2 Half-sib selection with test cross

Another way of evaluating genotypes to be composited is by conducting a test cross.

This variation of half-sib selection allows the breeder to more precisely evaluate the genotype of the selected plant by choosing the most suitable test cross parent. The half-sib lines to be composited are selected based on a test cross evaluation not progeny performance.The tester may be an inbred, in which case all the

progeny lines will have a common parental gamete.

Like half-sib selection with progeny test, this procedure is applicable to cross-pollinated species in which sufficient seed can be produced by crossing to grow a

replicated testcross progeny trial. However, in procedures in which self-pollination is required, the method cannot be applied to species with selfincompatibility.

In season 1, the breeder selects 50–100 plants from the source population. A tester parent is pollinated with pollen from each of the selected plants.The crossed seed from the tester as well as the open-pollinated selected plants are harvested separately. In season 2, the test cross progenies are grown in replicated plots. In season 3, an equal amount of open-pollinated seed from 5–10 superior plants is composited and grown in isolation for openpollination to occur.

Pollen from each selected plant may be used to pollinate a tester plant and self-pollinate the selected plant. Also, in season 3, equal quantities of selfed seed may

be composited and planted in isolation. 3 Interpopulation improvement methods The purpose of this group of recurrent selection schemes is to improve the performance of a cross between two populations. To achieve this, interpopulation heterosis is exploited. The procedures are appropriate when the breeder’s goal is hybrid production. Developed by P.E. Comstock and his colleagues, the procedures allow the breeder to improve two genetically different populations for GCA and SCA, thereby improving their crossbred mean.