Indexed In
  • Open J Gate
  • Genamics JournalSeek
  • Academic Keys
  • JournalTOCs
  • CiteFactor
  • Ulrich's Periodicals Directory
  • Access to Global Online Research in Agriculture (AGORA)
  • Electronic Journals Library
  • Centre for Agriculture and Biosciences International (CABI)
  • RefSeek
  • Directory of Research Journal Indexing (DRJI)
  • Hamdard University
  • EBSCO A-Z
  • OCLC- WorldCat
  • Scholarsteer
  • SWB online catalog
  • Virtual Library of Biology (vifabio)
  • Publons
  • Geneva Foundation for Medical Education and Research
  • Euro Pub
  • Google Scholar
Share This Page
Journal Flyer
Flyer image

Research Article - (2018) Volume 9, Issue 1

Leaf Rust Resistance of 35 Wheat Cultivars (Lines)

Li J1#, Shi L1,2#, Wang X1, Zhang N1, Wei X1, Zhang L1, Yang W1* and Liu D1,3
1Department of Plant Pathology, College of Plant Protection, Agricultural University of Hebei, Biological Control Center for Plant Diseases and Plant Pests of Hebei, P.R. China
2Institute for the Control of Agrochemicals, MOA, Beijing, P.R. China
3Graduate School of Chinese Academy of Agricultural Sciences, Beijing, P.R. China
#Contributed equally to this work
*Corresponding Author: Yang W, Department of Plant Pathology, College of Plant Protection, Agricultural University of Hebei, Biological Control Center For Plant Diseases And Plant Pests Of Hebei 289 Lingyusi Street, 071001 Baoding, Hebei, P.R. China, Tel: +86-312-7528585 Email:

Abstract

Wheat leaf rust caused by Puccinia triticina (Pt) is one of most severe fungal diseases threatening global wheat production. Rational utilization of the diversified leaf rust resistance (Lr) in different wheat cultivars is still the most efficient method to control this disease. Here in this study, 35 wheat cultivars collected from China main wheat growth region were tested for their seedling resistance to 16 different Pt races. Seedlings of 20 tested wheat cultivars showed high resistance phenotype to at least one Pt race. Various molecular markers closely linked to fifteen designated Lr genes were applied and only three Lr genes (Lr1, Lr10 and Lr26) were identified in some of the tested cultivars. All cultivars were then inoculated with bulked Pt races mixed with even of 10 pathotypes at adult plant stage to detect the adult plant resistance (APR). Five cultivars including Liangxing 66, Hemai 9735, Luyuan 301, Jimai 17 and Taishan 027 showed typical APR reaction in the field. Our results indicate that the diversity of known Lr genes in the tested wheat cultivars is relative low, but 10 of them contained more durable leaf rust resistance and can be released in wheat production and can be used as resistance breeding resources.

Keywords: Wheat; Leaf rust resistance; Adult plant resistance

Introduction

Wheat leaf rust caused by Puccinia triticina Eriks (Pt) is one of the most severe fungal diseases on wheat worldwide. Yield losses caused by this disease range from 5% in resistance cultivars to 62.7% in susceptible one under favorable conditions [1], along with reduced protein level and softness equivalent scores in the grain [2]. There were several destructive epidemics of wheat leaf rust in 1969, 1973, 1975 and 1979 in China, especially caused sporadic but dramatic yield losses in the Yellow-Huai areas of China [3]. With the trend of global warming and high density of cultivation, wheat leaf rust has expanded its infection area to the major wheat planting region. The very recent epidemics of wheat leaf rust in China occurred in 2012 [4]. Rational utilization of the diversified leaf rust resistance (Lr) in different wheat cultivars, especially local ones, is still the most efficient method to control this disease. Hence, maintaining a level of resistance is an important goal in many wheat breeding programs. To date, 76 Lr genes have been formally cataloged in the wheat genome [5]. Many of the Lr genes were derived from alien species of wheat, including Lr19 from Agropyron elongatum [6], Lr26 from Secale cereale[7] and Lr47 from Aegilops speltoides etc [8]. Majority of these genes showed race-specific resistance, whereas others showed adult plant resistance (APR). Race specific or so-called seedling resistance Lr genes are easy to lose their function during large scale cultivation due to the high selection pressure on Pt races. For example, after widely used in breeding program from the 1980s, Lr26 gene was reported to be overcome by newly emerged virulent Pt races in China at the year of 1999 [8]. On the other hand, APR genes are more durable and normally show resistance to multiple fungal pathogens. Therefore, investigation on Lr genes in different wheat cultivars will greatly facilitate the wheat breeding program and utilization of the resistance in wheat leaf rust control.

Methods of detecting Lr genes in various wheat cultivars include traditional gene postulation and genetic co-segregation analysis, as well as molecular marker-assisted identification. Based on the gene-to-gene theory, gene postulation has been widely used in identification of both Lr genes from wheat and newly emerged races from Pt. [9-13]. However, the accuracy of gene postulation results may be influenced by several factors, including selection of pathogen races, inoculation conditions, genetic backgrounds of the plants and personal experience. During the last decade, molecular marker-assisted identification of Lr genes has been well established and various markers (STS, SCAR and CAPS) linked to different Lr genes have been developed. So far, more than 20 molecular markers closely linked to various Lr genes, including Lr9, Lr10, Lr19, Lr21, Lr24, Lr26, Lr34, Lr37 and Lr47 etc. [14-18]. Combination of both traditional gene postulation and molecular markers has greatly improved the accuracy of Lr gene identification procedures [12,19,20].

The initial work of identifying Lr genes in released wheat cultivars was started from the 1980s in China [9,11,13,20,21]. Various Lr genes identified in different wheat cultivars provide valuable resources for wheat breeding program and resistance gene pyramiding. However, with the rapidly emerged high virulent Pt races and large number of newly released wheat cultivars, there are still urgent needs for identification of Lr genes. The 35 cultivars (lines) were from the main wheat growth region and some of them were used as the resistance breeding resources and some of them had been or will be released in China. Little information of wheat leaf rust resistance is known. Therefore, identifying Lr genes is important for sustainable gene deployment and for breeding new resistant cultivars. This study was designed to identify both gene postulation and molecular markers in 35 mainly cultivated wheat cultivars from China.

Materials And Methods

Wheat germplasm and P. triticina pathotypes

Thirty-five winter wheat cultivars were collected from mainly cultivated ones in China (Table 1). Thirty-five wheat near-isogenic lines (NIL) carrying different Lr genes in Thatcher background were kindly provided by the USDA-ARS Cereal Disease Laboratory and included in the gene postulation assay (Table 1). Thatcher and Zhengzhou 5389 were used as susceptible control. Sixteen isolated Pt races (FHHT, TCHT, PBGP, TCQT, PCGT, FHQT, RCHT, PCLT, NCRT, THST, FCGT, FHGQ, PHQT, FCQT, PBQT and FHQT) were designated following the naming system [22].

Test cultivars (lines) Leaf rust pathotypes
FCGT FCQT FHGQ FHHT FHQT FHST NCRT PBGP PBQT PCGT PCLT PHQT RCHT TCHT TCQT THST
TcLr1-RL6003 ;1 ; ;1 ;1 2 ;1 3 4 3 4 3 3 3 4 4 3
TcLr2a-RL6016 ; ; 1 1 2 ;1 ;1 ;1 ;1 2 ; ;1 3 4 4 3
TcLr2b-RL6019 ;1 1+ 3 4 4 1+ 4 3 1 4 4 ; 4 4 3 4
TcLr2c-RL6047 3 3 3 4 3 3 3 4 3 3 3 3 0 4 3 4
TcLr3-RL6002 3 3 3 4 4 3   1 4 3 3 3 3 3 3 3 4
TcLr3bg-RL6042 4 3 3 4 3 3 3 4 3 3 3 3 3 ; 4 4
TcLr3ka-RL6007 2 3 1 1 3 3 3 ;1 3- ;1 3 3 1 ; 3 3
TcLr9-RL6010 ;0 ; 0 0 0 ; 0 0 0 ;0 0 0 ; 1 ;1
TcLr10-RL6004 3 3 4 4 3 3 4 ;1 3 3 3 3 3 4 3 3
TcLr11-RL6053 3 3 3 4 3 3 3 4 3 3 1 3 3 4 3 4
TcLr14a-RL6013 3 3 2 4 4 3- 3 4 3 3 4 3 3 4 3 4;
TcLr15-RL6052 4 3 ;1 ;1 4 ; 1 4 3 ;1 3 3 1; 4 1 3
TcLr16-RL6005 ;1 ; 3 3 3 3 ;1 ;1 2 2+ 1; 3 2 2 2 4
TcLr17-RL6008 1 2 2 1 2 3 2 ;1 1; 1 ;1 2+ 2 1 1 3
TcLr18-RL6009 3 3 2 4 3 3- 3 4 3 3 3 4 4 4 4 4
TcLr19-RL6040 ;1 ; ; ; 0 ; ; ;1 0 ;1 0 ; 1; ;1 0; ;1
TcLr20-RL6092 3 - ;1 ; 4 ; 4 4 3 3 3 3 3 2 4 4
TcLr21-RL6043 3 3 3- 4 3 2 3 4 - 3 2 1+ 4 4 4 4
TcLr23-RL6012 ;1 1 1+ ; 1; 2 1; ;1 - 3 1; 1 1 ;1 ;1 3
TcLr24-RL6064 ;1 ; ; ;1 ; ;1 ;1 ;1 ;1 ;1 ;1 ;1 ;1 0 1; ;
TcLr25-RL6084 3 3 3 4 4 3 4 4 3 3 3 3 3 4 4 4
TcLr26-RL6078 4 3 3 4 4 3 3 2 2 3 3 3 3 4 3 3
TcLr28-RL6079 0 0 ; ; 0 3 ; 0 ; ; 0; 0 0 0 ; 4 ;
TcLr29-RL6080 ;1 1; ;1 ;1 0 1; ;1 1 ; 1 1 1; ;1 ; ;1 ;1
TcLr30-RL6049 0 1 2 4 ;1 1 3 ;1 2 1 2 ;1 3 3 2 2
TcLr32-RL5497-1 3 2 3 2 4 2 ;1 ;1 2 2 2 3 3 ;1 2 2
TcLr36-E84018 ;1 1 1+ ;1+ 1; 1; 1 ;1 ;1 1 ;1 2 1 ;1+ 1; ;1
TcLr38-RL6097 ;1 ;1 ;1 ; ; 1; 0 1 ; 2 1 ;1 2; ;1 ;1 ;
Lr39- KS86WGRC02 ; 1+ 2 4 3 1; 0 3 1 1 2 1; 3 3 3 3
Lr42- KS90WGRC11 ; ;1 2 ; 0 1 3 ; 1; 0 0 1; 3 ; ;1 ;
TcLr44-RL6147 1 1+ 1 2 3 3 1 ;1 1 1 1 1 2 ;1 1 ;1
TcLr45-RL6144 ;1 ;1 1; ; ;1 1; ;1 0 ;1 0 ;12 1 1 3 1 ;1
Pavon76-Lr46 ;1 ;1 ;1 ; 3 ; 3 3 1; ; 3 1 3 ; ; 4
Lr50- KS96WGRC36 ; 3 4 4 4 3 3 1 3- ;1 ; 3 1 4 2 4
TcLrB-RL5688 4 3 4 4 3 3 3 4 3 3 4 4 4 4 3 3
Liangxing 66 1; 3- ;1 ; 2 3- 1 1 3- 2 2 3 2 ; 2 3
PH01-24 ;2 3 4 2 3 2 2 1 3 2 2 1 3 2 2 3
Zi6135 3 3 1 2 3 3- 2 3 3- 2 2+ 3 2+ 2 3 3
Hemai9735 2 3 2 1 2 3 3 1 3 3 3 3 3 1 ; 3
Zhouyuan 187 ; ;1 ;1 ; 3 ; 3 1 3 3 3 3 3 ; 0 3
Bin 02-47 3 3- 2 4 3 2+ 1 4 2+ 1 1 2+ 2 4 1 2
Liao 9518 ;1 ; ;1 ; 1 ;1 ;1 ;1 3 3 1 2+ 1 ;2 1;2 2
Yan 896063 ; 1+ ;1 ;1 1 2 1 1 2 1 1 3 2 ;1 1 2
Linkang 5025 2 2 2; ;1 2+ 2 3 1 3 1 2 3 1 ;1 2 2
Taishan 269 3 3 2 4 3 3 3 4 3 3 3 3 3 4 3 4
Hemai 9803 2 3 2 4 3 3 2 4 3 2 3 3 2 4 3 4
Luyuan 301 2 3 4 4 3 2+ 3 2 2 1 3 3 3 4 3 3
Taishan5024 3 3 3 4 3 3 3 4 3 4 3 3 3 4 4 4
Lainong 9214 ;1 2 ;1 ;1 4 3 3 ; 3- 2 2 3 3 ; 2 2
Jimai17 3 3 2 4 2 2+ ;12 2 2+ 1 12 2 2 4 1 2
Zemai No.1 ; ; ;1 ;1 2 ;1 3 2 2 1 3 3 3 ;4 3 0
Yannong 15 ;1 1+; ;1 ;1 ; ;1 12 ;1 3 ; 1 1 2 ;1 3 2;1
Weimai No.8 0 ; ;1 ;1 1 ;1 2 2 1 3 1 3 3 ; 3 3
Yan 861601 ;1 1+ 2 1 1 1 1 ;1 ;1 ;1 ;1 2 1 ;1 1 2
Linmai No.4 2 3 4 3 4 3 1 4 3 4 3 3 1 4 4 3
Laizhou 953 ;1 1+ 2 1 1 1 1 ;1 ;1 ;1 ;1 4 1 ;1 1 2
Luyuan 9160471 2 3 4 3 4 3 1 4 3 4 3 3 1 4 4 3
Binzhou 98-6 3 1+ ;1 ;1 1 1 1 ; ;1 1 ;1 1; 2 ;1 1; 3
Yan 5286 ;1 ; ;1 ;1 ; ;1 1 2 2+ 3- 3 3 3 3 1 3
Liao 9629 3 1 2 4 4 1; 3 ; 1 4 3 3 4 ;1 1 3
Liao 9638 0 1+ ;1 ;1 3 1 2 1 2 2 2 2 2 1 1 2
Yan 5158 3 2+ 2 4 3 2+ 1 2 2+ 3 2 2+ 3 3 3 4
Taishan 027 0 3 2+ 4 4 2+ 3 ; 3 3 ; 3 3 4 3 3
Liao 9514 2 3 1 ;1 3 1 2 4 ;1 1 3 3 2 ;1 2 3
Linmai No.6 3 3 2 ; 4 1 3 ; 3 1 3 3 3 ; 4 4
Yan103 4 3 3 4 4 3 0 4 3 4 3 3 1 3 3 3
Yan C96 ;1 3- ;1 ;1 3 2+ 0 2 2 1 2 2+ 1 ;1 1 2
Weimai No.6 4 3 4 4 3 3 3 4 3 2 3 3 3 4 2 4
Weimai No.7 0 3 4 4 4 3- 3 4 3 4 3 2 3 4 2 4
PH01-35-2 3 3 2 3 2 3- 1 ; 3- 3 1 4 2 3 2 3
Thatcher 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4
Zhengzhou 5389 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4

Note: 0: Immune Response, No Sign of Infection; ;: Hypersensitive Chlorotic or Necrotic Flecks; 1: Small Uredinia Surrounded by Necrosis; 2: Small Uredinia Surrounded by Chlorosis; 3: Moderate Size Uredinia without Necrosis or Chlorosis; 4: Large Uredinia without Necrosis or Chlorosis, + =: Uredinia Somewhat Larger than Normal, - =: Uredinia Somewhat Smaller than Normal.

Table 1: Infection types (ITs) of collected wheat cultivars and Lr near isogenic lines to 16 different Puccinia triticina races at seedling stage.

Postulation of leaf rust resistance genes at seedling stage

All the collected wheat cultivars, Lr-NILs and susceptible controls were inoculated by those of 16 Pt races at the seedling stage in the greenhouse with 3 biological replicates. Briefly, 8-10 seeds for each wheat material were sown in 25 cm × 18 cm × 7 cm iron trays with a pasteurized mixture of soil and compost for inoculation of each Pt race. Sixteen sets, each containing collected cultivars and Lr-NIL were grown separately with three biological replicates. Seven-day-old seedlings were inoculated separately with each of the sixteen Pt races. Inoculated plants were placed in a dew chamber overnight at 18°C to 20°C and then transferred to greenhouse chambers at 18°C to 22°C. Infection types (ITs) were recorded at 12 days after inoculation according to the 0 to 4 scales as described [23,24]. The presence of Lr genes in the seedlings of these collected cultivars was postulated by comparing the ITs according to the rules of gene postulation [25].

Evaluation of adult plant resistance (APR) in the fields

Field evaluations of APR to wheat leaf rust were conducted in cropping seasons of 2007-2008 and 2008-2009 at Baoding, Hebei, China. All the 35 collected wheat cultivars, as well as the susceptible cultivars Thatcher and Zhengzhou 5389 were grown in two rows, with 2 m length and 30 cm space, based on a randomized complete block design with three replicates. Spreader rows of cultivar Zhengzhou 5389 were planted perpendicular and adjacent to the rows of tested cultivars. Inoculation was conducted at the stem elongation stage by spraying an equivalent mixture of 10 Pt races (FHHT, TCHT, PBGP, TCQT, PCGT, FHQT, RCHT, PCLT, NCRT and THST) in urediniosporewater suspension with added Triton® (0.03% W/V). When leaves of the susceptible cultivar Zhengzhou 5389 were fully rusted, phenotype was recorded following the described scale [26] and the percentage of infected leaf area was visually estimated as infected leaf area index (LRS) according to the modified Cob scale (Supplemental Table S1).

Molecular markers-assisted identification of Lr genes

DNAs were extracted from leaves of 7-day-old seedling plants of collected wheat cultivars using CTAB method. Various molecular markers, including STS, SSR and SCAR markers, closely linked to specific Lr genes were derived from previous researches. Molecular markers of Lr1 [27], Lr9 [28,29], Lr10 [30], Lr19 [31], Lr20 [32], Lr21 [14], Lr24 [33,34], Lr26 [16], Lr28 [35,36], Lr29 [37], Lr32 [38], Lr34 [17,18], Lr35 [39], Lr37 [40], Lr38 [41] and Lr47 [8] were used in this study to screen all the collected 35 wheat cultivars. The sequences of all primers are provided in Supplementary Table S2. PCR reactions were performed in volumes of 20 μL containing 2.0 μL 10× buffer (containing Mg2+), 0.4 μL 10 mmol/L dNTP, 50 ng of each primer, 50 ng of the extracted DNA and 0.8 U Taq DNA polymerase (Sangon, Shanghai). PCR programs were designed according to corresponding references (Supplemental Table S3). The PCR product was separated on a 0.8% agarose gel in 0.5 × TBE buffer and stained with ethidium bromide, then photographed under UV light.

Results

Postulation of seedling resistance genes

Infection types (ITs) of all the collected cultivars and Lr-NILs to 16 Pt races were recorded in Table 1. The most efficient seedling Lr genes with relative low ITs to major epidemic Pt races are Lr9, Lr19, Lr24, Lr29, Lr36 and Lr38. However, after gene postulation, we could not detect any of these genes in the 35 collected wheat cultivars.

Five cultivars, including Liao 9518, Zemai No.1, Yannong 15, Weimai No.8 and Laizhou 953, were postulated to carry Lr1 gene because TcLr1 displayed resistance to FHHT, FCGT, FHGQ, FCQT, FHST and FHQT pathotypes, while susceptible to the other tester races. These five cultivars displayed low infection type “;1” to pathotypes FHHT, FCGT, FHGQ, FHST, FCQT and FHQT, also displayed low infection types to other pathotypes (Table 1). Especially for Laizhou 953, it may also carry another two Lr genes (Lr3 and Lr32). Four cultivars, including Binzhou 98-6, Bin 02-47, Linmai No.4 and Yan 5185 showed similar phenotype with Lr-NIL TcLr3. They may also carry other Lr genes due to the phenotype difference from TcLr3.

Lr26 was present in 11 cultivars, including Luyuan 301, Zemai No.1, Weimai No.8, Yan 861601, Laizhou 953, Binzhou 98-6, Yan 5286, Liao 9629, Liao 9638, Yan 5158 and YanC96. All these cultivars were postulated to carry Lr26 and other Lr genes because they were but not only resistant with two Lr26 avirulent pathotypes (PBGP and PBQT).

Other phenotypic correlation such as Yan 896063 with TcLr32, Yan 861601 with TcLr17 and TcLr32, Zhouyuan 187 and PH01-35-2 with TcLr10 and Taishan 269 with TcLr18, have been demonstrated based on their resistant responses in Table 1.

Identification of Lr genes by molecular markers

Various molecular markers, including STS, SSR and SCAR markers, closely linked to specific Lr genes were derived from previous researches. Molecular markers of Lr1, Lr9, Lr10, Lr19, Lr20, Lr21, Lr24, Lr26, Lr28, Lr29, Lr32, Lr34, Lr35, Lr37, Lr38 and Lr47 were used to screen the genome DNAs extracted from the collected 35 wheat cultivars. Corresponding PCR segments for three molecular markers linked to Lr1, Lr10 and Lr26, respectively, were amplified in some of the cultivars.

Lr1 was identified using STS marker WR003 (760 bp) in ten wheat cultivars, including Weimai No 8, Yannong 15, Zemai No.1, Liao 9518, Zi 6135, PH01-24, Yan C96, Yan 103, Laizhou 953 and Linmai No.4 (Figure 1). Lr10 was identified using STS marker Fl2245/Lr10-6/r2 (310 bp) in two wheat cultivars, including Zhouyuan187 and PH01-35-2 (Figure 2). Lr26 or 1B/1R chromosome translocation of Secale cereal was identified using two markers Glu-B3 (636 bp, Lr26 negative) and ω-secalin (1076 bp, Lr26 positive). Fourteen wheat cultivars including Luyuan 301, Zemai No.1, Weimai No.8, Yan 861601, Laizhou 953, Luyuan 9160471, Binzhou 98-6, Yan 5286, Liao 9629, Liao 9638, Yan 5158, Yan 103, Yan C96 and Weimai No.6, showed a positive band of Lr26 (Figure 3). Information of Lr genes identified by both gene postulation and molecular markers were summarized in Table 2.

plant-pathology-microbiology-specific-primer-linked

Figure 1: PCR amplification using specific primer linked to Lr1 in the test cultivars M: DL2000 Marker, N: TcLr1, T: Thatcher, S: water. The cultivars of carrying Lr1: 2 (PH01-24), 3 (Zi 6135), 7 (Liao 9518), 16 (Zemai No.1), 17 (Yannong 15), 18 (Weimai No.8), 20 (Linmai No.4), 21 (Laizhou 953), 31 (Yan 103), 32 (Yan C96).

plant-pathology-microbiology-amplification-specific-primer

Figure 2: PCR amplification using specific primer linked to Lr10 in the tested cultivars M: DL2000Marker, N: TcLr10, T: Thatcher, S: water. The cultivars of carrying Lr10: 5.

plant-pathology-microbiology-test-cultivars

Figure 3: PCR amplification using specific primer linked to1BL/1RS in test cultivars M: DL2000Marker, N: TcLr26, T: Thatcher, S: water. The cultivars of carrying 1BL/1RS: 12 (Luyuan 301), 16 (Zemai No.1), 18 (Weimai No.8), 19 (Yan 861601), 21 (Laizhou 953), 22 (Luyuan 9160471), 23 (Binzhou 98-6), 24 (Yan 5286), 25 (Liao 9629), 26 (Liao 9638), 27 (Yan 5158), 31 (Yan 103), 32 (Yan C96), 33 (Weimai No.6).

Germplasm Pedigree Adult stage
IT Disease index
(LRS)
Gene postulation
Liangxing 66 Ji 991102/Ji 935031 124 5 Lr3, APR, +
PH01-24 - ;13 15 +
Zi 6135 - 4 90 +
Hemai 9735 - 4 15 APR, +
Zhouyuan 187 - ;12 5 Lr10, +
Bin 02-47 - ;1 - Lr3, +
Liao 9518 77115-1-2-9-1/Lumai 13 ;1 - Lr1, Lr3, +
Yan 896063 - ;1 - Lr32, +
Linkang 5025 - 4 100 -
Taishan 269 Lumai18/Lumai14 4 75 Lr18
Hemai 9803 - ;2 10 +
Luyuan 301 Jiamai 16/121 4 25 Lr26, APR, +
Taishan 5024 - 4 55 -
Lainong 9214 Lumai No.7/YexuanNo.1 ;1 - +
Jimai 17 Linfen 5064/Lumai13 3 20 APR, +
Zemai No.1 Xu 9935/Yanyou 361 ;1 - Lr1, Lr26, +
Yannong 15 Youbao//ST2422/464 ;13 5 Lr1, +
Weimai No.8 88-3149/Aus621108 ;1 - Lr1, Lr26, +
Yan 861601 - ;1 - Lr32, Lr17, Lr26,+
Linmai No.4 Lumai23/Lin9015- 4 55 Lr3
Laizhou 953 Zao5/Yexuan1/7832110-1 ;13 15 Lr1,Lr3, Lr26, Lr32, +
Luyuan 9160471 - 4 95 +
Binzhou 98-6 - ;13 5 Lr3, Lr26, +
Yan 5286 Lumai14/945015 ;1 - Lr3, Lr26, +
Liao 9629 89B08-3-10-1-8/Lumai23 4 75 Lr26,+
Liao 9638 Shan160/Lumai 22 ;1 - Lr26, +
Yan 5158 Yanhangxuan No.2/Yannong 15 ;1 - Lr3, Lr26, +
Taishan 027 - 4 25 APR,+
Liao 9514 - 4 90 +
Linmai No.6 86Jian22/84-346 ;1 - +
Yan 103 Lumai14//Wei132/87ren20 4 80 -
Yan C96 - 4 65 Lr26
Weimai No.6 77107-15-7-4/T770-5 4 45 +
Weimai No.7 Lin550/Qianni/Zhong 312 ;1 - +
PH01-35-2 - 4 40 Lr10, +
Zhengzhou5389   4 100 -

A range of infection types is indicated by more than one infection type, with the predominant type listed first. e.g. 124.

Table 2: Field evaluation for leaf rust resistance and gene postulation of 35 selected wheat cultivars.

Evaluation of adult plant resistance in the field

Adult plant resistance (APR) of all the 35 selected wheat cultivars were evaluated in the field by artificial inoculation of ten-mixed Pt races. The whole experiments were repeated twice in the crop seasons of 2007-2008 and 2008-2009 at Baoding, Hebei, China.

In total of 22 tested wheat cultivars showed a resistance or slow rusting phenotype in the field (Table 2). Relatively higher resistance (IT=0;1) was observed in 17 wheat cultivars, which might be associated with corresponding postulated Lr genes and/or other major resistance genes. Among these cultivars, three wheat cultivars including Lainong 9214, Linmai No.6 and Weimai No.7 may carry novel leaf rust resistance genes and/or other not tested major Lr genes. Five wheat cultivars including Liangxing 66, Hemai 9735, Luyuan 301, Jimai 17 and Taishan 027 showed very typical APR or slow rusting phenotype, thus highly susceptible (IT=3 or 4) during seedling stage, highly susceptible (IT=3 or 4) but low disease index (LRS<25) during adult plant stage. Since we have already ruled out the existence of the widely distributed APR gene Lr34, Lr35 and Lr37 in any of the selected wheat cultivars using molecular markers, we speculate that these five wheat cultivars may carry novel APR genes and/or other not tested APR genes.

Discussion

The first wheat leaf rust resistance gene Lr1 derived from Aegilops speltoides was designated in 1946 and subsequent BAC-cloning research showed that this gene encode a CC-NBS-LRR protein [42]. Lr1 is a major resistance gene following the gene-for-gene theory [43]. It still shows resistance to few of the Pt races with low virulence in China. In this study, Lr1 has been identified in five wheat cultivars (Weimai No.8, Yannong 15, Zemai No.1, Liao 9518 and Laizhou 953) by both gene postulation and molecular markers.

Two cultivars were postulated to carry Lr10, and this postulation was further validated by molecular markers. Lr10 was reported to encode a receptor-like protein kinase [44]. Currently, it showed resistance to only one Pt race PBGP in our study.

In the present study, Lr26 was the most commonly identified Lr gene among the 35 tested cultivars. The presence of Lr26 gene may relate more to its connotation with wide spread adaptability and higher yield rather than the resistance it confers to avirulent Pt pathotypes [45]. Lr26 was introduced with the 1BL/1RS chromosome translocation wheat lines including Lovrin10, Lovrin13, Kavkaz, Aurora, Neuzucht and Predgornia from Europe to China in the 1970s, which were subsequently widely used in breeding programs for improving the quality and resistance of a large number of high yielding wheat cultivars in the 1980-1990s [46]. Lr26 has lost its function toward most of the Pt races in China. During our investigation, 14 wheat cultivars were validated as Lr26-carrying or 1BL/1RS chromosome translocation wheat lines by molecular markers. Many of these wheat cultivars have 1BL/1RS ancestors in their pedigree. Three cultivars including Luyuan 9160471, Yan 103 and Weimai No. 6 were not postulated to carry Lr26 at seedling stage, the reason may be the background of the cultivars effected the expression of Lr26 or the environment effect the Lr26 expression in the test cultivars.

Lr17 and Lr32 still showed some resistant to few tested Pt races and these two genes have been postulated in only one and two cultivars, respectively. There was only one cultivar postulated to carry Lr18. However, this gene has already lost its function to major epidemic Pt races in China.

Conclusion

Based on all these results, we strongly recommend wheat breeders to introduce other functional seedling Lr genes such as Lr9, Lr19, Lr24, Lr28, Lr29, Lr36, Lr38, Lr42, Lr45 and Lr47 etc. into mainly cultivated wheat cultivars in China.

Based on our evaluations for leaf rust resistance of these 35 selected wheat cultivars, 17 cultivars showed a high resistance and 5 showed a slow rusting phenotype. The other 13 cultivars were fully susceptible to the mixture of Pt races at adult plant stage. So far, thirteen APR genes (Lr12, Lr13, Lr22a, Lr22b, Lr34, Lr35, Lr37, Lr46, Lr48, Lr49, Lr67, Lr68 and Lr74) have been identified in wheat. Utilization of APR genes will greatly expand the lifespan of rust resistance in the field condition. Since we did not detect any of the widely distributed APR gene Lr34, Lr35 and Lr37 in any of the selected wheat cultivars using molecular markers, we speculate that those five wheat cultivars may carry novel APR genes and/or other not tested ones. The ratio of wheat cultivars carrying APR genes is relative low, thus there are urgent needs to pyramid more APR genes in wheat cultivars planted in China.

Acknowledgments

The study was funded by National Key Basic Research Program of China (2013CB127700), National Natural Science Foundation of China (30771391), Modern Agricultural Industry System of Wheat Industry in Hebei Province, Natural Science Foundation of Hebei Province (C2013204065).

References



Copyright: This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.