A study on nitrogen-fixation in some groundnut lines resistant to bacterial wilt.
A total of 21 groundnut lines (14 resistant to bacterial wilt (Pseudomonas solanacearum) and 7 susceptible) were evaluated for nitrogen fixation at the seedling stage following inoculation with P. solanacearum and Rhizobium spp. and spontaneous infection in the field. Nodule number and nitrogen content/plant were lower in resistant than susceptible lines, indicating that the capacity of nitrogen fixation of resistant lines was normally poor compared to susceptible lines. Differences were noted between resistant and susceptible lines in the frequency and position of Rhizobium infection and in their root morphology under the same cultural conditions. The results suggested that resistance to root invasion from external microorganisms differed between resistant and susceptible genotypes. The similar mechanism of resistance to the invasion from bacterial wilt and Rhizobium was suggested to be partly responsible for the fact that resistant varieties generally had a lower yield potential than susceptible varieties in groundnut-producing regions of China.