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Priorities in maize breeding

Priorities in maize breeding

Because of its shallow roots, maize is susceptible to drought, so one of the current top priorities in maize breeding is developing new varieties that are more drought tolerant. However, the exact mechanisms of what makes some plants more drought tolerant are not well understood. Scientists are currently trying to learn more about these mechanisms.

Another priority in developing new maize varieties, like in many crops, is that of higher yield. Higher yield means there is more food per plant, per growing space. This is especially important in countries where hunger is a problem, particularly where there is no more space for growing additional plants. However, the amount of food a plant will yield is a complicated matter, affected by many genes and also the environment.

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Maize yields have greatly increased over the last century in large part due to plant breeding.
(thanks to Sara Larsson for this figure)

Resistance to diseases and pests is also important, as plants that are diseased or eaten by pests will yield less food. Developing breeds that are better able to utilize nitrogen in the soil or are resistant to pests reduce the need for fertilizers and pesticides, thus cutting costs for farmers and reducing toxins and pollutants in our environment.  Maize breeders would also like to increase the nutrition of maize, for example increasing the amount of protein and nutrients such as vitamin A. Maize is also susceptible to a parasitic weed known as striga (known as “witchweed” in Africa). This plant, although it has a beautiful flower, grows on the roots of maize (and other grasses), stunting the growth and decreasing the yield of the plant.

Some diseases of maize:

  • Corn smut or common smut (Ustilago maydis)
  • Maize dwarf mosaic virus (various strains of Potyvirus)
  • Stewart's Wilt (Pantoea stewartii)
  • Common Rust (Puccinia sorghi)
  • Goss's Wilt (Clavibacter michiganese)
  • Gray Leaf Spot (Cercospora sorghi)
  • Bacterial leaf spot (Xanthomonas campestris)
  • Brown stripe downy mildew (Sclerophthora rayssiae)
  • Southern blight (Sclerotium rolfsii)

Some pests of maize:

  • Corn earworm (Helicoverpa zea)
  • Fall armyworm (Spodoptera frugiperda)
  • Common armyworm (Pseudaletia unipuncta)
  • Stalk borer (Papaipema nebris)
  • Corn leaf aphid (Rhopalosiphum maidis)
  • European corn borer (Ostrinia nubilalis)
  • Corn silkfly (Euxesta stigmatis)
  • Lesser cornstalk borer (Elasmopalpus lignosellus)
  • Corn delphacid (Peregrinus maidis)
  • Western corn rootworm (Diabrotica virgifera)
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