Effect of root exudates from different tomato genotypes on broomrape (O. aegyptiaca) seed germination and tubercle development

Nine accessions of wild species and six cultivated tomato genotypes were evaluated for their resistance to Orobanche aegyptiaca. They differed in the number of tubercles fixed on their roots, emerged shoots of broomrape and broomrape dry weight. The wild species L. pennellii LA 716, L. hirsutum PI 247087, L. pimpinellifolium hirsute and L. chilense LA 1969 were shown to be the most resistant to O. aegyptiaca. Moderate levels of resistance were obtained in L. hirsutum B, L. hirsutum LA 1777 L. peruvianum D4×D5, L. peruvianum CMV sel INRA, Ferum, Cervil, Levovil and UC 82-B. Among the cultivated tomato genotypes, Tresor (hybrid Fl), Levovil and Momor were the most susceptible hosts to Orobanche aegyptiaca. Similar results were also obtained in a hydroponic co-culture system where L. pennellii LA 716 and L. hirsutum PI 247087 were the most resistant, whereas Ferum, Tresor and Momor were the most susceptible. The root exudates of Ferum, Tresor and Momor induced far greater germination of O. aegyptiaca seeds than those of L. hirsutum PI 247087 and L. pennellii LA 716. Moreover, root exudates of L. pennellii LA 716 inhibited the germination of O. aegyptiaca seeds. Their use as an irrigation liquid, in pot experiments, on the susceptible genotypes (Momor and M82) was a relatively efficient control method since both the number of tubercles and the biomass of O. aegyptiaca decreased when watered with L. pennellii LA 716 exudates, while spike emergence was retarded.