Perspectives on Applied Aspects of Breeding for Rust Resistance

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Perspectives on Applied Aspects of Breeding for Rust Resistance

  1. 1. Perspectives on Applied Aspects of Breeding for Rust Resistance 2013 BGRI Technical Workshop New Delhi, India Moderator: Ravi P. Singh
  2. 2. Panelists: •  Vinod Prabhu, Indian Agricultural Research Institute (India) •  Goodarz Najafian, Seed and Plant Improvement Institute (Iran) •  Peter Njau, Kenya Agricultural Research Institute (Kenya) •  Francois Koekemoer, Sensako (South Africa) •  Jim Anderson, University of Minnesota (USA) •  Yuchun Zou, Sichuan Academy of Agricultural Sciences (China)
  3. 3. A successful variety is the sum of various traits- integrating simultaneous improvement for multiple traits is the only way forward Core traits (ideally should be present in all CIMMYT wheats) „ High and stable yield potential „ Durable resistance to Rusts- Stem (Ug99), Stripe and Leaf „ Water use efficiency/ Drought tolerance „ Heat tolerance „ Appropriate end-use quality Additional traits for specific mega- environments „ Durable resistance to diseases and pests ® Septoria leaf blight (ME2) ® Spot Blotch (ME5) ® Tan Spot (ME4) ® Fusarium – head scab and myco-toxins (ME2/4/5) ® Karnal bunt (ME1) ® Root rots and nematodes (ME2) „ Enhanced Zn and Fe concentration (ME1/5)
  4. 4. Challenges to wheat breeding ● Under resourced programs- financially and human- (some other crops more remunerative than wheat) ● High expectations for making fast progress with complex traits such as grain yield, stress tolerance, end-use quality, durable disease resistance ● Inadequate phenotyping facilities to detect smaller differences (often high CVs in trials, disease nurseries) ● Poor training in universities for field based research Stronger collaboration and partnerships essential
  5. 5. Breeding for rust resistance ●  Longer-term objective versus short-term emergency response to handle situations such as Ug99, aggressive yellow rust race ●  Only few investing on the search for new resistance genes but many programs worldwide depend on this-- potentially leading to limited genetic diversity at a given time ●  Many publications on linked markers for resistance genes but only few useful when tried by breeding programs-- cost and logistics remains a major issue ●  Understanding the genetic basis of resistance in varieties is often post analysis-- a reality unlikely to change unless diagnostic markers for effective resistance genes are developed
  6. 6. Race-specific resistance to stem rust on 6DS •  Race-specific gene for Ug99 resistance mapped on 6DS in several CIMMYT/US wheats •  Similar effects as SrTmp or SrCad •  Close to Sr42 •  Resistance enhanced with other APR genes Lopez-Vera et al. 2013 (manuscript under review)
  7. 7. Utilizing and deploying resistance more responsibly- gene stewardship ●  Evergreen debate however unlikely to happen unless §  ? §  ? ●  Importance of larger genetic diversity for resistance genes versus few genes used more responsibly ●  Using race-specific vs. quantitative adult plant resistance ●  Role of multi-pathogen resistance genes such as ABC transporter Lr34/Yr18/Sr57/Pm38/Sb1/Bdv1 in conferring resistance durability ●  Scientists of various disciplines working together Resistance breeding need to remain simple for adoption by large number of breeding programs
  8. 8. Building complex adult plant resistance to stem rust for durability Diversity for slow rusting, minor Sr genes: 13 genomic regions identified in CIMMYT wheat through bi-parental and association mapping studies 1A 1B 2B 3B 3D 4A 4D 5B 6B 7B 7D wPt0128 wPt4987 wPt1560 wPt1328 Lr46 Yr29 Sr58 Pm39 wmc154 wPt9668 41.4 53.4 csSr2 gwm533 Barc133 wPt2921 GBS76 gwm604 wPt1304 GBS558 14.0 15.3 20.3 21.75 gwm371 csLV46 wPt6997 wPt5749 wPt4487 68.1 77.2 87.8 gwm165 gwm192 Lr67 Yr46 Sr55 Pm46 wPt3774 wPt1922 Cfd13 wPt5333 wPt5037 0.0 3.7 29.7 31.5 45.4 csNLRR gwm146 Lr68 wPt5343 wPt7351 Lr34 Yr18 Pm38 Sr57 126.1 126.8 Sr2 Yr30 Lr27 Pm Four genes with pleiotropic genetic effects on multiple diseases now known:! Sr2/Yr30/Lr27/Pm, Lr34/Yr18/Pm38/Sr57, Lr46/Yr29/Sr58/Pm39, Lr67/Yr46/Pm46/ 8.5 10.4 wPt7200 wPt7750 wPt8460 wmc175 82.0 92.8 100.7 118.8 wPt2565 csLV34wPt2689 wPt1029 51.0 58.5
  9. 9. Integrating resistance to Ug99 race of stem rust fungus in CIMMYT wheats Mexico (Cd. Obregon-Toluca/El Batan)- Kenya International Shuttle Breeding: a five-year breeding cycle) Cd. Obregón 39 masl High yield (irrigated), Water-use efficiency, Heat tolerance, Leaf rust, stem rust (not Ug99) Toluca 2640 masl Yellow rust Septoria tritici Fusarium El Batán 2249 masl Leaf rust, Fusarium Njoro, Kenya 2185 masl Stem rust (Ug99 group) Yellow rust ●  Targeted crosses for shuttle breeding made in 2006 and 1st group of populations planted in Kenya in 2008 ●  2000 F3/F4 populations undergo Mexico-Kenya shuttle ●  High yielding, resistant lines derived from 1st group of Mexico- Kenya shuttle distributed worldwide in 2011, 2012 and 2013
  10. 10. Progress in grain-yield potential of new bread wheat lines developed since the launch of Borlaug Global Rust Initiative (1st year yield data from: Ciudad Obregon, Mexico 2005, 2010 and 2013) Several fold increases in new breeding lines derived from crosses made progressively over years with higher yields than the checks 0 5 10 15 20 25 <60 60-64 65-69 70-74 75-79 80-84 85-89 90-94 95-99 100-104 105-109 110-114 >115 Numberofentries(%) Grain yield (% Tacupecto 2001 or Roelfs 2007) 0.1% (4 entries) 2.1% (104 entries) 4.5% (426 entries) 2005 n=4814 mean 80% 2010 n=4956 mean 90% 2013 n=9436 mean 94%
  11. 11. Ug99 stem rust resistance in 604 wheat entries included in various international trials for distribution in 2013/2014 ( 46% entries possess high to adequate adult-plant resistance & another 46% carry diverse race-specific resistance genes often in combination with Sr2 and other minor APR genes Adult plant resistance Stem rust Entries Race-specific Entries category severity (%) No. % genes No. % Near-Immune Resistant 1 19 3 Sr13 27 4 Resistant 5-10 52 9 Sr22 7 1 Resistant- Mod. Res. 15-20 133 22 Sr25 54 9 Moderately Resistant 30 71 12 Sr26 5 1 Sr1A.1R 9 1 Mod. Res.- Mod. Sus. 40 29 5 Sr42: 6DS gene 88 15 Mod. Sus.- Susceptible 50-100 12 2 SrHuw234 7 1 SrND643 74 12 Sr? 12 2
  12. 12. Increased yield potential of new wheat varieties contributes to enhance productivity in farmers’ fields and fast adoption Yield increase Yield increase R2 Time period per year (%) per year (kg/ha) Year vs Yield 1951-2012 2.15 78 0.882 1951-1960 4.98 88 0.664 1961-1970 3.51 113 0.410 1971-1980 1.69 72 0.220 1981-1990 1.08 54 0.207 1991-2000 1.59 84 0.449 2001-2010 1.15 62 0.567 2001-2013 1.63 114 0.553 Average wheat grain yield trends in farmers fields in Yaqui Valley, Mexico from 1951-2013 despite a reduction in number of irrigations from six to four Source: K. Sayre 0 1000 2000 3000 4000 5000 6000 7000 8000 1950 1960 1970 1980 1990 2000 2010 GrainYield(kg/ha) Year of Harvest Yield = -1.52 x 10 to the fifth + 78.7 kg/ha/year r2 = 0.887 Yield Increase/year = 2.13%

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