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Crop Improvement PLS 386 September 9, 2005

Crop Improvement PLS 386 September 9, 2005. Outline of topics: (pp. 107-137 in text) I. Conventional plant breeding II. Methods of breeding III. Breeding goals IV. Hybrid corn success story V. Seed certification process. Crop Improvement PLS 386 p. 2. Conventional plant breeding

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Crop Improvement PLS 386 September 9, 2005

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  1. Crop Improvement PLS 386 September 9, 2005 Outline of topics: (pp. 107-137 in text) I. Conventional plant breeding II. Methods of breeding III. Breeding goals IV. Hybrid corn success story V. Seed certification process

  2. Crop Improvement PLS 386 p. 2 • Conventional plant breeding • (as opposed to genetic engineering) • Domestication preceded plant breeding • Mendel’s work - 1860s ‘laws of inheritance’ • Intentional plant breeding has been practiced only about 100 years (much less for some crops)

  3. Crop Improvement PLS 386 p. 3 Basic steps in conventional plant breeding 1. Determine the breeding objective(s) 2. Assemble genetic variability (raw material) 3. Recombine the variation (cross, hybridize) 4. Select desirable recombinants 5. Evaluate the selections

  4. Crop Improvement PLS 386 p. 4 Sources of heritable variation for plant breeders 1. Adapted cultivars (=cultivated variety) 2. Older ‘landraces’ 3. Recombinants and elite lines 4. Plant introductions 5. Wild plants 6. Induced mutation

  5. Crop Improvement PLS 386 p. 5 Limitations of plant breeding 1. Long duration 2. Limited to crossing within species 3. Lower selection efficiency 4. Large segregating populations are needed

  6. Crop Improvement PLS 386 p. 6 Common breeding methods (Methods vary depending on crop’s breeding system) Self-pollinating species:(wheat, soybeans, tomatoes) 1. Mass selection 2. Pedigree selection 3. Backcross breeding 4. Hybrid production

  7. Crop Improvement PLS 386 p. 7 Common breeding methods Cross-pollinating species: (corn, squash, fescue) 1. Mass selection 2. Hybrid breeding (requires ability to inbreed, or self-pollinate) 3. Polycrosses / Synthetic production 4. Clonal selections (vegetatively-propagated)

  8. Crop Improvement PLS 386 p. 8 Breeding goals 1. Higher yield 2. Photosynthetic efficiency (light interception, leaf angle, stomatal frequency) Leaf Area Index =LAI=area of leaf surface per area of soil 3. Growth habit (determinate, dwarf, etc.) 4. Early maturity 5. Improved harvest index

  9. Crop Improvement PLS 386 p. 9 Harvest index = proportion of crop that is of economic importance. In wheat, grain yield usually is the economic yield: 2 tons of grain, 3 tons of straw H.I. = 2 tons grain/(2+3)=2/5 or 0.40. In other words, 40% of the biomass produced is the harvested part (unless straw is also sold)

  10. Crop Improvement PLS 386 p. 10 Hybrid corn story: Before 1930, most farmers grew open-pollinating (OP) varieties By the 1940s, double-cross hybrids were more popular By early 1960’s single-cross hybrids took over.

  11. Crop Improvement PLS 386 p. 11 Hybrid corn story: continued Figures from book (pp. 122-123) Overhead from Crop Science article.

  12. 128 112 96 (1.76) 80 64 bushels/acre 48 32 (1.00) 16 (0.02) 0.002

  13. Crop Improvement PLS 386 p. 12 Breeding goals, continued 6. Yield stability 7. Yield per se vs. yield components 8. Improved quality 9. Pest resistance 10. Lodging resistance / shattering resistance 11. Heat/Drought resistance 12. Winter hardiness

  14. Crop Improvement PLS 386 p. 12 Seed certification process Four classes of commercial seed: 1. Breeder seed - plant breeder keeps this 2. Foundation seed - first grow-out of breeder seed 3. Registered seed - larger fields from foundation seed 4. Certified seed - produced from foundation or registered seed. This is sold to producers.

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