Effect of CryIIIA Protein Production in Nodules on Pea-Pea Leaf Weevil (Coleoptera: Curculionidae) Interactions

Abstract

Experiments were conducted in a greenhouse to determine the effects of genetically engineered strains of Rhizobium leguminosarum that contain the Bacillus thuringiensis subsp. tenebrionis cry IIIA gene attached to a constitutive lacZ promoter (Cl-pBtt-LZ), a conditional nifH promoter (Cl-pBtt-nH), or that contained the host plasmid without the cnj III gene (Cl-pRK311) on viability of pea leaf weevil, Sitona lineatus (L), larvae and compensatory growth of pea plants. CryIIIA protein production in pea nodules decreased survival and development of S. lineatus larvae and nodule damage. Strain Cl-pBtt-nH, which expresses CryIII protein only during nitrogen fixation, was more effective than Cl-pBtt-LZ. An experiment was conducted with hydroponically grown peas to determine the effects of rhizobial strain, 50% denodulation, and 50% defoliation on compensatory growth of foliage and nodules. Results indicated that nodule biomass was lowest and highest in plants inoculated with Cl-pBtt-LZ and C1-pBtt-nH, respectively. Denodulation had no effect on shoot biomass of control plants, but reduced shoot biomass of plants expressing the cry III gene. Denodulation also reduced standing nodule biomass. Defoliation had no significant effect on shoot biomass of plants inoculated with the control strains and Cl-pBtt-LZ, but was reduced in plants inoculated with Cl-pBtt-nH and that had not been defoliated. Defoliation had no affect on nodule biomass. Final root biomass was reduced by defoliation, but was not affected by rhizobial strain or denodulation.