physicochemical

SHIVANI et. al.
of sprinkler were maintained for a period of 3-4 days
after inoculation. Further, water spray technique was
used to maintain high disease pressure during crop
season. The water spray was discontinued after 21
days and the disease observation were recorded
when the disease severity was stabilized and there
was no further increase in severity following 1-9 point
scale (Shinde et al.,1994). Data obtained were
statistically analysed using the chi-square test to
ascertain goodness of fit of F2 generation for the
inheritance of resistance and its gene action.
RESULTS AND DISCUSSION
The data on wilt incidence was recorded at
the crop seedling, vegetative and flowering stages.
The parents GMU 1946, GMU 2914-15 and GMU 1702
showed < 10% wilting even at maturity stage during
2005-06, 2006-07 and 2007-08. Hence they were
considered as resistant. Among susceptible
genotypes, Nira exhibited 100% mortality at seedling
stage, while Manjira and Sagarmuthyalu exhibited 50-
70% mortality during vegetative stage. The plants
of parents and F 1
s rated from 0.0 – 5.0 with most
plants rating 1.0 or 3.0 on 1- 9 scale based on
percentage of plants wilted. In F 2
, plants with rating
up to 3.0 were considered resistant to generate ratio.
The plants rating from 5.0 to 9.0 were considered
susceptible. The F 1
’s of all the crosses in the present
study were resistant indicating dominance of
resistance in these genotypes. In F 2
population of
cross Nira and GMU 1946, of the total of 415 plants,
253 were resistant and 162 were susceptible giving
a good fit to ratio of 9:6:1(resistant, moderately
susceptible and susceptible) indicating that
resistance is governed by two additive genes in the
resistant cultivar tested. However, GMU 2914-15 in
crosses with Nira, Manjira and Sagarmuthyalu gave
a total of 398,442 and 432 plants, respectively out of
which 217 in cross Nira x GMU 2914-15, 254 in cross
Manjira x GMU 2914-15 and 238 in cross
Sagarmuthyalu x GMU 2914-15 were resistant and
181in Nira x GMU 2914-15, 188 in Manjira x GMU
2914-15 and 194 in Sagarmuthyalu x GMU 2914-15
were susceptible. In these crosses, a ratio of 9:7
was obtained indicating that the resistance in these
parents is governed by two dominant genes with
complimentary gene actions (Table 1). In the cross
Nira x GMU 1702, the F2 plants segregated in the
ratio of 13:3 indicating inhibitory type of gene action
for the inheritance of Fusarium wilt.
The present findings indicate that the
Fusarium wilt resistance is simply inherited involving
two dominant genes. The resistance can be
transferred to susceptible varieties and will help in
developing wilt resistant safflower varieties with good
agronomic attributes for achieving the desirable
improvement in the yield in safflower.
Table 1. Fusarium wilt response of F 1
and F 2
plants of 3 susceptible safflower genotypes with
resistant genotype GMU 1946
Cross F 1
reaction
No. of F 2 plants
Expected
ratio
X 2 value
(p