ORIGINAL ARTICLE Efficacy of Bacillus subtilis native strains for biocontrol of Phytophthora crown and root rot of pistachio in Iran Mohammad Moradi 1 & Fatemeh Jafari Nejad 2 & Gholam Hosein Shahidi Bonjar 2 & Seyed Reza Fani 3 & Badrosadat Mahmudi Mimand 1 & Claudia Probst 4 & Mehrdad Madani 5 Received: 20 July 2017 /Accepted: 11 May 2018 # Sociedade Brasileira de Fitopatologia 2018 Abstract In Iran, Phytophthora crown and root rot of pistachio trees (also known as gummosis) destroys a significant number of fertile and non- fertile trees each year. To identify potential biocontrol agents effective in controlling pistachio gummosis, 200 soil samples were collected from 19 pistachio growing regions in Kerman province. Out of the 321 strains tested for antagonistic activity against Phytophthora pistaciae, 13 were selected as potential inhibitors of the disease. The tested strains were able to inhibit Phytophthora growth in dual culture, volatile and non-volatile assays by 14–72%, 12–68% and 27–85%, respectively. The highest inhibition was achieved by three strains identified as Bacillus subtilis using phenotypic characteristics, biochemical and physiological tests as well as sequencing the 16S rRNA genomic region for each strain. Co-inoculation experiments of six months old pistachio seedlings with P. pistaciae and the three selected B. subtilis strains reduced mortality rates by up to 80%. B. subtilis strain BSIPR35 was identified as the most promising biocontrol agent in greenhouse experiments. The ability of the selected strains to withstand drought, high temperature and salinity stresses was further tested. The growth of the strains was reduced under abiotic stresses ranging from 22 to 94%. All strains had the same growth under drought stress, while in salinity and under high temperature strain BSIPR35 acted superiorly compared to the other two strains. The bacterial strains may be effective in inhibiting gummosis in vivo, which requires further investigations. Keywords Bacillus subtilis . Phytophthora . Biological control . Gummosis . Pistachio . Root and crown rot Introduction Pistachio (Pistacia vera) production in Iran is constantly af- fected by biotic and abiotic factors. Among them, crown and root rot disease (also known as gummosis), soil salinity, drought and high temperature fluctuations are the most impor- tant factors, causing remarkable crop damage each year. Several species within the genus Phytophthora have been re- ported to cause gummosis in Iran (Banihashemi 1994; Mirabolfathy et al. 2001; Fani et al. 2006; Mostowfizadeh- Ghalamfarsa et al. 2008). Phytophthora pistaciae and P. drechsleri are the species most frequently found in pistachio orchards (Mirabolfathy et al. 2001; Fani et al. 2006). Gummosis can reduce the number of trees by up to 80% over a 5 to 10 year period (Moradi et al. 2017) and, consequently, has an enormous impact on pistachio production. The yearly damage caused by the disease has been estimated to range between 2 and 11% (Moradi et al. 2017). Monoculture cropping, traditional cultural practices in combination with Section Editor: Wagner Bettiol * Mohammad Moradi moradi@pri.ir 1 Pistachio Research Center, Horticultural Sciences Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Rafsanjan, Iran 2 Department of Plant Protection, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran 3 Plant Protection Research Department, Yazd Agricultural and Natural Resources Research and Education Center (AREEO), Yazd, Iran 4 Irrigated Agriculture Research and Extension Center, Washington State University, Prosser, WA, USA 5 Department of Soil Science, College of Agriculture, University of Manitoba, Winnipeg, MB, Canada Tropical Plant Pathology https://doi.org/10.1007/s40858-018-0226-0