| Abstract |
Numerous types of both conventional (based only on inbred lines) and nonconventional (where at least one parent is not an inbred line) maize hybrids may be produced. Conventional hybrid types include single crosses, three way crosses and double crosses. Single cross hybrids are based on two parental inbred lines whereas three way crosses first require the production of a single cross hybrid followed by its use as a female parent crossed to a male inbred line. Double cross hybrids are the product of crossing two distinct single crosses. Single crosses are popular in the developed world because of their high yield performance and uniformity. However, they are expensive and difficult to produce as the female parent on which the hybrid seed is produced is typically a relatively low yielding inbred line. Three way and double cross hybrids overcome this difficulty as the female parent in these conventional hybrid types is a single-cross hybrid. Disadvantages of double cross hybrids is that they need seven separate production fields including four blocks to maintain and produce the inbred lines, two fields to produce the two single-cross hybrids, and finally a production field to form the double cross hybrid. At present, three way cross hybrids are the most common maize hybrids types grown in much of the developing world. |
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