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RA 00110.pdf - OAR@ICRISAT

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6<br />

P o p u l a t i o n<br />

c r o s s e s<br />

6<br />

P o p u l a t i o n<br />

c r o s s e s<br />

5<br />

Random<br />

mated<br />

p o p u l a t i o n s<br />

5<br />

48.11 + .17 X<br />

Random<br />

mated<br />

p o p u l a t i o n s<br />

4<br />

3<br />

I n b r e d (S 1 )<br />

p o p u l a t i o n s<br />

4<br />

3<br />

= 30.80 + .63 X<br />

I n b r e d ( S 1 )<br />

p o p u l a t i o n s<br />

2<br />

0 1 2<br />

Cycles o f S 1 l i n e per s e s e l e c t i o n<br />

2<br />

0 1 2<br />

Cycles of RF s e l e c t i o n<br />

Figure 5. Average response in index values to 2 cycles of selection.<br />

years and results have been summarized (Fig. 5).<br />

Each data point is an average of 160-480 plots<br />

(depending on the cycle or type of material). Thus,<br />

standard errors are quite small, and data points are<br />

estimated very precisely. Although the variety crosses<br />

have increased at similar rates for both S 1 per se and<br />

RFS selection, it is clear that these increases are due<br />

to different genetic changes. When the populations<br />

were tested as random-mated populations, S 1 per se<br />

selections increased more than the RFS selections.<br />

Thus, heterosis was increased more with RFS selection.<br />

Also, the inbred populations selected using the<br />

S, per se method increased more rapidly than the<br />

random-mated populations, resulting in a reduction<br />

in inbreeding depression. There was no change in<br />

inbreeding depression with RFS selection. These<br />

comparisons should give a reasonably accurate<br />

assessment of the relative advantages of these two<br />

methods, because total breeding effort is very similar<br />

in the two cases.<br />

P o s s i b l e s e l e c t i o n l i m i t f o r v a r i e t y c r o s s i m p r o v e d b y RFS<br />

P o s s i b l e s e l e c t i o n l i m i t f o r v a r i e t y c r o s s i m p r o v e d by S 1 p e r se<br />

Time ( c y c l e s o f s e l e c t i o n )<br />

Figure 6. Selection limits for reciprocal full-sib selection ( R F S ) and S 1 per se as imagined for the future.<br />

118

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