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Inbreeding

  • Arnel R. Hallauer
  • J. B. Miranda Filho
  • Marcelo J. Carena
Chapter
Part of the Handbook of Plant Breeding book series (HBPB, volume 6)

Abstract

Maize is a naturally cross-pollinated crop and dispersion of pollen grains (male gametes) is achieved by wind currents, system that favors cross-pollination. The plant has a separate male and female inflorescence (monoecious) which makes relatively easy to produce seed by artificial hybridization and self-pollination for inbreeding. The tassel (male inflorescence with staminate flowers) is at the top of the plant arising from the shoot apical meristem. The ear (female inflorescence with pistillate flowers) is usually located in the middle of the stalk (at the sixth of seventh node from the top of the plant) and originates from the axillary bud apice. During development flowers become unisexual. Apical dominance is present on stalks with multiple ears (prolific genotypes). The male florets usually mature before than the female florets (protandry). Genotype and environmental conditions (e.g., stress) influence the difference in maturity of male and female florets. Pollen shed occurs after anther exertion from each spikelet and begins in the main tassel branch (central spike or rachis). Each spikelet has two florets and pollen shed starts from the upper flower. Spikelets are in pairs: pedicellate and sessile. Each spikelet has a pair of glumes. Within the glumes each floret is also enclosed with thin scales (a lemma and a palea). Two of the three anthers are located adjacent to the palea and the third one is located adjacent to the lemma. The number of pollen grains dispersed by the tassel depends on the genotype and/or vigor of the plants. Hybrids, for example, shed more pollen than inbred-lines. Some open-pollinated varieties, however, shed even more pollen than hybrids. Ear shoots are formed of husks (modified leaves) and silks emerging from the cob. The silks are functional stigmas and there is one stigma for each potential kernel. Silk emergence progresses from the bottom to the tip of the ear. High temperatures and low-moisture availability may cause silk growth to stop and not be ready for fertilization at the time of pollen shed. The ear branch or shank is formed of nodes and short internodes.

Keywords

Inbreeding Depression Epistatic Effect Recurrent Selection Single Cross Maize Breeding 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Arnel R. Hallauer
    • 1
  • J. B. Miranda Filho
    • 2
  • Marcelo J. Carena
    • 3
  1. 1.Department of AgronomyIowa State UniversityAmesUSA
  2. 2.University of São PauloSão PauloBrazil
  3. 3.Department of Plant Sciences #7670North Dakota State UniversityFargoUSA

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