physicochemical

J.Res. ANGRAU 39(1&2)25-27, 2011
INHERITANCE OF RESISTANCE TO FUSARIUM WILT IN SAFFLOWER
(Carthamus tinctorius L.) GENOTYPES
D. SHIVANI, CH. SREELAKSHMI and C. V. SAMEER KUMAR
Agricultural Research Station, Tandur,
Acharya NG Ranga Agricultural University, Rajendranagar, Hyderabad - 501 141
ABSTRACT
Fusarium wilt of safflower caused by Fusarium oxysporum f.sp carthami is a major constraint to safflower
yield in peninsular India. Though considerable efforts have been made to breed varieties with durable resistance, it
has not yet been fully achieved, probably due to the fact that genetics of host- plant inheritance is not well understood.
Three safflower genotypes with consistent resistance over more than 3 years of testing were selected to study the
inheritance of resistance. F2 plants of cross Nira x GMU 1946 segregated into resistant and susceptible plants to
give a good fit ratio of 9:6:1. However in Manjira x GMU 1946 and in other crosses with GMU 2914-15 as male parent,
plants segregated into R and S plants to give a ratio of 9:7 indicating the resistance in these parents is governed by
two dominant genes with complementary type of gene action. In the cross Nira x GMU 1702, the F2 plants segregated
in the ratio of 13:3 indicating inhibitory type of gene action.
Key words: Fusarium wilt, safflower, inheritance
Fusarium wilt of safflower caused by
Fusarium oxysporum f.sp carthami is a major
constraint yield in peninsular region of India (Kalpana
et al., 1993). The fungus is seed borne inflicting
disease on the crop at any growth stage affecting all
aerial parts. It can cause losses ranging from 10-
100% under conditions favouring the disease
(Chakrabarthy, 1980). The long lasting, achievable
and economical method to combat disease is varietal
resistance. Despite the fact that considerable efforts
have been put to generate resistant varieties with
durable resistance, still this has not been fully
achieved, probably due to the fact that the genetics
of resistance of the host is not explored and exploited
to the fullest. The major setback appears from the
complexity of resistance and limited work done on
genetics of resistance. One dominant, one recessive
or two dominant with complimentary gene action or
additive gene action were reported in the crosses of
various genotypes with diverse susceptible
genotypes (Anonymous, 1975). However, it is not
clear whether these reported genes represent the
same loci because allelic tests in most cases were
not performed. The situation is further complicated
because of the lack of near isogenic lines and
knowledge of expression of the genes. The present
study describes the inheritance of disease in three
resistant and susceptible genotypes of safflower.
MATERIALS AND METHODS
The material consisted of three resistant
genotypes viz., GMU 1946, GMU 2914-15 and GMU
1702 with diverse pedigree (Table 1). The genotypes
gave consistent resistance reaction over more than
3 years of testing. To study the inheritance of
resistance, these were crossed with susceptible
varieties, viz., Nira, Manjira and Sagarmuthyalu to
generate enough F1 seed during rabi 2007-08. The
F1 from all the crosses were advanced for testing
the F2 generation against Fusarium wilt during rabi
2008-09. Some F1 seeds were also kept for testing
along with the F2 in the next growing season. One
row of parents alternating with the F1 and 15-20 rows
of F2 progenies of the crosses were sown in October
2008 in the wilt nursery at ARS, Tandur. The row
length was kept as 4 m with row spacing of 40 cm.
The plants were raised in normal in the wilt sick plot
and the crop was inoculated for disease development
when the plants were at seedling and vegetative stage
in Nov-Dec using field screening technique
(Bockelman, 1973). Mass culture of Fusarium
oxysporum f.sp carthami was prepared on sorghum
grains. The flasks were inoculated with the culture
and incubated for seven days to get profuse fungal
growth. The contents of the flasks were mixed with
soil to build up inoculum in the wilt sick plot. To ensure
higher disease build- up especially in drought
conditions, a spray of inoculum were given 20-25
days after sowing and humid conditions with the help
e-mail ID: rishith_sree@rediffmail.com
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