Inheritance of resistance to broomrape in sunflower inbred line LIV-17

Abstract

Genetic resistance to broomrape (Orobanche cumana Wallr.) in sunflower is the most effective way to control the parasite. The objective of this study was to determine the inheritance and gene action for broomrape resistance in sunflower inbred line LIV-17. This line was first tested and found to be resistant to broomrape, in heavily infested locations in Spain and Turkey, where races F and G were predominant. Resistant line was crossed with susceptible line HA-26-PR and F1, F2 and F3 generation were developed. All plants in F1 generation were susceptible, indicating recessive inheritance. The segregation ratios in F2 generation had a goodness of fit to the expected ratio 3(S):1(R), indicating that broomrape resistance was controlled by a single recessive gene. Testing of the F3 generation gave a more precise evaluation and enabled differentiation between homozygous and heterozygous susceptible plants. The respective F3 families segregated, as expected, in 1 (homozygous S): 2 (heterozygous S): 1 (homozygous R) ratio, confirming that this line is resistant to broomrape when gene was present in homozygous recessive condition. From the breeding perspective, recessive nature of resistance to broomrape in LIV-17 highlights the necessity to introduce resistance genes into both parental lines in order to obtain resistant hybrid.