Growth-defense tradeoffs and source-sink relationship during both faba bean and lentil interactions with Orobanche crenata Forsk

Abstract Orobanche crenata Forssk., a root holoparasitic weed, represents a major biotic threat of legumes in the Mediterranean region. O. crenata could reduce the yield up to 90%. In this study, the effect of O. crenata on biomass production and partitioning of some faba bean and lentil cultivars were investigated through pot assays. During the first stage of infection, reductions in host biomass were observed on susceptible and resistant faba bean cultivars (53.84 and 27.02%, respectively for Lobab and Misr 3) and on susceptible lentil cultivar (Zaaria). However, during the last stage (host plant maturity), combined biomasses of susceptible faba bean (35.69 g) and lentil (8 g) cultivars were similar to those of non-infested plants (32.45 and 6.62 g, respectively). Considering biomass partitioning over the various host parts, O. crenata parasitism on susceptible faba bean and lentil cultivars greatly increased host root dry mater, but delayed and reduced host reproduction. The relative weight of parasite and host organs were also studied. Thus, a marked decrease of root relative weight was observed during the last developmental stages (up to 63%) accompanied simultaneously with the increase of relative parasitic weight (35.87%). Results suggested that legumes-O. crenata interactions were governed by growth-defense tradeoffs during the early stage of infection, whereas source-sink relationships explained the dry weight diversion from host to parasite during the last phases of the interaction.