Toward a better understanding of the genetic architecture of sunflower (Helianthus annuus) resistance to the parasitic plant Orobanche cumana

Abstract

The plant parasite Orobanche cumana is a major threat for the sunflower crop. The emergence of new, virulent “races” during the ten past years reinforced the need to develop new approaches, knowledge and tools in order to control this pest efficiently. Breeding is the most sustainable approach to control broomrape in the field. A RIL population derived from a cross between HA89 and LR1, an inbred line bred from an interspecific cross with Helianthus debilis had been previously characterized for resistance to O. cumana race E, but no data is available for new races. The aim of this study was to characterize the HA89xLR1 RIL population for resistance to race F and to identify QTLs associated with this resistance. The population was phenotyped by counting the number of healthy broomrape tubercles and the rate of tubercle necrosis on young sunflower plants raised in a growth chamber with four biological replications. Differences in l resistance were observed among the RIL population, with some resistant genotypes and some highly susceptible genotypes. The polymorphism of 111 SNP markers previously mapped on a consensus genetic map was used for the QTL detection. Four QTLs were detected on four linkage groups (LG01, LG07, LG15 and LG17), with two QTLs controlling the number of tubercles per plant and two others controlling necrosis. This study suggests that the resistance to O. cumana race F is controlled by several QTLs affecting differently the number of tubercle and the induction of tubercle necrosis.