Influence of chickpea genotype and Bacillus sp. on protection from Fusarium wilt by seed treatment with nonpathogenic Fusarium oxysporum

Seeds of kabuli chickpea cultivars ICCV 4 and PV 61 were treated with conidia of nonpathogenic Fusarium oxysporum isolate Fo 90105 suspended in methylcellulose (3 x 106 conidia.seed-1), or with methylcellulose alone, and sown in soil artificially infested with 500 or 1,000 chlamydospores.g-1 of F. oxysporum f. sp. ciceris race 5. At an inoculum concentration of 500 chlamydospores.g-1, seed treatment with Fo 90105 significantly increased the incubation period of the disease by 11 (ICCV 4) or 25 (PV 61) days, and reduced the final disease incidence, disease intensity and the standardized area under the curve of disease intensity over time. This protection from disease was higher and more consistent in PV 61 than in ICCV 4. However, it was annulled with an inoculum concentration of 1,000 chlamydospores.g-1, except for the incubation period in PV 61 which was increased by 10 days. When ICCV 4 seeds were treated with Fo 90105 (3 x 106 conidia.seed-1) and/or Bacillus sp. isolate RGAF 51 (1 x 107 cfu.seed-1), then sown in infested soil, there was no influence by the Bacillus isolate on protection conferred by Fo 90105. However, the degree of protection by the nonpathogenic F. oxysporum was higher and more consistent when plants from treated seeds were grown in sterile sand for 6 days, then transplanted into infested soil.