RA 00110.pdf - OAR@ICRISAT

Table 4c. Prediction equations, advantages, and disadvantages for intrapopulation improvement using full-sib selection.
Advantages
Disadvantages
1.
2.
3.
4.
5.
1.
2.
Time per cycle can be two growing seasons.
Easily recombined because only one pollination for each new full sib required.
General advantages of family testing such as control of G x E interaction.
Good control of additive variance in numerator.
Can maintain good Ne because each selected FS has two parents so Ne is twice as large as
when selecting an equal number of selfed males.
Phenotypic variance is a little larger than with half-sib selection.
Have to be careful to pollinate each ear after good silk emergence to keep up seed number in
maize. In pearl millet this would not be a problem.
improved for yield, prolificacy has increased. In the
RFS scheme prolificacy is exploited to both self and
cross single plants. One plant from population A is
matched with one from population B. The second
ear of each is self-pollinated and 2 d later the top ears
are crossed. At harvest only reciprocal crosses
between parents that have set selfed seed are chosen
for testing. Since they are genetically the same, the
crossed top-ears can be bulked together to form one
entry. If 200 are tested, as for RHS, 10% can be
selected and still have an N e of 20 for each population
because each entry tests a plant from both populations
at once. If cost is a major concern, 100 entries
could be tested with 20 selected from each, so only
half as many yield-trial plots are used as for RHS.
There is an increase in the phenotypic variance of
RFS over RHS so all is not in favor of RFS. Table 5
shows the prediction equations for RHS and RFS.
Jones et al. (1971) compare the two schemes.
Reciprocal Inbred Line Tester Selection
Another reciprocal scheme of some value is to use an
inbred tester (RIS). In this scheme plants from populations
A and B are selfed and also crossed to an elite
Table 4d. Prediction equations, advantages, and disadvantages for intrapopulation improvement using line selection.
S, line per se
S 2 line per se
Advantages
Disadvantages
1.
2.
3.
1.
2.
3.
4.
5.
Large numerator in the prediction equation.
Additive (A) x A epistasis coefficient is the square of the A coefficient, so A x A, if it exists,
would be utilized with this scheme.
Inbred maize lines selected for line per se yield so that they are superior for seed production.
If overdominance is present in large amounts, line per se selection may be poor procedure.
G x E interaction is amplified with inbreeding in maize so is more of a factor with line per se.
Requires nursery work both in making up families and recombining.
Requires three growing seasons.
Difficult to get good stands and also other yield trial problems.
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