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Pulse Nitrogen Fixation: A Key to Improve Global Crop Production

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Keynote Presentation 07 by Tom Sinclair at the International Conference on Pulses in Marrakesh, Morocco, 18-20 April 2016

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Pulse Nitrogen Fixation: A Key to Improve Global Crop Production

  1. 1. Pulse Nitrogen Fixation: A Key to Improve Global Crop Production
  2. 2. Nitrogen Accumulation Required for Crop Growth • Every new cell requires nitrogen • Maximum metabolic activity requires nitrogen • Redistribution of nitrogen required to maximize seed growth
  3. 3. Perspective on N2 Fixation Research Energy crisis of 1970’s spurred major new efforts in N2 fixation Assumed that bacteria partner was key to increasing N2 fixation Now, clear that host plant is the dominate partner in regulating N2 fixation Failure in perspective still resonates today
  4. 4. Host Plant Control of N2 Fixation Foster effective fixers (nodule sanctioning) Unique features of nodules regulate fixation rate Closed water system Oxygen flux to nodule interior Sensitivity to N feedback Fixation highly integrated into plant circulation Water Nitrogen (rarely, carbon critical)
  5. 5. Nodule Sanctioning R.F. Denison The American Naturalist 2000, 156:567-576
  6. 6. O2 5-555 5 – 60 µmol m-3
  7. 7. Interior O2 concentration: 5 – 60 µmol m-3 Infected cell O2 Km: 30 – 50 µmol m-3 Usual mitochondria O2 Km: 100 – 130 µmol m-3 (Millar et al., 1996, Plant, Cell, Env. 18:715-726)
  8. 8. Hence, at O2 = 40 µmol m-3 Infected cell activity = 0.44 – 0.57 Vmax Mitochondria activity = 0.24 – 0.28 Vmax Therefore, ineffective bacteria may have respiration about half of effective bacteroids That is, sanctioning
  9. 9. Feedback Regulation
  10. 10. Biswas and Gresshoff (2014) Int J Mol Sci 15:7380-7397
  11. 11. N-compounds Sucrose Water Circulatory System N-compounds Water
  12. 12. Drought Limitation
  13. 13. Soil Drying →
  14. 14. Identification of N2 Tolerant Germplasm ~ 3,500 Plant Introductions Field Screen Low petiole ureide ~ 250 PI Selections Field Screen N accum. under drought 24 PI Selections Glasshouse Test ARA with drying soil 11 Tolerant PIs
  15. 15. Soil Drying → Soil Drying →
  16. 16. Hutcheson x PI 471938 (drought sensitive) (drought tolerant) Heterozygous Inbred Families (HIF) Thirteen HIFs tested Is N2 fixation tolerance trait readily transferred to progeny?
  17. 17. N2 Fixation Drought Tolerance Limited Transpiration Maturity Group Parental Pedigree1 Antecedents2 Rank Antecedent With Trait Rank Antecedent With Trait R02-1325 V 93705-35-1 x PI 227557 93705-35-1 = Jackson x KS 4895 1 50% PI 227557 25% Jackson 8 No known source N05-7432 VIII N7002 x N98-7265 N7002 = N7001 x Cook N98-7265 = Hutcheson x PPI 471938 2 25% PI 471938 3 12.5% PI 416937 R05-5559 V UA4805 x PI 471938 UA4805 = Hartz 5545 x KS 4895 3 50% PI 471938 linear No known source N04-9646 VII Boggs x NTCPR94- 5157 Boggs = G81-152 x Coker 6738 NTCPR94-5157 = Davis x N73-1102 N73-1102 = Tracy x Ransom 4 No known source 4 No known source N06-7194 VIII N98-7265 x N93-110-6 N98-7265 = Hutcheson x PI 471938 N93-110-6 = Young x PI 416937 5 25% PI 471938 5 25% PI 416937 R09-1069 V R01-52F x Ozark R01-52F = R93-5455 x Minsoy R93-5455 = Jackson-derived line x PI 416937 Ozark = Holladay x DP 415 6 6.25% Jackson 1T 12.5% PI 416937 N06-7543 VII NC-Roy x N8001 NC-Roy = Holladay x Brim N8001 = N7001 x Cook 7 No known source 7 12.5% PI 416937 R07-5235 V R01-52F x R02-6268F R01-52F = R93-5455 x Minsoy R93-5455 = Jackson-derived line x PI 416937 R02-6268F = KS 4895 x Jackson 8 31.25% Jackson 9 12.5% PI 416937 R09-1121 V R01-888F x R05-5559 R01-888F = Jackson x KS 4895 R05-5559 = UA 4805 x PI 471938 9 25% Jackson 25% PI 471938 1T No known source R07-7044 V Lonoke x NTCPR94- 5157 Lonoke = Manokin x Asgrow 6297 NTCPR94-5157 = Davis x N73-1102 N73-1102 = Tracy x Ransom 10 No known source 6 No known source Progress in Developing Elite Breeding Lines (AR & NC)
  18. 18. Simulated Yield Response to N2 Fixation Drought Tolerance 75 % (wet) Median 25 % (dry) Use Africa Results instead
  19. 19. Conclusions  Host sanctioning in suppressing retarding expansion of ineffective bacteria  Host regulates circulation of water and N compounds controlling N2 fixation rates  Host regulates N2 fixation rate during water- deficit conditions
  20. 20. Mating of Jackson with several high-yielding lines (1993) Jackson x KS 4895
  21. 21. 100 200 300 400 -60 -30 0 30 60 90 Consistent Yield Gain Check Yield (g m-2 ) YieldDiffer.(gm-2 ) [R01-581F-Check]
  22. 22. 75 85 95 105 115 125 135 0 10 20 30 40 R01-416F R01-581F Jackson:75 KS4895: 91 N accumulation (mg plant-1 ) Frequency(%)
  23. 23. Initial screen for N2 Fixation Drought Tolerance Cultivar R5 to R7 N Accum Decrease Drought/WW Jackson 1 0.86 CNS 2 0.72 Coker 368 1 0.72 Roanoke 3 0.67 SCE 82-222 3 0.55 Coker 156 7 0.53 Asgrow 7372 6 0.46 SCE 82-303 7 0.19 Sall and Sinclair. 1991. Plant Soil. 133:31-37.

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