Abstract

RUIZ-CISNEROS, María Fernanda et al. Incidence and causal agents of root diseases and its antagonists in apple orchards of Chihuahua, México. Rev. mex. fitopatol [online]. 2017, vol.35, n.3, pp.437-462. ISSN 2007-8080.  https://doi.org/10.18781/r.mex.fit.1704-3.

The incidence of root diseases was estimated in apple orchards from Chihuahua, Mexico. Three hundred isolates (fungi and Oomycetes) were identified in samples of root tissue and soil of trees with infectious damage symptoms and disease symptom-free trees. At the same time, putatively antagonistic agents were isolated and subsequently identified. The pathogenicity of fifteen selected isolates (eight fungi and seven Oomycetes), was tested in twelve apple rootstocks under greenhouse conditions. In addition, the in vitro antagonistic activity of Trichoderma and Bacillus species was evaluated against seven of the selected Oomycetes. The incidence of infection damage of roots in 20 tested orchards was 17% (1-40%). Fusarium was the most widely distributed fungi (67.8%). The distribution of the other organisms was variable. Four species of Trichoderma were identified, with T. gamsii being the most widely distributed (72.5%). Bacillus spp. substantially reduced the radial growth (>90%, p=0.05) of Phytophthora cactorum. Eleven rootstocks were susceptible to Pythium ultimum y Phytophthora cactorum C3. The G.935, Standard and M.25 rootstocks were the most resistant with 0% incidence. The antagonistic species of both genera inhibited the in vitro growth of P. cactorum (86.4-93.8%, p= 0.05), respect to Pythium species, and therefore, they might be used as biological control agents.

Keywords : Bacillus spp.; Fusarium spp.; Phytophthora cactorum; Trichoderma spp.; ITS region; molecular identification.