Rhizobial survival and nodulation of chickpea as influenced by fungicide seed treatment

The survival of Rhizobium ciceri on chickpea (Cicer arietinum cv. Myles) se ed, treated separately with 1 of 4 commercial fungicides, i.e., Apron(R), A rrest 75W(R), Crown(R), or Captan(R), was examined under laboratory conditi ons using standard serial dilution and plate count techniques. The resultin g effects of fungicide-Rhizobium interactions on nodulation, N-2 fixation, and plant growth were assessed in a controlled environment. Fungicide treat ment decreased the number of viable rhizobia on the seed. In general, the t oxicity of the fungicides in terms of rhizobial viability increased in the following order: Control = Crown < Arrest = Apron < Captan. Although Crown had no effect on rhizobial viability assessed under laboratory conditions, it significantly reduced nodulation, percent N derived from the atmosphere (%Ndfa), and shoot dry matter. Seed treated with Arrest and Captan decrease d nodule dry weight and %Ndfa, but only Arrest reduced dry matter yield. Ap ron had no effect on any of the parameters measured at the early pod-fillin g stage and was compatible with the chickpea inoculum used in this study.