Proceedings of the Fifth Asian Regional Maize Workshop - Search ...

Table 3. Response to selection for resistance to fi rst-generation and second-generation European
corn borer in BS9 (Adapted fran Klenke et 81., 1986).
Populations
First-generation
Second generation
-----------------
Rating Yield Rating Yield
1-9t Q/ha 1-9 Q/ha
859 CO
C1
C2
C3
Chan:, X t
LSD (0.05)
3.6 60.7 6.4 53.1
3.6 65.0 5.9 47.5
2.8 52.4 5.7 44.4
2.5 56.2 4.4 40.8
2.7 47.9 4.4 44.0
-31.1 -21.1 -31.2 -17.1
1.4 13.8 1.3 13.8
+ Rating scale of 1 (resistant) to 9 (susceptible).
4: Change of C4 relative to CO.
Table 4. Responses to selection for decreased root rot infection and increased stalk strength
after seven cycles of selection in Lancaster SUre Crop (Adapted fran Devey and Russell, 1983) .
Cycle of Root rot Stalk Days to Ear per Grain
selection 'rating strength flower 100 plants yield
1-6+ kg no.~ no. Q/ha
CO 3.3 28.7 16.0 94.5 66.5
C1 3.0 36.0 18.6 93.0 66.3
C2 2.0 42.0 19.3 97.5 66.3
C3 2.3 46.5 18.9 93.0 61.8
C4 2.2 47.9 18.4 91.5 54.4
C5 1.8 52.5 18.7 88.5 50.2
C6 1.6 54.0 20.4 81.0 46.9
C7 1.3 59.6 21.8 75.5 40.1
b -0.26** 4.7** 2.7** ns. -1.2
~ Rating scale of 0.5 (resistant) to 6.0 (susceptible).
,.. Days after July 1.
considered in selection. If one increases the number of traits included in selection, the
selection intensity is reduced for each trait 'and slower progress is realized for each trait.
For the examples of Klenke et 81. (1986) and Devey and Russell (1983) for pest resistance, only
one trait (pest resistance) was included in selection. Consequently, the populations they
developed can be placed in the category of "genetic stocks". Both populations (BS9C4 and
Lancaster C7) have good resistance to the pest considered in selection, but they have limited
value in breeding programs.
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