Progress in research on breeding for resistance to broomrape

Abstract

Sunflower broomrape (Orobanche cumana Wallr.) is a parasitic angiosperm regarded as one of the most serious production constraints in many sunflower-producing countries. Historically, sunflower breeders have been successful in developing cultivars resistant to this parasite but the introduction of new resistance sources has been frequently followed by the appearance of new pathogenic races overcoming the resistance. The present review sets out to examine the principal achievements in this field that took place during the last decades focusing in the most recent advances in research. In recent years, several research groups have made relevant contributions on breeding for resistance and development of control strategies. Following the identification and characterization of new virulent races, new sources and mechanisms of resistance have been developed and characterized at the genetic and molecular level. There have been also important contributions to the knowledge of the biology and genetics of the parasite that will contribute to understand the dynamics of broomrape populations and race evolution. Important advances have also been made in the use of imidazolinone (IMI)-resistant hybrids as an alternative method of control. Most of the studies on sunflower breeding for resistance to O. cumana have been concentrated so far in the host plant but, in spite of recent advances, little in known in important aspects of the parasite side such as breeding system and genetics of virulence. An unsolved problem is the existing uncertainty in the designation of races and resistance genes identified in different countries. There is a need for international cooperation in this area using common differentials and molecular tools. Emphasis is given to the need for a multidisciplinary approach ranging from studying the mechanisms underlying resistance in the host plant to the reproductive biology and genetics of traits related to parasitism in O. cumana. The combination of long term strategies involving the complete host-parasite system and the integration of classical and molecular approaches is expected to contribute to the development of more durable sources of resistance and to improve sunflower performance in areas infested by broomrape.