MAIZE (Zea mays L.) To, Dr Saba Tabasum By IMRAN JAFFAR MSc (Hons.) 2 rd semester DEPARTMENT OF PLANT BREEDING & GENETICS
Maize – The New World Cereal Origin: Mexico Early Spread: Through New World
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)
The Corn Plant See Fig. 5.26, p. 127
Corn Flowers
Corn Flowers, closer up
The Corn Fruit
Evolution of Corn
Corn Relatives Teosinte Zea diploperennis
Wild Ancestor of Corn: Teosinte Structure of Maize: grass, has terminal staminate inflorescence (=tassels) and lateral pistillate inflorescence (=ear; silks = styles)
Wild Ancestor of Corn: Teosinte Structure of Maize: grass, has terminal staminate inflorescence (=tassels) and lateral pistillate inflorescence (=ear; silks = styles)
Changes from Teosinte to Corn Teosinte Corn 1.Non-shattering pistillate inflorescence (cob) 2.Corn grains open, glumes soft 3.Cupule with 2 fertile spikelets, not one 4.Cupules 4-10 ranked, not 2-ranked 5.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
Early development of corn
Types of Corn 1.Pod corn (husklike glumes) Differences: mainly related to types of starch (hard vs. soft) in grain.
Types of Corn 1.Pod corn (husklike glumes) 2.Dent corn (soft center) Differences: mainly related to types of starch (hard vs. soft) in grain.
Types of Corn 1.Pod corn (husklike glumes) 2.Dent corn (soft center) 3.Flint corn (all hard) Differences: mainly related to types of starch (hard vs. soft) in grain.
Types of Corn 1.Pod corn (husklike glumes) 2.Dent corn (soft center) 3.Flint corn (all hard) 4.Popcorn (core of soft) Differences: mainly related to types of starch (hard vs. soft) in grain.
Types of Corn 1.Pod corn (husklike glumes) 2.Dent corn (soft center) 3.Flint corn (all hard) 4.Popcorn (core of soft) 5.Flour corn (all soft) Differences: mainly related to types of starch (hard vs. soft) in grain.
Types of Corn 1.Pod corn (husklike glumes) 2.Dent corn (soft center) 3.Flint corn (all hard) 4.Popcorn (core of soft) 5.Flour corn (all soft) 6.Sweet corn (sugars remain) Differences: mainly related to types of starch (hard vs. soft) in grain.
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.
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”
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
Inbred Lines Inbred Parent 1
Inbred Lines Inbred Parent 1Inbred Parent 2
Inbred Lines
“Single Cross” Corn problem was that inbred parents not very productive, so it is difficult to produce enough seeds for farmer start with four inbred lines, make 2 single cross hybrids, then cross the single cross hybrids to produce the seed corn -= double cross corn Solution = “Double Cross” Corn
Hybrid Corn
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
Corn – Natural Diversity Corn types, Peru farm fieldCorn variants
Corn in the U.S.
Sweet Corn Field Corn: in endosperm sugars starches
Sweet Corn Field Corn: in endosperm sugars starches Mutant Genes 1.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)
Sweet Corn, continued Field Corn: in endosperm sugars starches Mutant Genes 2.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
Sweet Corn, Continued 3.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.”
Sweet Corn, Continued 3.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
Corn – the C4 crop Photosynthesis – different pathways “Normal” = C3 C4 photosynthesis – less photorespiration under warm climates
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
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