Thursday Lecture – Corn

1. Thursday Lecture – Corn Reminder: Exam I - Tuesday 2/22 Reading: Textbook, Chapter 5

2. From Wall Street Journal

3. Quiz • Flour is ground-up ________________ (part of grain) • Name an Old World Cereal crop: • A New World Cereal crop:

4. Sorghum Likes it Hot and Dry Origin: Ethiopia

5. Main Types of Sorghum • Four main types: • grain sorghums • sweet sorghum (animal feed) • Sudan grass (related species) • broomcorn See Fig. 5.22, 5.24, p. 125

6. Millets – A Mixed Bag See Table 5.4, p. 126 Finger millet – Eleusine coracana Pearl millet – Pennisetum glaucum

7. Maize – The New World Cereal Origin: Mexico Early Spread: Through New World

8. Maize – The New World Cereal Origin: Mexico Early Spread: Through New World Note on the name: Corn = small vegetables (barley, peas, lentils) Maize = from Carib word (spanish mais)

9. The Corn Plant See Fig. 5.26, p. 127

10. Corn Flowers

11. Corn Flowers, closer up See Fig. 5.26, p. 127

12. The Corn Fruit

13. Evolution of Corn See Fig. 5.28, p. 130

14. Teosinte Corn Relatives Zea diploperennis

15. Wild Ancestor of Corn: Teosinte • Structure of Maize: grass, has terminal staminate inflorescence (=tassels) and lateral pistillate inflorescence (=ear; silks = styles)

16. Wild Ancestor of Corn: Teosinte • Structure of Maize: grass, has terminal staminate inflorescence (=tassels) and lateral pistillate inflorescence (=ear; silks = styles)

17. Changes from Teosinte to Corn See Fig. 5.28, 5.30, p. 130, 132 • Teosinte  Corn • Non-shattering pistillate inflorescence (cob) • Corn grains open, glumes soft • Cupule with 2 fertile spikelets, not one • Cupules 4-10 ranked, not 2-ranked • Corn – primary branches short, with pistillate ear • Changes were thought to be controlled by single gene changes (analysis of 50,000 segregating progeny) • More recently, shown to be somewhat more complicated

18. Early development of corn

19. See Fig. 5.29, p. 131 Types of Corn Differences: mainly related to types of starch (hard vs. soft) in grain. • Pod corn (husklike glumes)

20. See Fig. 5.29, p. 131 Types of Corn Differences: mainly related to types of starch (hard vs. soft) in grain. • Pod corn (husklike glumes) • Dent corn (soft center)

21. See Fig. 5.29, p. 131 Types of Corn Differences: mainly related to types of starch (hard vs. soft) in grain. • Pod corn (husklike glumes) • Dent corn (soft center) • Flint corn (all hard)

22. See Fig. 5.29, p. 131 Types of Corn Differences: mainly related to types of starch (hard vs. soft) in grain. • Pod corn (husklike glumes) • Dent corn (soft center) • Flint corn (all hard) • Popcorn (core of soft)

23. See Fig. 5.29, p. 131 Types of Corn Differences: mainly related to types of starch (hard vs. soft) in grain. • Pod corn (husklike glumes) • Dent corn (soft center) • Flint corn (all hard) • Popcorn (core of soft) • Flour corn (all soft)

24. See Fig. 5.29, p. 131 Types of Corn Differences: mainly related to types of starch (hard vs. soft) in grain. • Pod corn (husklike glumes) • Dent corn (soft center) • Flint corn (all hard) • Popcorn (core of soft) • Flour corn (all soft) • Sweet corn (sugars remain)

25. Breeding of Maize • traditionally, bred by selection - look for plants in population that have desirable traits, save seeds, and then cultivate these for next generation.

26. Breeding of Maize • traditionally, bred by selection - look for plants in population that have desirable traits, save seeds, and then cultivate these for next generation. Hybrid Corn • Start with inbreeding  initially produce weaker plants “inbreeding depression”

27. Breeding of Maize • traditionally, bred by selection - look for plants in population that have desirable traits, save seeds, and then cultivate these for next generation. Hybrid Corn • Start with inbreeding  initially produce weaker plants “inbreeding depression” • Cross different inbred lines  hybrid exhibits heterosis, better than either parent

28. Inbred Parent 1 Inbred Lines

29. Inbred Parent 1 Inbred Parent 2 Inbred Lines

30. Inbred Lines

31. “Single Cross” Corn • problem was that inbred parents not very productive, so it is difficult to produce enough seeds for farmer Solution = “Double Cross” Corn • start with four inbred lines, make 2 single cross hybrids, then cross the single cross hybrids to produce the seed corn -= double cross corn

32. Hybrid Corn

33. How to cross corn? • Solution - remove tassels from seed parent • Solution A = manual labor (college students?) - physically detassel corn • Solution B = technological - use male sterile plants • Problem with solution B - in 1970s, bulk of hybrid corn utilized one type of male sterile parent  susceptible to disease • disease = southern corn blight - wiped out U.S. crops early 70s • solution - back to detasseling; develop new lines of male sterile corn

34. Corn – Natural Diversity Corn variants Corn types, Peru farm field

35. Corn in the U.S.

36. Sweet Corn Field Corn: in endosperm sugars  starches

37. Sweet Corn • Field Corn: in endosperm sugars  starches • Mutant Genes • Sugary (su) – slows sugar  starch • Result: more water-soluble carbohydrates, sweeter, different texture • Standard Sweet Corn • Room Temp. – 50% sugar loss (24 hrs); 5-10 C – 60% (3 days)

38. Sweet Corn, continued • Field Corn: in endosperm sugars  starches • Mutant Genes • Sugar enhancer (se) • Result: higher sugars; sweet, creamy endosperm • Sugar loss – same as for standard sweet corn • Germination – about same as for standard sweet corn

39. Sweet Corn, Continued • Shrunken (sh2) = “supersweet” • Sugar levels 4-8 X higher; higher lipids; lower starch; different texture (tougher pericarp) • Storage: room temp., 48 hrs. – 2X sugar content vs. standard • at 4 C, sugar loss very slow • Poor germination; “Husks are ugly. Remove for display.”

40. Sweet Corn, Continued • Other genetic modifiers: waxy (wx); brittle (br); brittle2, amylose extender (ae)  used in combinations with other genes, will provide new varieties of sweet corn • Important Note: Variants are recessive genes, so they must be planted in isolation from field corn and sometimes from other sweet corns

41. Corn – the C4 crop Photosynthesis – different pathways “Normal” = C3 C4 photosynthesis – less photorespiration under warm climates

42. Forage Grasses • Grasses – important for forage, hay, silage • uses land that is marginal for other agricultural applications • - in North America, many forage grasses are introduced species

43. Forage Grasses • Grasses – important for forage, hay, silage • uses land that is marginal for other agricultural applications • - in North America, many forage grasses are introduced species • Cades Cove, Great Smoky Mountain National Park • cattle production based on pastures of fescue (Festuca) • leases expired  periodic burning  encourage native grasses (bluestem, Indian grass, etc.)  will benefit wildlife • More general application: warm season grasses better adapted to our climate, with periodic summer drought, can be more productive than cool season grasses without irrigation

44. Thursday Lecture – Legumes Reminder: Exam I - Thursday 2/22 Reading: Textbook, Chapter 6