1. Fig 1. Distribution map of stem rust disease in Iraq during 2009/10.
Occurrence and Race Analysis of Wheat Stem Rust in Iraq Emad Al-Maaroof 1, Les Szabo 2, Kumarse Nazari 3, Azad Naser 4, Abdul Hamid AbdulRazak 4, Saman Ali 4, Laith Amin 4 , Hatem Hussien 4, Nabez Rasheed 4 and Mahdi Laize 4 1. Faculty of Agricultural Sciences, Sulaimani University, Sulaimania, Iraq; 2. USDA-ARS Cereal Disease Laboratory, Minnesota University, St Paul, USA; 3.International Center for Agriculture Research in the Dry Areas (ICARDA), Tel Hayda, Allepo, Syria; 4. Agriculture Research Directorates, Ministry of Agriculture, Iraq. Corresponding author
BGRI 2012 Technical Workshop
September 1- 4, 2012 Beijing,
CHINA
Introduction
stem rust of wheat caused by Puccinia graminis f. sp. tritici, was a feared disease in many wheat-growing regions of the world. The disease has successfully been controlled in the world by introduction of the semi-dwarf resistant wheat cultivars during the 1970s. Resistance of wheat cultivars were based mainly on Sr31 gene introduced from Secale sacales. In addition to the high levels of resistance to stem rust, powdery mildew and stripe rust diseases, the new wheat cultivars gave significant yield advantage. Stem rust has again become a major cause for concern with the emergence of a new strain of the disease in Eastern Africa. The report "Sounding the Alarm on Global Stem Rust", issued 29 May 2005 by the Expert Panel on the Stem Rust Outbreak in Eastern Africa, unequivocally declared Ug99 to be a strategic threat to global wheat production including Iraq. The potential impact of stem rust is particularly serious in Iraq and could become a serious problem to irrigated wheat production in the northern regions.
Material and Methods
Extensive surveys were conducted in most of wheat growing area's during season by using GPS in monitoring black stem rust pathogen in Iraq. Surveillance were conducted in 300 farmer fields and research stations. Disease response, geo-referenced information were collected using standard surveillance protocol developed by Durable Rust Resistance in Wheat (DRRW) project and. Response of the commercial bread and durum wheat cultivars to stem rust were evaluated in all the surveyed fields. GPS and disease incidence and severities were used in development of the distribution map of yellow rust by Dr. Dave Hodson, The International Focal Point of surveillance activities. Virulence analyses of P. graminis populations were conducted at 11 locations by exposing stem rust biological trap nurseries to the natural population of the pathogen in the field. Disease scoring on the biological trap nurseries were conducted using disease severity and infection types on each genotype. Single pustules of stem rust samples collected from different wheat cultivars were analyzed on stem SR differential set at Sulaimani University. While five single pustule samples were sent to cereal disease laboratory, USDA for DNA analyses.
Results and Discussions
High attention should be focused on this fact since severe infections were detected on some wheat cultivars in some fields which are closed to the Iranian border where the Ug 99 was detected. The highest incidence of the disease were recorded in Erbil and Deqar in 2010, while low incidence of stem rust (1.3%) was detected only in some wheat fields in Sulaimani and Nineveh during The high incidence of the disease in2010 was due to favorable environmental conditions, high rainfall in coupled with warm winter.
Table 1. Occurrence and distribution of stem rust disease
in wheat fields during 2009/10 and 2010/11seasons in Iraq.
Province
No. of W.P
2010
None
No. of
W.P
2011 L M H
Sulaimani 42 2 1
116 39 3
Erbil 51 16 4 8
148
143 28
Nineveh 32
Garmian
Diala 20 6
Mesan 10
Deqar 17 5 12
Wasit
Baghdad 7
Duhok
Total
209 27 9 11
330
204 47
Results of virulence analyses of P. graminis population revealed that virulence against the known resistant genes Sr6, Sr9e, Sr13, SrTmp, Sr14, Sr28 and Sr36 were detected in the natural populations of the pathogen at adult plant stage in the field. Evaluation of the 4th stem rust screening nursery to P. graminis f. sp tritici at different stages and development of the host plant under natural infection conditions, revealed that about 42% of the tested genotypes showed resistant reaction to the pathogens and 21% of the genotypes were moderately resistant, while 33% showed moderately susceptible reaction and 12% were susceptible. High disease severity and infections were detected on Quaiu and most of Quaiu derivatives {Fig 2). PBW 343 and some of its derivatives showed moderately susceptible reaction (30MS) to P. graminis f. sp tritici which is similar to the infection type obtained by the race Ug99 on the same cultivar.
Race analysis of stem rust samples at seedling stage indicated identification of three physiological races of Pgt from different agro ecological zones in Iraq during 2010/11 season. Pgt races showed differences in virulence spectrum on stem rust resistant genes. Race RKTRF representing Sulaimania wheat fields showed virulence on Sr5, 6, 7b, 8a, 9a, 9b, 9d, 17, 21, 30, 36, 38, Tmp and Mcn. Race MKPLF from Erbil showed virulence on Sr5, 6, 7b, 8a, 9d, 9g, 17, 30, 36, 38, and Mcn. While race NGTJC from Dyala was virulent on Sr5, 6, 7b, 9b, 10, 30, 36, 38 and Mcn. single pustule culture analyzing of stem rust samples at seedling stage revealed that all Pgt samples are not belonging to Ug99 group. This result was confirmed by DNA analyzing of single pustule samples of P. graminis f,sp. tritici at USDA advance rust labs.(Table 2).
Results of the extensive surveys in wheat growing area’s revealed that only trace infection of stem rust were detected in some wheat fields late in the season in Suliamani during 2008/2009 season, while during low to high infections of the disease were detected in some wheat fields in sulaimani, Neneveh and most wheat fields in Erbil, Garmian also central and southern parts of Iraq (Fig 1). stem rust appearance in sulaimani is not usual since it is cold area and the disease has never been seen previously there.
Fig 2. High infection of stem rust on Quaiu
derivatives at adult plant stage
Table 2. DNA analyses of five single pustule
isolates of P. graminis f. sp. tritici from Iraq
TTKSF1
TTKSF2
TTKSK1
TTKSK2
TTTSK1
TTTSK2
TTKST1
TTKST2
TTKSP
PTKST
CDL_PGT_A003 CC CT
CDL_PGT_A007 GG AG
CDL_PGT_A010 TT
CDL_PGT_A013
CDL_PGT_A014 AA
CDL_PGT_A017
CDL_PGT_A021
CDL_PGT_A022
D11- Iraq 000
D11- Irq 001
D11-Irq 002
D11-Irq 003
D11-Irq 004
CDL_PGT_A003 ? CC
neg
CDL_PGT_A007 GG
CDL_PGT_A010 TT
CDL_PGT_A013
CDL_PGT_A014
CDL_PGT_A017
CDL_PGT_A021 AA
CDL_PGT_A022
Fig 1. Distribution map of stem rust disease in Iraq during 2009/10.