RA 00015.pdf - OAR@ICRISAT

In an experiment to determine the effect of plot
size in detecting susceptibility differences between
cultivars, trials with plots of 4.8 and 20.0
m 2 were compared. Results of these trials, in
which 13 cultivars were tested show the smaller
plot size to be at least equal in efficiency in
detecting differences, both in percentage of borer
damage and in yield (Table 39). This was a
welcome result, for it will permit additional
replication without increased demand on seed or
land. The susceptibility rankings of the cultivars
were in good general agreement in the two trials;
C-235 and L-345, both desi types, were the least
susceptible while the kabuli types suffered most
damage.
In a preliminary attempt to screen the germplasm
collection for susceptibility, 8894 lines
were sown in unreplicated small plots, with two
check cultivars alternating after every 20 lines. H.
armigera attacks were scored at the green-pod
stage, and the percentage of damage was recorded
when the pods were harvested. There was
a fertility gradient across the field and H. armigera
was more common in the better growing
areas. Pod damage ranged from 0 to more than
50 percent in the check plots, so the individual
records from the unreplicated germplasm lines
can have little value, except perhaps in indicating
the more obviously susceptible. Of the check
plots, 28 percent of the C-235 (n = 219) and 19.5
percent of the BEG-482 (n = 221) were free from
H. armigera damage, but only 11 percent of the
8 629 germplasm lines harvested had no damage.
This is interpreted as an indication that C-235,
and to a lesser extent BEG-482, are less susceptible
than the majority of the germplasm cultivars.
This was not unexpected, as both checks
are well-adapted desi cultivars that have been
grown generally without pesticide protection.
Although the natural infestation of H. armigera
in the screening trials was augmented by
the release of laboratory-bred moths, infes-
Table 39. Comparison of pod-borer damage and yields of 13 cultivars tested in small (4.8 m 2 ) and large
(20.0 m 2 ) plots in randomized blocks with four replicates.
% Borer damage a Yield
Cultivars Small plot Large plot Small plot Large plot
(arcsin scale) (g/m2) (g/m2)
C-235 4.9 3.4 82.5 118.0
BR-70 4.4 10.6 47.7 68.8
L-345 3.0 2.6 60.4 74.6
L-2937 7.0 6.9 79.8 91.4
850-3/27 18.1 12.6 59.8 139.3
JGC-1 7.5 8.3 76.9 113.0
IC-6037 4.9 6.6 73.5 95.0
RS-11 6.1 7.1 81.0 84.2
NP-34 12.0 8.1 69.4 71.4
P-3090 18.2 16.6 68.5 55.2
NEC-143 13.3 11.0 44.4 79.1
Rabat 13.6 14.5 61.3 72.2
IC-682 9.5 9.3 77.3 86.0
S.E.± 9.33 15.35
c . v . ( % ) 21.5 22.0 27.4 34.8
a percent borer damage, bated on arcsin transformation.
10S