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

The survival of Rhizobium ciceri on chickpea (Cicer arietinum cv. Myles) seed, treated separately with 1 of 4 commercial fungicides, i.e., Apron, Arrest 75W, Crown, or Captan, was examined under laboratory conditions using standard serial dilution and plate count techniques. The resulting effects of fungicide-Rhizobium interactions on nodulation, N2 fixation, and plant growth were assessed in a controlled environment. Fungicide treatment decreased the number of viable rhizobia on the seed. In general, the toxicity 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 decreased nodule dry weight and %Ndfa, but only Arrest reduced dry matter yield. Apron had no effect on any of the parameters measured at the early pod-filling stage and was compatible with the chickpea inoculum used in this study.