resistance level conferred by plants
with Lr34 is higher under growth chamber and green
house condition. The gene seems to be effective under
field conditions at average daily temp 0˚C - 20˚C and
helps in reducing disease progress [24]. Reference [11]
had indicated that environment has a significant influ-
ence on terminal disease reaction for leaf rust. Reference
[16] showed that Yr18 may display inadequate resistance
under some environmental conditions. It is present in
many subcontinental varieties including some released in
pre green revolution era. A marker associated with
csLV34 locus on chromosome 7D was found associated
with Lr34/Yr18 gene. Two predominant allelic size vari-
ants csLV34a and csLV34b were identified. A strong as-
sociation was observed with the presence Lr34/Yr18
gene and csLV34b allele. However lines having Lr34/
Yr18 gene and positive for csLv3 4a allele were rare. The
lineage of this gene is tracked back to varieties Mentana
and Ardito developed in Italy during early 1990’s [45].
This gene has been cloned and was shown that Lr34/
Yr18/Pm38/Ltn1 is the same gene [51].
9. Lr46/Yr29
A slow rusting gene identified in the cultivar Pavon
and was found located on chromosome 1B by crossing
with a monosomic series of adult plant leaf rust suscepti-
ble cultivar Lal Bahadur [52]. This is the 2nd named mi-
nor gene involved in slow rusting. The leaf rust resis-
tance gene Lr46 and yellow rust resistance gene Yr29 are
tightly linked or Pleotropic [53]. Its effect is similar to
Lr34/Yr18 as it does not provide complete immunity to
plants. Infected adult plants carrying Lr46 have longer
latency period as compared to control without this gene
[54]. The plants with this gene also show higher rate of
fungal colonies abortion with out any chlorotic or ne-
crotic effects and also decrease the colony size. The re-
sistance conferred by this gene is not of hypersensitive.
Reference [41] determined that the microsatellite locus
Copyright © 2013 SciRes. OPEN ACCESS
M. H. Khan et al. / Agricultural Sciences 4 (2013) 292-301
Copyright © 2013 SciRes. OPEN ACCESS
Xwmc44 is located 5.6-cM proximal to the putative QTL
for Lr46. Leaf tip necrosis (Ltn) has been reported to be
highly correlated with the presence of Lr46/Yr29 [55].
Efforts are underway to clone this gene
Accumulating minor genes for attaining desired level
of resistance in a variety is a challenging task [56] as it
requires identification of parents with minor genes,
crossing them in specific schemes following back cross
or top cross approach, maintaining desirable population
size and selection of desirable genotypes from segregat-
ing populations. The crossing schemes and selections
strategies used for breeding major genes based resistance
are not suitable for b r ee ding min or g ene resistance.
The modified pedigree method used for breeding ma-
jor gene based resistance can not give any progress for
minor gene based resistance. Reference [52] compared
different crossing and selection schemes for working out
their efficiency in terms of genetic gains and cost effi-
ciency. The influence of type of cross and selection
scheme was minimal on main grain yield. They found
that selection of parents was the most important feature
in breeding for achieving desirable results. They also
reported that mean rust severity of top cross progenies
was less as compared to simple cross because two par-
ents contributed resistance factors to the top cross proge-
nies. Non selected bulk method was found to be least
effective and selected bulk method as the most attractive
schemes in terms of genetic gain and cost efficiency. An
example of breeding for minor gene based resistance is
the development of wheat stock resistant to leaf and yel-
low rust at CIMMYT.
Since early days of breeding for minor genes, plants
and lines with infection intensity of 20 % - 30% and com-
patible infection type were targeted. This led to the de-
velopment of wheat varieties Nacozari F 76, Pavon F 76
and several others [56] which were released not only in
Mexico but also in Ethiopia, Bangladesh, Pakistan and
other countries. Pavon was released in 16 countries with
different names (Table 2). This material provided the
foundati on for breeding for minor gene resistance.
In Pakistan the varieties Uqab 2000 (CROW’S’/NAC/
BOW’S’), Bhakkar -02 (P-102 /P IMA//F 3.71/TRM/3/ PVN)
and Seher-06 (CHIL/2*STAR/BOW/ CROW/BUC/PVN/
3/VEE#10) have this type of resistance. Bhakkar-02 has
dominated the mega wh eat cultivar Inqilab91 sin ce 2005
after Inqilab 91 was hit by yellow rust epidemic and Se-
her-06 is gaining popularity now, due to its higher yield
and better resistance to leaf and yellow rusts. The variety,
Table 2. Derivatives of Pavon (VCM/CNO/7C/3/KAL/BB) released in different part of the world.
S. No Country Variety Year Pedigree
1 Algeria Citra 78 1978 CM8399-D-4M-3Y-1M-1Y-0Y-0DZA
2 Algeria Chellif 78 1978 CM8399-D-4M-3Y-0M-0DZA
3 Bangladesh Pavon 76-Bgd 1979 CM8399-D-4M-3Y-1M-1Y-1M-0Y-0BGD
4 Bolivia Pilanchu 80 1980 CM8399-D-4M-3Y-1M-0M-1-14Y-0BOL
5 Bolivia Totora Ibta 80 1980 CM8399-D-4M-3Y-1M-1Y-1M-0Y-0BOL.
6 Chile Victoria 1981 CM8399-D-4M-3Y-0M-0CHL
7 Chile Marib 1 1983 CM8399-D-4M-3Y-1M-1Y-1M-0Y-0YMD
8 Chile Onda Inia 1982 CM8399-D-4M-3Y-1M-1Y-0M-0CHL
9 Egypt Giza 162 1988 CM8399-0 EGY
10 Ethiopia Pavon 76-Eth 1982 CM8399-D-4M-3Y-1M-1Y-1M-0Y-0ETA
11 Mexic o Pavon F 76 1976 CM8399-D-4M-3Y- 1 M-1Y-1M-0Y-0MEX.
12 Morocco Baraka 1988 CM8399-0MAR
13 Nigeria Samwhit 6 1990 CM8399-0NER
14 Pakistan Pavon Pak 1978 CM8399-D-4M-3Y-1M-1Y-1M-0Y-0PAK
15 Peru Elgavilon 1982 CM8399-D-4M-3Y-1M-1Y-0Y-0PER
16 Tanzania Azimio 87 1987 CM8399-D-4M-3Y-1M-1Y
M. H. Khan et al. / Agricultural Sciences 4 (2013) 292-301
Uqab 2000 proved the best option for the rain fed north-
ern Pakistan after severe epidemic of yellow rust in
An example of breeding for durable rust resistance out
side CIMMYT is the wheat breeding program of Ayub
Agricultural Research Institute, Faisalabad-Pakistan. The
germplasm of wheat (about 1200 accessions) was sc r ee ne d
under artificial inoculation with mixture of races and the
parents having partial resistance for leaf/yellow rust were
selected [57]. This germplasm was crossed to pyramid
genes for high yield and rust resistance. The main focus
was accumulation of minor genes for rust resistance be-
cause this type of resistance mechanism is considered
more durable and is effective for many races rather than
single race [58]. The parents selected were used to con-
struct back crosses, top crosses and double crosses.
Mostly selected bulk method was used as described by
reference [39] to advance the filial generations to con-
serve maximum genetic diversity. In F2 generation, 2500
- 3000 plants were raised. Heads were taken from plants
having desirable plant type and were bulked to raise F3
generations. From F3 - F6 generations, plants were se-
lected on the basis of good plant type and rust intensity.
The heads were taken from the plants having rust inten-
sity ranging 0% - 30% preferably with R/MR/MS type of
Various lines were selected from this material and
tested for yield and disease reaction. Two varieties
Shafaq-06 and Lasani-08 having durable type of resis-
tance were approved for general cultivation in the Pun-
jab-Pakistan [59,60]. These varieties are high yielding
and possess durable resistance to leaf and yellow rust.
Lasani-08 was also found resistance to stem rust (Ug 99)
in the year 2007 at Kenya.
Pyramiding of several genes into one cultivar can be
an effective strategy to use resistance genes to enhance
durability of wheat resistance to leaf and stem rust [3].
Durable resistance may be achieved by combination of
several genes encoding partial resistance. Gene pyra-
miding through conventional methods is difficult and
time-consuming because it requires simultaneous tests of
the same wheat breeding materials with several different
rust races before a selection is made. Usually, it is not
feasible for a regular breeding program to maintain all
necessary rust races needed for this type of work. There-
fore, MAS is a powerful alternative to facilitate new
gene deployment and gene pyramiding for quick release
of rust-resistant cultivars. Molecular markers such as
STS or SCAR and CAPS are available for leaf rust r esis-
tance genes Lr1, Lr9, Lr10, Lr19, Lr21, Lr 24, Lr25, Lr28,
Lr29, Lr34, Lr35, Lr37, Lr39, Lr47 and Lr51. Enzymatic
marker (endopeptidase Ep-D1c) for Lr19 has also been
developed [61]. Microsatellite (SSR) and AFLP markers
for some Lr genes such as Lr 3bg, Lr18, Lr40, Lr46 and
Lr50 have been developed by reference [62,63]. Mo-
lecular markers are available also for stem resistance
genes such as Sr2, Sr9a, Sr22, Sr24, Sr26, Sr31, Sr36
and Sr39. Some of the markers have been used in MAS,
but markers for some of the genes are not diagnostic for
the genes and must be improved and markers for other
genes are not available. At the present time, the research
of stem rust in wheat has focused on identifying more
resistance genes to control Ug99. According to the Farm
and Ranch Guide report, currently 50% of winter wheat
and 70% to 80% of spring wheat used in the USA are
susceptible to Ug99. Moreover, 75% - 80% of the breed-
ing materials are susceptible to Ug99 and most stem rust
resistance genes deployed in breeding programs have
been overcome by this new fungus
/ag_news/ productio n_news/pro10.txt).
Microsatellite marker closely linked to resistance gene
Sr40 has b een also ob tained [64,65 ]. D ate thr ee genes for
leaf rust resistance in wheat Lr1, Lr10 and Lr21 [66]
have been isolated cloned and sequenced. They all have
sequences that encode nucleotide binding site (NBS)-leu-
cine-rich repeat (LRR) regions, which are characteristic
of disease resistance genes in plants. Molecular descrip-
tion of these genes in wheat provides a unique biological
system to study the molecular mechanisms of wheat-
pathogen interaction and transduction as well as the re-
sistance gene function, evolution and diversity. This will
allow further manipulation of wheat resistance genes to
increase the resistance durability by genetic transforma-
tion of wheat.
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