HETEROSIS FOR YIELD AND YIELD ATTRIBUTING TRAITS IN SAFFLOWER 24
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 25